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\begin{titlepage}
\begin{Large}
\hspace*{13.0cm}
\parbox[t]{50mm}{
{\bf Version 1.1.3}\hfill\\
{\bf 28.05.1999}\hfill\\
}
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\vspace{10mm}

\begin{center}
\fbox{\rule[-15mm]{0mm}{18mm}
\parbox{150mm}{
\begin{center}
{\Huge\bf Quality Assurance and Control} \\
\hfill \\
{\Huge\bf Reference Document} \\
\hfill \\
\hfill \\
\hfill \\
{\LARGE\bf for ATLAS MDT Chamber Construction} \\
\end{center}
}}
\end{center}
\vspace{20mm}

\begin{center}
{\LARGE\bf Hubert Kroha}
\vspace{2mm}

{\LARGE Max-Planck-Institut f\"ur Physik, Munich
}
\end{center}
\vspace{40mm}


\noindent
{\Large Guidelines for the implementation of the quality assurance and quality control procedures
during the construction of the Monitored Drift Tube (MDT)}

\centerline{\Large Chambers for the ATLAS Muon Spectrometer.}
\vspace{7mm}

\centerline{\Large (Version prepared for the MDT Production Readiness Review, 16--17 June 1999.)}
\clearpage
\pagestyle{empty}

\vbox to \textheight{\vfill}
\clearpage

\end{titlepage}

\tableofcontents
\clearpage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Introduction--The Quality Assurance Plan}
%
The performance goals of the ATLAS muon spectrometer require unprecedented 
mechanical precision in the construction of the large 
number of Monitored Drift Tube chambers (1194) built at many production sites (11)
over a period of more than 4 years. At the same time, the reliability the large number of
drift tubes (371000) and chambers must be very high.

Measurement of the wire locations in assembled chambers and verification of their
accuracy with the X-ray tomograph can only be performed
for a fraction of the chambers, approximately $15~\%$.

The strategy for the distributed, large-scale production of the 
precision chambers is to guarantee the mechanical precision of drift tubes and
assembled chambers by the design of the components and of the assembly method and tooling
supplemented by an extensive monitoring program and detailed quality assurance
plan for all production sites.

In addition, in a common quality control program of
the important parameters for the reliability and performance of individual drift
tubes and of assembled chambers are tested. The quality control tests are
designed such that they safely detect bad drift tubes and chambers while they
can be performed at all production sites and keep up with the production rate.
Only small failure rates are acceptable in the production process. The main
purpose of the tests is to provide quick feed back for adjustment of the
assembly tooling in the case of problems.

Faulty chamber components and drift tubes will be rejected. The failure rate
of assembled drift tubes must not exceed the few percent level.
Chambers failing the quality control tests have to be repaired
(identification of leaks, sputtering of noisy tubes);
faulty tubes in a chamber which cannot be recovered will be disconnected.
Chambers exceeding the mechanical accuracy requirements can be recovered
by measureing the wire locations with the X-ray tomograph. Only in exceptional
cases chambers will have tobe rejected.

\noindent
The quality assurance procedures for MDT chamber construction
can be broken down into the following steps:

\begin{enumerate}

\item Chamber Components and Materials,

\item Drift Tube Assembly,

\item Drift Tube Test,

\item Chamber Assembly,

\item Chamber Test,

\item Transport and Storage.

\end{enumerate}

The quality assurance procedures for each step are decribed in this document.
Quality control of the electronics and data aquisition to be mounted
on the chambers during installation in the ATLAS detector will be described
in separate documents.

Detailed archiving of the monitoring and test data is necessary in order
to monitor and control the production process and to provide complete
documentation for the operation of the chambers. The data will be stored
in local quality assurance data bases at the production sites and as well as
in a central production data base.

The central data base contains the information needed to monitor
the production and evaluate the quality of the chambers to be installed
and which will be kept for the operation of the muon spectrometer.

In the local data bases all available data from assembly monitoring and
quality control should be kept until the completion of all chambers
to allow the detection and tracing of problems during chamber production.

In addition, the information about
delivery and stock of components and the completion, transport and storage times
of drift tubes and chambers is kept in the local and central production data bases
at different levels.

The production sites are requested to report all problems occuring during tube
and chamber assembly. Production should not continue before the problems are not
understood and solved in consultation with the other production sites.

An internal review of each production site will take place before
module~0 construction at the site in order to ensure that all procedures
and tools follow the specifications.

Before the start of series production, each production site will be qualified
based on the data from module~0 construction and test.

This document gives the guidelines and serves as reference for the implementation
of the quality assurance procdures and quality control tests at the MDT chamber
production sites.

The document and regularly updated versions are available at

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/document.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Documentation}
%
Information relevant for quality assurance and control of the MDT chamber construction 
is contained in the following documents:

\begin{enumerate}

\item {\bf Technical Specifications of Chambers and Assembly Tooling:}

\begin{itemize}
 
\item Technical Design Report for the ATLAS Muon Spectrometer and updates.

\item Drift tube assembly tooling: 

http://atlasinfo.cern.ch/Atlas/GROUPS/MUON/mdt/mdthere/mdt3.html,

http://lepton.phys.washington.edu/\~ atlas/Tube\_ Assembly/tube\_ assembly.html.

\item MDT chamber design and chamber assembly tooling:

http://atlasinfo.cern.ch/Atlas/GROUPS/MUON/mdt/mdthere/mdt3.html.

\item On-chamber gas distribution:

http://hpfrs6.physik.uni-freiburg/\~{}mohr/scan\_ text.html

\item Alignment platforms (barrel and endcap chambers):

http://atlasinfo.cern.ch/Atlas/GROUPS/MUON/alignment/.

\end{itemize}

\item {\bf Procurement Documents for Chamber Materials:}

Tendering documents and contracts with suppliers for the chamber components listed below.

\item {\bf Drift Tube Assembly Manual:}

Describes all steps of drift tube assembly including QA/QC procedures.
The assembly plan will be partially implemented in a Tube Assembly Control Program.

\item {\bf Chamber Assembly Manual:}

Describes all steps of chamber assembly including QA/QC procedures.
The assembly plan will be implemented in a {\bf Chamber Assembly Control Program}.

The use of the monitoring devices, the handling of the glue and the
installation of the gas distribution system are described in more detail in separate manuals.

\item {\bf The Quality Assurance and Quality Control Reference Document (this document):}

Describes the quality assurance strategy and procedures
including guidelines for the quality control tests and instructions for handling,
transport and storage of chamber materials, drift tubes and assembled chambers.

\end{enumerate}

These general manuals serve as reference and guidelines for the preparation of
the assembly and quality control manuals at each production site
and for the implementation of coherent quality assurance procedures.

\section*{Other Documents Related to MDT Quality Assurance Procedures:}
%
\subsection*{General}
%
\begin{enumerate}

\item
ATLAS Collaboration, A.~Airapetian et al., 
{\sl ATLAS Muon Spectrometer Technical Design Report},
CERN/LHCC/97-22, May 1997.

\item 
F.~Linde et al., {\sl MDT Quality Assurance for Module~0 MDT Chambers},
ATLAS Internal Note, ATL-MUON-98-238, May 1998 (replaced by this document).
\end{enumerate}

\subsection*{Specifications and Procurement of Components}
%
\begin{enumerate}

\item 
Technical Specification (Barrel Chambers), {\sl Supply of Aluminum Alloy Extruded Profiles
for the ATLAS Muon Spectrometer (Module-Zero Chambers, Barrel)},
for Price Enquiry: DO-98010, October 1998
(NIKHEF).

\item
Technical Specification, {\sl Supply of Gold-Plated Tungsten-Rhenium Fine Wire
for the ATLAS Muon Spectrometer (Module-Zero Chambers)},
for Price Enquiry: DO-1045107, September 1998
(CERN).

\item 
Technical Specification, {\sl Supply of Thin-Walled Precision Aluminum
Alloy Tubes
for the ATLAS Muon Spectrometer (Module-Zero Chambers)},
for Invitation to Tender: IT-2549/EP/ATL, November 1998
(CERN).

\item 
Technical Specification, {\sl Supply of Endplugs (Endplug Body)
for the ATLAS Muon Spectrometer},
for Invitation to Tender: IT-2575/EP/ATL, May 1999
(CERN).

\item
Hedgehog boards and mezzanine cards,

http://ohm.bu.edu/bmc/summer\_ pcbs/hedgehog\_ spec.html

(Boston University).

\end{enumerate}

\subsection*{Drift Tube Assembly}
%
\begin{enumerate}

\item
R.~Dumps et al., {\sl A Prototype Wiring Automate for the Twister/Tango
Based Endplug of the ATLAS Muon Drift Tubes},
ATLAS Internal Note, ATL-MUON-98-267, January 1999                                                                                            
(CERN).

\item
University of Michigan ATLAS group, {\sl Michigan Wiring Table, 
MDT Tube Assembly Electronics Control and Computer Program},

http://ganesh.physics.lsa.umich.edu/\~{}atlas

(Michigan).

\item
H.~Kroha and A.~Manz, {\sl Laser Welding for the Ground Contact of MDT Tubes},
May 1999,

draft {\bf Laser Welding Manual},

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/laserwelding/laserwelding\_ doc.ps (.pdf),
laserwelding\_ doc.fig2.ps, laserwelding\_ doc\_ fig3.ps, laserwelding\_ doc\_ fig4.ps

(MPI Munich).

\end{enumerate}

\subsection*{Chamber Assembly}
%
\begin{enumerate}

\item
H.~Kroha and S.~Schael,
{\sl Optical Monitoring System for the MDT Assembly Stations},
ATLAS Internal Note, MUON-NO-156, April 1997
(MPI Munich).

\item
G.~Kaptsis et al., {\sl Mechanical Design of the BIS Module Zero MDT Chamber},
ATLAS Internal Note, ATL-MUON-98-242, June 1998
(Thessaloniki).

\item
G.~Ciapetti et al., {\sl A QA/QC System to Monitor the Planarity of the Tube Layers
in MDT Chambers Construction},
ATLAS Internal Note, ATL-MUON-98-255, September 1998
(Rome~I).

\item
V.~Bartheld et al., {\sl Construction of the Full-Scale Prototype
of a BOS MDT Chamber},
ATLAS Internal Note, ATL-MUON-98-256, October 1998,

http://wwwatlas.mppmu.mpg.de/mdt.html

(MPI Munich).

\item
V.~Bartheld et al., {\sl The Construction and Performance
of the BOS~98 MDT Prototype Chamber},
ATLAS Internal Note, May 1999

(MPI Munich).

\item
D.~Kalkbrenner, H.~Kroha and A.~Manz, {\sl Glue Dispenser for MDT Assembly
and Glueing Instructions}, January 1999,

draft {\bf Glueing Manual},

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/glueing/glue\_ manual.ps

(MPI Munich).

\item
H.~Kroha, {\sl BOS Chamber Assembly Quality Assurance Plan},
February 1999,

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/bos\_ assembly\_ plan.ps (.pdf)

(MPI Munich).

\item
H.~Kroha, {\sl BOS Chamber Assembly and Test Plan},
February 1999,

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/bos\_ assembly\_ test.ps (.pdf)

(MPI Munich).

\item
H.~Kroha, {\sl BOS Chamber Production and QA/QC Data Base Structure},
February 1999,

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/bos\_ qaqc\_ db.ps (.pdf)

(MPI Munich).

\item
Task Owners Chamber Assembly, {\sl Chamber Assembly Manual},
April 1999,

http://www.lnf.infn.it/\~{}curatolo/BMLmanual.draft/

\item
University of Freiburg, {On-Chamber Gas System for the Barrel MDT Chambers}, March 1999, and
{\bf Assembly Description for the MDT On-Chamber
Gas Distribution}, May 1999,

draft {\bf Gas Distribution Installation and QA Manual},

at http://hpfrs6.physik.uni-freiburg/\~{}mohr/scan\_ text.html

(Freiburg).

\item 
H.~Kroha and A.~Ostapchuk, {\sl Optical Monitoring
of MDT Chamber Assembly}, April 1999,

draft {\bf Monitoring Manual},

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/monitoring/monitoring.ps (.pdf)

(MPI Munich).

\end{enumerate}

\subsection*{Drift Tube Test}
%
\begin{enumerate}

\item 
V.T.~Braic et al., {\sl Leak Detection System for Mass-Production
of Drift Tube Detectors}, 
ATLAS Internal Note, ATL-MUON-98-225, March 1998,

http://nuweb.jinr.ru/\~{}dcbp/atlas/QAQC/gasleak/foto.htm

(Dubna).

\item
M.~Cambiaghi et al., {\sl An Electromagnetic Micrometer (EMMI) to Measure Wire Location
Inside an ATLAS MDT Drift Tube},  
ATLAS Internal Note, ATL-MUON-98-259, November 1998
(Pavia, Rome).

\item
A.~Balla et al., {\sl MDT Wire Tension Measurement Using an Electrostatic Method},
ATLAS Internal Note, ATL-MUON-98-264, November 1998
(Frascati).

\item
Pavia and Roma~I Atlas Groups, {\sl The Pavia--Roma~I MDT QA Facility},

ftp://cobra1.pv.infn.it/pub/MDT/mdt\_ qa.ps.gz

(Pavia, Rome~I).

\item
A.~Albanese et al., {\sl Quality Assurance and Quality Control for
ATLAS Drift Tubes at the Cosenza Production Site},
description of setup and quality control test plan,

ftp://fermi.cs.infn.it/atlas\_ qaqc

(Cosenza).

\item
University of Michigan ATLAS group, {\sl Michigan Leak Detector},

http://ganesh.physics.lsa.umich.edu/\~{}atlas

(Michigan).
\end{enumerate}

\subsection*{Chamber Test}
%
\begin{enumerate}

\item
D.~Drakoulakos et al., {\sl The High-Precision X-ray Tomograph
for Quality Control of the ATLAS MDT Muon Spectrometer},
CERN-OPEN-97-023, July 1997
(CERN).

\item
CERN X-Ray Tomograph, http://wwwcn.cern.ch/\~{}xtomo.

\item
C.~Bacci et al., {\sl Design of a Cosmics Test Site for the Quality Assurance and
Quality Control (QAQC) of Full MDT Chambers},
ATLAS Internal Note, ATL-MUON-98-241, June 1998
(Rome~III).

\item
N.~Hessey, A.~Staude and T.~Trefzger, {\sl Cosmic Ray Test Stand at the LMU Munich},
ATLAS Internal Note, ATL-MUON-98-266, December 1998
(LMU Munich).

\item
H.~Kroha, {\sl BOS Chamber Assembly and Test Plan},
February 1999,

ftp://wwwatlas.mppmu.mpg.de/outgoing/qaqc/bos\_ assembly\_ test.ps (.pdf)

(MPI Munich).

\end{enumerate}

\clearpage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\chapter{Chamber Components}
%
The main chamber components and materials to be controlled are:

\begin{enumerate}

\item Precision aluminum tubes.

\item Gold-plated W-Rh wire.

\item Precision endplugs and endplug components.

\item Spacer components.

\item Components of the optical alignment system.

\item On-chamber gas distribution system.

\item Faraday cages and patch panels.

\item Glue (several types).

\item Hedgehog boards.

\item Mezzanine cards with readout electronics.

\item Temperature and magnetic field sensors.

\item Protective covers.
\end{enumerate}

Quality and tolerances of the chamber components delivered to the
chamber production sites are controlled in four steps:

\begin{enumerate}

\item Quality assurance by the supplier

\item Central monitoring of material production including sample tests at 
an responsible institute.

\item Acceptance tests and visual inspection at the chamber production sites.

\item Specification for packing, transport, storage and handling
of the components.

\end{enumerate}


\section{Aluminum Tubes}
%
The thin-wall aluminum tubes for the drift tubes of the MDT chambers follow
tight mechanical tolerances with respect to the outer and inner diameter
and the straightness in order to be suitable for the precision assembly of the chambers.

The tubes are cleaned on the inside and outside
by the manufacturer according to a cleaning procedure defined in detail
which has been approved by the collaboration after
ageing tests. The cleaning procedure must not be changed without the agreement
of the collaboration and after new ageing test have been performed with the
new cleaning procedure.

The mechanical tolerances and the cleanliness of the tubes must be
conserved during all further transport, storage and handling of the bare
tubes and of the assembled drift tubes (see: Drift Tube Assembly and Storage).

The precision aluminum tubes are procured  centrally via CERN.

\subsection{Quality Control by Supplier}
%
The following quality control tests of the bare tubes are required from the 
supplier with certification:

\begin{enumerate}

\item Chemical and mechanical analysis and ultrasonic test of the tube raw materials.

\item Geometrical tolerances of extruded tubes.

\item Geometrical tolerances of drawn and straightened tubes.

\item Geometrical tolerances, including straightness, of at least $10\%$ of finished
tubes of each batch.

\item Visual inspection of inside and outside of at least $10\%$ of finished
tubes of each batch, including proper deburring of tube ends.

\end{enumerate}

Each finished tube is identified by a bar code (industrial format 39B) which
contains the production run number, a sequential tube identifcation number, tube length
and a date and appears also in alphanumeric form. The bar code is written
in locations along the tube which will not be attached to the spacer in case
additional cleaning is required for glueing.

Quality control documents and data with reference to the tube bar code are
provided to the collaboration
and are kept in the {\bf Production Data Base} for monitoring of the production.

Detection of small holes on the tube walls by the supplier, e.g.\ with the eddy current
method, is too expensive. Therefore, the walls of all drift tubes
have to be tested for gas tightness at the chamber production sites.

\subsection{Production Monitoring}
%
Production monitoring is done centrally at CERN including
the following sample tests per batch of tubes delivered to the chamber production sites:

\begin{enumerate}

\item Visual inspection, inside and outside (obvious defects or holes, cleaning,
deburring, straightness).

\item Geometrical tolerances with 3D metrology.

\item Chemical and mechanical analysis of the finished tube material.

\item Metallurgical analysis of the finished tubes.

\item Chemical analysis of inner tube surface (monitoring of cleaning procedure).

\item Quality control of cleaning procedure over time with the ageing test stand.

\end{enumerate}

In case of failed tests, the supplier is notified and the affected batches are
returned.

During tube assembly at the production sites, each tube is visually inspected at the inside and outside
for obvious defects, proper deburring and cleanliness.

\subsection{Tube Transport and Storage}
%
The aluminum tubes are cleaned on the inside and outside by the manufacturer.
Afterwards, the tubes are kept under clean conditions and
are not cleaned anymore at the chamber production sites, especially not
on the inside.

The tubes are transported and stored under the following conditions:

\begin{enumerate}

\item The tubes are always transported in stable wooden boxes like the ones
used for delivery by the manufacturer.

\item The individual tubes are kept separated from each other and held such that
that they cannot move inside the transport box.

\item The tube ends are closed and protected with soft plastic caps.

\item Inside the transport box and in storage, the tubes are enclosed in air-tight
plastic bags containing dehumidifier bags.

During longer storage periods, the enclosing plastic bags should be filled
with inert gas to prevent corrosion.

\end{enumerate}


\subsection{Quality Control at Production Sites}
%
Quality control tests of the bare tubes at the chamber production sites are summarized in Table~1.


\section{Wire}
%
The gold-plated tungsten-rhenium sense wire for the drift tubes is procured centrally via CERN.

\subsection{Quality Control by Supplier}
%
The following quality control tests of the wire are required from the supplier with certification:

\begin{enumerate}

\item Measurement of tensile strength at beginning and end of each spool.

\item Test of precentage of gold plating at beginning and end of each spool.

\item Visual and microscopic inspection of gold plating quality for at least first meters
of each spool.

\end{enumerate}

Each wire spool is certified and labelled with date, wire length and production run number.

\subsection{Production Monitoring}
%
Production monitoring is done centrally at CERN including
the following sample tests per production run:

\begin{enumerate}

\item Measurement of wire diameter.

\item Microscopic inspection of gold plating quality.

\item Inspection of cleanliness.

\item Measurement of tensile strength.

\item Measurement of electrical conductivity.

\end{enumerate}

In case of failed tests, the supplier is notified and the affected batches are
returned.

\subsection{Quality Control at Production Sites}
%
Quality control at the chamber production sites is summarized in Table~1.


\section{Endplugs}
%
The endplugs for the drift tubes consist of the following components:

\begin{enumerate}

\item Injection moulded insulator made of Noryl GFN3 which contains $30\%$ glass fiber and is
machined to be concentric and coaxial with the aluminum ring reference surface.

\item Precisely machined metal inserts in the plastic body:

\begin{enumerate}

\item Aluminum ground ring with precise reference surface for drift tube
tube positioning on assembly combs and precise front face for accurate
endplug insertion.

\item Central brass insert holding the wire locator in a precisely concentric
and coaxial hole with respect to the reference surface.

\end{enumerate}

\item Precise wire locator, machined separately and held in the concentric hole
of the brass insert with an injection moulded Noryl clip.

\item Copper wire crimp tube inserted in central brass piece.

\item Brass sealing cap with signal pin to be screwed onto the brass insert.

\item Injection moulded Noryl gas connector sealed with two O-rings between
the front face of the plastic body and the signal cap.

\item Brass ground pin in contact with the aluminum ring through a threaded hole
and a nut with lock washer.

\item O-ring for gas seal of the plastic endplug body in the aluminum tube.

\end{enumerate}

The endplugs and their components are not individually labelled for cost reasons.
Endplugs of different production batches are kept in separate boxes at each
production site and are not mixed during tube assembly to help tracing
of problems.

The endplug components are procured centrally via CERN.
At least parts of the endplugs have to be assembled 
at the chamber production sites.

\subsection{Quality Control by Supplier}
%
The following quality control tests of the endplugs and their components
are required from the suppliers with certification for a fraction of at
least $2\%$ of the endplugs:

\begin{enumerate}

\item Visual inspection of the injection 
moulded piece: smooth surfaces without air bubbles or cracks, especially in the
O-ring grooves.

\item Inspection of the bulk of the injection moulded piece by cutting
longitudinally through the center: no enclosed bubbles larger than 0.2~mm in diameter, 
no cracks.

\item Metal inserts must not detach under specified force.

\item Visual inspection of machined endplug components:

Proper cleaning and deburring, smooth surfaces, no sharp edges, no metal chips,
no scratches, no air bubbles or cracks in plastic piece.

\item Test of fitting of components.

\item Verification of all mechanical tolerances of endplug and wire locator
with 3D metrology.

\end{enumerate}

\subsection{Production Monitoring}
%
The production is monitored by responsible institutes which centrally
perform the following sample tests per production batch:

\begin{enumerate}

\item Visual inspection of all parts:
Proper cleaning and deburring; smooth surfaces, no sharp edges, no metal chips,
no scratches, no air bubbles or cracks in the plastic parts.

\item Test of fitting of all components.

\item Verification of all mechanical tolerances 
of endplug and wire locator with 3D metrology.

\item Inspection of the bulk of the injection moulded piece by cutting
the endplug longituinally through the center: no enclosed air bubbles, no cracks.

\item High voltage test of a fraction of endplugs per production batch  
assembled in drift tubes filled with dry nitrogen: leakage currents below
2~nA up to a voltage of 5~kV.

\item Measurement of the shape and diameter of the wire locating hole
and of the concentricity with respect to the endplug reference surface
with a CCD camera.

\end{enumerate}

In case of failed tests, the supplier is notified and the affected batches are
returned.

\subsection{Quality Control at the Production Sites}
%
Quality control tests at the chamber production sites are summarized in Table~1.

During assembly of the endplugs at the production sites and during
preparation for tube assembly, all endplug components, including 
wire locator and crimp tube, are visually inspected for obvious defects
(no sharp edges, proper deburring, no metal chips, 
no scratches, no air bubbles or cracks in the plastic parts).

All O-rings are inspected for obvious defects during assembly on the endplug.
The O-rings must not be exposed to light during
storage or assembled on the endplugs to prevent ageing.

The endplug components are cleaned in an ultrasonic cleaning bath using
only pure ethanol. Other cleaning fluids are not allowed.

\section{Spacer Components}
%
The extruded aluminum spacer profiles are procured centrally via a responsible
institute which monitors the production. Machining of the profiles to reach the
final mechanical tolerances is the responsibility of each production site.

The mechanical tolerances of the extruded and cut profiles are verified
by the supplier and the responsible institute for each batch delivered.

The mechanical tolerances of the machined spacer components are verified
for each chamber at the chamber production sites. The glue gaps between
cross plates and tubes layers are verified during spacer assembly (see the
{\bf Chamber Assembly Manual}). The functioning of the sag compensation system is tested
after assembly on the spacer.

\section{Optical Alignment System Components}
%
The components of the ATLAS optical alignment monitoring systems installed on the
chambers during assembly are:

\begin{enumerate}

\item Components of RASNIK monitors (LED with mask, custom-fabricated lens
and CCD with infrared filter with housings)
for the in-plane alignment system.

\item Mounting platforms for components of the projective alignment monitors.

\item Mounting platforms for the axial/praxial alignment monitors.

\end{enumerate}

The components are procured centrally from industry
by responsible institutes which monitor the production and perform
sample tests of the optical quality of the lenses (focal length within $\pm 3$~mm of the
nominal value and mismatch between optical and geometrical center $<1$~mm) and of the electrical
functionality of light sources and CCDs.

The focal length of the RASNIK lens is specific for each monitor 
and engraved on the lens holder.
It is specified to be within $\pm 3$~mm of the nominal value (1/4 of the
distance between mask and CCD). This tolerance corresponds to a
maximum forseen longitudinal range of adjustment of $\pm 12$~mm of the
light source with mask with respect to the lens. This can be verified
on a special RASNIK test stand at the chamber production sites prior to
the assembly of the spacer. Otherwise the lens is rejected.

As part of the chamber assembly procedure,
each in-plane alignment monitor is adjusted and fully tested on the
spacer (sharp and analysable image of the center of the mask with sufficient brightness)
before permanent fixation with glue (see the {\bf Assembly Control Plan} in the {\bf Appendix}).

The RASNIK components on the spacer must not move after the first zero-reading;
otherwise the in-plane alignment system has to be zeroed again on a granite table.
In order to detect and trace potential errors of the in-plane alignment system,
it is recommended to cover the fixation points of the
in-plane alignment components on the spacer with special paint used in
air craft industry which indicates by colour change if a component has moved.

Correct relative orientation of the RASNIK mask and CCD is important for the analysis software
and ensured with labelling by the supplier.

The use of the RASNIK systems is described in {\bf RASNIK Manuals} by the responsible
institutes.

\section{On-Chamber Gas Distribution System}
%
The components of the on-chamber gas system are centrally procured
by a responsible institute which monitors the
production and the quality control by the suppliers.

The gas manifolds are preassembled at the chamber production sites and tested
for gas tightness and flow rate per tube (see Table~3). After mounting on the
chamber, the gas system is leak tested together with the whole chamber (see Tables 4 and 5).

Assembly and test of the on-chamber gas system is described
in the {\bf On-Chamber Gas System Manual} by the responsible institute.

\section{Faraday Cages and Patch Panels}
%
The fabrication and quality control of the Faraday cages and patch panels 
for readout electronics and optical, temperature and B-field monitors are
the responsibility of each institute.

\section{Glue}
%
All glue types used for chamber assembly are epoxy resin based two-component glues.
They have been selected because they provide
sufficient strength in contact with aluminum and handling and curing
time are suitable for chamber series production.
In dedicated tests and during chamber prototype construction,
the shrinkage of the selected glues was found to be small enough to prevent
significant chamber deformations. Epoxy resin based glues are
known to be radiation tolerant far beyond the radiation levels
in the ATLAS muon spectrometer.

Only glue from one supplier, Ciba Geigy, will be used at all production sites.
The selected glue types are all widely used standard products of the supplier
with well known properties and reliability and have been exclusively used
for the construction of all prototype MDT chambers.

The quality of the glue is guaranteed by the supplier.
Glue storage and handling follow strictly the
recommendations by the glue supplier.
Storage time and conditions of the glue is monitored at the
chamber production sites. 

Details of the glue types and the glueing procedures are given in the
chapter {\bf Chamber Assembly}.

\section{Hedgehog Boards}
%
The hedgehog boards are delivered to the chamber production sites fully tested
and certified. 
They are either delivered clean in sealed packages or they have to be
cleaned in an ultrasonic cleaning bath at the chamber production site before
installation.
After unpacking or cleaning, the boards are handled only with gloves.

All boards are visually inspected for obvious defects upon delivery.
Correct positioning of the electrical contact holes is verified on a template
in order to avoid forces on the endplugs when the boards are installed.

Installation of the boards and high voltage test on the chamber takes place
in the chamber test stands at the production sites. 
The boards stay on the chamber.

\section{Mezzanine Cards}
%
The mezzanine cards with the readout electronics are delivered to the 
chamber production sites fully tested
and certified. The boards are visually inspected for obvious defects upon
delivery. Mounting of the cards on the chamber and
high voltage and functionality test will take place either in the local
chamber test stand or in the central storage area at CERN as soon as the
cards have been delivered.

\section{Temperature and B-Field Sensors}
%
The temperature and B-field sensors, including cables, are procured and 
fabricated centrally by responsible institutes and are sample tested by them.
The function of each sensor is tested at the chamber production site
before the installation on the chamber.

\section{Protective Covers}
%
The material for the protective covers for installation in the detector will 
be procured centrally. Cutting to size and installation on the chambers
is done at the chamber production sites.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Drift Tube Fabrication}
%
\section{Drift Tube Assembly}
%
Operation of the large number of drift tubes in the ATLAS muon spectrometer
requires very high reliability with respect to wire tension, gas thightness and high voltage
stability. At the same time, the sense wires have to be
centered in the precision aluminum tubes with high accurcay: with $\pm 10~\mu$m rms relative
to the endplug reference surfaces in the $y$ and $z$ coordinates of the 
azimutally oriented tubes and with a tolerance of $\pm 100~\mu$m with respect
to the inner tube wall envelope. The wire tension has to stay inside tight
tolerances in order to predict the wire sag with high accuracy.

During series production, typically 50--100 drift tubes per day have to be assembled
and tested at each production site.
Because of the large number of tubes, rejection of only few
percent of the assembled drift tubes can be afforded after the quality control tests.

The drift tube assembly procedures are designed to guarantee the high precision
and reliability of the drift tubes:

\begin{enumerate}

\item The drift tubes are assembled in a temperature controlled clean room
of class 50000. 

\item The room temperature is controlled to be $20\pm 1^\circ$C.
This allows to set the tube length and the wire tension of the assembled tubes 
with sufficient accuracy.

\item Automatic or semi-automatic wiring stations are used.

Manual handling of the wire is minimized.

\item Colinearity of the endplug and tube axes, the relative azimutal
orientation of the two endplugs of a drift tube and the drift tube length
(defined as the distance between the aluminum front faces of the endplugs)
at a given temperature are mechanically determined by the assembly tooling.

\item Critical parameters of the drift tube assembly process are controlled
by computer.

% tube temperature, jigging temperature, wire tension and pre-tension, pre-tensioning time,
% parameters of the tube crimping and wire crimping mechanisms.

\item The wire is over-tensioned for a defined time interval in order to minimize wire creeping.

\end{enumerate}

The {\bf Drift Tube Assembly Manual} contains
detailed instructions for handling and assembly of the drift tubes.
The main drift tube assembly steps are implemented in
a {\bf Drift Tube Assembly Control Program}.

In particular, the following procedures are applied to maintain the quality of the drift tubes:

\begin{enumerate}

\item The tubes are stored in the temperature controlled wiring room 
before assembly to adapt to the temperature.

\item Each individual tube is identified by its bar code which is read 
into the data base directly with a bar code scanner just before wiring.

\item The tube wiring room is cleaned regularly.

\item During work in the tube wiring room, hair and shoe protection,
coats and gloves certified for clean rooms are used. Before entering the
clean room, clothes are changed in a separate chamber.

\item Before assembly, the endplugs are cleaned in an ultrasonic cleaning bath.
Only pure ethanol is allowed for cleaning of Noryl plugs.

\item The bare tubes, the endplugs, the wire and the assembled tubes are visually
inspected before, during and after the wiring procedure (see Tables~1--3).
They are only handled with gloves certified for clean rooms.

\item The sense wire is inserted into the tubes directly from the spool without
additional cleaning and risk of contamination.

\item It is recommended to orient the tubes such during tube wiring that the
bar codes are accessible when the tubes are inserted into the chamber assembly jig.

\end{enumerate}

\section{Drift Tube Ground Contact}
%
A reliable ground contact between aluminum tube and the aluminum ground ring of the
endplug which is long-term stable is ensured by laser spot welding at the tube ends 
with at least three spots per endplug.
Detailed instructions for the laser welding process are given in the 
{\bf Laser Welding Manual for Drift Tube Ground Contact}.

The quality of the laser welds is verified by the following procedures:

\begin{enumerate}

\item Visual inspection for each tube during (all welds) and after (random sample of tubes) laser welding:
welds at correct place,
no deformations on the endplug reference surface, visible quality in agreement with reference
welds.

In case of problems, the laser and setup are adjusted and the welding 
is redone.

\item Inspection of randomly selected welded drift tubes under a microscope:
no obvious cracks in the welding spots.

In case of problems, the laser and setup are adjusted and the welding on the affected tubes
is redone.

\item At the start of production, a sample of welds from each production site is
evaluated metallurgically by cutting and inspection under the microscope.

\end{enumerate}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\section{Drift Tube Transport and Storage}
%
The assembled drift tubes are transported and stored
under the following conditions:

\begin{enumerate}

\item The tubes are always transported in stable wooden boxes like the ones
used for delivery of bare tubes by the manufacturer.

\item The individual tubes are kept separated from each other and held such that
that they cannot move inside the transport box.

\item The tube ends and endplugs are covered and protected with soft plastic caps
like the ones used for the transport of bare tubes.

\item Inside the transport box and in storage, the tubes are enclosed in air-tight
plastic bags containing dehumidifier bags.

\item After assembly and test, the drift tubes are always kept gas sealed until the
gas distribution system is installed on the chamber. 

It is recommended to store and transport the drift tubes filled with inert gas
in order to prevent corrosion.

\item During transport, only temperature variations in the range $0-50^\circ$C are allowed.

(This means that the wire tension can increase temporarily by up to 45~g (1.5~g/${}^\circ$C)
above the nominal tension of 350~g at $20^\circ$C, i.e.\ by $13\%$.)

\item During storage, the temperature has to stay within the range $10-30^\circ$C.

\end{enumerate}


\chapter{Drift Tube Test}
%
Successful operation of the large number of drift tubes in the ATLAS experiment
requires, in addition to the high mechanical accuracy in the wire location,
very high reliability of the tubes with respect to high voltage
stability, gas tightness and minimized risk of ageing.

Quality control tests of the drift tubes are a major part of the
chamber construction. They must ensure the reliability of the drift tubes
over their long lifetime. At the same time the tests are designed such that
they can be performed routinely and in reproducible manner and fast enough to keep
up with the speed of the tube production at a rate of 50-100 tubes per day
at each production site. Automatized tubes test stands operated
under computer control are in preparation (see Figure~2).

The following quality control tests are performed for each assembled drift tube
at the tube production sites:

\begin{enumerate}

\item Visual inspection.

\item Wire tension (oscillation frequency) measurement.

\item Wire location measurement.

\item Gas pressure and leak test of the whole drift tube.

\item HV stability test:

\begin{enumerate}

\item Leakage current measurement.

\item Cosmic count rate measurement (optional).

\end{enumerate}

\end{enumerate}

The mechanical tolerances are tested for a random sample of drift tubes per day.

The ground contact resistance between tube and the aluminum ground ring of the
endplug is measured for a random sample of drift tubes after production and
monitored over time for selected drift tubes before assembly and in an assembled chamber.

If drift tube and chamber production sites do not coincide, instructions for packing and
transport of the assembled drift tubes have to be observed.

The following tests are recommended to be performed
at the accepting site for a random sample of the delivered drift tubes:

\begin{enumerate}

\item Visual inspection (defects on endplugs or tubes).

\item Leak test of endplugs.

\item Ground contact resistance (as Table~3).

\end{enumerate}

The wire tension (oscillation frequency) is measured 
at the chamber production sites for each drift tube before assembly 
in the chamber.

During all tests, individual drift tubes are identified by their bar code with
a bar code scanner.

The drift tube quality control tests performed at all production sites 
are summarized in Tables~2 and 3. The test procedures are explained in the following. 
Table~4 gives an overview of the drift tube quality control equipment planned to be used
at the production sites.


\section{Wire Tension Measurement}
%
The gravitational sag of the wires has to be controlled within a tolerance of $\pm 10~\mu$m
in order to predict the wire position between the tube ends with sufficient accuracy.
The wire sag $s$ between the wire locators is related to the wire tension $T$ 
by $s=g\pi\rho d^2 L^2 / (32~T)$ where $g$ is the gravitational acceleration.

Measurement of the ground mode wire oscillation frequency $\nu$ allows to 
determine the tension $T$ of the wire with density $\rho$, diameter $d$ and length $L$
according to the relation $T=\pi \rho d^2 L^2 \nu^2$ and, using the above relations,
directly the wire sag $s= g/ (32~\nu^2)$
independent of geometrical and material parameters of the wire.

The wire tension is required to stay within a tolerance of $\pm 5\%$ of the nominal value
of 350~g at the nominal temperature of $20\pm 1^\circ$C (the wire ground mode frequency
therefore has to stay within $\pm 2.5\%$ of the nominal value).
During wire tensioning and tension measurement, the
tube temperature has to be controlled and measured with this accuracy. 
The wire tension is measured immediately after drift tube assembly to give feed-back to the
tube assembly and tested again after at least two weeks before installation in the chamber
in order to minimize the risk of wire creep or slippage.

The measurements of the wire oscillation frequency
and of the corresponding temperature are stored in the central data base for the accepted tubes
installed in the chamber.
All measurements including history are kept in the local data bases for reference and tracing of problems.

The instruments used for wire oscillation frequency measurement at the production sites
are summarized in Table~4. An example with a commercial tension meter is shown in Figure~1.

\section{Wire Location Measurement}
%
Measurements of the wire locations at the tube ends in the two transverse coordinates
are performed with two methods (see Table~4).

\begin{enumerate}
\item X-ray measurement:
 
For the wire position measurement, the tube ends are held in a jig in the same way and in the same azimutal orientation
as later in the chamber assembly jig. Reference wires with known distances are embedded in the V-block holding
the endplug. With two X-ray sources illuminating the tube under a stereo angle close to the endplug,
shadows of the sense and the reference wires are projected
onto two X-ray CCDs (see Figures~3 and 4). Using the reference wire grid,
the $y$ and $z$ positions of the sense wire can be reconstructed with respect to the endplug reference surface
(on which it is supported on the jig) with a resolution of $2~\mu$m. The measurement determines the wire position
as in the chamber independent of the roundness of the endplug reference surface.
A second measurement after rotating the tube around its axis by $180^\circ$ determines the wire location
for both orientations of drift tubes in the chambers and tests if the wire is held correctly
by the wire locator.

The layout of a wire location measurement station for series production is shown in Figure~6.

The straightness of bare and assembled drift tubes including coaxiality of the endplugs with respect
to the tube (see Tables~1 and 2) can be tested on the same jig (tubes interferences and wire displacements).

\item Electromagnetic pickup measurement:
 
Signals of an alternating current circulating through the sense wire is picked up by two coils on opposite sides
of the tube (see Figure~5). The difference in the signal amplitudes allows to determine the wire
displacement from the center in the plane of the coils with a resolution of $2~\mu$m. 
By rotating the tube on the support points on the endplug reference surface, the wire displacement
from the center of the reference surface in both transverse coordinates can be determined.                                          

\end{enumerate}

The measurement setups are regularly aligned and recalibrated with a calibration tube.
Tubes are accepted if the  measured wire locations at both ends are
within $\pm 25~\mu$m of the centers of the endplug reference surfaces in the $y$ and the $z$
coordinates (defined by the endplug orientation).
The tolerance corresponds to 2.5 times the required rms of $10~\mu$m of the wire location in
individual drift tubes.

The wire location measurements should be performed for azimutally oriented tubes, for example by means
of the tube clocking piece installed on one endplug which is used during chamber assembly
and which seals the tube after tube quality control until installation of the gas system on the chamber.
In this way, the wire locations can be determined in a common coordinate system, for instance
the ATLAS coordinate system. This helps for the tracing of problems and
allows to make contact with the X-ray tomograph measurements and to improve their reliability.
It is therfore particularly important for chambers with mechanical problems which need to be
recovered by X-ray tomograph measurement.

For the module~0 chambers, the wire locations in all tubes will be measured. During
series production, the measurement of only a fraction of the tubes produced per day is required
to test the quality of the precision endplugs and the tube assembly tooling.
The results for accepted tubes installed in the chambers are stored in the central data base;
all measurements including history are kept in the local data bases for reference and tracing of problems.

\section{Gas Pressure and Leak Test}
%
Each complete drift tube (including endplugs and tube wall) has to pass a gas pressure 
test at 1.5 times the nominal overpressure of 2 bar for safety reasons.
Afterwards the tubes are visually inspected and tested for gas leaks.

A tight limit of $1\cdot 10^{-8}$~bar~l/s is required for the gas leak rate
of each individual drift tube in the MDT chambers at the nominal operating pressure of 3 bar
in order to prevent back diffusion and gas contamination. 
The direct detection of holes
in the tube walls by the manufacturer, e.g.\ with the eddy current method,
proved to be too expensive. Therefore the whole drift tube including endplugs and tube
walls has to be leak tested. 

For this purpose, the drift tubes are fully enclosed in a container.
The drift tubes in the container are filled
with an Ar:CO${}_2$ gas mixture with helium admixture up to 3 bar overpressure
to perform the required pressure test.
Subsequently, the argon or helium leak rate into the evacuated container
is measured at the nominal overpressure of 2 bar with a mass spectrometer of helium
leak detector (see Figures~7 and 8).

For the many different tube lengths in the endcap chambers an alternative method
is also used. The leakage of the whole tube is measured in
evacuated fixtures at the tube ends (endplugs) and with
a fixture moved along the tube using a helium leak detector (see Figure~9).

A drift tube is accepted if its individual leak rate at 2 bar overpressure is 
demonstrated to be below $1\cdot 10^{-8}$~bar~l/s. 
The test results for accepted tubes installed in the chambers are stored in the central data base;
all measurements including history are kept in the local data bases for reference and tracing of problems.

The gas leak test is the most time consuming part of the drift tube quality control.
Automated leak test stands are prepared which measure the daily tube production
over night under computer control (see Figure~2 and Table~4). A large number of tubes is either
tested simultaneously in multi-tube containers or sequentially in many single-tube
containers (see Figure~8). In the automated test stands, the leak test is
integrated with automatic wire tension measurement and leakage current measurement
for the high voltage stability test.


\section{High Voltage Stability Test}
%
The high voltage stability of the drift tubes is tested
with Ar:CO$_2$ (93:7) at 3 bar because this is the baseline gas mixture and
particularly sensitive to imperfections of inner tube wall and wire.

Tests have shown that the leakage currents of good drift tubes 
with this gas mixture at 3 bar are typically 70~pA/m at the nominal operating point
at 3080~V ($2\cdot 10^4$ gas gain) and 120~pA/m and 520~pA/m at 3190~V ($4\cdot 10^4$ gas gain)
and 3400~V ($16\cdot 10^4$ gas gain), respectively. These currents are close to the
expectation from the cosmic count rate.

A common high voltage stability test is defined as measurement of the drift tube
leakage current at 3400~V with a sensitivity of 1~nA which the existing commercial
HV systems provide. 
The high voltage is ramped up slowly, typically in steps of 100~V. The tube current at each step
is limited to be less than 2~nA/m (measured after settling time). 
The duration of the high voltage test at 3400~V is limited to 10 minutes.

Drift tubes are accepted if the tube leakage current at 3400~V is below 2~nA per meter tube length.
The test results for accepted drift tubes installed in the chambers are stored in the central data base;
all measurements including history are kept in the local data bases for reference and tracing
of problems.

Optionally, the following additional high voltage tests will be performed at a number of
production sites for all or a fraction of the drift tubes (see Table~4):

\begin{enumerate}

\item Monitoring of the leakage current over night at the nominal operating point at 3080~V.

\item Measurement of the leakage current with increased sensitivity with pA-meters.

\item Measurement of the cosmic count rate at 3190~V ($2\times$ the nominal gas gain).

\item Monitoring of the cosmic count rate over night at the nominal operating point at 3080~V.

\item Measurement of the signal rate and shape with a radioactive source.

\end{enumerate}

The test results are recorded in the local data bases.

To improve the comparibility of the cosmic count rate measurements at different sites,
readout electronics using the BNL preamplifier and shaper is prepared at BNL for a common test.

In the automated drift tubes test stands, wire tension, leak rate and leakage current measurements
are integrated (see Figure~8).


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{0.90}

\begin{center}
\noindent
{\bf Table~1:} Quality control tests of drift tube materials at the chamber production sites 
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline   
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction if failed} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline

& & & &\\
\multicolumn{5}{l}{\bf Aluminum tube} \\ [1mm]

Visual inspection      & no obvious defects or holes, proper cleaning, & reject tube,    & central & 1: sample test/box \\
of inside and outside  & deburring, straightness, bar code, packing & notify supplier &         & 2: every tube before wiring \\
& & & &\\

Outer diameter envelope,   & $29970\pm 15~\mu$m & reject box & central & sample test/box \\
from 8 points on circumference   &               &  & &\\
& & & &\\

Wall thickness,   & $400\pm 30~\mu$m & reject box & central & sample test/box \\
at 8 points on circumference   &               &  & &\\
& & & &\\

Length $L$     & $L\pm 0.5$~mm ($L\le 4$~m) & reject box & central & sample test/box \\
               & $L\pm 0.7$~mm ($L >  4$~m) & & &\\
& & & &\\

Straightness   & insertion into jig   & reject tube, & central & sample test/box \\
               & without difficulties & notify supplier & & \\
\hline

& & & &\\
\multicolumn{5}{l}{\bf Wire} \\ [1mm]

Visual inspection & no defects of gold-plating,      & reject spool & central & 1: first meters and every 400~m \\
                  & proper cleaning, no kinks        &              &         & \hphantom{1:} per spool under microscope, \\
                  &                                  &              &         & 2: inspection during wiring \\
& & & &\\
\hline

& & & &\\
\multicolumn{5}{l}{\bf Endplug} \\ [1mm]

Visual inspection & proper cleaning and no obvious defects  & reject endplug, & central & 1: sample test/batch \\
                  & of plastic, O-rings, wire locator,      & notify supplier &         & 2: each endplug before wiring \\
                  & Al reference surface, crimp tube        & & &\\
& & & &\\

Outer diameter envelope,         & $30010\pm 10~\mu$m & reject batch & central & sample test/batch \\
from 8 points on circumference   &                    &              &         &            \\
({\bf optional}) & & & &\\                                                                                                                 
& & & &\\

Wire locator outer diamter       & within tolerance   & reject batch & central & sample test/batch \\
& & & &\\
\hline\hline

\end{tabular}
\end{center}

%\end{tabular}
\end{sidewaysfigure}
\clearpage


\begin{sidewaysfigure}
\renewcommand{\arraystretch}{1.10}

\begin{center}
\noindent
{\bf Table~2:} Quality control tests of drift tubes at the chamber production sites
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction if failed} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline

& & & &\\
\multicolumn{5}{l}{\bf Drift tube} \\ [1mm]

Visual inspection     & no obvious damage of tube or endplug,     & reject drift tube,      & local & each tube after wiring,\\
                      & no visible defects of tube and            & adjust wiring station   &       & before chamber assembly \\
                      & wire crimp, tube correctly sealed & & &\\
& & & &\\

Aluminum tube outer & less than 30.020~mm  & reject drift tube,   & local & sample test/day,  \\
diameter envelope   &                      & adjust tube crimping &       & shortly after wiring  \\
in endplug region   &                      & setup                & &\\
& & & &\\

Aluminum tube outer & less than 30.010~mm  & reject or repair tube, & local & sample test/day,  \\
diameter envelope   &                      & adjust tube crimping   &       & after laser welding \\
at tube end         &                      & or laser welding setup & &\\
& & & &\\

Length $L$     & Nominal length $\pm 0.25$~mm  & reject drift tube,    & local & 1: sample test/day \\
               & at $20\pm 1^\circ$C    & adjust wiring station &       & 2: each tube on chamber assembly jig \\
& & & &\\

Relative azimutal        & $\pm 10$~mrad  & reject drift tube,    & local & 1: sample test/day \\
orientation of endplugs  &                & adjust wiring station &       & 2: each tube on chamber assembly jig \\
& & & &\\

Straightness    & insertion into jig     & reject drift tube & local & 1: sample test/day  \\
                & without difficulties   &                   &       & 2: each drift tube during chamber assembly \\
& & & &\\

Tube ground contact  & less than 100~m$\Omega$ & repeat laser welding & local & 1: sample test/day  \\
resistance           & per endplug             &                      &       & 2: monitoring of selected tubes over time \\
(for 5~mA current)   & & & &\\
& & & &\\
\hline\hline

\end{tabular}
\end{center}

\end{sidewaysfigure}
\clearpage


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{0.90}

\begin{center}
\noindent
{\bf Table~3:} Quality control tests for all drift tubes at the chamber production sites
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction if failed} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline

& & & &\\
\multicolumn{5}{l}{\bf Drift tube} \\ [1mm]

Room temperature & $20\pm 2^\circ$C & adjust & local & during tube tests \\
& & & &\\

Relative humidity      &                   &        & local & monitoring    \\
({\bf optional}) & & & &\\
& & & &\\

Temperature of tube & $20\pm 1^\circ$C & adjust temperature & local & during tube assembly \\
                    &                   & or tension         & &\\
& & & &\\

Temperature of tube & known within $\pm 1^\circ$C & repeat measurement & central & during wire tension measurement \\
& & & &\\

Wire tension             & within $\pm 5\% $      & reject drift tube & central  & 1: shortly after tube wiring \\
(from oscillation        & of the nominal value   &                   &          & 2: after min.\ two weeks, before assembly \\
frequency meas.)         & at $20\pm 1^\circ$C   & & &\\
& & & &\\

Wire location      & within $\pm 25~\mu$m of the & reject drift tube,  & central & sample test on day of wiring, \\
at the tube ends   & center of the endplug ref.  & inspect endplugs and  & & tube held as in assembly jig, \\
                   & surface in $y$ and $z$       & wiring station        & & incl.\ test of coaxiality of endplugs, \\
& & & & measurements at 0 and $180^\circ$   \\
& & & &\\

Gas pressure test      & no obvious leaks  & reject drift tube,     & local & \\
at 3 bar overpressure  &                   & inspect endplugs,      & &  \\
                       &                   & adjust wiring station  & &  \\
& & & &\\

Gas leak rate             & less than $10^{-8}$~bar~l/s & reject drift tube, &  central & after pressure   \\
at 2 bar overpressure     &                            & inspect endplugs,     & & test  \\
& & adjust wiring station & &\\
& & & &\\

HV stability test: & less than 2~nA/m & reject drift tube,             & central  & with Ar:CO${}_2$ (93:7) at 3 ~bar \\
leakage current    &                  & inspect endplugs, tubes, wire  &          & and 3400~V  \\
& & & &\\                                                                                                                  

HV stability test: & within $\pm 3\sigma$  & reject drift tube, & central   & with Ar:CO${}_2$ (93:7) at 3 bar \\
cosmic count rate  & of nominal value      & inspect endplugs, tube, wire   &  & and 3190~V     \\
({\bf optional}) & & & & \\
& & & &\\

\hline\hline

\end{tabular}
\end{center}

%\end{table}
\end{sidewaysfigure}
\clearpage

\renewcommand{\arraystretch}{0.95}
\begin{sidewaysfigure}

\begin{center}
\noindent
{\bf Table~4:} Drift tube test equipment at the production sites
\vspace{2mm}

%\begin{footnotesize}

\begin{tabular}{|l|l|l|l|l|l|} \hline\hline
{\bf Site} & {\bf Wire tension}      & {\bf Wire position} & {\bf Leak rate}    & {\bf HV test}           & {\bf HV test}  \\
           & {\bf (osz.\ frequency)} &                     & {\bf (whole tube)} & {\bf (leakage current)} & {\bf (cosmic rate)} \\ \hline

{\bf Freiburg} & Excitation in B-field & Brandeis X-ray & As Frascati             & HV system with & Yes \\
               &                       & system         &                         & pA-meter       &     \\
\hline

{\bf LMU/MPI}   & CAEN SY502 meter,      & Brandeis X-ray  & Pressure rise in evacuated       & HV system with   & BNL preamp., \\
(accept.\ test) & excitation in B-field  & system, MPI jig & volume at endplug (8 tubes sim.) & 1~nA sensitivity & shaper       \\
\hline

{\bf NTU Athens} & CAEN SY502 meter,     & Electromagnetic, & As Frascati or Pavia          & Keithley current meter & \\
                 & excitation in B-field & as Pavia, Rome   &                               & with 1~nA sensitivity  & \\
\hline

{\bf Univ.\ Athens} & \multicolumn{5}{c|}{as NTU Athens} \\
 & \multicolumn{5}{c|}{        (after module~0)} \\ \hline

{\bf Thessaloniki} & excitation in B-field & & & CAEN SY127 (40 channels), & \\
(accept.\ test) & & & & 1~nA sensitivity HV system & \\ \hline

{\bf Frascati} & Electrostatic excit.,      & Electromagnetic  & Helium leak detector,      & CAEN SY546 (96 channel)     & Yes \\
               & multi-channel system,      & micrometer,      & 60 single-tube containers  & 1~nA sensitivity HV system, &  \\
               & integration with leak test & as Pavia, Rome   &                            & integration with leak test  &  \\
\hline

{\bf Cosenza}  & CAEN SY502 meter,          & Electromagnetic  & As Pavia,                  & CAEN SY546 (96 channel)      & \\
               & excitation in B-field      & micrometer,      & automatic control system   & 1~nA sensitivity HV system,  & \\
               & integration with leak test & as Pavia, Rome   &                            & integration with leak test   &  \\
\hline

{\bf Pavia}    & As Rome                    & Electromagnetic  & Argon mass spectrometer,   & HV system (10 channels)      &  \\
               &                            & micrometer       & 10 single-tube containers  & with pA-meter,               &  \\
               &                            &                  & (commercial system)        & integration with leak test   &  \\
\hline

{\bf Rome}     & Excitation in B-field,     & Electromagnetic  & As Frascati or Pavia,      & As Pavia & \\
               & multi-channel              & micrometer       &                            &          &  \\
\hline

{\bf NIKHEF}   & Mechanical excitation,     & Electromagnetic, & As Frascati                 & Multi-channel HV system,   & Yes \\
               & piezo-electric measurement & as Pavia/Rome    &                             & integration with leak test &     \\
\hline

{\bf Dubna}    & Excitation in B-field, & Brandeis X-ray   & Helium mass spectrometer,       & CAEN SY546 (96 channel) & BNL preamp., \\
(also for MPI) & meter custom design    & system, MPI jig  & multi/single-tube containers    & 1~nA sensitivity HV system & shaper  \\
\hline

{\bf Protvino} & Excitation in B-field, & Brandeis X-ray   & Mass spectrometer &  &  \\
               & meter custom design    & system           &                   &  &  \\
\hline

{\bf Boston}   & Excitation in B-field, & Brandeis X-ray   & Mass spectrometer,   & Multi-channel HV system,   & Yes \\
               & meter custom design    & system           & multi-tube container & integration with leak test &     \\
\hline

{\bf Michigan} & As Seattle             & Electromagnetic  & Helium leak tester,         & Multi-channel HV system  &   \\
               &                        & micrometer,      & evacuated volume at end-    &  & \\
               &                        & as Pavia, Rome   & plug and moving along tube  &  & \\
\hline

{\bf Seattle}  & Excitation in B-field, & Electromagnetic, & As Michigan  & As Michigan  &  \\
               & meter custom design    & as Pavia/Rome    &              &  &   \\
\hline\hline
\end{tabular}
\end{center}

%\end{footnotesize}

\end{sidewaysfigure}
%
\clearpage

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Chamber Assembly}

\section{Assembly Setup}
%
\subsection{Assembly Room}
%
The MDT chambers are assembled in a climatized room in clean environment.
The following requirements are important to control the mechanical precision
and stability of the chamber construction:

\begin{enumerate}

\item
The temperature in the assembly room is controlled such that that it is stable
and uniform within $20\pm 0.5^\circ$C above the surface of the assembly table
and within $20\pm 1^\circ$C in the rest of the assembly room.

\item
Temperature differences between the outer cross plates and the end combs 
(measured with the temperature probes on the spacer and temperature sensors
on the combs)
should be below $0.5^\circ$C during the glueing process
in order to avoid unwanted wire offsets between adjacent layers.

\item
The relative humidity in the assembly room is controlled to be $50\pm 10\%$
to ensure proper curing of the glue.

\item 
The assembly room is cleaned regularly.

\item 
During work in the assembly room, hair and shoe protection,
coats and gloves certified for clean rooms are used. Before entering the
clean room, clothes are changed in a separate chamber.

\end{enumerate}

Emergency power is needed in order to restore the climatization quickly after
a power failure during glue curing. The vacuum underpressure must not fall
below the tolerance before power is restored.

\subsection{Granite Table}
%
A granite table surface with absolute flatness of at least $20~\mu$m serves
as reference for the setup of the assembly jigging. To guarantee the flatness
of the granite table and therefore the alignment of the assembly jigging
over the whole time period of chamber production, it is recommended to
follow the following procedures:

\begin{enumerate}

\item The table is kinematically supported on 3 feet as specified by the
manufacturer and on a stable concrete floor.

\item The planarity of the table has to be measured after setting it up in the
climatized room and before installation of the assembly jigging.

The measurement is best done by professionals using tilt meters.

If necessary, the required planarity has to be recovered by polishing the surface
after installation and measurement of the table in the assembly room.

\item It is recommended to inspect the feet of the table regularly (every week).
The load of the table must be only on the 3 kinematical supports;
additional feet installed for security reasons must always be free of load
(indicated by a loose nut).
If this should not be the case, the feet have to be adjusted (best by professionals);
chamber assembly can continue only after at least 2 days to allow for relaxation of the
table to its original shape.

\item No installations on the table which are firmly connected to the floor.

\item Load on the table must not exceed the design value as specified by the
manufacturer.

\item The surface of the granite may have to be cleaned before installation of the
jigging. Cleaning should be done only with special fluid and cloth recommended
by the manufacturer of the table.

\item The granite table must be kept under constant and uniform environmental conditions
which are monitored continuously after setup and measurement as specified by the
manufacturers. This includes:

\begin{enumerate}

\item Constant and uniform illumination (even with tube layer on combs).

\item Constant relative humidity, typically $50\pm 10\%$.

\item Constant and uniform temperature within $\pm 0.5^\circ$C long-term 
(monitored with temperature probes on the granite).

\item Temperature gradient between top and bottom of the table below $0.2^\circ$C
(monitored with temperature probes on the granite).

\end{enumerate}

\item The planarity of the granite table surface (where accessible) 
and the alignment of the jigging have to be measured regularly 
(initially every 3 months). Tilt meters are recommended for this purpose.

\end{enumerate}


\subsection{Assembly Tooling}
%
The components of the assembly jigging are measured before or after the installation
on the granite table:

\begin{enumerate}

\item $z$-distances and $y$-coordinates of cylinders in the V-grooves of the combs
(on a 3D coordinate measureing machine).

\item Height of the sphere towers with the different interfaces
(on a 3D coordinate measureing machine).

\item $y$, $z$ and angular alignment of the comb lines installed on the assembly table
(with optical or mechanical gauges).

\item $y$-coordinates of the V-grooves of the end comb lines installed on the assembly table
(using a feeler gauge) to make sure the combs have not been deformed by mounting them.

\end{enumerate}

The alignment of the comb lines is measured in regular time intervals (typically 3 months
which corresponds to the construction of about 6 chambers).
The data are stored in the local production data bases for reference and tracing of errors.

The assembly jigging is visually inspected regularly and cleaned when necessary.

The following labelling of the assembly jigging is proposed:

\begin{enumerate}

\item Mark readout and high voltage side on assembly table.

\item Mark chamber coordinate system on granite table.

\item Mark sequential numbers of tube insertion on both end combs.

\item Mark reference side on assembly table.

\item Mark sphere support towers with numbers.

\item Mark tower with fixed sphere position.

\item Mark tower interfaces including correspondence to towers.

\item Mark identifiers of force compensation supports on granite table,
corresponding with DB.

\item Mark location of transfer blocks for alignment platform positioning on combs.

\item Mark chamber identifier (ATLAS numbering scheme) on RO and HV cross plate outer surfaces
and on protective covers.

\end{enumerate}

During the 12 hour curing time of the glue for the assembly of a tube layer, the
vacuum suction force of the tubes in the combs has to be continuously active
and must not be lost in case of a power failure.
Otherwise the accuracy of the tube layer cannot be guaranteed and the layer may
have to be discarded. The vacuum underpressure is
continuously monitored. Emergency power should be available.
The reaction time depends on how long the vacuum system can maintain the underpressure
with pump off.

\section{Preparation of Chamber Components}
%
Before entering the assembly room, all chamber components go through a final
quality control procedure. The quality of the components is verified by
consulting the quality control documentation by the suppliers and the information
in the production data base (see the {\bf Assembly Control Plan} in the {\bf Appendix}).

All components, except for the drift tubes which
are stored dust-free conditions, are carefully cleaned, the cleaning is
verified and the components are properly labelled. All components are stored
in the temperature controlled assembly room at least 12 hours before assembly
in order to adapt to the temperature of $20^\circ$C.

The following labelling of components is proposed:

\begin{enumerate}

\item Mark readout and high-voltage side cross plates.

\item Mark orientation to top multilayer on all cross plates and long beams.

\item Mark identifiers of the in-plane alignment, cross plate sag and sphere monitors
on the spacer corresponding with DB.

\item Mark locations of mask, lens and CCD of permanent and temporary RASNIK monitors
on cross plates and long beams.

\end{enumerate}


\section{Qualification of Personell}
%
The assembly of a chamber is carried out by 3 operators as described
in the {\bf Chamber Assembly Manual}.

Operator 3 coordinates the work in the assembly room and the preparation of materials, 
ensures that all assembly and quality control steps are performed correctly according to the
{\bf Assembly Control Plan} and operates the monitoring devices for assembly control
with the help of the {\bf Assembly Control Program}.
He also operates the crane during assembly.

The operator team starts its work only after detailed instructions and training
on all assembly and quality assurance procedures. 

The {\bf Production Manager} (physicist or engineer) supervises the whole chamber
assembly process and makes sure that the quality assurance instructions are correctly followed.
He evaluates the monitoring data and has to be consulted when alarms occur.
Critical steps have to be approved by him as defined in the {\bf Assembly Control Plan}.
He is also responsible that the operators are correctly instructed and trained.


\section{The Chamber Assembly Process}
%
All steps of the MDT chamber construction 
procedures are described in detail
in the {\bf Chamber Assembly Manual} of each production site and, in addition, in associated
manuals for specific components and procedures
({\bf Assembly Monitoring Manual}, {\bf Gas System Installation Manual},
{\bf Glueing Manual}).

The detailed work and quality assurance plan for chamber assembly is described in the local
{\bf Assembly Control Plan} which to a large extent will be implemented in software,
the {\bf Assembly Control Program}, to control the process with the help of a computer
which also aquires and analyzes the monitoring data.

\subsection{Monitoring of Chamber Assembly}
%
Monitoring and control of all critical parameters of the assembly process
is essential to guarantee the quality and precision of the chambers, in particular since
only a fraction of the chambers can be measured completely and with sufficient accuracy
after construction. The monitoring and test data taken during assembly
are kept in the local production data base for reference and tracing of problems.

The following parameters are measured and monitored during chamber assembly (see Tables~5 and 6):

\begin{enumerate}

\item Climatization of the assembly room (temperature and relative humidity).

\item Temperature of the cross plates (with the temperature probes to be installed on the spacer)
and of the end combs.

\item Vacuum underpressure for tube suction in the combs.

\item Identification of each drift tube and its location in the chamber via the
bar code using a bar code scanner. This includes automatic verification that the tube 
has been accepted by the quality control tests.

\item Uniform tube length and azimutal orientation of endplugs (by visual inspection).

\item Horizontal glue gap between tubes in combs (by visual inspection with illumination
from underneath) to verify the tube straightness (relevant for the $100~\mu$m tolerance on the
wire concentricity with respect to the tube wall).

\item Height (in $y$ coordinate) of endplug reference surface on the combs to verify
proper fitting and suction of tubes in the combs.

Measurement devices used are: feeler gauges, tilt meters or laser monitors (see Figure~10).

\item Uniform glue distribution with glue dispenser (visual inspection) and glue curing time.

\item Stability of the in-plane alignment monitor readings and of the planarity
of the assembly jigging using the in-plane alignment system (RASNIK monitors).

\item Precision of the vertical stacking of tube layers in the $y$ and $z$ coordinates
using proximity RASNIK monitors (sphere monitors) with large masks mounted
close to the spheres at the 4 ends of the two outer cross plates and the in-plane alignment
system for the middle cross plate.

\item Measurement of angluar deviations  $\Delta\theta_x$, $\Delta\theta_y$ and $\Delta\theta_z$
(around the $x$-, $y$- and $z$-axes) of the axial/praxial and the projective
alignment platforms from alignment with the axes of the chamber
coordinate frame.

The measurements are performed with an optical angle measuring device developed at Brandeis University (BCAM) and
adapted for this purpose by Saclay (for relative alignment of platforms), and with feeler gauges and tilt meters
after installation of the platforms and after assembly of each further tube layer.

\item Monitoring of the forces (measured with strain gauges)
applied to the long beams by the automatic force
compensation system which is used for the BM and BO chambers to compensate the gravitational
sag of the cross plates when supported on the sphere towers during assembly.

\item Monitoring of the gravitational sag of the two outer cross plates during assembly
and test of the chambers using RASNIK monitors temporarily installed on the cross plates
between the long beams (recommended for the BM and BO chambers initially).

\item Regular verification of the planarity of the granite table and the alignment
of the jigging (combs and sphere towers); see section {\bf Assembly Tooling}.

\end{enumerate}

The {\bf Assembly Control Program} automatically generates alarms if any of the
monitored parameters is outside the tolerances. Resulting actions are:

\begin{itemize}

\item Immediate corrections for the chamber currently under construction
(see the {\bf Assembly Control Plan} in the {\bf Appendix}).

\item The monitoring data are stored in the local production data base as reference
for tracing of errors.

\item If the deviations cannot be completely eliminated:

The problem is reported and the data are recorded in the central data base;
the chamber is flagged for measurement in the X-ray tomograph.   

\end{itemize}

More details on assembly quality control and monitoring procedures are given in the
{\bf Monitoring Manual} and the {\bf Assembly Control Plan} in the {\bf Appendix}.

\subsection{Calibration of the Optical Monitors}
%
The optical monitoring devices require careful calibration (see the {\bf Monitoring Manual}):

\begin{enumerate}

\item The angular orientation around the $x$-axis of the masks of the in-plane alignment RASNIK monitors
relative to the surface of the assembly table has to be measured with an accuracy of 10~mrad
for the barrel chambers. This allows to measure the gravitational sag ($y$ displacement of the middle cross plate) 
of even the longest barrel chambers with an accuracy of $5~\mu$m after compensation of the wire sag of
up to $350~\mu$m relative to the zero-readings of the in-plane monitors on the assembly jigging.

The calibration can be done after assembly of the spacer by moving the middle cross plate
supported on the sphere towers in $z$ direction parallel to the surface of the granite table
by about 1~mm and measuring the change in the $y$ and $z$ readings of the in-plane monitors.

The resolution in the angle measurement between mask and CCD around the $x$-axis by the
RASNIK image analysis software is much better than 10~mrad and does not contribute to the
error.

The calibration data have to be stored in the central data base.

\item The zero-readings of the in-plane alignment RASNIK monitors on the flat granite table
are needed as reference for the measurement of deformations of the chamber during
assembly, test (in the cosmic ray test stand and the X-ray tomograph) 
and operation in the ATLAS detector.

Readings of the in-plane monitors are taken as part of the chamber construction procedure
after each glueing step, for assembly of the spacer and of the tube layers (see the {\bf Appendix}).
The readings have to be stable within $\pm 10~\mu$m during the assembly of the chamber.
The average or a selection of the readings is taken as zero-reading for the future
operation of the chamber.

The zero-readings of the in-plane alignment monitors and their readings after each glueing
step are stored in the central data base.

\item The zero-readings of the RASNIK cross plate sag monitors
are needed as reference for the measurement of the sag of the cross plates during
assembly and test (in the cosmic ray test stand and the X-ray tomograph).

The zero-readings are taken with the cross plates suspended at one end from a crane
such that there is no deformation. They can be verified by measuring the cross plate
sag in the initial and inverted orientation of the spacer on the jigging after
adjustment of the long beams on the middle cross plate (see the {\bf Appendix}).

The zero-readings of the cross plate sag monitors 
are stored in the local production data base.

\item The angular orientation around the $x$-axis
of the masks of the RASNIK sphere monitors relative to the surface of the granite table
has to be measured and regularly recalibrated with an accuracy of $50~\mu$rad.
This accuracy is needed in order to measure the $y$ and $z$ positions of the spheres
(where the masks are mounted) with a precision of $5~\mu$m over the measurement
range of 52~mm for 3-layer chambers and 78~mm for 4-layer chambers.
(The same is true for the reference sensors on the granite table for a laser
sphere monitoring system with transparent MPA-ALMY sensors.)

The calibration measurement can be done with a tilt meter on the granite table and
and on the housing of the large mask in which it has been accurately aligned with
respect to an external reference surface. Optical measurement of the mask orientation
with a pendulum in front of it using a tilt meter to measure the orientation of the
granite table has also been proposed.

The angle measurement between mask and CCD around the $x$-axis by the
RASNIK image analysis software has to be at least as accurate as the calibration
in order not to increase significantly the $y$ and $z$ measurement error of the sphere monitors.
Optimized RASNIK analysis programs have shown $30~\mu$rad angular resolution.

Once the angular orientation of the sphere monitor CCD has been precisely measured
in this way with respect to the surface of the assembly table on which it is permanently mounted,
the mask orientation on the sphere holders mounted on the next chamber can be
measured the same way without calibration. Nevertheless, regular recalibration is
necessary in order to be sure that the CCD holder has not moved.

The calibration data are stored in the local production data base.

\end{enumerate}

\subsection{Glueing Procedures}
%
The following glue types are used for chamber assembly:

\begin{enumerate}

\item For spacer assembly, glueing of tube layers to the spacer and
mounting of gas distribution bars:

Ciba Geigy Araldite 2014 (AW 139/ XB 5323) with high viscosity to
fill the large glue gaps with shrinkage $<1\%$, setting (usage) time of 40 minutes,
curing time of 3.5 (5) hours to achieve minimum shear strength of 1 (10)~N/mm${}^2$
at $23^\circ$C on aluminum and a shelve time of 3 years at $18-25^\circ$C.

As alternative with higher peeling strength, 3M Scotch-Weld DP~460 is under
consideration which otherwise has similar properties as Araldite 2014 with
about $1.5\%$ shrinkage.

The glue is applied with a manual glue dispenser with static mixer.
It will be cured for 12 hours during chamber assembly.

\item For glueing of tubes on tubes:

Ciba Geigy Araldite 2011 (AW 106/ HV 953U) with viscosity of $40-45$~Pa
after mixing at $23^\circ$C,
setting (handling) time of 105 minutes in glue container and 90 minutes exposed to air,
curing time of 7 (10) hours
to achieve minimum shear strength of 1 (10)~N/mm${}^2$ at $23^\circ$C
on aluminum and a shelve time
of 3 years at $18-25^\circ$C.

The glue is applied in premixed form on a complete tube layer inserted in
the assembly combs using an automatic glue dispenser with a speed
of typically 20-30 minutes for a layer depending on chamber size
which leaves enough reserve in case of problems. Up to 90 minutes
glue handling time can be accepted with the proper control of
out-of-plane deflections of tubes in the assembly process.

Good control of the amount and location of the glue distributed
on the tube layer by design of the glue dispenser is important to minimize
glue shrinkage and out-of-plane deflections of tubes
which can affect the mechanical accuracy of the chambers.

The glue will be cured for 12 hours during chamber assembly.
Handling of the premixed glue and the automatic glue dispensers
is described in the {\bf Glueing Manual}.

\item For glueing of alignment platforms, Faraday cage mouting bars,
in-plane alignment monitor components, temperature and B-field sensors:

Ciba Geigy Araldite 2012 (AW 2104/ HW 2934) with viscosity as
Araldite 2011, setting (usage) time of 5 minutes, curing time of
20 (105) minutes to achieve minimum shear strength of 1 (10)~N/mm${}^2$
at $23^\circ$C on aluminum and a shelve time of 3 years at $18-25^\circ$C.

\end{enumerate}

All surfaces glued must be cleaned with alcohol and dried before glueing
according to the glue handling specifications. This includes the components
of the spacer, the gas system, Faraday cages, on-chamber monitors and alignment
platforms.

The tubes are stored and transported in air-tight bags at all times
after cleaning by the manufacturor. The bags 
are only opened and packed inside the clean rooms for tube assembly and test
and for chamber assembly at the production sites.
The tubes are handled with plastic gloves only in order to avoid contamination.
If nevertheless tubes get contaminated by dust or grease etc.,
they have to be carefully cleaned
with ethanol without destroying the bar code and bending the tubes.

Details about the glueing processes during chamber assembly and the
associated quality assurance are described in the {\bf Chamber Assembly Manual}
and the {\bf Glueing Manual}.

For each glueing step, an aluminum test piece is glued simultaneously
from the same glue mixture as used for the
chamber assembly to evaluate independently the proper
curing of the glue. The glue on the chamber is inspected after the
nominal curing time. If the glue should not cure as required even after
an extended time period, the tube layer or even the whole chamber have to be discarded
depending on the assembly step.


\subsection{Assembly Control Plan}
%
The {\bf Assembly Control Plan} contains detailed instructions for
quality assurance and quality control during the construction of a MDT chamber.

An example for the construction of BOS MDT chambers is given in the {\bf Appendix}.
The plan is intended as guideline for the preparation of the
local QA/QC plan and for the implementation of the QA/QC procedures
in an {\bf Assembly Control Program}.

\subsection{Assembly Control Program}
%
Following the specifications in the {\bf Assembly Control Plan},
the {\bf Assembly Control Program} allows to verify all major
assembly steps, acquires and analyzes the data of the monitoring devices, stores the data
in the local production data base and issues alarms if parameters are out of tolerances.
In most cases the control program will be based on the LABVIEW package.

The schematical layout of an {\bf Assembly Control Program} is shown in Figure~11.
Figure~12 shows an example of a graphical user interface for the control program.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Chamber Test}
%
The following quality control tests are performed for each chamber 
at the production sites immediately after assembly to provide fast feed back (see Tables~7 and 8):

\begin{enumerate}

\item Tests of chamber mechanics on the kinematical supports:

\begin{enumerate}

\item Measurement of the gravitational sag of the chamber before and after sag compensation with
the in-plane alignment monitors.

\item Measurement of the gravitational deformation of the cross plates with the cross plate
sag monitors (recommended for BM and BO chambers).

\end{enumerate}

\item Gas pressure and leak test of the whole chamber.

\item High voltage stability test with mounted electronics.

\begin{enumerate}

\item Leakage current measurement.

\item Cosmic count rate measurement (optional).

\end{enumerate}

\item Evaluation of performance in cosmic ray test stand.

\end{enumerate}

The following tests are performed for each chamber after transport
to CERN and during chamber storage (see Table~9):

\begin{enumerate}

\item Acceptance test at CERN: visual inspection.

\item Acceptance test at CERN: gas leak test.

\item Monitoring of gas pressure in sealed chambers over storage time.

\item If final readout electronics installed during storage: high voltage stability test
and operation test of electronics.

\end{enumerate}

The following tests are performed for selected chambers after transport
to CERN and during chamber storage (see Table~10):

\begin{enumerate}

\item Measurement of wire coordinates with the CERN X-ray tomograph.

\item Monitoring of wire tension in one chamber per production site over storage time.

\item Monitoring of drift tube ground contact in one chamber per production site over storage time.

\end{enumerate}

Details of the chamber quality control tests are described in the following.
Examples of the test sequence are given in the sections
{\bf Chamber Test Program at the Production Sites} and
{\bf Chamber Test Program at CERN}.

\section{Gas Pressure and Leak Test}
%
Immediately after assembly, the chambers with in-chamber gas distribution system
have to be pressure tested at an overpressure of 3 bar which is 1.5 times the nominal
overpressure of 2 bar used during chamber operation.

After the pressure test, the complete chamber is tested for gas leaks at the
nominal overpressure of 2 bar with an inert gas. For the same reasons as
explained for the single-tube leak test, the leak rate of a complete chamber
including the gas distribution system has to be below $2\cdot 10^{-8}$~bar~l/s per tube.

The leak rate is determined by monitoring the pressure drop and together with the 
temperature difference between the chamber and a gas tight reference volume (see Figures~13 and 14).
With the sensitivities of differential manometers
($\Delta p/p = 10^{-4}-10^{-5}$) and calibrated temperature sensors
($0.1^\circ$C) distributed on the chamber (permanent or temporary ones)
and on the reference volume,
the test takes several days in order to be able to detect
a pressure drop in the chamber corresponding to the required
leak rate limit.

The duration of the test is limited by the accuracy of the temperature monitoring.
The reference volume should be close to the chamber and thermally coupled to it
to minimize temperature differences. The temperature of the chamber should be uniform.
Performing the test in a temperature controlled room helps to accelerate it.

The same leak test is performed as acceptance test after delivery of the
chamber to CERN. During the whole storage time,
the chambers stay filled with the baseline gas at 3 bar and the gas pressure is
monitored with cheap manometers together with the temperature.

Contact addresses for differential manometers for the test are:
JINR Dubna (see Figure~14) and Brandeis University.

All test results including history are recorded in the local production data base
for reference and tracing of problems.
The leak rate limit and faulty tube identifiers are stored in the central data base.

\section{High Voltage Stability Test}
%
After installation of the high voltage and readout boards at the production sites, 
a high voltage stability test is performed with the baseline gas at 3 bar. 
The leakage current per channel should be below 2~nA/m~$+5$~nA at 8 times the nominal gas gain.
For Ar:CO${}_2$ (93:7) gas mixture, this corresponds to a test high voltage of 3400~V.
The high voltage is ramped up carefully as for the single-tube high voltage test
where the current per channel is limited to be below 2~nA/m~$+5$~nA.

Optionally, the cosmic count rate per tube at the nominal operating point is measured
and recorded in the local data base.

The high voltage stability test is repeated after installation of the final
readout electronics which for a large fraction of the chambers has to take place 
in the storage area after the chamber test at the production sites.
For these chambers, also a minimum operation test of the final electronics
has to be performed which is practical with the setup in the storage area (e.g.\ without
external cosmic trigger).
It includes test of all electronics interconnections with pulser, verification of
signals from all tubes, measurement of noise level, random rate and uniformity
of response.

All test results including history are recorded in the local production data base
for reference and tracing of problems.
The results of the high voltage stability test, including faulty tube identifiers,
are recorded in the central data base.

\section{Cosmic Ray Test Stand}
%
The performance of each chamber is evaluated in a cosmic ray test stand at the
production site with the baseline gas at the nominal operating point. One or
several chambers simultaneously are tested in a tower with trigger chambers
(see Figure~15). The chambers are installed with their kinematical supports
on rails as in the ATLAS detector. The in-plane alignment system, cross plate
sag monitors if existing and the temperature sensors on the chamber should be
continuously active.

Chambers are accepted after all channels have shown the expected performance stable
over a period of 1--2 weeks. The measurements are stored in the local
data base. Examples of parameters to be monitored are: drift tube efficiency,
noise level, random rate, maximum drift time, resolution as a function of $x$,
local wire displacements and uniformity of all channels.

Faulty drift tubes discovered during the operation of the chamber are recorded
in the central data base.

\section{Wire Location Measurement in Cosmic Ray Teststands}
%
Several cosmic ray test stands in preparation for the barrel chambers (see Figure~15) 
allow to test 3 or more chambers simultaneously in horizontal orientation. 
By selecting high-momentum particles with
a lead absorber and using the two outer chambers
with precisely known wire locations (e.g.\ from X-ray tomograph measurement)
as reference for the reconstruction of tracks of cosmic rays in the tower,
the wire locations in the tested chamber in the middle can be reconstructed.
Useful information about the wire positioning accuracy and possible systematic
shifts can be obtained already after a data taking time of typically 10 hours.
Second coordinate measurement of the tracks with accurcay of typically 1~cm
is needed.

The 3 chambers are aligned with respect to each other with tracks.
Rotations between the MDT chambers and between MDT and second coordinate
chambers around the vertical $y$ axis must be limited by construction of the
rail support system of the chambers in the same way 
as in the ATLAS muon spectrometer. The tolerances for the rotation angles
depend linearly on the second coordinate resolution; for a second coordinate
resolution of 1~cm, the rotation angles $\theta_y$ must be smaller than 1~mrad
in order not to deteriorate significantly the first-coordinate resolution.

During the measuring time, the relative chamber alignment has to be stable
and is monitored with optical sensors.

Simulations show that after half a day of data taking,
the wire locations in the horizontal $z$ coordinate can be measured with
an accuracy of $10-50~\mu$m depending on the setup.
The measurement accuracy is limited by systematics from autocalibration and
alignment stability. Tests will be performed with the Barrel DATCHA 
test stand at CERN.

For measurement of the wire $y$ coordinates, the acceptance for cosmic
tracks in a horizontal tower is limited;
a reconstruction accuracy of typically $50-100~\mu$m
is expected under the above conditions. The average $y$-pitch
and the separation between multilayers can be measured with considerably
higher precision. The statistics can be improved by rotating the
tested chamber around the $x$-axis. More detailed studies are in progress.

For the endcap chambers, the feasibility of measuring wire locations
in a configuration where the test chamber is oriented vertically,
with wires horizontal as at $\phi=0$ in the ATLAS detector, will be
investigated.

The wire coordinate measurements and the measurement errors of the tested chamber 
are recorded in the local and central data bases.

\section{Wire Tension Measurement}
%
During the storage time, in one chamber per production site
the wire tension (oscillation frequency) is monitored for a large fraction of the
drift tubes to obtain information about the long-term behaviour.

Devices for practical wire oscillation frequency measurement in complete chambers have been developed
at JINR Dubna (excitation in a magnetic field) and at LNF Frascati (electrostatic excitation).

\section{The CERN X-Ray Tomograph}
%
The X-ray tomograph at CERN (see Figure~16) scans a whole chamber horizontally 
with two X-ray sources under a stereo angle of $30^\circ$ to measure the wire positions in
a global coordinate system in the $y-z$ plane. The shadows of the wires in all layers are reconstructed
on the X-ray detector images.

The X-ray tomograph has been tested with recent MDT prototype chambers.
The results of a typical X-ray scan of the BOS prototype chamber (along the readout side)
are shown in Figure~17: distributions of the residuals of the measured wire positions with
respect to a fitted ideal grid including correction for the observed gravitational deformation
of the readout-side cross plate due to external moments  (sag by $-17~\mu$m for this scan). 
The fitted parameters $y$- and $z$-pitch and $y$-separation between multilayers 
agree well within the measurement errors with the expectation from the construction 
of the assembly jigging. From repeated scans at the
same position and for the same orientation of the chamber in the tomograph one estimates the
measuring accuracy of the X-ray tomograph to be about $5~\mu$m rms in $z$
and $10~\mu$m rms in $y$ direction. This is sufficient to verify the accuracy of the
MDT chambers.

The CERN X-ray tomograph provides a scan capacity of typically one chamber per week including the
chamber setup time. This allows to measure a fraction of about $15\%$ of all chambers built. 
Initially, approximately the same fraction will be measured for each production site.

The purpose of the X-ray tomograph measurements of MDT chambers is to

\begin{itemize}

\item qualify production sites with the scan results of the module~0 chambers,

\item verify the mechanical accuracy of the chambers on the basis of a sample test,

\item provide feed back to the production sites about systematic deviations
from the mechanical specifications,

\item measure the coordinates of all wires in chambers flagged for the X-ray tomograph
because of problems discovered during assembly or transport.

\end{itemize}

After measurement in the X-ray tomograph, the wire coordinates of a chamber are known
with higher accuracy than specified for the chamber construction. The fraction of
scanned chambers therefore will be used in the ATLAS detector even if outside the
mechanical tolerances. Only in exceptional cases chambers will have to be discarded
because of large distortions detected by the X-ray measurements.
Chambers with cutouts in the multilayers require special attention
in the X-ray tomograph measurement schedule.

The barrel chambers are installed in the tomograph with their kinematical
supports and on rails as in the ATLAS detector. External moments deforming the 
chamber must be avoided. The endcap chambers have to be mounted in
a special support frame for the horizontal scan.
The temperature in the X-ray tomograph room is controlled
to be $20\pm 0.5^\circ$C as on the assembly table. The temperature of the chamber
is monitored during the measurememts with an accuracy of $0.1^\circ$C.
Each scan is performed twice in order to test the reproducibility of the
measurement and to verify bad wire positions. 

The measurements are performed for 3 bar gas pressure in the chamber; for module~0
chambers also at 1 bar to determine the effect of the pressure on the positioning
of the alignment platforms.

Repeating the scan at the same $x$-position after
inverting the chamber around the $x$-axis helps to disentangle gravitational
deformations of the cross plates on the supports from wire displacements caused
during chamber construction. This will be done for the characterization of the module~0
chambers. Additional information about cross plate deformations during the X-ray scans
is provided by cross plate sag monitors. The mechanical stability of the cross plates
and the effect on the wire positioning accuracy after the chamber assembly should
get special attention in the X-ray tomograph measurements of all types of module~0
chambers.

The X-ray tomograph measurements provide the following information:

\begin{enumerate}

\item $y$ and $z$ coordinates of all wires at the tube ends (in active scan mode)
at known temperature including extra scans at the $x$-position of cutouts.

This allows to recover chambers outside the mechnical tolerances.

\item $y$ and $z$ coordinates of wires embedded in special gauge blocks mounted on the
alignment platforms to verify their positioning accuracy.

\item Parameters extracted from the wire coordinate measurements
on readout and high-voltage side for evaluation of the quality of the chamber
and of the construction procedure:

\begin{enumerate}

\item Average $z$ pitch. 

\item $z$-pitch for each layer.

\item Average $y$-pitch.

\item $y$-distance between adjacent layers.

\item $y$-distance between multilayers.

\item $z$-shift between adjacent layers.

\item $z$-shift between multilayers.

\item Global deformations of the chamber in the $y-z$ plane (fit vs.\ cross plate monitor measurements).

\item Systematic deformations of individual layers in the $y-z$ plane (fit vs.\ cross plate monitor measurements).

\item Rms of the residual distributions of the measured wire coordinates with
respect to the nominal wire grid in $y$ and $z$.

\item Rms of the residual distributions of the measured wire coordinates with
respect to the nominal wire grid in $y$ and $z$, separate for each layer.

\item Deviations of residuals from Gaussian distribution; number of wires outside $\pm 3\sigma$.

\end{enumerate}

\end{enumerate}

The X-ray tomograph data, wire coordinates, analyzed mechanical parameters and the temperature
of the chamber for the different scans, are stored in the central data base.


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{1.10}

\begin{center}
\noindent
{\bf Table~5:} Quality control tests during chamber assembly.
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction if failed} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline

& & & &\\
\multicolumn{5}{l}{\bf Environment} \\ [1mm]

Room temperature       & $20\pm 1~\circ$C & adjust & local & before glueing \\
& & & &\\

Relative humidity      & $50\pm 10~\%$     & adjust & local & before glueing \\
& & & &\\

Atmospheric pressure   &                   &        & local & monitoring     \\
({\bf optional}) & & & &\\
& & & &\\

Temperature of outer cross plates & $20\pm 0.5^\circ$C & adjust & local & uniform, before glueing \\
& & & &\\

Temperature of end combs & $20\pm 0.5^\circ$C & adjust & local & uniform, before glueing \\
& & & &\\

Temperature difference & $<0.5^\circ$C & adjust & local & during glueing \\
outer cross plates--end combs  & & & &\\
\hline

& & & &\\
\multicolumn{5}{l}{\bf Spacer assembly} \\ [1mm]

Glue gaps between tube layer & $200-1000~\mu$m  & adjust & local & both orientations of cross plates \\
on combs and cross plates    &                  &        &       & around $z$-axis                  \\
& & & &\\
\hline

& & & &\\
\multicolumn{5}{l}{\bf On-chamber gas system} \\ [1mm]

Leak rate  & less than $10^{-6}$~bar~l/s  & repair or replace & local & for preassembled gas manifolds \\
& & & &\\

Flow rate/tube  & equal within $10\%$  & repair or replace & & for preassembled gas manifolds \\
& & & &\\
\hline\hline

\end{tabular}
\end{center}

%\end{table}
\end{sidewaysfigure}
\clearpage


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{0.90}

\begin{center}
\noindent
{\bf Table~6:} Quality control tests during chamber assembly (cont.)
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction if failed} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline

& & & &\\
\multicolumn{5}{l}{\bf Assembly of tube layers} \\ [1mm]

Vacuum suction  & at nominal value & adjust & local & tube positioning on combs during glueing  \\
underpressure   & & & &\\
& & & &\\

Horizontal gaps between tubes  & not more than two adjacent     & relocate drift tubes & local & before glueing \\
                               & tube walls touching,           & & &\\
                               & no adjacent endplugs touching  & & &\\
& & & &\\

Height of endplug              & within $\pm 20~\mu$m           & relocate drift tubes & local & before glueing \\
reference surfaces on jig      & of nominal value in $y$        & & &\\
& & & &\\

Stability of in-plane          & within $\pm 10~\mu$m            & adjust               & central & after each glueing step \\
monitor readings               & of nominal value in $y$ and $z$ &                      &         & (definition of zero of in-plane monitors), \\
(image displacement) & & & & after correction for middle \\

Sphere locations               & within $\pm 10~\mu$m            & adjust               & local   & before each glueing step, \\
                               & of nominal value in $y$ and $z$ &                      &         & with sphere and in-plane monitors \\
& & & &\\

Outer cross plate sags         & zero within $\pm 10~\mu$m       & adjust               & local & before glueing of a layer, \\
on the assembly table          & & & & measured with temporary        \\
({\bf optional})               & & & & cross plate sag monitors \\
& & & &\\

Middle cross plate sag         & zero within $\pm 20~\mu$m       & adjust               & local & before glueing of a layer, \\
on the assembly table          & & & & measured with in-plane monitors plus \\
({\bf optional})               & & & & outer cross plate sag correction \\
& & & &\\
\hline

& & & &\\
\multicolumn{5}{l}{\bf Alignment Platforms} \\ [1mm]

Angular alignment of    & within $\pm 60~\mu$rad, $\pm 200~\mu$rad,   & store data  & central & after each glueing step (initially);   \\
axial/praxial platforms & $\pm 80~\mu$rad around $x$-, $y$-, $z$-axes &             &         & tolerances include accuracy of recon-   \\
                        & with chamber coord.\ axes, orthog.          &             &         & struction of thermal and gravitational  \\
                        & $\pm 100~\mu{\mathrm rad}\times$~cross plate length&      &         & deformations with the in-plane system  \\
& & & &\\

Angular alignment of    & within $\pm 200~\mu$rad, $\pm 80~\mu$rad,   & store data  & central & tolerances include accurcay of recon-  \\
projective platforms    & $\pm 80~\mu$rad around $x$-, $y$-, $z$-axes &             &         & struction of thermal and gravitational  \\
                        & with chamber coordinate axes                &             &         & deformations with the in-plane system   \\
& & & &\\
\hline\hline

\end{tabular}
\end{center}

%\end{table}
\end{sidewaysfigure}
\clearpage


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{1.10}

\begin{center}
\noindent
{\bf Table~7:} Quality control tests of all assembled chambers at the production sites
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction if failed} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline


& & & &\\
\multicolumn{5}{l}{\bf Mechanical Tests} \\ [1mm]

Sag of chamber &  & store data & central & $y$ readings of  \\
on kinematical supports & & & & in-plane monitors \\
before sag compensation   & & & &  \\
& & & &\\

Sag of chamber            & within $\pm 20~\mu$m  & adjust sag compensation  & central & $y$ readings of  \\
on kinematical supports   & of nominal wire sag   & until within tolerance,  & & in-plane monitors \\
after sag compensation    &                       & store data               & &  \\
& & & &\\

Deformation of cross plates  & $<20~\mu$m  & store data & central & with temporary cross \\
on kinematical supports      & & &                                & plate sag monitors \\
({\bf recommended for BM, BO}) & & & & and FEA model \\
& & & &\\

Rel.\ angular alignment of & see Table~6   & store data  & local & tolerances include accuracy of recon-  \\
alignment  platforms       &               &             &         & struction of thermal and gravitational  \\
on kinematical supports    &               &             &         & deformations with the in-plane system    \\
after sag compensation,    & & &                                   & (measurements as during assembly) \\
with 1 and 3 bar pressure  & & & & \\

\hline\hline

\end{tabular}
\end{center}
\hfill

%\end{table}
\end{sidewaysfigure}
\clearpage


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{0.95}

\begin{center}
\noindent
{\bf Table~8:} Quality control tests of all assembled chambers at the production sites (cont.)
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction if failed} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline

& & & &\\
\multicolumn{5}{l}{\bf Operation Tests} \\ [1mm]

Gas pressure test      & test done,        & repair gas manifold,   & central  &   \\
at 3 bar overpressure  & no obvious leaks  & repair/disconnect      &          &                   \\
                       &                   & faulty tubes, store ID &          &                   \\
& & & &\\

Gas leak rate         & less than $2\times 10^{-8}$~bar~l/s  & repair gas manifold, & central & after pressure  \\
at 2 bar overpressure & per tube                             & repair/disconnect    &         & test       \\
                      &                                      & faulty tubes, store ID &       &        \\
& & & &\\

HV stability:   & less than 2~nA/m~$+5$~nA & replace electronics  & central & with installed electronics boards,  \\
leakage current & per channel            & boards; identify,    &         & baseline gas at 3 bar \\
                &                        & sputter/disconnect   &         & and nominal and $8\times$ nominal   \\
                &                        & faulty drift tubes,  &         & gas gain                            \\
                &                        & store ID             & &\\
& & & &\\

HV stability:     & within $\pm 3\sigma$     & identify noisy       & local   & with installed electronics boards,  \\
cosmic count rate & of nominal value         & channels,            &         & baseline gas at 3 bar \\
({\bf optional})  &                          & store ID             &         & and nominal gas gain  \\
& & & &\\

Operation in    & evaluation of performance: & make chamber     & local   & with test electronics,  \\
cosmic ray test & noise level, efficiency,   & operational,     &         & baseline gas at 3 bar   \\
stand           & random rate, max.\ drift time,  & store ID of &         & and nominal gas gain    \\
                & resolution vs.\ $x$, uniformity, & faulty tubes & & \\
                & local wire displacement,   & & &\\
                & stable performance of all  & & &\\
                & channels over 1--2 weeks   & & &\\
& & & &\\

Wire location    & no systematic deviations   & store wire location         & central & track reconstruction \\
measurement      & from expected wire grid    & data incl.\ meas.\ errors,  &         & in cosmic ray tower  \\
with cosmic rays &                            & adjust assembly tooling     &         &  \\
({\bf optional}) &                            &                             & & \\
& & & &\\
\hline\hline

\end{tabular}
\end{center}
\hfill

%\end{table}
\end{sidewaysfigure}
\clearpage


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{1.10}

\begin{center}
\noindent
{\bf Table~9:} Quality control tests of all assembled chambers after transport to CERN and during storage
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction on failure} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline

& & & &\\
Visual     & no visible damage  & perform possible      &   & acceptance test after transport  \\
inspection &                    & repairs, mark chamber &   & to CERN  \\                                                                     
           &                    & for X-ray tomograph   &   &          \\
           &                    & and full leak test    &   &          \\
& & & &\\

Gas leak rate & less than $2\times 10^{-8}$~bar~l/s per tube & repair gas manifold, & central & 1: full leak test for one chamber per \\
at 3 bar      &                                              & repair/disconnect    &         & transport to CERN (acceptance test)  \\
              &                                              & faulty tubes, store ID &       & or if visible damage of chamber \\
              &                                              &                        &       & 2: monitoring of pressure (at known \\
              &                                              &                        &       & temperature) over storage time \\
& & & &\\

HV stability:   & less than 2~nA/m~$+5$~nA & replace electronics  & central & after mounting of final electronics, \\
leakage current & per channel              & boards; identify,    &         & with baseline gas at 3 bar and            \\
                &                          & disconnect faulty    &         & nominal and $2\times$ nominal  \\
                &                          & tubes, store ID      &         & gas gain     \\
& & & &\\
Operating test  & evaluation of performance: & replace electronics, & local   & after mounting of final electronics, \\
                & pulser test (correct       & make chamber         &         & with baseline gas at 3 bar           \\
                & connections), signals      & operational          &         & and nominal operating conditions     \\
                & from all channels, noise   &                      &         &                                      \\
                & level, random rate, uniformity &                  &         &                                      \\
& & & &\\

\hline\hline

\end{tabular}
\end{center}
\hfill

%\end{table}
\end{sidewaysfigure}
\clearpage


\begin{sidewaysfigure}
%\begin{table}[p]
\renewcommand{\arraystretch}{1.05}

\begin{center}
\noindent
{\bf Table~10:} Quality control tests of selected chambers from each production site after transport to CERN and during storage
\vspace{2mm}

\begin{tabular}{lllcl}

\hline\hline
& & & &\\
{\bf Test} & {\bf Acceptance criteria} & {\bf Reaction on failure} & {\bf Data base} & {\bf Comment} \\ [1mm]
\hline
& & & &\\

Wire location   & $\pm 20~\mu$m rms in $y$ and $z$ & store wire location & central & 1: sample test/production site \\
measurement with& with respect to the    & data and chamber ID,          &         & 2: for chambers with expected  \\
X-ray tomograph & expected wire grid     & adjust assembly tooling&         & \hphantom{2:} mechanical problems \\
(incl.\ location&                        & in case of deviations, &         &                         \\
of wire on the  &                        & measure chambers since &         &                         \\
alignm.\ platforms) &                    & problem first detected &         &                         \\

& & & &\\
Wire tension      & within $\pm 5\%$      & store data,               & central & for one chamber/production site  \\
(from oscillation & of the nominal tension& notify production sites,  &         & at regular intervals over storage time \\
frequency meas.)  & value at given        & measure other chambers    &         & (temperature meas.\ to $\pm 1^\circ$C) \\
                  & temperature           & & &\\
& & & &\\

Tube ground        & less than 100~m$\Omega$  & store data,               & central & for one chamber/production site  \\
contact resistance & per endplug              & notify production sites,  &         & at regular intervals over        \\
(for 5~mA current) &                          & measure other chambers    &         & storage time                     \\
& & & &\\

\hline\hline

\end{tabular}
\end{center}
\hfill

%\end{table}
\end{sidewaysfigure}
\clearpage

\section{Chamber Test Program at the Production Sites}
%
\begin{itemize}

\item[1] Install chamber in leak, high voltage and cosmic ray test stand
with kinematic supports as in ATLAS.

\item[2] Chamber pressure test.

\begin{itemize}
\item[2.1] Connect gas supplies.

Fill chamber with Argon or $N_2$ to 4 bar pressure.

Identify and repair obvious leaks, disconnect faulty tubes.
Store ID of faulty/repaired tubes in data base (central).
\hfill $\longrightarrow$ DB

If no obvious leaks, reduce gas pressure to 3 bar.
\end{itemize}

\item[3] Chamber leak test.

\begin{itemize}
\item[3.1] Monitor changes of gas pressure and temperature difference
of the chamber with respect to a reference volume with a differential manometer
in intervals of 12 hours over several (2-10) days depending on
sensitivity of the temperature and pressure measurements.

\item[3.2] Calculate leak rate limit from temperature-corrected
pressure drop in the chamber.

Stop when required leak rate limit is reached.

If required leak rate limit is not reached after the time period expected
from the measuring sensitivity:
identify and repair leaks, disconnect faulty tubes. Repeat leak test from 3.1.

After successful leak test: store leak rate limit in data base (central).
\hfill $\longrightarrow$ DB
\end{itemize}                                                                                    

\item[4] After start of leak test with no obvious leaks detected:
Install hedgehog boards (already tested individually).

Boards are installed properly cleaned using gloves.

\item[5] Install mezzanine cards with test electronics; connect to DAQ system.

\item[7] Store all optical monitor and temperature sensor readings in data base (local).
\hfill $\longrightarrow$ DB

Store longitudinal in-plane monitor $y$-readings (gravitational sags of the chamber)
before sag adjustment in data base (central).
\hfill $\longrightarrow$ DB

\item[8] Compensate sags of the chamber with the sag compensation systems of the
two long beams.

\item[9] Store all optical monitor and temperature sensor readings in data base (local).
\hfill $\longrightarrow$ DB

Store longitudinal in-plane monitor $y$-readings (gravitational sags of the chamber)
after sag adjustment in data base (central).
\hfill $\longrightarrow$ DB

Read all optical monitors and temperature sensors on the chamber
continuously during chamber tests.

\item[10] Measure relative angular alignment of alignment platforms with optical angle monitors
as during assembly at 1 and 3 bar gas pressure.

\item[11] High voltage stability and operating test with installed readout electronics.

\begin{itemize}
\item[11.1] Fill chamber with baseline gas to 3 bar.

Operate chamber at baseline operating point within tolerances.

\item[11.2] Document gas composition and electronics settings in data base (local).
\hfill $\longrightarrow$ DB

\item[11.3] Monitor temperature, gas pressure, high voltage and chamber currents at each step.

\item[11.4] Turn on high voltage: start at 1~kV below operating voltage, ramp up in 100~V steps
until voltage corresponding to a gas gain of $16\cdot 10^4$ is reached.

At each step, limit chamber currents to stay below 5~nA/tube.

If high voltage cannot be raised with this current limit: identify faulty channels.

If caused by electronics: replace boards.

If caused by drift tubes: disconnect tubes.

Record disconnected tube IDs in data base (central).
\hfill $\longrightarrow$ DB

\item[11.5] At the nominal operating voltage: identify channels with
cosmic count rate outside $\pm 3\sigma$ of nominal value.

Record noisy channel IDs in data base (central).
\hfill $\longrightarrow$ DB

\item[11.6] Sputter faulty tubes due to leakage current.

Record sputtered tube IDs in data base (central).
\hfill $\longrightarrow$ DB

\item[11.7] Repeat HV test from 10.4.

Record faulty tube IDs in data base (central).
\hfill $\longrightarrow$ DB

Store chamber currents and cosmic count rates at operating voltage and at voltage
corresponding to a gas gain of $10^5$ in data base with temperature, gas pressure and
high voltage values (local).
\hfill $\longrightarrow$ DB
\end{itemize}                                                                                    

\item[12] Operation of chamber
in cosmic ray test stand at baseline operating point
for at least one week.

\begin{itemize}

\item[12.1] Monitor temperature, high voltage, gas pressure, chamber currents, count rates
and optical monitor readings continuously.

\item[12.2] Evaluation of chamber performance.

Sensitive parameters among others:
noise level, tube efficiency, random rate, minimum and maximum drift time,
local wire displacements, position resolution as function of $x$, uniformity.

Store in data base (local).
\hfill $\longrightarrow$ DB

Make chamber operational.

\item[12.3] Optional: Reconstruction of global wire locations with reconstruction of cosmic ray
tracks in tower of three chambers.
\hfill $\longrightarrow$ DB
\end{itemize}

\item[13] Store optical monitor and temperature sensor readings on the chamber
at the end of the chamber tests.
\hfill $\longrightarrow$ DB

\item[14] Keep chamber filled and sealed with baseline gas at 3 bar during all future transport
and storage. 

Monitor temperature and gas pressure of the chamber.
\end{itemize}



\section{Chamber Test Program at CERN}
%
\begin{itemize}

\item[1] Acceptance test of chamber after arrival in the storage area at CERN:

\begin{itemize}
\item[1.1] Chambers are installed on their kinematical supports during storage.

\item[1.2] Store optical monitor, temperature sensor and gas pressure readings
on the chamber (after first arrival and after every future transport).
\hfill $\longrightarrow$ DB

\item[1.3] Visual inspection of each chamber for visible
damage; flag chambers for X-ray tomograph measurement and full leak test.

\item[1.4] Leak test at 3 bar (as at the production sites)
of one chamber per transport  
(acceptance test) or if incidences during transport or visible damage.

Store leak rate limit in data base (central).
\hfill $\longrightarrow$ DB
\end{itemize}

\item[2] Wire location measurement with the X-ray tomograph at CERN:

\begin{itemize}
\item routinely for selected chambers as soon as possible after arrival of a transport 
to provide feedback to the production sites,

\item for chambers with problems discovered during construction,

\item for chambers with visible damage after transport.

\end{itemize}

\begin{itemize}
\item[2.1] Install chamber in the X-ray tomograph
on the kinematical supports and rails as in the ATLAS detector.

Compensate chamber gravitational sag as specified for horizontal chambers.

\begin{itemize}
\item[2.1.1] Handling and transport of chambers at CERN only with supervisor nominated by production site present.

\item[2.1.2] Transport of chamber in special transport frame provided by production site.

Handling of chamber with tooling provided by production sites.
\end{itemize}

\item[2.2] Monitor optical monitor and temperature sensor readings on the chamber
during measurements in the X-ray tomograph. \hfill \hbox to 2cm{\hfill $\longrightarrow$ DB}

\item[2.3] X-ray scans: close to each end of the chamber (including wires on alignment platforms) and at the ends
of cut outs. 

Repeat each scan to check reproducibility.

Store reconstructed wire coordinates ($y$ and $z$ at $x$-position of scan) for each scan
in data base with temperature and optical monitor readings (central).
\hfill $\longrightarrow$ DB
\end{itemize}

\item[3] Monitor gas pressure (with temperature) of the chamber during storage time.

Store data in data base (local).
\hfill $\longrightarrow$ DB

\item[4] High-voltage and operating test after installation of final readout electronics
(already tested individually):

\begin{itemize}
\item[4.1] Document electronics settings in data base.
\hfill $\longrightarrow$ DB

\item[4.2] Monitor temperature, gas pressure, high voltage and chamber currents at each step.

\item[4.3] Turn on high voltage: start at 1~kV below operating voltage, ramp up in 100~V steps
until voltage corresponding to a gas gain of $1.6\cdot 10^5$ is reached.

At each step: limit current to stay below 5~nA/channel.

If high voltage cannot be raised with this current limit: identify faulty channels.

If caused by electronics: replace boards.

If caused by drift tubes: disconnect tubes if voltage cannot be raised to nominal value.

Record faulty tube IDs in data base (central).
\hfill $\longrightarrow$ DB

\item[4.4] Store chamber currents at operating voltage and at voltage
corresponding to a gas gain of $1.6\cdot 10^5$ in data base with temperature, gas pressure and
high voltage values (local).
\hfill $\longrightarrow$ DB

\item[4.5] Operating test of final electronics setup:

Pulser test of connections, signals in all channels, random rate,
evaluation of noise level and uniformity.

Store in data base (local).
\hfill $\longrightarrow$ DB

Make chamber operational.
\end{itemize}                                                                                    

\item[5] Store optical monitor and temperature sensor readings on the chamber
before transport to ATLAS cavern for detector installation (central).
\hfill $\longrightarrow$ DB

\end{itemize}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Chamber Transport and Storage}
%
Chambers are transported and stored in the following condition:

\begin{enumerate}

\item The chambers are transported and stored with
Faraday cages (protection of the endplugs) and protective covers
(protection of the tubes) installed.

\item The chambers are transported and stored suspended on their
kinematical supports in a special frame inside a closed container.

\item After test at the production sites, the chambers are kept filled
with the baseline gas at 3 bar during all further transport and storage.

\item The chambers are enclosed in an air-tight plastic bag containing
dehumidifier bags.

\item The temperature of the chambers is monitored during transport and storage.

Temperature gradients on the chamber must not exceed $10^\circ$C
during transport and storage to prevent mechanical deformations.

\item During transport, only temperature variations in the range $0-50^\circ$C are allowed.

(This means that the wire tension can increase temporarily by up to 45~g (1.5~g/${}^\circ$C)
compared to the nominal tension of 350~g at $20^\circ$C, i.e.\ by $13\%$. The supports in the
transport frame have to be able to cope with length variations of the chambers of up to 0.5~cm.)

\item During storage, the temperature has to stay within the range $10-30^\circ$C.

\item Shocks are limited during transport and are monitored during transports to CERN.

\end{enumerate}


\section{Local Chamber Storage and Transport to CERN}
%

\begin{itemize}
\item[1] Dismount test electronics (mezzanine cards only).

\item[2] Install chamber in local storage and transport frame.

\item[3] Store all optical monitor and temperature sensor readings after installation
in transport frame.
\hfill $\longrightarrow$ DB

\item[4] Chamber stays filled with baseline gas at 3 bar during transport and storage.

\item[5] Enclose chamber air-tight in plastic bag.

\item[6] Monitor temperature and humidity in storage room.
Protect chambers from temperature gradients.

\item[7] Monitor gas pressure during storage with cheap manometer on the chamber.
\hfill $\longrightarrow$ DB

\item[8] Store optical monitor, temperature sensor and gas pressure readings
before transport to CERN.
\hfill $\longrightarrow$ DB

\item[9] Transport, load, unload chambers according to handling instructions
(only with certified supervisor present).

Monitor temperature on the chamber and record shocks during transport.

\end{itemize}

\section{Chamber Transport and Storage at CERN}

\begin{itemize}

\item[1] Transport chamber to storage area at CERN.
Load, unload chamber according to handling instructions
(only with certified supervisor present).

Transport in transport frame.

\item[2] Store chamber in transport frame.

Store all optical monitor and temperature sensor readings
immediately after installation of chamber in storage area.\hfill \hbox to 2cm{\hfill $\longrightarrow$ DB}

\item[3] Enclose chamber air-tight in plastic bag during storage and transport.

\item[4] Leak test of the chamber with the baseline gas at 3 bar
immediately after installation in the storage area (as 10.8).

\item[5] Monitor temperature and humidity in storage room.
Protect chambers from temperature gradients.

\item[6] Monitor gas pressure during storage with the cheap manometer on the chamber.

\hfill $\longrightarrow$ DB

\item[7] After arrival of final electronics boards: install on stored chambers and
connect to DAQ.

\item[8] High-voltage and operating test with installed electronics boards (as 10.9).

\item[9] Store all optical monitor and temperature sensor readings
before transport to ATLAS cavern for detector installation.
\hfill $\longrightarrow$ DB

\end{itemize}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\clearpage

\chapter{Monitoring of Chamber Production}
%
The quality control data for chamber materials, drift tube production and chamber
construction will be stored in the production data base in order to monitor the
production and identify the source of problems at each production site and
for the whole collaboration. It is important to keep track of the
history and time relations of the quality control and monitoring
measurements performed during chamber construction. Each individual tube is identified
by a bar code which is read directly into the data base with a bar code
scanner everytime the tube is handled in the construction process.

\section{Central Production Data Base}
%
Data relevant for the global monitoring of the chamber production and for the
later operation of the chambers are kept in the central production data base.
Each production site is required to report the necessary data 
as soon as they are available. The data base will be implemented using the
Microsoft ACCESS package, a relational data base for Windows,
and will be maintained by the Rome MDT group.
The content and structure of the central data base as far as quality control information
is concerned are described in Table~11.
An ACCESS data base template and instructions for the implementation are available at

http://mulflx.roma1.infn.it/atlas/rmwork.

In the ACCESS data base structure, each object is associated with a table. 
The following objects have been defined for the central MDT production data base: 
`Tube', `Layer', `Multilayer', `Spacer' and `Chamber' tables.
The rows of the table correspond
to the different data entries related to the object (`items') and the columns (`fields') contain the
data associated with each item. Relationships between different tables are defined via a common field
(`primary key') in the linked tables. 

\section{Local Production Data Base}
%
The history of the quality control tests and the full monitoring data
(see the {\bf Assembly Control Plan} in the {\bf Appendix})
have to be kept in the local production data bases of the production sites.
These data are essential for reference and tracing of problems.
It is recommended to keep as much information as possible. The suggested minimum
content with a possible ACCESS structure of the local data base is described in Table~12.
A template for implementation in ACCESS is available at

http://mulflx.roma1.infn.it/atlas/rmwork.

The {\bf Assembly Control Program} communicates directly with the local ACCESS data base.

\clearpage


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\include{qa_doc_dbin}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\include{bos_assembly_plan}

%\vbox to \textheight{\vfill}
%\clearpage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\markboth{\sc FIGURES}{\sc FIGURES}
\markright{\sc FIGURES}

{\Huge\bf Figures}

\addcontentsline{toc}{chapter}{\protect\numberline{}{Figures}}

\begin{itemize}

\item[] {\bf Figure~1:} 

Setup for wire tension measurement in drift tubes
with a commercial tension meter using the oscillation frequency excited
in a magnetic field (Cosenza).

\item[] {\bf Figure~2:}

Graphical user interface for a drift tube test control program (Cosenza).

\item[] {\bf Figure~3:} 

Principle of the stereo X-ray measurement of wire positions in
drift tubes with respect to reference wires in the jigging (Brandeis University).  
                                                        
\item[] {\bf Figure~4:}

Endplug holder with X-ray CCD for wire position measurement with
X-rays (Brandeis University, LMU Munich). 

\item[] {\bf Figure~5:}

Principle of the electromagnetic wire position measurement in
drift tubes with two pick-up coils. The tube is rotated by $90^\circ$ to measure
both transverse coordinates (Pavia, Rome).

\item[] {\bf Figure~6:}

Quality control test stand for wire position measurements in
drift tubes in series production (here for the stereo X-ray method). 
The tube is held during the measurement in the same way as in the combs for chamber assembly 
(MPI Munich, LMU Munich, Dubna).

\item[] {\bf Figure~7:}

Drift tube gas leak test stand with single- and multi-tube containers. The
leakage of helium from the drift tubes into the evacuated containers is measured
with a mass spectrometer (Dubna).

\item[] {\bf Figure~8:}

Integrated drift tube leak and high voltage test stand
with up to 60 single-tube containers. The tubes are tested sequentially with a
mass spectrometer under computer control (Frascati).

\item[] {\bf Figure~9:}

Drift tube gas leak test stand with fixtures at the endplugs as well as sliding
along the tube which allow to measure helium leakage through endplugs or tube walls into 
evacuated volumes with a mass spectrometer (system developed for endcap chambers with
many different tube lengths; Michigan).

\item[] {\bf Figure~10:}

Control of tube placement on the end combs during chamber assembly
with a laser system (Rome).

\item[] {\bf Figure~11:}

Schematical layout of the chamber assembly control software (MPI Munich).

\item[] {\bf Figure~12:}

Graphical user interface for a chamber assembly control program with display
of monitoring data (Thessaloniki).

\item[] {\bf Figure~13:}

Gas leak test stand for complete MDT chambers with differential manometer
and reference volume (Dubna).

\item[] {\bf Figure~14:} 

Differential manometer with reference volume for chamber leak test stands (Dubna).

\item[] {\bf Figure~15:}

Cosmic ray test stand for the operation test of chambers at the
production sites. Several chambers can be tested simultaneously. With a tower
of three chambers, wire positions can be reconstructed (LMU Munich).

\item[] {\bf Figure~16:}

X-ray tomograph setup at CERN.

\item[] {\bf Figure~17:}

Distributions of the residuals in $y$ and $z$ of the wire locations measured in a typical
X-ray tomograph scan of the BOS prototype chamber (readout side) with respect to an ideal wire grid.

\end{itemize}

\clearpage
\end{document}
