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  \title[]{Construction and Test of a Full Prototype Drift-Tube Chamber for the Upgrade of the
ATLAS Muon Spectrometer at High LHC Luminosities}
  \author[]{B.~Bittner\inst{1} \and J.~Dubbert\inst{1} \and O.~Kortner\inst{1} \and H.~Kroha\inst{1} \and A.~Manfredini\inst{1} \and S.~Ott\inst{1} \and R.~Richter\inst{1} \and P.~Schwegler\inst{1} \and D.~Zanzi\inst{1} \and O.~Biebel\inst{2} \and A.~Engl\inst{2} \and R.~Hertenberger\inst{2} \and A.~Zibell\inst{2}}
  \institute{%
  \inst{1}Max-Planck-Institut f\"ur Physik, Munich \hspace{1cm} \inst{2} Ludwig-Maximilians University, Munich}
  \date{12$^\textrm{th}$ Pisa Meeting on Advanced Detectors}

  \begin{document}
  \begin{frame}{} 
    \begin{columns}
    \begin{column}{0.49\textwidth}
    \parbox[t][\columnheight]{\textwidth}{%
    \begin{block}{Abstract}
    \begin{minipage}[c]{0.98\linewidth}
	\small
	For the planned high-luminosity upgrades of the Large Hadron
	Collider (LHC) background rates of neutrons and gamma rays of up to
	14\,kHz/cm$^2$ are expected which exceed the rate capability of the
	current ATLAS precision muon tracking detectors, the Monitored Drift Tube (MDT)
	chambers, with a drift tube diameter of 30\,mm.  So called sMDT chambers with a
	drift tube diameter of 15\,mm have been developed  for upgrades of the ATLAS
	muon spectrometer. A full sMDT prototype chamber has been constructed and
	tested in a muon beam at CERN and with cosmic muons at high gamma irradiation
	rates of up to 23\,kHz/cm$^2$. The chamber design and construction
	procedures will be discussed. The test results demonstrate the required track
	reconstruction efficiency and spatial resolution of the sMDT chambers at
	background rates well beyond the maximum expected value. The sense wire
	locations in the prototype chamber have been measured with few \textmu m
	precision with cosmic rays using precise reference chambers and confirm a wire
	positioning accuracy of better than the 20\,\textmu m required.
    \end{minipage}
    \end{block}

\vfill

\begin{columns}
\begin{column}{0.45\linewidth}
    \begin{block}{Drift Tube Design}
      \begin{minipage}{0.98\linewidth}
      \centering
	\includegraphics[width=0.85\linewidth]{MDT-Rohr}
	\\
	\vspace{3mm}
            \footnotesize
	    \centering
            \begin{tabular}{ll}
              \rowcolor{blue2} Outer tube diameter\ \ & 15\,mm $\pm$ 0.1\,mm\\
              \rowcolor{blue3} Tube wall & 0.4\,mm Al\\
              \rowcolor{blue2} Anode wire& 50 \textmu m W-Re\\
              \rowcolor{blue3} Gas & Ar/CO$_{{\text{2}}}$ = 93/7\\
              \rowcolor{blue2} Pressure& 3\,bara\\
              \rowcolor{blue3} Operating voltage & 2730\,V\\
              \rowcolor{blue2} Gas gain& 20000\\
              \rowcolor{blue3} Max.\ drift time & 185\,ns\\ 
            \end{tabular}
       \end{minipage}
    \end{block}

\end{column}

\hfill

\begin{column}{0.5\linewidth}

  \begin{block}{Advantages of Smaller Drift Tubes}
  \begin{minipage}{0.98\linewidth}
  \begin{itemize}
    \item \alert{7.8$\times$ lower detector occupancy}
    \begin{itemize}
      \item Shorter max. drift time (700$\rightarrow$185\,ns)
      \item Tube diameter (14.6$\rightarrow$7.1\,mm)
    \end{itemize}
    \item \alert{Less space charge}
    \begin{itemize}
	\item $\sim R^3$ for $\gamma$'s
	\item $\sim R^4$ for charged hadrons
	\item[$\Rightarrow$] Improvement by factor 8 and 16, resp.
    \end{itemize}
    \item \alert{Twice the number of layers in the same volume}
    \begin{itemize}
      \item More robust pattern recognition
      \item Better tracking efficiency
    \end{itemize}
    \item \alert{Easy to integrate into the existing infrastructure}
  \end{itemize}
  \end{minipage}
  \end{block}


\end{column}
\end{columns}

\vfill

    \begin{block}{Drift Tube Production and Quality Assurance}
      
      \begin{columns}
        
        \begin{column}{0.48\linewidth}
          \begin{minipage}{0.98\linewidth}
            \begin{itemize}
              \item 1204 tubes produced, 3 different lengths
              \item Entirely manual production, manpower 4 persons
              \item Production rate: up to 160 tubes / day
            \end{itemize}

            \vspace*{5mm}

            \textbf{Full quality assurance of all tubes}

            \vspace*{2mm}

            \begin{itemize}
              \item Wire tension measurement,\\
                limit (350 $\pm$ 15) g
              \item Gas leak test, limit 1 $\times$ 10$^{\text{-5}}$
                mbar L/s
              \item HV dark current measurement at\\
                3010 V, limit 5 nA
            \end{itemize}            

            \begin{center}
              \footnotesize
              \begin{tabular}{l|c|c|c}
                Test & Tested Tubes & Passed & Failure Rate (\%)\\
                \hline
                Wire Tension & 1204 & 1129 & 6.3$^{\text{1}}$\\
                Leak Test & 1171 & 1164 & 0.6\\
                HV & 1164 & 1159 & 0.4\\
                \textbf{Total} & \textbf{1204} & \textbf{1116} & \textbf{7.7}\\
              \end{tabular}
            \end{center}
            {\footnotesize $^{1)}$ High failure rate at beginning of
              prod. only, later $<$1\%}
            
          \end{minipage}
        \end{column}
        \begin{column}{0.48\linewidth}
          \begin{minipage}{0.98\linewidth}
            \begin{center}
              \includegraphics[width=0.8\linewidth]{tubes_production}  
            \end{center}
            \begin{center}
              \vspace*{-10mm}{\tiny Daily tube production}
            \end{center}

            \begin{center}
              \includegraphics[width=0.8\linewidth]{wire_tension_wrong_tube_length}  
            \end{center}
            \begin{center}
              \vspace*{-10mm}{\tiny Measured wire tension}
            \end{center}

            %%% \begin{center}
            %%%   \includegraphics[width=0.8\linewidth]{wire_tension_vs_time}  
            %%% \end{center}
            %%% \begin{center}
            %%%   Slight relaxation of wire tension with time (expected,
            %%%   wires were not pre-tensioned)
            %%% \end{center}
          \end{minipage}
        \end{column}

      \end{columns}

    \end{block}

\vfill

    \begin{block}{Chamber Assembly Procedure}

\begin{columns}
\footnotesize
\begin{column}{0.17\linewidth}
\includegraphics[width=\linewidth]{first_layer}
\\Inserting first tube layer into jigs.
\end{column}
\begin{column}{0.17\linewidth}
\includegraphics[width=\linewidth]{second_layer}
\\Gluing of second tube layer.
\end{column}
\begin{column}{0.17\linewidth}
\includegraphics[width=\linewidth]{glue_spacer}
\\Applying glue for spacer frame.
\end{column}
\begin{column}{0.17\linewidth}
\includegraphics[width=\linewidth]{spacer_glued}
\\Spacer frame glued to first ML.
\end{column}
\begin{column}{0.17\linewidth}
\includegraphics[width=\linewidth]{finished_chamber}
\\Finished chamber.
\end{column}

\end{columns}
    \end{block}

\vfill

    \begin{columns}
    \begin{column}{0.58\textwidth}
    \begin{block}{Precision Assembly Jiggs}
	\centering
   	\includegraphics[height=11cm]{jigging}
    \end{block}
    \end{column}


    \begin{column}{0.4\textwidth}
    \begin{block}{Finished Chamber}
    \centering
	\includegraphics[height=11cm]{trapezkammer}
    \end{block}
    \end{column}
    \end{columns}
    }
    \end{column}
    \hfill
    \begin{column}{0.49\textwidth}
    \parbox[t][\columnheight]{\textwidth}{%
%        \begin{block}{\scshape{Modular Gas System}}
%	\begin{columns}
%	\begin{column}{0.68\textwidth}
%            \begin{itemize}
%            \item Allows any chamber shape\\ 
%              (trapezoidal, rectangular
%              etc.)
%            \item Primary gas bar distributes gas along each multilayer
%            \item Interconnections between tubes of different layers
%            \end{itemize}
%	    \end{column}
%	    \begin{column}{0.3\textwidth}
%            \begin{center}
%              \includegraphics[width=0.6\textwidth]{new_gas_bar}  
%            \end{center}
%	    \end{column}
%	    \end{columns}
%        \end{block}
        \begin{block}{Front-End Electronics}
        \begin{columns}
	\begin{column}{0.75\textwidth}
	\small
            \begin{itemize}
            \item New passive front-end cards\\
              High connector density necessitates 3-dimensional
              design
            \item Compatible with ATLAS active front-end cards and
              readout scheme
            \item New Amplifier-Shaper-Discriminator chip under
              development
            \end{itemize}
	\end{column}
	\begin{column}{0.2\textwidth}
	\centering
            \includegraphics[width=0.6\textwidth]{smdt_hh_hv}
         \end{column}
	 \end{columns}
        \end{block}

\vfill

\begin{block}{Wire Position Measurement}
\begin{minipage}{0.98\linewidth}
\small
\textbf{Cosmic ray test stand, LMU Munich}

Used to test all ATLAS MDT chambers constructed in Munich (accuracy: 5\,\textmu m)
\begin{columns}
\begin{column}{0.38\textwidth}
	\begin{center}
		\includegraphics[width=0.9\linewidth]{wire_pos_comb}
	\end{center}
\end{column}
\begin{column}{0.58\textwidth}
	\begin{itemize}
		\item reconstruction of muon tracks in the reference chambers
		\item extrapolation to the test chamber
		\item compare the reconstucted tracks with the hits in the test chamber
	\end{itemize}
	\vfill
	Results:
	\begin{itemize}
	\item Deviations of the wires from the (optimized) target positions are with \textcolor{red}{19\,\textmu m} for $\delta_y$ and \textcolor{red}{16\,\textmu m} for $\delta_z$ well within the requirements of 20\,\textmu m.
	\item Good agreement with the design values
	\end{itemize}
\end{column}
\end{columns}
\vspace{5mm}

\begin{columns}
\begin{column}{0.6\textwidth}
\begin{center}
\begin{tabular}{c|c|rcl}
\textbf{Parameter} & \textbf{nominal} & \multicolumn{3}{c}{\textbf{measured}} \\
\hline
   d$_{y}$  &  15.100\,mm  & $15.1018$&$\pm$&$0.0003$\,mm \\
   d$_{z}$  &  13.078\,mm  & $13.091$&$\pm$&$0.007$\,mm \\
   $y_\text{skip}$	  &  7.550\,mm & $7.550$&$\pm$&$0.0005$\,mm\\
   ML dist. & 90.400\,mm & $90.382$&$\pm$&$0.010$\,mm\\
\end{tabular}
\end{center}
\end{column}
\begin{column}{0.38\textwidth}
\begin{center}
\includegraphics[width=0.6\linewidth]{wire_grid}
\end{center}
\end{column}
\end{columns}

\end{minipage}
\end{block}

%    \begin{block}{Chamber Performance without Background}
%\begin{columns}
%\begin{column}{0.3\textwidth}
%\centering
%\includegraphics[width=0.9\textwidth]{setup_beam_image}
%\end{column}
%\begin{column}{0.3\textwidth}
%\includegraphics[width=\textwidth]{resolution_vs_r}
%\end{column}
%\begin{column}{0.3\textwidth}
%\includegraphics[width=\textwidth]{efficiency_vs_r}
%\end{column}
%
%\end{columns}
%
%\begin{itemize}
%\item average single tube resolution: (108$\pm$2)\,\textmu m (128$\pm$2\,\textmu m without time slewing corrections.
%\item average 3$\sigma$ single tube efficiency: 94\%.
%\end{itemize}
%
%    \end{block}

\vfill

\begin{block}{Measurements at High Background Rates}
\textbf{Measurement principle:} Central tube layers of the chamber irradiated, outer (shielded) layers used for tracking of cosmic muons.
\begin{columns}
\begin{column}{0.3\textwidth}
\small
\textbf{GIF 2011}
\begin{itemize}
\item 150\,GBq $^{137}$Cs source
\item flux up to 10\,kHz/cm$^2$
\end{itemize}

\textbf{Tandem accelerator 2011}
\begin{itemize}
\item 20\,MeV protons
\item flux up to $>$100\,kHz/cm$^2$
\end{itemize}
\end{column}
\begin{column}{0.3\textwidth}
\centering
\includegraphics[width=0.98\textwidth]{analysis_sketch}
\end{column}
\begin{column}{0.25\textwidth}
\centering
\includegraphics[width=0.98\textwidth]{tandem_setup}
\end{column}
\end{columns}

\vspace{5mm}

\textbf{Analysis strategy:}
\begin{minipage}{0.98\textwidth}
\small
\begin{enumerate}
\item Use track reconstructed in shielded part of the chamber to determine off-track residuals in irradiated tubes.
\item Correct for track uncertainty and multiple scattering due to low energy muons $\Rightarrow$ resolution $\sigma$.
\item Determine 3$\sigma$ efficiency.
\end{enumerate}
\end{minipage}

\end{block}

\vfill

\begin{block}{Results}

\begin{minipage}{0.96\linewidth}
\setlength{\fboxrule}{4pt} 
\fcolorbox{red}{white}{%
\begin{columns}
\begin{column}{0.49\textwidth}
\centering
\setlength{\fboxrule}{4pt} 
\includegraphics[height=9cm]{resolution_vs_background_hit_rate}
\end{column}
\begin{column}{0.49\textwidth}
\centering
\includegraphics[height=9cm]{efficiency_vs_background_hit_rate}
\end{column}
\end{columns}
}
\end{minipage}

\begin{columns}
\begin{column}{0.55\textwidth}
\centering
\begin{minipage}{0.90\textwidth}
\small
Iterative calculation of the gas gain with Diethorn's formula:
\vspace{3mm}
\begin{center}
$G = \left[\frac{E_{\mathsf{wire}}}{3 E_{\mathsf{min}}}\right]^\frac{r_{\mathsf{wire}}E_{\mathsf{wire}}\ln{2}}{\Delta V}$
\end{center}
\vspace{3mm}

where $E_{\mathsf{wire}}$ is the electric field at the sense wire which depends on the space charge density and thus the background flux.
\vspace{3mm}

$G_0$ = nominal gain = 20\,000.
\end{minipage}
\end{column}
\begin{column}{0.42\textwidth}
\centering
\includegraphics[height=9cm]{gaindrop}
\end{column}
\end{columns}

    \end{block}

\vfill

    \begin{block}{Conclusions}
      \begin{minipage}{0.98\linewidth}
	\begin{itemize}
		\item Successful construction of 1200 drift tubes with low failure rate.
		\item Chamber assembly procedures and time frame (1 chamber per week) validated.
		\item Wire positioning accuracy (20\,\textmu m) validated with cosmic muons.
		\item Measured up to the highest expected rates of 14\,kHz/cm$^\mathsf{2}$, 1175\,kHz/tube:
		\begin{itemize}
			\item Tracking efficiency $>$70\% per tube and $>$99\% with 8-layered chamber.
			\item Spatial resolution $<$140\,\textmu m per tube and $<$50\,\textmu m with 8-layered chamber.
		\end{itemize}
		\item[$\Rightarrow$] \alert{Fulfill all requirements for operation at High Luminosity-LHC.}
	\end{itemize}
      \end{minipage}
    \end{block}
}
    \end{column}
    

    \end{columns}


  \end{frame}
\end{document}


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