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\begin{document}

\begin{frontmatter}

\title{Performance of Drift Tube Detectors at Very High Counting Rates at High-Luminosity LHC}

% if there is only one institution, use this form:
%\author{John Author, Giovanna Autore}
%\address{University of Wisdom, Physics City, Scienceland}

% else, use optional labels to link authors explicitly to addresses,
% as shown below:
\author[B]{O.~Biebel},
\author[A]{B.~Bittner},
\author[A]{J.~Dubbert},
\author[B]{R.~Hertenberger},
\author[A]{O.~Kortner},
\author[A]{H.~Kroha},
\author[A]{A.~Manfredini}
\author[A]{S.~Nowak},
\author[A]{S.~Ott},
\author[A]{R.~Richter},
\author[B]{A.~Ruschke}
\author[A]{Ph.~Schwegler},
\author[A]{D.~Zanzi}, 
\author[B]{A.~Zibell}
\address[A]{Max-Planck-Institut f\"ur Physik,
	F\"ohringer Ring 6, 80805 M\"unchen, Germany}
\address[B]{Ludwig-Maximilians-Universit\"at M\"unchen, Am Coulombwall 1, 85748
Garching, Germany}

\end{frontmatter}

% \centerline{\itshape Abstract}

The performance of pressurized drift-tube chambers at very high background 
counting rates has been studied at the Gamma Irradiation Facility (GIF) at CERN 
and in an intense 20~MeV proton beam at the Munich Van-der-Graaf tandem accelerator 
for applications as large-area precision muon tracking detectors at high-luminosity 
upgrades of the Large Hadron Collider (LHC). The present ATLAS muon drift-tube (MDT) 
chambers with 30~mm tube diameter are designed to cope with $\gamma$ and neutron 
background rates of up to 500~Hz/cm$^2$ or 300~kHz/tube. Background rates of up to 14~kHz/cm$^2$ 
and 1150~kHz/tube are expected at LHC upgrades. The test results for $\gamma$ irradiation rates 
of up to 1400~kHz/tube and 8.5~kHz/cm$^2$ and for proton rates up to 2800~kHz/tube and 
1330~kHz/cm$^2$ show that by reducing the drift-tube diameter to 15~mm while leaving the 
other operating parameters unchanged, the rate capability is vastly increased. 
With the 3.8 times shorter maximum drift time of 185~ns the drift-tube occupancy per unit length 
is reduced by a factor of 7.6. The degradation rate of the drift-tube spatial resolution 
due to space charge effects is reduced by more than an order of magnitude. 
The shorter maximum drift time allows also for a reduction of the
adjustable deadtime of the MDT readout electronics from 790~ns to the minimum of 175~ns 
leading to a decisive improvement of the the muon hit reconstruction efficiency.







%The performance of pressurized drift-tube chambers at very high background counting rates
%has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense
%20~MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications
%as large-area precision muon tracking detectors at high-luminosity upgrades of the 
%Large Hadron Collider (LHC). The present ATLAS muon drift-tube (MDT) chambers with
%30~mm tube diameter are designed to cope with $\gamma$ and neutron background rates 
%of up to 500~Hz/cm$^2$ or 300~kHz/tube. Background rates of up to 14~kHz/cm$^2$ and 1150~kHz/tube   
%are expected at LHC upgrades. The test results for $\gamma$ irradiation rates of up to 1400~kHz/tube
%and 8.5~kHz/cm$^2$ and for proton rates up to 2800~kHz/tube and 1330~kHz/cm$^2$ 
%show that by reducing the drift-tube diameter to 15~mm while leaving the other operating parameters 
%unchanged, the rate capability is vastly increased. With the 3.8 times shorter maximum drift time of 185~ns
%the drift-tube occupancy per unit length is reduced by a factor of 7.6. The degradation rate
%of the drift-tube spatial resolution due to space charge effects is reduced by more than 
%an order of magnitude. The shorter maximum drift time allows also for a reduction of the
%adjustable deadtime of the readout electronics from 790~ns to the minimum of 175~ns
%reducing the degradation rate with the background counting rate of the single-tube efficiency 
%for detecting the correct muon hit within 3 times the drift-tube resolution by a factor of 4.
%With improved signal shaping, an improvement by a factor of 6.5 is expected.
%With a maximum of 2 times 6 tube layers, a chamber spatial resolution   
%of better than $40~\mu$m and a tracking efficiency of better than $99\%$ is achieved 
%at background rates reaching far beyond the rates expected at high-luminosity LHC
%with little degradation compared to the performance without irradiation.
 




\end{document}
