Development of fast high-resolution muon drift-tube detectors for high counting rates

✍ Scribed by B. Bittner; J. Dubbert; S. Horvat; O. Kortner; H. Kroha; F. Legger; R. Richter; S. Adomeit; O. Biebel; A. Engl; R. Hertenberger; F. Rauscher; A. Zibell

• Publisher: Elsevier Science
• Year: 2011
• Tongue: English
• Weight: 648 KB
• Volume: 628
• Category: Article
• ISSN: 0168-9002
• DOI: 10.1016/j.nima.2010.06.306

✦ Synopsis

Pressurized drift-tube chambers are efficient detectors for high-precision tracking over large areas. The Monitored Drift-Tube (MDT) chambers of the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC) reach a spatial resolution of 35 mm and almost 100% tracking efficiency with 6 layers of 30 mm diameter drift tubes operated with an Ar:CO 2 (93:7) gas mixture at 3 bar and a gas gain of 20 000. The ATLAS MDT chambers are designed to cope with background counting rates due to neutrons and g rays of up to about 300 kHz per tube which will be exceeded for LHC luminosities larger than the design value of 10 34 cm À 1 s À 1 . Decreasing the drift-tube diameter to 15 mm while keeping the other parameters, including the gas gain, unchanged reduces the maximum drift time from about 700 to 200 ns and the drift-tube occupancy by a factor of 7. New drift-tube chambers for the endcap regions of the ATLAS muon spectrometer have been designed. A prototype chamber consisting of 12 times 8 layers of 15 mm diameter drift tubes of 1 m length has been constructed with a sense wire positioning accuracy of 20 mm. The 15 mm diameter drift-tubes have been tested with cosmic rays in the Gamma Irradiation Facility at CERN at g counting rates of up to 1.85 MHz.