W. L. Ebenstein

Particle identification using the time-over-threshold method in the ATLAS Transition Radiation Tracker

Abstract Test-beam studies of the ATLAS Transition Radiation Tracker (TRT) straw tube performance in terms of electron–pion separation using a time-over-threshold method are described. The test-beam data are compared with Monte Carlo simulations of charged particles passing through the straw tubes of the TRT. For energies below 10 GeV , the time-over-threshold method combined with the standard transition-radiation cluster-counting technique significantly improves the electron–pion separation in the TRT. The use of the time-over-threshold information also provides some kaon–pion separation, thereby significantly enhancing the B-physics capabilities of the ATLAS detector.

Straw tube drift-time properties and electronics parameters for the ATLAS TRT detector

Abstract The basic drift-time measurement properties of the proportional tubes (straws) of the ATLAS TRT detector and the impact of the parameters of the front-end electronics on performance are discussed. The performance of two different front-end electronics prototypes has been studied in detail at very high counting rate and is reported here.

Electron identification with a prototype of the Transition Radiation Tracker for the ATLAS experiment: ATLAS TRT collaboration

Abstract A prototype of the Transition Radiation Tracker (TRT) for the ATLAS detector at the LHC has been built and tested. The TRT is an array of straw tubes which integrate tracking and electron identification by transition radiation into one device. Results of experimental measurements and of comparisons with Monte-Carlo simulations are presented for the electron identification performance as a function of various detector parameters. Under optimal operating conditions, a rejection against pions of a factor 100 was achieved with 90% electron efficiency.

Recent aging studies for the ATLAS transition radiation tracker

The transition radiation tracker (TRT) is one of the three subsystems of the inner detector of the ATLAS experiment. It is designed to operate for 10 yr at the LHC, with integrated charges of /spl sim/10 C/cm of wire and radiation doses of about 10 Mrad and 2/spl times/10/sup 14/ neutrons/cm/sup 2/. These doses translate into unprecedented ionization currents and integrated charges for a large-scale gaseous detector. This paper describes studies leading to the adoption of a new ionization gas regime for the ATLAS TRT. In this new regime, the primary gas mixture is 70%Xe-27%CO/sub 2/-3%O/sub 2/. It is planned to occasionally flush and operate the TRT detector with an Ar-based ternary mixture, containing a small percentage of CF/sub 4/, to remove, if needed, silicon pollution from the anode wires. This procedure has been validated in realistic conditions and would require a few days of dedicated operation. This paper covers both performance and aging studies with the new TRT gas mixture.

A super high rate straw drift chamber

Abstract We have devised a technique to read out a sense wire inside a straw tube in many independent sections without bulky plates between sections, thus reducing the occupancy considerably. Based on this technique, a prototype chamber is constructed, which is suitable for extremely high rate environments.

Tracking performance of the transition radiation tracker prototype for the ATLAS experiment

A prototype of the Transition Radiation Tracker (TRT) for the ATLAS experiment at the CERN LHC has been built and tested at the CERN SPS. Detailed studies of the drift-time measurements, alignment technique, hit registration efficiency, track and momentum accuracy were performed. A coordinate measurement accuracy of 150 Pin for a single TRT drift tube and momentum resolution of 0.8% for 20 GeV pions in a 1.56 T magnetic field were achieved. The results obtained are in agreement with the expected tracking performance of the ATLAS TRT

An X-ray scanner for wire chambers

The techniques to measure the position of sense wires and field wires, the gas gain and the gas flow rate inside wire chambers using a collimated and filtered X-ray beam are reported. Specific examples are given using barrel modules of the Transition Radiation Tracker of the ATLAS experiment.

Acceptance tests and criteria of the ATLAS transition radiation tracker

The Transition Radiation Tracker (TRT) sits at the outermost part of the ATLAS Inner Detector, encasing the Pixel Detector and the Semi-Conductor Tracker (SCT). The TRT combines charged particle track reconstruction with electron identification capability. This is achieved by layers of xenon-filled straw tubes with periodic radiator foils or fibers providing TR photon emission. The design and choice of materials have been optimized to cope with the harsh operating conditions at the LHC, which are expected to lead to an accumulated radiation dose of 10 Mrad and a neutron fluence of up to 2middot1014 n/cm2 after ten years of operation. The TRT comprises a barrel containing 52 000 axial straws and two end-cap parts with 320 000 radial straws. The total of 420 000 electronic channels (two channels per barrel straw) allows continuous tracking with many projective measurements (more than 30 straw hits per track). The assembly of the barrel modules in the US has recently been completed, while the end-cap wheel construction in Russia has reached the 50% mark. After testing at the production sites and shipment to CERN, all modules and wheels undergo a series of quality and conformity measurements. These acceptance tests survey dimensions, wire tension, gas-tightness, high-voltage stability and gas-gain uniformity along each individual straw. This paper gives details on the acceptance criteria and measurement methods. An overview of the most important results obtained to-date is also given