D.J. White

Study of straw proportional tubes for a transition radiation detector/tracker at LHC

Abstract The most relevant properties for operation of straw proportional tubes at LHC are described. Particular attention is paid to the possibility of straw operation in a strong magnetic field and a high radiation environment.

The Atlas TRT straw proportional tubes: performance at very high counting rate

Abstract Results on analog front-end electronics and straw performance studies at high counting rates are described. Prototypes of the electronics have been tested at counting rates up to 17.5 MHz. A drift-time accuracy of 180 μm and a drift-time measurement efficiency of 53% were obtained at 17.5 MHz. The expected counting rate is between 5 and 15 MHz (depending on straw position) for the Atlas straw tracker at LHC design luminosity, leading to an estimated drift-time accuracy at 160 μm and hit registration efficiency of 68% for the average counting rate of 10 MHz. These results are in a good agreement with detailed MC simulations and could be improved with better front-end electronics.

System tests of radiation hard optical links for the ATLAS semiconductor tracker

A prototype optical data and Timing Trigger and Control transmission system based on LEDs and PIN-diodes has been constructed. The system would be suitable in terms of radiation hardness and radiat ...

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.

The design, status and performance of the ZEUS central tracking detector electronics

Abstract The readout system developed for the ZEUS central trackign detector (CDT) is described. The CTD is required to provide an accurate measurement of the sagitta and energy loss of charged particles as well as provide fast trigger information. This must be carried out in the HERA environment in which beams cross every 96 ns. The first two aims are achieved by digitizing chamber pulses using a pipelined 104 MHz FADC system. The trigger uses a fast determination of the difference in the arrival times of a pulse at each end of the CTD. It processes this data and gives information to the ZEUS global first level trigger. The modules are housed in custom-built racks and crates and read out using a DAQ system based on Transputer readout controllers. These also monitor data quality and produce data for the ZEUS second level Trigger.

The technique of z-coordinate determination using a time-difference measurement for the zeus central tracking detector

A method to determine the z-coordinate of a track using a time-difference measurement has been developed for the ZEUS Central Tracking Detector. It has been demonstrated that a spatial resolution of 50 mm can be obtained under normal chamber operating conditions. This corresponds to a time-difference resolution of 330 ps. A method of minimizing nonlinearities in the time-to-distance response is described. This uses an inductor to form a matching network to achieve resistive termination of the chamber. Test beam measurements from a prototype chamber are presented, demonstrating the effects of the chamber surface field and beam incidence angle on the time-difference resolution.

Radiation-hard optoelectronic data readout for the ATLAS SCT

The ATLAS experiment is currently in the final pre-production design phase to allow timely installation at the CERN Large Hadron Collider in 2005. The sub-systems closest to the interaction point--the tracking detectors, will be subject to significant total radiation dose at high flux. Optical data transmission has been chosen for the Pixel and SemiConductor Tracker to both deliver timing and control information to the detector modules and transmit tracking data to the remote counting room. Of considerable concern is the radiation hardness, both transient and total dose, of not just the optoelectronic components but also the driver/receiver electronics. In this paper we report on total dose radiation testing of the VCSEL driver and photodiode receiver ASICs designed using a range of techniques in a nominally radiation-soft process. Both ASICs will be shown to be tolerant to a total gamma dose of 100 kGy and a total neutron fluence (1 MeV equiv.) of 2 X 1014 n/cm2, as required for this system. Single-event upset (SEU) studies have also been carried out using a high-energy pion beam, showing the system to be sufficiently robust to SEU at an ATLAS- like particle flux.

The design and performance of the ZEUS Central Tracking Detector z-by-timing system

Abstract The ZEUS Central Tracking Detector utilizes a time difference measurement to provide a fast determination of the z coordinate of each hit. The z -by-timing measurement is achieved by using a Time-to-Amplitude Converter which has an intrinsic timing resolution of 36 ps, has pipelined readout, and has a multihit capability of 48 ns. In order to maintain the required sub-nanosecond timing accuracy, the technique incorporates an automated self-calibration system. The readout of the z -by-timing data utilizes a fully customized timing control system which runs synchronously with the HERA beam-crossing clock, and a data acquisition system implemented on a network of Transputers. Three dimensional space-points provided by the z -by-timing system are used as input to all three levels of the ZEUS trigger and for offline track reconstruction. The average z resolution is determined to be 4.4 cm for multi-track events from positron-proton collisions in the ZEUS detector.