Bochum 1998 – wissenschaftliches Programm
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HK: Hadronen und Kerne
HK 60: Instrumentation VI, Detector Systems
HK 60.1: Gruppenbericht
Donnerstag, 19. März 1998, 14:00–14:30, A
Development of the PesTOF Time of Flight Counter for the LHC experiment ALICE — •U. Frankenfeld1, E. Badura1, J. Eschke1, J. Luehning1, U. Lynen1, C. Neyer1, Yu. Pestov2, H. Sann1, H.-R. Schmidt1, B. Schreiber1, R. Schulze1, H. Stelzer1, and A. Wörner1 — 1Gesellschaft für Schwerionenforschung, Darmstadt — 2Budker Institute of Nuclear Physic, Novosibirsk, Rußland
The PesTOF Spark Counter (gaseous parallel-plate detector working in the streamer/spark mode) is a very promissing option for the ALICE-TOF system. It makes use of a semi-conductive anode and a highly quenching gas mixture to limit the spark discharge to an area of 1−2 mm2. The time resolution depends on the overvoltage (voltage above spark threshold) applied over the spark gap which can be as good as 25 ps. The counter is operated at a pressure of 12 bar in order to obtain 4-5 primary electrons from a minimum ionizing particle which results in an efficiency of ≥ 95%. The counter is read out via strip lines, which allow a two-dimensional position reconstruction with high precision. We have built new prototype PesTOF counters which have already many of the mechanical features foreseen for their application for ALICE. In order to stay within reasonable cost margins one of the R&D goals is a counter which is suitable for mass production. The performance of new prototype Spark Counters was measured both in test beams as well as in the framework of the NA49 experiment. Furthermore, the long term stability was investigated in a dedicated laboratory setup. In order to cope with the specific features of the spark pulse a new type of double threshold discriminator (DTD) has been developed and prototype chips have been produced and tested on the counter. Also, several TDC concepts have been implemented as ASIC’s and first test results are available.
The performance parameters of the new prototype are close to those expected from previous measurements at Novosibirsk. The long term stability test, in which up to 9 counters were operated at ALICE conditions (4.5 kV, 10 Hz/cm2 rate), showed stable operation over the whole test period (280 days).
Another important part of the investigations which will be presented is the search for new gas mixtures,