Data Acquisition System for Quality Tests of the ATLAS Muon Endcap Trigger Chambers.

Jacek Wasilewski, Andrzej Napieralski, Zbigniew Kulesza
Technical University of Lodz, DEPARTMENT OF MICROELECTRONICS AND COMPUTER SCIENCE, PL

Keywords: Thin Gap Chambers, ATLAS, CERN, Detectors

Abstract:
The ATLAS Collaboration is building a general-purpose pp detector which is design to exploit the full discovery potential of the high energy proton-proton interaction Large Hadron Collider (LHC) at CERN. The LHC offers a large range of physics opportunities, among which the origin of mass at the electroweak scale is a major focus of interest for ATLAS. The detector optimization is therefore guided by physics issues such a sensitivity to the largest possible Higgs mass range. The Thin Gap Chambers (TGCs) are detectors designed to detect the high transverse momentum muons in the endcaps of the ATLAS detector. The short response time of the TGCs makes it an ideal trigger system for selecting interesting events in the highly packed environment of the LHC accelerator. The TGCs are designed and built in Weizmann Institute and are tested at the Tel- Aviv University and at the Technion. The subject of this paper is the design and operation of the data acqusition system, which serves to automatize the procedure of testing the performance of the TGC detector, before are to be installed in the ATLAS experiment. There are three test benches to check the performance of TGC modules, two in Israel, in Technion and Tel-Aviv, and one in Kobe University in Japan. The purpose of this tests is too-fold. For each detector a detailed map of detection efficiency for the wires and strips is determined as well as their respective time resolution. At the test site the TGC units pass the following steps of processing • Preliminary checks • Efficiency test • Validation (Acceptance/Rejection) A visual inspection of the incoming TGC units is performed to check that no damage was done to them during transport.The cosmic ray telescope is 2,2 m high, 1,6 m wide and 2,5 m long. There are 11 slots with a distance of 20 cm between them. The top and the bottom layers consist of scintillators planes. A signal in coincidence from the two planes signals the passage of a cosmic muon. The next layers from the bottom and from the top consist of the so called Precision Chambers. The latter are made of TGC detectors which differ from the tested TGC chambers by their readout granularity. Their role is to accurately measure the positions where the muon crossed the chambers. The schematic diagram of cosmir ray telescope is shown in Figure 1. Accumulating events for a period of one week will permit a full mapping of the efficiency of each detector in the stack. The criteria for a good chamber is having 95% of its active area efficient at level of higher then 95% within a 25 nsec gate. If the unit failed the test it is removed from the test bench and returned to the Weizmann institute. After successfully passing this test, the detectors are flushed with CO2, sealed and prepared for the transportation to CERN.

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