Speaker
Description
Summary
For the detector commissioning at LHC planned in 2007, a sector assembly of the ATLAS muon-endcap
chambers is progressed intensively in CERN. The thin gap chamber (TGC) is used for the muon-endcap trigger
system. The muon endcap system covers the both endcaps of the detector (1.1<abs(eta)<2.4) to detect
isolated muons and give the level-1 muon trigger signal with two ranges of the transverse momentum (pt) of
low-pt > 6 GeV/c and high-pt > 20 GeV/c.
As at least three measurement points per track is necessary to identify a muon with even such coarse
momentum estimation, there are three TGC discs per endcap (one has three layers with triplet chambers, and
the other two discs have two layers each with doublet chambers). Every disc has commonly twelve sectors.
This 1/12 sector is a construction unit for the trigger muon endcap system for both the chambers and
electronics. The sector is also the unit for the trigger and readout system.
The electronics systems mounted on a sector are the front-end ASD (Amplifier-Shaper-Discriminator),
readout chain (pipeline buffers, derandomizers and parallel/serial converter), trigger decision logic for the
level-1 low-pt muon candidate signals, miscellaneous control and test circuits and Detector Control System
(DCS). We also mount modules for high-pt decision logic as well as readout data concentrator nearby the
sector, but these are not directly mounted on it.
Once the sector is installed in the whole ATLAS detector system in the cavern, one cannot access easily its
electronics as well as cables. We have to test the electronics system after completion of the sector and fix or
repair quickly if we find incomplete connection of cables or damage of electronics components. Furthermore
since the system involves the level-1 trigger generation logic, timing adjustment of the electronics at this
assembly stage is also the key issue from the signal synchronization point of view.
In order to check all the functionalities and adjust timing of the electronics system, it is necessary to do
almost full DAQ operation to the sector. We have made a lot of DAQ systems so far for the standalone
electronics consistency check or the integrated beam test with TGCs using the high energy muon beam. These
DAQ systems constructed have been dedicated for specific purposes, but none of them can be used in the
actual ATLAS online system, although various software codes in particular for individual module controls are
re-usable with minor modification. For the present electronics test of the sector assembly, we have reformed
the DAQ system once more. We made it with being fully complied with the ATLAS online software framework.
In this presentation we will describe the installation and mass-test procedure of electronics using this DAQ
system in detail and some experience to fix problems encountered actually in the sector assembly. We would
like to discuss the timing adjustment procedure in detail. If the adjustment in the sector level is done well,
then the timing signals in larger parts (disc, side or overall muon endcap) will be smoothly synchronized. We
discuss finally the front-end DAQ system itself and how we have evolved the system through the verification
process of the electronics installation.
