Speaker
Mr
Yasuyuki Okumura
(Nagoya University)
Description
The ATLAS Level1 endcap muon trigger selects interesting events containing muons with Pt greater than 6GeV/c from 40MHz proton-proton collisions. This system consists of 3,600 Thin Gap Chambers (TGCs) and the total number of readout channels is 320,000. This trigger logic is based on the coincidence between 7 layers of TGCs. All processes are performed on fast electronics within 2.5 micro seconds. To be ready for the first beam scheduled in 2008, we have succeeded in sending trigger signal of cosmic-ray muons with the synchronous operation at 40MHz and a fine signal timing adjustment. We will report on status of the commissioning and results from combined runs with other ATLAS detectors.
Summary
The ATLAS Level1 trigger system selects interesting events from the large amount of events produced with proton-proton collision. This system works as a pipeline trigger system with the 40MHz operation clock which is synchronous to the LHC proton-proton collision. The processing latency is required to be less than 2.5micro seconds. The reduction power is 100kHz from 40MHz.
The Level1 endcap muon system selects the interesting events which contains muons with Pt greater than 6 GeV/C, by estimating the muons momentum with 6 thresholds. The coverage of the endcap muon system is from eta=1.05 to 2.40. This system consists of 3,600 Thin Gap Chambers (TGCs) and the total number of readout channels is 320,000. The TGCs are wire chambers working in a limited proportional mode. The anode-to-cathode distance being 1.4 mm which leads to fast signals is consistent with the 40MHz collision rate. The 7 layers of TGCs are located in each endcap region of ATLAS detector. This trigger system checks the curvature of muons in toroidal-magnet field from the hit pattern on 7 layers, in order to estimate the transverse momentum. This process is performed by the fast electronics to make a trigger decision within the required latency. The trigger logic is based on the coincidence between 7 layers of TGCs. Every trigger module has delaying functionalities in each input port for timing adjustment, especially between layers.
By the end of April 2008, the TGCs and almost all infrastructures have been installed in ATLAS cavern, including the 100m optical fiber links between the experimental hall and the counting room. All electronics can be controlled from the ATLAS Control Room. The commissioning run with test pulse and cosmic ray signal is now in progress. With the test pulse signal, the timing adjustment between channels in the various layers has been implemented. With the cosmic-ray muon signal, we succeeded in sending the trigger signal to all ATLAS detectors. This was performed with all trigger modules under the synchronous operation to 40MHz, which is send to all the system as global operation clock.
For the first beam commissioning runs scheduled in 2008, various hardware bugs have been found, and fixed. In combined cosmic runs with all other ATLAS Detectors included, we succeeded in operating in a synchronous mode, and sending trigger signals from a multi-layers coincidence. From these results, it is confirmed that the all timing functionalities operate correctly; Furthermore we performed the signal timing adjustment with accuracy of 1ns in an environment that include a large amount of trigger modules. The scheme for the TGCs and Level1 endcap muon trigger system has been established with final infrastructures.
Primary author
Mr
Yasuyuki Okumura
(Nagoya University)
