12th Vienna Conference on Instrumentation - VCI 2010

Performance of the LHCb Muon System Triple-GEM detectors with First LHC Data

Not scheduled

HS 1 (TU Vienna)

Board: B23

Poster C

Speaker

Dr Davide Pinci (INFN - Sezione di Roma, Italy)

Description

Triple-GEM detectors with digital pad readout were chosen for the innermost region of the first LHCb muon station thanks to their excellent performances, in particular for what concerns rate capability and radiation hardness. These detectors, together with the MWPC used in the rest of the muon system, are used to built the muon trigger, operating at 40 MHz. Triple-GEM detector were constructed in INFN Cagliari and LNF and were installed on the experiment in Spring 2009. Installation was then followed by an extensive commissioning, and events were acquired with both pulser and cosmic triggers, to perform a careful detector timing and to optimize thresholds and HV operating point. Even with the low statistics available with current cosmic's data, Triple-GEM detectors show the expected performances. This presentation will focus on the installation, test, commissioning and first LHC beam performance of the LHCb Triple-GEM detector, the first Triple-GEM detector approved for installation in an LHC experiment and also the first one going into operations.

Summary (Additional text describing your work. Can be pasted here or give an URL to a PDF document):

Triple-GEM detectors with pad readout were chosen for the innermost region of the first LHCb muon station because, while meeting the performances required for the muon detector, they also showed a high rate capability and a very good radiation hardness that will permit a safe operation of these detectors during the 10 years experiment lifetime.

Triple-GEM detectors are used to construct the muon trigger condition at the lowest trigger level (40 MHz). The muon trigger requires that 5/5 stations fires to give a muon trigger. To increase trigger efficiency and system reliability each chamber is made of a pair of Triple-GEM detector, and the signal coming from each pad, after discrimination, is logically OR-ed with the corresponding pad of the facing detector.

After some years of R&D work the final detectors were built at INFN Cagliari and LNF in 2007 and were finally installed on the first muon station, M1, in Spring 2009. The M1 installation work was completed by mid-July, and was followed by extensive tests and commissioning of the detectors, in particular to perform the careful time alignment needed for the trigger. During October 2009 the full LHCb muon detector was commissioned with cosmics to improve the detectors' timing using real particles triggered by the calorimeters. Thresholds and HV operating point were also optimized, and spatial alignment was also verified.

Even if the cosmic rate in the LHCb cavern does not provide us with a sufficient statistics to perform significant measurements at the level of each front-end channel for the Triple-GEM chambers, a preliminary analysis show that these detectors exhibit the expected performances.

This presentation will focus on the installation, test and commissioning issues, and with cosmics and first beam performance of the LHCb Triple-GEM detector, the first Triple-GEM detector approved for installation in an LHC experiment and also the first one going into operations.