Quality control and beam test of GEM detectors for future upgrades of the CMS muon high rate region at the LHC

Abstract

Gas Electron Multipliers (GEM) are a proven position sensitive gas detector technology which nowadays is becoming more widely used in High Energy Physics. GEMs offer an excellent spatial resolution and a high particle rate capability, with a close to 100% detection efficiency. In view of the high luminosity phase of the CERN Large Hadron Collider, these aforementioned features make GEMs suitable candidates for the future upgrades of the Compact Muon Solenoid (CMS) detector. In particular, the CMS GEM Collaboration proposes to cover the high-eta region of the muon system with large-area triple-GEM detectors, which have the ability to provide robust and redundant tracking and triggering functions. In this contribution, after a general introduction and overview of the project, the construction of full-size trapezoidal triple-GEM prototypes will be described in more detail. The procedures for the quality control of the GEM foils, including gain uniformity measurements with an x-ray source will be presented. In the past few years, several CMS triple-GEM prototype detectors were operated with test beams at the CERN SPS. The results of these test beam campaigns will be summarised.

Development, characterization and qualification of first GEM foils produced in India

“…Electrical properties of the GEM foils were discerned by measuring its leakage current extended over a period of time after proper cleaning using adhesive roller. We divide electrical tests mainly in two types, quality control short or fast (QC fast) and quality control long (QC long) as per the CERN standards of quality control classification [23], which requires these two tests to be done in order to qualify these foils. The difference between QC fast and QC long lies in applying voltage for shorter or longer periods of time respectively, and monitoring the current.…”

Characterization of the water diffusion in GEM foil material

“…Furthermore, the measurements showed the presence of 0.004 g water at saturation level, compatible with what is obtained from the official datasheet by the manufacturer [6] or from the formula (1) for a value of RH = 37.5%. VKapton = 0.2625cm 3 (2) P Kapton = V Kapton * ρ Kapton = 0.2609g ( 4)…”

“…Due to its high rate capability 1MHz/cm 2 [2], excellent position and timing resolution, the GEM detector can easily meet the requirements of the high pseudorapidity region where a high particles flux is expected. The major part of the detector is the GEM foil where charge amplification phenomena occur in the presence of intense electric filed in the conical shape micro holes within a thickness of 60µm (50µm kapton cladded with 10µm copper on both sides) The installation of the triple-GEM detectors into muon stations at the end-cap region, as shown in figure 1, will improve muon momentum resolution, help to reduce the global muon trigger rate, assure a high muon reconstruction efficiency and increase offline muon identification coverage [3]. The GEM foil is exposed to water because of production process, and because of possible leaks allowing atmospheric humidity to enter the gas volume.…”

CMS GEM detector material study for the HL-LHC

“…The Gaseous Electron Multiplier (GEM) detector has been approved for the upgrade of the forward muon system of Compact Muons Solenoid (CMS) at Large Hadron Collider (LHC). The GEM detector provides good timing and position resolution and it meets the particle detection requirements in the eta region 1.6 < η < 2.2, where high particle flux 5 kHz/cm 2 is expected [2] [3]. The principal component of the detector is a GEM foil (Cu-cladded (5µm), micro perforated 60 µm-thick kapton film), that provides charge amplification thanks to the conical shape of very dense micro holes.…”