Speakers
Description
To extend the acceptance of the CMS muon spectrometer to the region 2.4<|η|<2.8, stations of triple-GEM chambers, called ME0, are planned for the CMS Phase 2 Upgrade. These large-area, micro-pattern gaseous detectors must operate in a challenging environment with expected background particle fluxes up to 150 kHz/cm2. Unlike traditional non-resistive gaseous detectors, the rate capability of large-area triple-GEM detectors is limited not by space charge effects, but by voltage drops on the chamber electrodes due to avalanche-induced currents flowing through the resistive protection circuits. We present a study of the irradiation of large-area triple-GEM detectors with moderate fluxes to obtain a high integrated hit rate. The results show drops as high as 40% of the nominal detector gas gain, which would result in severe loss of tracking efficiency. We discuss possible mitigation strategies leading to a new design for the GEM foils with electrode segmentation in the radial direction, instead of the “traditional” longitudinal segmentation. The advantages of the new design include maintenance of a uniform hit rate across different sectors, minimization of gain-loss without the need for voltage compensation, and independence of detector efficiency on background flux shape.
| First author | CMS |
|---|---|
| arnd.meyer@cern.ch | |
| Collaboration / Activity | CMS |
