Performance of a large size triple GEM detector at high particle rate for CBM Experiment at FAIR

TL;DR

This paper evaluates a large triple GEM detector's performance at high particle rates, demonstrating high efficiency and stability suitable for the CBM experiment at FAIR, with tests showing minimal efficiency loss and gain variation at rates up to 2.8 MHz/cm².

Contribution

It presents the first large GEM chamber prototype performance results under high-rate proton beam conditions for CBM experiment applications.

Findings

Efficiency > 96% at 375.2 V voltage difference.

Efficiency variation within 2% up to 2.8 MHz/cm².

Gain stability with only ~9% variation at high rates.

Abstract

In CBM Experiment at FAIR, dimuons will be detected by a Muon Chamber (MUCH) consisting of segmented absorbers of varying widths and tracking chambers sandwiched between the absorber-pairs. In this fixed target heavy-ion collision experiment, operating at highest interaction rate of $10~MHz$ for $Au+Au$ collision, after the first MUCH detector station in its inner radial ring will face a particle rate of $1~MHz/cm^2$. To operate at such a high particle density, GEM technology based detectors have been selected for the first two stations of MUCH. We have reported earlier the performance of several small-size GEM detector prototypes built at VECC for use in MUCH. In this work, we report on a large GEM chamber prototype tested with proton beam of momentum $2.36~GeV/c$ at COSY-J\"{u}elich Germany. The detector was read out using nXYTER ASIC operated in self-triggering mode. An efficiency higher than $96\%$ at $\Delta V_{GEM}~=~375.2~V$ was achieved. The variation of efficiency with the rate of incoming protons has been found to vary within $2\%$ when tested up to a maximum rate of $2.8~MHz/cm^2$. The gain was found to be stable at high particle rate with a maximum variation of $\sim~9\%$.