Reducing the background levels of GEM detectors in high-rate environments due to low-energy photons

The Micro-Pattern Gas Detector group at the University of Virginia (MPGD-UVa) has successfully built various large area Gas Electron Multiplier (GEM) detectors for multiple experiments at JLab. These detectors are capable of meeting all critical requirements of the high luminosity Super Bigbite Spectrometer (SBS) experiments, handling rates as high as 500 kHz/cm², and providing an excellent spatial resolution of 70 µm. However, the high background levels caused by the intense low-energy photon environment in SBS resulted in reduced efficiency, increased difficulty in tracking, and a shorter lifespan of the GEM detectors. Our research focuses on reducing the background hits created in the GEM detector due to radiation interactions (such as the photoelectric effect, Compton scattering, and pair production) with the chamber's components. To achieve this, a Geant4 simulation of a 10cm x 10cm GEM module has been developed to optimize the configuration of the cathode foil and the top GEM foil by varying their materials to mitigate the effects of high background rates. Three different prototypes of 10cm x 10cm GEM modules have been constructed using cathode and top GEM foils with conductive layers made up of three different materials: Al, Cu, and Cr. Data is collected while the prototypes are exposed to a high-intensity X-ray beam in the MPGD-UVa lab to validate the simulated results. The findings from this study will be presented.