Reducing the background levels of GEM detectors in high rate environments of SBS experiments at JLab

The Gas Electron Multiplier (GEM) detectors built at UVa are used for both front and rear tracking systems for SBS experiments at JLab. These detectors meet all critical requirements of the SBS program, including being able to handle rates as high as 500 kHz/cm2, and providing an excellent spatial resolution of 70 µm. However, a high background resulting from the intense low energy photon environment in SBS leads to reduced efficiency of the GEM detectors. Our research focuses on reducing the background hits created in the GEM detector due to radiation interaction with the chamber components through photoelectric effect, Compton scattering, and pair production processes. To achieve this, a Geant4 simulation of a 10cm x 10cm GEM module has been developed to optimize the cathode foil structure by varying its material, thickness, and effective area to lower the background rates. Prototype 10cm x 10cm GEM modules are constructed with different Cathode foil structures and data is taken while the prototypes are exposed to an X-ray beam in the detector lab at UVa to validate the simulated results.