Stability tests performed on the triple GEM detector built using commercially manufactured GEM foils in India

The Gas Electron Multiplier (GEM) technology is based on thin polymer foils cladded with copper on both the sides with a regular matrix of holes. Due to the limited manufacturing capacity of CERN, these GEM foils are now commercially manufactured also by Micropack Pvt. Ltd., a company based in India. In order to gain an insight on the behaviour of detectors built using the foils from Micropack, it is important to study various long and short term effects on these foils due to the applied voltage as well as the flux of the incident particles. In this paper, we report the effect on gain stability of triple GEM detectors due to the polarising field induced by X-rays on the polyimide foils. Also, reducing the size of the amplifying structure to the microscopic scale results in a quick mitigation of the space charge effects which in turn helps in attaining a stable gain at very high incident flux. We report on the measurements of variations in the effective gain at very high particle flux of the order of MHz/mm².