Studying secondary discharges with an optically read out GEM

Abstract

Gas Electron Multiplier (GEM) has become a commonly employed technology for modern high-rate particle and nuclear physics experiments. A key parameter for their long-term sustainability is stability against electrical discharges. Typically, these electrical breakdown events occur within the holes in the GEM foil, but they may also propagate into the gap between subsequent GEM foils resulting in secondary discharges. It is crucial to mitigate secondary discharges since they can result in irreparable damage to the detector. Accordingly, many successful methods have been developed to increase their stability against discharges. However, the propagation of discharges is still not fully understood. In this study, an optically read out GEM detector incorporating a sCMOS camera is developed as a new tool to investigate the formation of secondary discharges. We used optical imaging to capture the time evolution of the light from discharges. Studying the glow in instances leading and not leading to a secondary discharge, we pursue to determine the underlying mechanisms for discharge propagation.