Readout, commissioning and optimization of GEM Detector prototype for MOLLER experiment*

The Measurement of a Lepton-Lepton Electroweak Reaction (MOLLER) experiment proposes to measure the parity-violating asymmetry in electron-electron scattering. Experiment will be carried out at Jefferson Laboratory with the upgraded 12GeV electron beam by rapidly flipping the longitudinal polarization of the electrons. Gas Electron Multiplier Detectors will be used to measure the background of the experiment. A prototype GEM detector for MOLLER was designed and fabricated at UVa. In December 2022 this detector was commissioned and tested using APV-25 chip based Scalable Readout System (SRS) readout at the detector development laboratory at UVa. Prototype operation was very stable holding the required high voltage for extended periods of time. Initial high pedestal noise read by the SRS readout was improved significantly after slight modifications to the detector groundings. Cosmic data taken confirms good performance of the detector under a low rate environment. Prototype will be exposed to high intensity x-rays to confirm the performance under a high rate environment. Results from cosmic and x-ray testing will be presented. These results will be important in moving on to the manufacturing stage of MOLLER GEMs, and for the future detector development in general.