Optimization of High Voltage Distribution of Gas Electron Multiplier (GEM) Detectors for High Particle Rate at Jefferson Lab*

Measurement of the Neutron Magnetic Form Factor, GMn, experiment was completed in February 2022 at the Jefferson Laboratory. During the experiment large area Gas Electron Multiplier (GEM) Detectors had to be operated under unprecedented high hit rates exceeding 100 kHz/cm2. This resulted in high drain currents from high voltage divider leading to modified potential differences applied to the detector and lowered efficiencies. To rectify this a number of modifications were applied to the high voltage distribution of the detector. All modifications were tested using a 50 cm x 60 cm GEM chamber exposed to an X-ray beam at the University of Virginia. Initial modifications were tested at beam condition during the experiment in which the detector efficiency improved significantly. Modified high voltage schemes and characterization measurements will be valuable for future high rate GEM detector operations. Final modifications are to be tested during the upcoming experiment, Measurement of the Neutron Electric Form Factor, GEn. Preliminary results relevant to detector efficiency from the GEn experiment and from a simulated high rate environment at University of Virginia will be presented.