Design and fabrication of the GEM detector for MOLLER experiment*

The proposed MOLLER experiment at JLab will be measuring the parity violating asymmetry of longitudinally polarized electrons off unpolarized electrons. This measurement is aimed to expand the sensitivity to discover new physics beyond the standard model. Gas Electron Multiplier(GEM) detectors will be used in this experiment for spectrometer calibration and background measurements. The design and fabrication of a fully functional prototype GEM detector module were successfully completed at the University of Virginia in December. The prototype module was able to fulfill the mechanical stability and performance requirements during and after the fabrication process. The module was tested for low environments with cosmic particles, and will be tested for high environments with X-ray. The test results and observations of the prototype will be used in making adjustments to the detector module design, before starting the production of 32 GEM detector modules needed for the experiment. The steps of designing and fabrication of the detector prototype, and the results of the performance tests will be presented.