Design and Prototyping of Gas Electron Multiplier Chambers for the upcoming MOLLER experiment at Jefferson Lab

MOLLER experiment at JLab is set to measure the parity violating asymmetry in the scattering of longitudinally polarized electrons off unpolarized electrons. This measurement will significantly expand the sensitivity reach to discover new physics beyond the standard model both at lower energy scales(~100 MeV) and at high energy(multi-TeV). In this experiment Gas Electron Multiplier(GEM) detectors, arranged in a circular pattern around the beam pipe, will be used to track individual particles during calibration runs. A GEM chamber consists of 3 GEM foils glued on fiberglass frames and a 2D readout board and has a continuous inside gas flow during operation. The frames have to maintain the stability of the chamber and also the uniform distances between layers. In order to maximize electron detection area, the chamber is designed with a unique trapezoidal shape and a thin curvy edge at the beam pipe side. A complete set of stress-strain analysis and Gas flow simulations were done to ensure that this chamber design performs well under above requirements. A MOLLER GEM chamber prototype is under construction; preliminary test results will be presented.