Development and first results of the Yale PIXeY two-phase xenon detector

Abstract

PIXeY (Particle Identification in Xenon at Yale) is a two-phase (liquid/gas) xenon prototype time projection chamber with 3 kg active mass. PIXeY was built to optimize energy resolution and gamma/neutron discrimination, with a number of technological improvements over previous work. Parallel-wire grids, which control the drift and proportionalscintillation fields, are optimized both for light collection efficiency and field uniformity. High quantum efficiency Hamamatsu R8778 PMTs, high-reflectivity Teflon walls, and charge-light anti-correlation techniques are also incorporated. The first run of the detector has concluded, where all systems were tested both using LED calibration methods as well as using sources for calibration and spectral measurements. Ultimately our results were limited by PMT calibration issues, low light collection caused by saturation, and low drift fields constrained by high voltage hardware. The second run of the detector is currently underway with several improved components. The feedthroughs for higher voltages have improved to allow a much higher operating voltage, new PMT bases for more stable operation have been installed, and three new grids with transparencies between 92% and 97% have been added. Once the energy resolution studies have concluded, PIXeY will serve as a platform for future improvements, including multiple optical volumes and single wire readout for R&D on gamma-ray imaging.