Measuring Reflective Properties of PTFE for Applications in Liquid Xenon Detectors

The XENON100 experiment uses 161kg of liquid xenon divided in two concentric cylinders. The inner volume is the time-projection chamber, the outer volume is the veto, and they are separated by PTFE (Teflon) panels. In the region 350nm to 1200nm, PTFE has a measured reflectivity of 99%. However, xenon emits in the UV region, and the reflectivity distribution is not sufficiently understood here. The XENON group uses a vacuum spectrograph to attempt to determine a reflection distribution for the PTFE that encloses the XENON100 TPC. The spectrograph will be used to measure a reflectivity distribution for the type of PTFE used in the detector. Measurements will be repeated after the PTFE sample is cooled to deduce the effect of low temperature on the reflectivity distribution. In the future, this same tool can also be used to determine how low temperatures affect the quantum efficiency of the PMTs used in the XENON100 experiment.