Photomultiplier tube calibration for the Cubic Meter Dark Matter Time Projection Chamber

Abstract

This thesis concerns measurements I performed on photomultiplier tubes (PMTs) and lenses to be used in the Cubic Meter Dark Matter Time Projection Chamber (DMTPC) experiment. DMTPC is a new generation of detector, which takes the idea of a standard time projection chamber and adds in some additional optical elements, such as CCDs and PMTs. The goal of DMTPC is the directional detection of the dark matter. During the course of my measurements, I characterized both the absolute gains of DMTPC's eight PMTs, as well as the dark currents exhibited by each of the PMTs. Seven of the eight PMTs demonstrated gains on the order of 10 6-10 7, and one PMT did not function at all. Of the seven working PMTs, six of them had dark currents under 10 kHz, and one had an excessively high dark current over 10 kHz. These gain values for the PMTs will give DMTPC the means to measure the Z dimensions of the particle tracks it intends to image, and thus when combined with the information from the CCDs will allow for full track reconstruction. DMTPC will use lenses on their CCD cameras, and I also measured the transparency of these lenses, and discovered that they are opaque below approximately 350nm. These measurements will be essential for DMTPC, because they will provide information about the relative amounts of light the PMTs and CCDs on the detector will register, and thus provide key information for track reconstruction.