MainPage:Nuclear:Summer2014:PMTCharacterization

Abstract

The purpose of this project is to characterize large-diameter photomultiplier tubes (PMT) through scans along the surface of the PMT with a low-intensity, focused LED, thereby creating a plot of the surface area of the PMT with the gain at each section. Scanned PMTs can be better used in other testing because more is known about the gain across the entire front face, and thus if only a few photons need to be detected by the PMT, it can be better setup to detect those small amounts of light by positioning a spot with a higher gain in front of the source. The method of scanning said PMTs consists of a two axis step motor moving an LED light source on a 100 x 100 grid opposite the face of the PMT, with 30 pulses of light from the LED at each step. The step motor with a step of 1.8 degrees is moved 450 times each step resulting in a step length of…. (need to figure out the thread size to calculate this). Scans conducted in this manner have a high enough resolution to pick up most sensitive/non-sensitive spots on a PMT including the three supports along the side of the PMT which support the dynodes and other components inside the PMT. While this method of scanning PMTs has been conducted in the past, including at The Catholic University of America, the current scanning method will be used to characterize a PMT from the University of Virginia.