Measuring the gain of a photomultiplier tube

Photomultiplier tubes (PMTs) are used to detect light that comes from gamma-ray-initiated showers in the earth's atmosphere. The gains of the PMTs are key to determining the amount of light detected and, subsequently, the energy of the incoming gamma ray. In this thesis, a new method of measuring the gain of a PMT is proposed. It relates the PMT gain to the variance of the PMT signal divided by the average current. The new method is mathematically motivated, tested with a series of experiments, and verified using simulations. In addition, it is compared with an existing method of measuring the gain. The new method is shown to be able to predict the gain to within a constant of multiplication. This constant is intrinsic to each PMT and varies from one PMT to another