Optimization of the use of small inexpensive side-window photomultiplier tubes for scintillator readout

The 931B is a small inexpensive side-window photomultiplier tube (PMT) which has recently been found to be useful for the readout of scintillators. We present the results of a study to obtain improved performance from the PMT by facilitating the transport of light to the reflection type photocathode. Particular attention is given for the use of these PMTs for the readout of light guides, waveshifting and scintillating fibers. A CCD camera was positioned behind a glass envelope to simulate the photocathode to aid in quantifying the optimum combination of optical coupling and aiming of the fiber. We will also report on tests comparing a similar side-window PMT, the Thorn EMI model 9781B to the 931B. Tests on the operation of the side-window PMT at several orientations in a uniform magnetic field will also be reported. Comparisons between the side-window PMT and a RCA 31000M head-on tube will also be reported.<>