Behaviour of BeCu dynode photomultiplier tubes in high radiation fields and their use in fast neutron detection

In the course of conducting tests on photomultiplier tubes for use in the ZEUS detector, it was observed that the dark noise current of the tubes increased significantly when they were operated in high radiation fields. The behavior of the RCA 8575 was studied in mixed radiation fields consisting of protons, neutrons, and gamma rays. Pulse-height distribution studies and time-of-flight techniques were used to help determine the contribution to the dark-current increase attributable to each of the components of the radiation field. The studies indicate that neutron interactions with the tube´s BeCu dynodes are likely the most-efficient contributors to the observed increase in dark noise. These observations suggest that it may be possible to develop a fast neutron monitor based on a suitably modified photomultiplier tube with BeCu dynodes.<>