Tetrode Photomultiplier Base for High Magnetic Field Environments

A photomultiplier base for scintillation counters has been developed to be used with a four stage multiplier, the Hamamatsu R2107. The design described incorporates a high gain, low noise amplifier, to compensate for the low charge gain, on the order of 600, of the multiplier; the base also contains a discriminator ECL output stage to dtrive a twisted pair cable. The tests of scintillation counters using this base have been carried out in a magnetic field of a few hundred gauss. With only one layer of ferromagnetic shielding for this photomultiplier, efficiencies of > 95% were obtained for signals from minimum ionizing particles. Eighty counters of this type have been fabricated.