Design of Photomultiplier Socket Assembly with High Gain and Clean Output Signals for Tubes Viewing Organic Scintillator Light Pulses

Abstract

Two of the major problems in designing a socket assembly for a 56AVP photomultiplier viewing light pulses from an organic scintillator have been investigated. They are (1) optimization of the dynode voltage distributions for gain and pulse shape over a wide range of tube gains, and (2) proper grounding of the dynode bypass capacitors and coupling of the coaxial signal leads to the anode and dynodes so that clean signals appear at the output. The effects of varying the dynode voltage distributions were studied and results of improper distributions are discussed. A dynode voltage distribution is given which gave near optimum gain and pulse shape for several different 56AVP's viewing the light pulses from an organic scintillator illuminated by 239Pu alpha particles over a wide range of supply voltages and with anode currents up to 1 A. An electrical and mechanical layout is presented which results in electrically clean pulses from the 14th dynode and anode as well as clean integrated pulses from the lower dynodes; in addition, high gain is realized with adjustment of only the last dynode-to-anode voltage. Photographs of the output signals are shown for a wide range of tube gains, and curves of the relative gain and risetime as a function of tube voltage are given.