New photomultiplier active base for Hall C jefferson lab lead tungstate calorimeter

A new photomultiplier tube active base was designed and tested. The base combines active voltage division circuit and fast amplifier, powered by the current flowing through voltage divider. This base is developed to upgrade older photomultiplier bases of Jefferson Lab lead-tungsten calorimeter (about ~1200 crystals of PbWO₄ from the PrimEx experimental setup). This is needed for the extension of detectors´ rate capability to meet requirements of new Hall C proposal PR12-11-102 of measurements of the LIT separated cross sections and their ratio R = αL/αT in neutral-pion p(e,e´π⁰)p deep exclusive and p(e,e´no)X semi-inclusive scattering regions. New active base is direct replacement of older passive base circuit without adding of additional power or signal lines. However, it extends detectors rate capability with factor over 20. Moreover, transistorized voltage divider improves detector´s amplitude resolution due to reduction of photomultiplier gain dependence from tube anode current. The PMT active base is the invention disclosed in V. Popov´s U.S. Patent No. 6,791,269, which successfully works over ten years in several Jefferson Lab Cherenkov detectors. The following design is a new revised and improved electronic circuit with better gain stability and linearity in challenge to meet requirements of new Hall C experimental setup. New active base performance was tested using fast LED light source and Pr:LuAG scintillator and gamma sources. Electronics radiation hardness was tested on JLab accelerator. Results of testing R4125 Hamamatsu photomultiplier tube in new active base are presented.