Comparative study of ruggedness and reliability of gamma ray detectors based on a commercial high temperature PMT and a Schlumberger PMT at temperatures up to 185°C

We have evaluated gamma ray detectors built with a rugged YAP(Ce) scintillator and two kinds of photomultiplier devices: a commercial rugged PMT (rated for $200 ^{circ}\mathrm {C}$ operation) and a rugged ceramic PMT with a 1-in. window designed and built in house at the Schlumberger Princeton Technology Center. For oilfield applications, gamma ray detectors require reliable and stable performance during hundreds of hours of operation in the harsh well-logging environment (high shock levels and high temperature). Therefore, the focus of this evaluation was on the characterization of the photomultiplier reliability under high temperature and high shock conditions. Several gamma ray detectors have been built with a YAP scintillator (chosen for stable temperature performance) in two configurations: with a commercial high-temperature PMT and a 721x model Schlumberger PMT produced for its oilfield PNX tools [1].