Improvements in the Making of Special Photographic Emulsions for Nuclear Physics

Abstract

Low counter sensitivity is a serious limitation in many investigations. Sensitivity may be slightly increased by using Geiger-Muller tubes end-on, but even using the commercial end-window tubes,only 2-4% of the incident rays from calibrated 1131, Co60, and radium sources gave rise to registered counts, or the sensitivity of this system was 2-4%. Using CaWO4 crystals as scintillation counters in conjunction with a 1P21 photomultiplier and a Lucite rod between aluminum-foil-covered crystal and the photomultiplier. sensitivities of 24%, 38%, and 36% for Co60, radium, and I131, respectively, were obtained. Removal of Al foil, or Lucite rod, or both, and decrease in crystal thickness all decrease the sensitivity of the system. Curves of counts/min. as a function of pulse height are presented for various conditions.