Temperature Effects in Gas-Free Liquid Scintillators

The effects of reduction of temperature on the response of Dumont 6292 and RCA 5819 multiplier phototubes and on the light outputs of the gas-free liquid scintillators DPO, ¿NPO, and PBD, dissolved in xylene, have been measured from room temperature down to -35°C. Both 6292 and 5819 phototubes exhibit a small linear decrease in response with decreasing temperature. The light outputs of the liquid scintillators when excited by alpha particles increase markedly with decreasing temperature. The measurements indicate that under proper conditions it may be possible to obtain a liquid scintillator more efficient for alpha particles than crystal anthracene. Previous data using gamma-ray excitation carried out over a limited temperature range are in agreement with the alpha particle results.