Temperature dependence of NaI(Tl) scintillation spectrometer and it's correction method

The temperature dependence of NaI(Tl) scintillation spectrometer (2'' x 2''φ and 3'' x 3''φ) was investigated in the temperature range of practical operation. The instrument was set in the thermostatic chamber and the temperature was changed by 5degC interval. As the result, the drift of peak position of gamma-rays from 40K and 208Tl was found. We measured environmental radiation in the open air with thermometer to approach the subject in a practical influence. We found that the problem in the temperature dependence of NaI (Tl) scintillation spectrometer was not only the drift of pulse height distribution but the deterioration of energy resolution. To improve these problems, we proposed a simple method to correct pulse height distribution. (author)