Temperature dependence of pure CsI: scintillation light yield and decay time

The temperature dependence of the light emission for pure CsI crystals has been measured with photomultipliers, and photodiodes with wavelength shifters from 80-300 K. The light yield at 80 K is N subgamma=50,000+-5000 photons/MeV. This number was deduced from the number of electron-hole pairs produced in the photodiode, N sub e sub h =39,600+-1200. The light yield at room temperature is lower by a factor of 15.8+-1.0, giving 3200+-400 photons/MeV. Decay times were measured with a photomultiplier. At room temperature two fast decay components were observed with decay times of 6+-1 and 28+-2 ns. Below 180 K only one component is observed and at 80 K the decay time is 1015+-17 ns.