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 Nγ=50,000±5000 photons/MeV. This number was deduced from the number of electron–hole pairs produced in the photodiode, Neh=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.