Characteristics changes of unsealed NaI(Tl) detector under atmospheric moisture effect

S.I.Vasetsky, A.S.Gershun, V.Yu.Gres`, A.M.Kudin, T.A.Charkina, G.I.Yakhnis

Institute for Single Crystals, National Academy of Sciences of Ukraine, 60 Lenin Ave., 310001 Kharkiv, Ukraine

Received March 6, 1998

The light yield and energy resolution impairment of NaI(Tl) crystals being stored unsealed is associated with changes in the scintillation efficiency, e , and the light collection coefficient, t. It is just the depletion of the crystal in activator that is responsible for the e deterioration in the near-surface "dead" scintillator layer while changes in t are due to the surface enrichment in thallium, no matter what is the detector size. A simple test is proposed to detect the initial stages of the crystal moistening influenced on the NaI(Tl) crystal properties.

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