Gamma-Ray Induced Radiation Damage in ${\rm LaBr} _{3}{:}5\char"25{\rm Ce}$ and ${\rm LaCl} _{3}{:}10\char"25{\rm Ce}$ Scintillators

The effect of high dose $^{60}{\rm Co}$ gamma irradiation on photoelectron yield, energy resolution, optical transmission, scintillation time profiles and thermoluminescence glow curves of ${\rm LaBr}_{3}{:}5\%{\rm Ce}$ and ${\rm LaCl}_{3}{:}10\%{\rm Ce}$ crystals has been investigated. Both materials show lower yields and deteriorated resolutions after exposure to a strong $^{60}{\rm Co}$ source, however their transmission, yield proportionality, scintillation decay, and thermoluminescence remain unaffected. Initial scintillation characteristics can be retrieved neither by spontaneous recovery nor upon heating in vacuum.