Light output tuning for the long-length CsI(Tl) scintillators

Control over the mirror reflectivity of scintillator surfaces which is exerted due to imparting a special kind of roughness on crystal surfaces is one of the most technologically relevant, and thus commonly applied techniques of the assigned light output distribution in the detectors. As regards long-sample detectors (the ratio of crystal height to its transverse cross-section varies from 6 to 12), the use of this technique does not guarantee the stable light yield distribution on account of, firstly, the difference in activator concentration over the extent of long sample and, secondly, the local gradient in the activator concentration. This work studies such factors against the example of CsI(Tl) detectors that influence the choice of the effective mirror reflectivity of crystal surfaces. Established were such optimum values of the activator concentration and maximum admissible gradients of Tl ions concentration at which the uniform treatment of the surface guarantees the homogeneity of the light yield within ±0.5%, the sample-to-sample spread not exceeding ±2.5%.