The NaI:Tl and CsI:Tl crystals for effective detection of X-rays and low energy charged particles

Abstract

A method and technique for growth of large CsI:Tl crystals are considered. It has been shown that known CsI:Tl crystals additionally doped by Na and CO3 have a high light yield, good energy resolution, relatively low level of afterglow and radiation hardness up to 10 000 Rad. It has been demonstrated that solid solution of Tl in CsI matrix is stable up to 2000-2500 ppm of Tl. Simple test for observation of spinodal decay in solid solution is proposed for NaI and CsI single crystals. Analogy problems for NaI:Tl crystals are reviewed too. It has been shown that nature of ms-afterglow is connected with (Tl+)2. Intensity of afterglow increases with Tl concentration increasing. It has been shown that effective way to suppress the afterglow consists in crystal doping by oxygen to form (〖Tl〗^+-O_2^--〖Tl〗^+) center instead /(〖Tl〗^+-〖Tl〗^+). Recombination of electron and hole at oxygen-containing center is radiation-less and afterglow do not appears. Some problems and peculiarities of crystal growth in oxygen-containing atmosphere are considered.