RESEARCH ON SCINTILLATION CRYSTALS AND THEIR ACTIVATORS: I. ZONE MELTING AND ZONE LEVELING OF Lil(Tl), II. COMPACTION AND ACTIVATION OF SCINTILLATORS, II.EFFECT OF COLOR CENTERS ON THE SCINTILLATION OF KKT1)

摘要

In the preparation and growth of impurity activated inorganic scintillators one faces the problems of undesirable impurities in the start¬ing material and of difficulties in many host-activator systems in maintaining uniform activator concentration over reasonable distances. The techniques of zone melting and zone leveling, which should eliminate these problems, were applied to the preparation of thallium activated lithium iodide, a scintillator system in which it is known to be very difficult to incorporate a uniform thallium concentration with more standard crystal growth methods. Lithium iodide was successfully purified by zone melting; and a thallium doped ingot prepared by zone leveling the pure lithium iodide was found to be a scintillator of optimum pulse height with a uniform thallium concen¬tration, maintained for about half of the total ingot length of eight inches.