Thallium bromide (TlBr) is a semiconductor compound with a high atomic number and a wide bandgap, being a very promising material to be used as room temperature radiation detectors. In this work, commercial TlBr powder was used for growing crystals for detector applications. To reduce impurities, this material was purified by the zone refining technique. Trace impurities at ppb/ppm level were analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). The efficiency of the purification was evaluated through studies of the decrease impurities concentrations in the TlBr powder and in the purified materials. The crystal quality was verified by X-ray diffraction (XRD). To evaluate the crystal as a semiconductor detector, systematic measurements of the transmittance, resistivity, and the radiation response ( 241 Am, 57 Co, 125 I, and 133 Ba) gamma rays were carried out.

This paper reports the emission spectra, pulse heights, and decay curves of CsI(Tl) crystals with a Tl + concentration ranging from 10 6 to 10 2 mol under electron and alpha particle excitations. Larger pulse heights from the crystals with Tl + concentration of more than 10 3 mol were observed for a higher ionization density of alpha particle excitation compared with those of electron excitation. This enhancement may be explained in terms of the higher scintillation efficiency for higher Tl + concentration. Decay curves under electron and alpha particle excitations were compared with the decay curve under pulsed UV excitation. The observed decay curves were explained in terms of the sum of the three energy transfer processes to create excited states (Tl + ) : the prompt process, the diffusion process to Tl 0 , and the electron release process from Tl 0 to Tl ++ . Here, Tl 0 and Tl ++ were produced through (Tl + + electron) Tl 0 and [Tl + + hole (or )] Tl ++ .

Melanoma Cutâneo"-CNPQ pelo incentivo, sugestões neste trabalho e pelos testes " in vivo" das sondas desenvolvidas,

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