Development of TIBr semiconductor crystal for applications as radiation detector and photodetector

Author(s)

Icimone Braga de Oliveira

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Pesquisas Energéticas e Nucleares (IPEN/BT)
• Defense date: 2006-02-21

Examining board members

Margarida Mizue Hamada; Sonia Licia Baldochi; Noelio Oliveira Dantas; Silvio Bruni Herdade; Tufic Madi Filho

• Advisor: Margarida Mizue Hamada

Abstract

In this work, TlBr crystals were grown by the Bridgman method from zone melted materials. The influence of the purification efficiency and the crystalline surface quality on the crystal were studied, evaluating its performance as a radiation detector. Due to significant improvement in the purification and crystals growth, good results have been obtained for the developed detectors. The spectrometric performance of the TlBr detector was evaluated by 241Am (59 keV), 133Ba (80 e 355 keV), 57Co (122 keV), 22Na (511 keV) and 137Cs (662 keV) at room temperature. The best energy resolution results were obtained from purer detectors. Energy resolutions of 10keV (16%), 12keV (15%), 12keV (10%), 28keV (8%), 31keV (6%) and 36keV (5%) to 59, 80, 122, 355, 511 and 662 keV energies, respectively, were obtained. A study on the detection response at -20ºC was also carried out, as well as the detector stability in function of the time. No significant difference was observed in the energy resolution between measurements at both temperatures. It was observed that the detector instability causes degradation of the spectroscopic characteristics during measurements at room temperature and the instability varies for each detector. This behavior was also verified by other authors. The viability to use the developed TlBr crystal as a photodetector coupled to scintillators crystals was also studied in this work. Due to its quantum efficiency in the region from 350 to 500 nm, TlBr shows to be a promising material to be used as a photodetector. As a possible application of this work, the development of a surgical probe has been initiated using the developed TlBr crystal as the radiation detector of the probe. (AU)