engleski

Fast neutron detection using aluminum oxide TLDs

Self induced TL effect following fast neutron irradiation was investigated using two types of aluminum oxide TL detectors. The first set of detectors were polycrystalline ceramic detectors developed for accidental dosimetry purposes, doped with magnesium and yttrium, Al2O3:Mg, Y, made in Hungary. The second set contained very high sensitive single crystal detectors doped with carbon, Al2O3:C, developed in Russia. In a former study the self induced effect on the Al2O3:Mg.Y was investigated using the 27Al(n.a)24Na reaction to measure the neutron part in a mixed n+g irradiation field. The lowest detectable neutron dose was found to be about 0.5 Gy. The aim of this study was to check this method on high sensitive Al2O3:C detector, to improve the lowest detectable fast neutron dose and to compare the self induce effect on two types of detectors in a high energy neutron field. The detectors were packaged in light-tight black plastic and Lucite boxes of 320 mg cm-2 wall thickness and were irradiated with 14 MeV neutrons generated by a Van de Graaff accelerator. Two neutron doses were used, 0.1 Gy and 1 Gy. As the nuclei of the TLDs were activated by the neutrons some b decay-isotopes were generated. Since the detectors were read out after irradiation the interaction of these electrons within the crystals was after storage for several days revcaled as a second thermoluminescent signal. 24Na was selected among these b decay-isotopes as the indicator of the neutron dose while precautions were taken to eliminate interferences by other b emitters. Both TLDs were found suitable for fast neutron dosimetry. However, according our expectation, Al2O3:C's high sensitivity to both gamma's and neutrons makes this detector an appropriate dosimeter for low dose mixed neutron+gamma fields.

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