Angular dependence of the TL reading of thin α-A2O3: C dosemeters exposed to different beta spectra

The angular dependence of the thermoluminescent (TL) signal of thin α-Al₂O₃:C dosemeters was investigated for a series of beta-emitting radionuclides commonly employed in nuclear medicine and characterised by different mean energies (⁹⁹Tc, ¹⁷⁷Lu, ⁹⁰Sr/⁹⁰Y and ⁹⁰Y). Irradiations were performed in a controlled geometry, using a properly designed irradiator intended to realistically reproduce the situation of exposure of hospital personnel to beta-emitting pharmaceuticals. Under the conditions of extended source and short source to detector distance, the TL signal of thin α-Al₂O₃:C layers per unit irradiation time was observed to be independent on the angle of incidence within acceptable limits, particularly for those radionuclides with maximum energy >500 keV. This property may be easily explained by using simple physical considerations, such as the limited thickness of the dosemeters. The results confirm that these detectors are suitable for beta-ray extremity dose measurements, when the photon contribution is negligible, as in the case considered.