Study of combinations of TL/OSL single dosimeters for mixed high/low ionization density radiation fields

摘要

In this paper we discuss and compare the potential application of combined OSL/TL measurements using ~6LiF:Mg,Ti (TLD-600 is enriched of isotope 6Li which has a high cross-section for the reaction with slow neutrons) or ~7LiF:Mg,Ti (TLD-700 is enriched of 7Li isotope) and TLD-100 (natural isotopic composition) detectors. The OSL/TL duel readout of LiF:Mg,Ti as an ionization density discriminator avoids some of the difficulties inherent to the various types of discrimination mixed-field passive dosimeters, and in addition has several advantages. The preferential excitation of OSL compared to TL following high ionization density (HID) alpha irradiation, naturally explained via the identification of OSL with the "two-hit" F_2 or F_3 center, whereas the major component of composite TL glow peak 5 is believed to arise from a "one-hit" complex defect. This evidence allows near-total discrimination between HID radiation and low-ionization density (LID) radiation. Beta and alpha particle irradiations were carried out with ~(90)Sr/~(90)Y (~500 keV average energy) and ~(241)Am sources (4.7 MeV) respectively and neutron irradiations were carried out at the PTB (Germany) (En = 5 MeV) and RARAF (Columbia University, USA) (En = 6 MeV) accelerator facilities. The highest values of the FOM obtained was ~30 for neutron/gamma discrimination and ~110 for alpha/gamma discrimination using OSL/TL - peak 5 measurements in TLD-700.