Development of LiMgBO3:Tb3+ as a new generation material for thermoluminescence based personnel neutron dosimetry

Abstract

Personnel neutron dosimetry is of utmost importance due to high relative biological effectiveness (RBE) of neutrons compared with other ionizing radiation. Thermoluminescence (TL) is one of the most widely used techniques in this vital application where LiF:Mg,Ti is recognized as the benchmark material used world-over. However, its complex TL glow curve, complicated treatment procedure and loss of sensitivity upon reuse demand the development of new and more efficient materials. The present work reports the systematic development of the LiMgBO₃:Tb³⁺ phosphor for personnel neutron dosimetry applications along with detailed structural characterizations. The neutron irradiated TL study on LiMgBO₃:Tb³⁺ reveals a simple TL glow curve compared with the very complex pattern of LiF:Mg,Ti. The TL sensitivity for neutrons and the n/γ dose discrimination capability of LiMgBO₃:Tb³⁺ is found to be 2.2 times and 4.5 times higher, respectively, compared with that of the standard material. Also, the TL response up to 105 mSv of neutron dose shows excellent linearity and, most importantly, the fading of the TL signal even up to 90 days of storage is less than 10%. These features meet the ISO-21909 criteria for the practical applicability of this material as a TL based personnel neutron dosimeter. The detailed Photoluminescence (PL) emission and lifetime along with Electron Paramagnetic resonance (EPR) studies were carried out to delineate the underlying TL behaviour through identifying different neutron induced defect centres. Moreover, the trap parameters have been calculated using different methods in order to understand the TL kinetics.