Improved calculation of displacements per atom cross section in solids by gamma and electron irradiation

Gamma induced atom displacements in LYSO and LuYAP crystals as used in medical imaging applications

“…Firstly, the produced dpa damage is higher for the 48 V source, as it will be discussed later. The dpa damage accumulates mostly in the central crystals, being higher in about 88-89% than in the border ones for 511 keV, 44 Sc and 22 Na sources and in about 91% for 48 V source. The findings in LuYAP are similar.…”

“…The calculation procedure used in this work is based on the improved Monte Carlo assisted Classical Method (MCCM) introduced by the authors [22]. In few words, the MCCM consists in obtaining the density of atom displacements per total atoms in the material (displacements per atom or dpa) integrating over the calculated electron and positron fluence distributions.…”

“…In the frames of the MCCM procedure, it is possible to study the displacement cross section for each atomic specie in the crystals [22]. MCCM follows the McKinley-Feshbach approximation [26] for the primary knock-on atom formation and the Kinchin-Pease model [27] for the damage function, allowing to account the secondary atom displacements production (displacement cascades).…”

“…A first estimation in this sense was proposed by the authors, in which the preliminary results of the average atom displacements in-depth distribution were presented [1], based on the previously proposed methodology [20,21]. Recently, the authors proposed an improvement of this methodology allowing the determination of atom displacements distributions induced by gamma and electronic radiations in solids in terms of the displacement per atom cross section [22]. This allows us to improve and to extend the previous study in order to evaluate the volume distribution of the displacement damage in the detector, as well as to perform a better comparison between both crystals.…”

“…As gamma sources for this study we use three of the promising candidates for PET studies: 44 Sc (1.157 MeV maximum energy peak), 22 Na (1.275 MeV maximum energy peak) and 48 V (0.984 and 1.312 MeV maximum energy peaks). These sources are typically b þ emitters, but the emitted positrons are quickly annihilated.…”