Funct. Mater. 2023; 30 (2): 295-302.
Accounting for effective specularity in the DETECT2000 program when determining light collection coefficients using NaI(Tl) and BGO scintillators as an example
Institute for Scintillation Materials, National Academy of Sciences of Ukraine, 60 Nauki Ave., 61072 Kharkiv, Ukraine
The paper compares the light collection coefficients obtained for cylindrical NaI(Tl) and BGO scintillators in the DETECT2000 program and in the program characterizing the surface by its effective specularity. The results of the latter agree well with experiment. The best approximation of the results was obtained in the DETECT2000 program model of the UNIFIED optical surface, in which the roughness is specified by the &qout;fraction of specularly reflected rays&qout; parameter. Using this description of the surface in the DETECT2000 program, the dependence of the light collection coefficients on the contribution of specular reflection, optical absorption, reflection coefficient of the external reflector and scintillator size were studied. It is shown that the light collection coefficient of scintillators decreases with increasing effective specularity above 40 %, namely, by 4-8 % for NaI(Tl) and by 12-14 % for BGO, with different model parameters. This is due to an increase in the fraction of trapped light in the scintillator. It is also shown that the deterioration of the light collection coefficient is largely due to a decrease in optical absorption and, to a lesser extent, by a decrease in the reflectance of the external reflector and an increase in the scintillator size.
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