UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2026-06-11 23:58
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Conference: Bucharest University Faculty of Physics 2026 Meeting


Section: Nuclear and Elementary Particles Physics


Title:
A new look at the Monte Carlo efficiency transfer method applied in gamma spectrometry


Authors:
D. GURAU, D. STANGA, E. IONESCU, L. DONE


Affiliation:
National Institute of R&D for Physics and Nuclear Engineering-Horia Hulubei (IFIN-HH)-Romania


E-mail
doru@nipne.ro


Keywords:
gamma spectrometry, Monte Carlo simulation, model calibration, Monte Carlo efficiency transfer method.


Abstract:
MC efficiency transfer method extrapolate measured efficiencies from one geometry to a range of others geometries using MC simulation of photon transport. A new look at this method is obtained using the multiplicative model where the true FEP efficiency is given by the product between a correction factor and the computed FEP efficiency. Let’s consider for simplicity the efficiency transfer from a reference point source located on the detector axis at the position href to a source of interest located at coordinates (h,r). According to the multiplicative model, the true FEP efficiency for the source of interest efp_true (h,r,E,tetopt) is efp_true (h,r,E,tetopt)=[w(h,r,E,tetopt)/wref]*[efp_MC(h,r,E,tetopt)/efp_MC(href,0,Eref,tetopt)]* efp_true (href,0,Eref) where wref= w(href,0,Eref,tetopt), efp_MC(h,r,E,tetopt) and efp_MC(href,0,Eref,tetopt)] are, respectively, the computed FEP efficiencies for the source of interest and the reference source, efp_true (href,0,Eref) is the true FEP efficiency for the reference source, w(h,r,E,tetopt) and wref are, respectively, the correction factors corresponding to the point source of interest and the reference point source. The estimate of efp_true (h,r,E,tetopt) is given by efp_est(h,r,E,tetopt)=[west(h,r,E,tetopt)/wref_est]*[efp_MC(h,r,E,tetopt)/efp_MC(href,0,Eref,tetopt)]*efp_m (href,0,Eref) where efp_m (href,0,Eref) is the measured FEP efficiency of the reference point source taken as the estimate of efp_true (h,r,E,tetopt), efp_est(h,r,E,tetopt) is the estimate of efp_true (h,r,E,tetopt), west(h,r,E,tetopt) and wref_est are, respectively, the estimates of w(h,r,E,tetopt) and wref. It is known that west(h,r,E,tetopt)/wref_est approximately equals one within the limit of a small uncertainty (Gurau et al., 2026). As a result, one obtains efp_est(h,r,E,tetopt)=[efp_MC(h,r,E,tetopt)/efp_MC(href,0,Eref,tetopt)]*efp_m (href,0,Eref) If E=Eref, then one obtain the traditional MC efficiency transfer method. The multiplicative model reveals that the MC efficiency transfer method can be used even if E is different from Eref. If E is different from Eref then following equation is also valid efp_est(h,r,E,tetopt)=[efp_MC(h,r,E,tetopt)/efp_MC(h,r,Eref,tetopt)]*efp_m (h,r,Eref) This equation was used for obtaining a reference FEP efficiency curve for the photon energy range of 100-2000 keV by using only one radionuclide (e.g. 152Eu).


References:

D. Gurau, D. Stanga*, O. Sima L. Done. Evaluating the uncertainty associated with computed values of the full-energy peak efficiency used in gamma spectrometry measurements, Appl. Radiat. Isot., 230 (2026).

D. Gurau, D. Stanga*, L. Done, O. Sima, G. Ilie. Calibrating GESPECOR model of computing the full-energy peak efficiency of coaxial high-purity germanium detectors by Monte Carlo simulation. Appl. Radiat. Isot., 204 (2024)

Acknowledgement:
This work was supported by NUCLEU Program within the National Research Development and Innovation Plan 2022–2027, carried out with the support of Management Center of Research, Development and Innovation (CMCDI), project code PN 23-21.