Simulation of a NE213 γ-response function using an improved multi-parameter minimization procedure

The γ-response functions of a 15 cm diameter×6 cm thick NE213 detector were recently measured with standard 22Na, 60Co and 241Am γ-sources in order to calibrate the scintillation counter and were simulated in the present work with the MCNPX2.5e Monte-Carlo code. The MINUIT2 package, developed at C.E.R.N., was used to minimize the χ2 between measured and calculated pulse height distributions in order to derive the experimental resolution parameters. A C++ code was written to simulate various resolution broadening and background shapes. The results are in good agreement with the experimental response function except in the low-energy range (below 100 keV) which could be improved by a better description of the detector environment.