User-friendly Monte-Carlo program for the generation of gamma-ray spectral responses in complex source–detector arrangements
Introduction
One of the main problems in quantitative gamma-ray spectroscopy is the determination of absolute detection efficiency, for different energies, for different source-detector geometries and for different composition of voluminous sources. Most often the straightforward calibration methods are used, a number of semiempirical methods have also been developed, and finally the Monte Carlo simulations are occasionally used to generate the spectra and extract the desired efficiency 1, 2. This last method which generates the response function of the spectrometer, however, is unique when the deconvolution of continuous spectra is an object. Significant advance in this respect would represent the announced wide availability of response function of large Ge detectors for some standard source-detector geometries [3]. For non-standard cases one has to resort to some of the general simulation programs which are more or less cumbersome to use. The best known and the most sophisticated one is the CERN “GEANT” package developed to simulate the workings of complex particle detectors, which, when used for Ge detectors, needs adjustments for low energies and requires large computing resources, both in speed and memory [4].
To overcome these problems we have developed a dedicated and user-friendly program PHOTON which simulates the passage of photons through different media of different geometries, of which some may be declared as active media (sources and/or detectors) and others as passive media (scatterers and absorbers only), every one with given properties. The output is the spectral response of every detector involved, single, or in coincidence with any other. The program may be run on any PC with more than 1 MB RAM, starting with 386, the mathematical coprocessor being not necessary though significantly speeding up the execution.
Section snippets
The simulation algorithm
The transport of photons in a medium is necessarily coupled with the transport of electrons (and positrons). In the energy range from about 50 keV to some 10 MeV, which is of interest here, the photons interact mostly by the photoelectric and the Compton effects and by the production of pairs, while other effects have much smaller cross sections. In all the interactions the photon energy is thus transferred to electrons which ionize the medium and emit the braking radiation. From ionizations the
Definition of the source–detector system
The detection system is defined by means of the configuration data file. Greatest attention is given to the easy and convenient description of the source(s), the detector(s) and the passive media. Configuration data file consists of a number of sections which begin and end with the key words for a given section. The description of all the media involved consists of the names of the different zones, their shapes, dimensions, densities and chemical composition. Prismoidal, cylindrical and
Testing the program
The program was tested in a number of ways. For the calculation of the detection efficiency the program was tested on the case of the reference (3×3) NaI(Tl) detector and point sources at source–to–detector distances of 3, 10 and 25 cm. In the range of up to 1 MeV, as compared to the tabulated values, the accuracy is better than 5%, from 1 to 2 MeV it is better than 8% and for energies over 2 MeV the agreement is within 10%.
The quality of the simulation of the spectral response was, among others,
References (8)
- et al.
Nucl. Instr. and Meth. B
(1985) - et al.
Nucl. Instr. and Meth.
(1975) - et al.
Nucl. Instr. and Meth.
(1976) - R.L. Heath, INEL summary of activities related to nuclear data on the internet, Workshop on DOE Nuclear Data Program...
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