Simulating Decay Energy Spectra Using Geant4

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Ockri, Timothy R.
Koehler, Katrina E.
Fitzgerald, Ryan P.
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Houghton University
Decay Energy Spectroscopy (DES) uses high energy resolution (~1 keV FWHM at 5 MeV [1]) microcalorimeters to measure the total energy of each decay from an embedded radioactive source. A histogram of these energies enables the determination of radionuclide composition, useful for both nuclear safeguards and metrology. In some fraction of decays, some of the decay energy is not thermalized when a particle such as a gamma ray, X-ray, or electron escapes the detector. The probability of this happening depends on the location of the parent nucleus in the absorber, the types and energies of particles released in the decay, and the material,size, and shape of the absorber. A library of possible spectra is created by simulating different shapes and sizes of detector absorbers and compositions, locations, and distributions of sources using the Monte-Carlo particle simulation software Geant4. With Decay Energy Spectroscopy SIMulation for Absolute Total Efficiency (DESSIMATE), a python graphical user interface for visualization, an experimental spectrum can be expressed as a linear combination of these simulated spectra. This will allow the total activity of each radionuclide in a measured sample to be determined. This method can potentially be used in the certification of Standard Reference Materials (SRMs) with precisely known massic activities (defined as unit activity per unit mass).
XLI Annual Rochester Symposium for Physics Students, University of Rochester (Rochester, NY), April 15, 2023.
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