Spectral Analysis of Cryogenic Microcalorimeter Data with Modified Peak Shapes

摘要

Cryogenic microcalorimeter detectors have successfully demonstrated capability of resolving complex gamma-ray peaks from plutonium isotopes with an order of magnitude higher energy resolution than traditional HPGe (High-purity Germanium) detector. Spectral analyses have been carried out with the FRAM (Fixed-Energy, Response Function Analysis with Multiple Efficiency) isotopic analysis code in order to determine plutonium isotopic composition of the samples. However, results have indicated the need for development of new peak fit functions since peak shapes in microcalorimeter data are different from HPGe. This is caused by multiple factors such as 1) a fundamentally different detection mechanism, 2) variability in pixel-to-pixel energy resolution, 3) increased sensitivity to gain drift due to ultra-high energy resolution, and 4) peak offsets due to complex energy calibration. Hence, alternative peak fitting algorithms have been explored to describe real microcalorimeter peak shapes, and qualities of fits were evaluated. As a result, spectral analysis software was modified to achieve better peak fitting for microcalorimeter spectra and its overall impact on spectral analysis will be presented.