Application of a silicon drift detector to measuring internal conversion electrons and analysis of their spectra

Small-volume, low-capacitance semiconductor X-ray silicon drift detectors (SDDs) have an excellent ability to resolve closely spaced X-ray lines. But the application to electrons is less known. We designed a detector system and performed spectrometry using SDDs for radionuclides emitting mono-energetic internal conversion electrons (ICEs) with energies from 129 keV to 656 keV. The system is compact, maintains simple readout electronics, and provides high-resolution measurements of ICEs without cooling to liquid nitrogen temperatures and without bulky lead shielding. Preliminary measurements using 137Cs and 131mXe are conducted to verify that SDDs are suitable as ICE spectrometers. Unlike that of X/γ spectrometry, the shape of the ICE spectra is a non-Gaussian distribution with apparent kurtosis. Therefore, a Pearson IV distribution function combined with a Levenberg–Marquardt fitting algorithm is utilized to analyze the ICE spectra quantitatively. The ratios of the net counts of ICE peaks for 137Cs and 131mXe as measured using SDDs with these fitting approaches are consistent with those reported in literature with a relative deviation of less than 3.4%.