A Dual-Channel Spectrometer Based on 1mm-Thick SDDs for the Study of Nuclear Beta Decays

We present the ASPECT-BET project developing a dual-channel SDD-based spectrometer designed to achieve high-precision measurements of beta decays across a broad energy range (spanning from 10 keV to 1 MeV). The adoption of SDDs in electron spectroscopy represents a relatively novel approach, with promising preliminary results already observed in the TRISTAN project, which focuses on accurate beta spectroscopy of Tritium decay. The primary objective of ASPECTBET is to extend the research, including more energetic radioactive sources to study allowed and forbidden nuclear beta decays. To achieve this goal, we have incorporated larger (8 mm diameter) and thicker (1 mm-thick) detectors to enhance the absorption capability of the spectrometer, and a CSA featuring a larger feedback capacitance. Furthermore, by utilizing two SDDs arranged one in front of the other, post-acquisition data processing can be applied to eliminate partial energy depositions in detectors caused by undesirable effects such as electron backscattering or escape of characteristic X-rays. An assessment of the energy resolution achieved at the Mn-Kα (5.9 keV) fluorescence line, obtained by exposing the spectrometer to a 55Fe calibration source, is presented. A FWHM below 200 eV is achieved under conditions of a 1 μs peaking time and cooling at -23 °C, indicating the potential suitability of the spectrometer for high-energy beta decay studies.