Measurement of nuclear decay data for beta decay and electron capture using metallic magnetic calorimeters

Accurate fractional electron capture probabilities and beta spectra measurements are vital in radionuclide metrology. When determining the SI unit of activity, Becquerel, using primary activity measurements e.g . by Liquid Scintillation Counting (LSC), decay data on beta decay and electron capture are essential. These data are also crucial for validating theoretical calculations and for numerous applications, including nuclear medicine, nuclear energy and waste management or neutrino physics research. Additionally, accurate data on the photon emission intensities from radionuclides undergoing electron capture (EC) is vital for calibrating X-ray and gamma-ray detectors. In the literature, most decay data concerning beta decay and electron capture is derived from old measurements or theoretical calculations having large or underestimated uncertainties. Recent measurements using cryogenic detectors revealed these discrepancies. Metallic Magnetic Calorimeters (MMCs) are cryogenic detectors that have demonstrated impressive performance in beta spectra, total decay energy, and X-ray measurements. Their key features include high energy resolution, a low energy threshold, excellent energy linearity, and nearly % detection eciency at low energies. This thesis employs MMCs in the Decay Energy Spectroscopy (DES) mode, also known as measurement mode, to measure the decay data for specic radionuclides undergoing beta decay (like 14C) and electron capture (such as 125I, 54Mn, 59Ni, and 51Cr). Emphasis is placed on the source preparation step to address spectral distortions that can arise from certain types of radionuclide samples. The obtained results showed improvement in uncertainties and are in large part in agreement with the literature values and those from the BetaShape calculation code.

cryogenic detector, radionuclide metrology, nuclear decay data, decay energy spectroscopy, fractional electron capture probability ratio, Beta spectrum

Full document (EN) : https://theses.hal.science/tel-04417104