Determination of Fractional Electron Capture Probabilities of ⁵⁹Ni by Means of Metallic Magnetic Calorimeters

The fractional electron capture probabilities of ⁵⁹Ni were measured using metallic magnetic calorimeters (MMCs). ⁵⁹Ni was one of the radionuclides chosen as a part of the European Metrology Research (EMPIR) project MetroMMC. The measurement was performed by using the decay energy spectroscopy (DES) technique, where the radionuclide is embedded in the absorber to have a 4π geometry. Two different source preparation techniques adapted for the measurement are also discussed: electroplating on gold foil and micro-drop-dispensing on gold nanofoam. The total energy spectra obtained from both sources are compared with each other, and the measured fractional electron capture probabilities are compared with those available in the literature and from the BetaShape code.