Speaker
Description
Investigation of double beta decay (β+EC, EC/EC) of 58Ni was performed at the Modane underground laboratory (LSM, France, 4800 m w.e.) using the ultra-low background spectrometer Obelix and a sample of natural Ni. Spectrometer Obelix is based on P-type coaxial HPGe detector with a sensitive volume of 600 cm3 and relative efficiency of 160 %. The detector part of the cryostat is encircled by several layers of roman and low-active lead and flushed with radon-depleted air. The sample of natural nickel, containing ~68% of 58Ni with a total mass of ~21.7 kg was prepared in a shape of Marinelli beaker and placed on the Obelix detector. Three experimental runs were performed with the investigated sample in 2014 - 2017 years. New experimental limits (at 90% CL) on half-lives of β+EC and EC/EC decays of 58Ni to excited states of 58Fe were obtained in these investigations, improving the previous experimental limits by approximately two orders of magnitude.
