Browsing by Subject "low-background counting"

An experimental study of the two-neutrino double-beta (2νββ) decay of 150Nd to various excited final states of 150Sm was performed at Triangle Universities Nuclear Laboratory (TUNL). Such data provide important checks for theoretical models used to predict 0νββ decay half lives.

The measurement was performed at the recently established Kimballton Underground Research Facility (KURF) in Ripplemeade, Virginia using the TUNL-ITEP double-beta decay setup. In this setup, two high-purity germanium detectors were operated in coincidence to detect the deexcitation gamma rays of the daughter nucleus. This coincidence technique, along with the location underground, provides a considerable reduction in background in the regions of interest.

This study yields the first results from KURF and the first detection of the

coincidence gamma rays from the 0+₁ excited state of 150Sm. These gamma rays

have energies of 334.0 keV and 406.5 keV, and are emitted in coincidence through a 0+₁→2+₁→0+_gs transition. The enriched Nd₂O₃ sample obtained from Oak Ridge

National Laboratory consists of 40.13 g 150Nd. This sample was observed for 391 days, producing 29 raw events in the region of interest. This count rate gives a half life of T_1/2 = (0.72+0.36_−0.18 ± 0.04(syst.)) × 1020 years, which agrees within error with

another recent measurement, in which only the single deexcitation gamma rays were detected (i.e., no coincidence was employed). Lower limits were also obtained for decays to higher excited final states.