The TUNL-ITEP ββ decay setup was originally located in the TUNL Low-Background Counting Facility (LBCF), a well-shielded room located in the basement of the Duke University Physics Department. This room, known casually as "the cave", has a concrete ceiling several feet thick. The three floors above the laboratory as well as the roof of the building provide additional shielding. Overall, there was approximately 10 mwe overburden reducing the cosmic-ray flux.

The ββ decay setup was used in the TUNL LBCF to investigate the ββ decays of ¹⁰⁰Mo and ¹⁵⁰Nd to excited states of ¹⁰⁰Ru and ¹⁵⁰Sm respectively, as well as double-electron capture (ECEC) to excited final states (see Kidd et al.).

The double beta decay of ¹⁰⁰Mo to the excited 0⁺₁ state of ¹⁰⁰Ru was successfully observed and a half-life of [6.0_-1.1^+1.9(stat) ± 0.6(syst)] × 10²⁰ years was determined (see Hornish et al.). Limits were placed on decays to higher excited states. Further measurements were done from 2003 to 2005 with an improved determination of the coincidence efficiency, which lowered the systematic uncertainty. These results have been submitted to Nuclear Physics A.

The ββ decay of ¹⁵⁰Nd to excited states of ¹⁵⁰Sm was also investigated, though it was found that the enriched source was contaminated with ²³²Th decay products. The background from these contaminants was too high in our regions of interest to extract a competitive half-life limit. The source was returned to Oak Ridge National Laboratory for purification in late 2007, and has recently been reinstalled at our underground facility.

Finally, ECEC on ¹¹²Sn to the 1871 keV excited state of ¹¹²Cd was investigated for about 100 days.

created by M.F. Kidd
This reaction is significant because it may provide an alternate route for determining the electron neutrino mass. If the excited state in the daughter nucleus is degenerate with the parent nucleus, the phase space for two-neutrino ECEC is suppressed. The subsequent de-excitation provides a clear signature for the neutrinoless ECEC. Observing this reaction would establish the Majorana nature of the neutrino, and given the magnitude of the resonance enhancement, the effective electron neutrino mass could be calculated. Our search above ground yielded no events, allowing us to place a lower limit on the half-life of 1.3 × 10¹⁹ years at 90% CL (see Kidd et al. and references therein). This investigation was continued when we moved underground to the Kimballton Underground Research Facility.