Using a target of PbF2, the thick-target yield from the (19)F(α,n) reaction was measured from E(α)=3.5-10 MeV. From these results, we infer the thick-target neutron yields from targets of F2 and UF6 over this same alpha-particle energy range.

Flux-averaged cross sections for cosmogenic-neutron activation of natural tellurium were measured using a neutron beam containing neutrons of kinetic energies up to ∼800 MeV and having an energy spectrum similar to that of cosmic-ray neutrons at sea level. Analysis of the radioisotopes produced reveals that Ag110m will be a dominant contributor to the cosmogenic-activation background in experiments searching for neutrinoless double-β decay of Te130, such as the Cryogenic Underground Observatory for Rare Events (CUORE) and the Sudbury Neutrino Observatory Plus (SNO+). An estimate of the cosmogenic-activation background in the CUORE experiment has been obtained using the results of this measurement and cross-section measurements of proton activation of tellurium. Additionally, the measured cross sections in this work are also compared with results from semiempirical cross-section calculations.

Nuclear explosions expose ubiquitous materials to large numbers of neutrons, producing a variety of radioactive isotopes. To simulate such phenomena from both fission and thermonuclear explosions, we irradiated 29 different targets with approximately 3 and 14 MeV neutrons and measured the beta-delayed gamma rays using germanium detectors. For each neutron energy, the expected radioisotopes, half-lives, and gamma ray energies were deduced. From measurements of the ratios of activities of the radionuclides produced by neutron irradiations, we were able to identify several materials that are particularly sensitive to the neutron energy spectra.

Recent discussions about the origin of the so-called gallium anomaly have motivated a remeasurement of the half-life of Ge71. We have conducted three separate measurements using dedicated planar Ge detectors - one with Fe55 as a standard, one with Co57 as a standard, and one standalone Ge71 measurement. Our results yield a half-life of 11.468±0.008 days, which is consistent with, but significantly more precise than, the currently accepted value. With this experiment, the potential explanation of the gallium anomaly being due to an unexpectedly long Ge71 half-life has been ruled out, leaving the anomaly's origin as an open question.

Measurements of beta-delayed gamma-ray spectra following 14-MeV neutron-induced fissions of 232Th, 238U, and 237Np were conducted at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Spectra were collected for times ranging from 1 min to 14 h after irradiation. Intensity ratios of gamma-ray lines were extracted from the data that allow identification of the fissioning isotope.© 2013 Elsevier B.V. All rights reserved.

The nuclear reactions C12(C12,α)Ne20, C12(C12,p)Na23, and C12(C12,n)Mg23 are the primary reactions in carbon burning, which occurs as part of several stellar processes. The Gamow window, which describes the energy range where most of these reactions take place, is typically around 1.5 MeV in the center-of-mass frame. Direct measurements of the cross sections at this energy are difficult due to the large Coulomb barrier present between the carbon nuclei; however, a successful surrogate measurement can provide the branching ratios between these reactions while avoiding the C12+C12 Coulomb barrier. An experiment was performed using inelastic scattering of 40 MeV α particles on Mg24 as a possible surrogate for the C12+C12 compound nucleus.

We present the performances of two 92% enriched 130TeO2 crystals operated as thermal bolometers in view of a next generation experiment to search for neutrinoless double beta decay of 130Te. The crystals, 435 g each, show an energy resolution, evaluated at the 2615 keV γ-line of 208Tl, of 6.5 and 4.3 keV FWHM. The only observable internal radioactive contamination arises from 238U (15 and 8 μBq/kg, respectively). The internal activity of the most problematic nuclei for neutrinoless double beta decay, 226Ra and 228Th, are both evaluated as <3.1 μBq/kg for one crystal and <2.3 μBq/kg for the second. Thanks to the readout of the weak Cherenkov light emitted by β/γ particles by means of Neganov–Luke bolometric light detectors we were able to perform an event-by-event identification of β/γ events with a 95% acceptance level, while establishing a rejection factor of 98.21% and 99.99% for α particles.

We present here an innovative cryogenic light detector capable to measure a few tens of eV signal thanks to the amplification assisted by the Neganov–Luke effect. The thermal signal boost in the presence of an electric field allows us to improve the signal-to-noise ratio reaching a baseline noise of around 20 eV. This device – coupled to an enriched 130TeO2 bolometer (435 g) – registered 160 eV Cherenkov light signal induced by 2615 keV 208Tl with a signal to noise ratio about 6:1. Since α particles emitted in decays of natural radionuclides do not produce the Cherenkov radiation, we were able to achieve an efficient α∕γ separation in the region of interest for neutrinoless double beta decay of 130Te (Q-value is 2527 keV). Specifically, a rejection factor of 99.9% for α particles was obtained with a 98.3% acceptance of β∕γ events. The achieved α rejection efficiency is required to reduce the dominant α background in the follow-up of the CUORE experiment (CUPID), a ton-scale bolometric search with particle identification.

The CUPID-Mo experiment, located at the Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20Li2Mo100O4 (LMO) calorimeters, each equipped with a Ge light detector for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double-β decays of Mo100 to the first 0+ and 2+ excited states of Ru100 using the full CUPID-Mo exposure (2.71kgyr of LMO). We measure the half-life of 2νββ decay to the 01+ state as T1/22ν→01+=(7.5±0.8(stat.)-0.3+0.4(syst.))×1020yr. The bolometric technique enables measurement of the electron energies as well as the γ rays from nuclear deexcitation and this allows us to set new limits on the two-neutrino decay to the 21+ state of T1/22ν→21+>4.4×1021yr(90% c.i.) and on the neutrinoless modes of T1/20ν→21+>2.1×1023yr(90% c.i.), T1/20ν→01+>1.2×1023yr(90% c.i.). Information on the electrons' spectral shape is obtained, which allows us to make the first comparison of the single and higher state dominance 2νββ decay models for the 01+ excited state of Ru100.

The CUPID-Mo experiment to search for 0$ u\beta\beta$ decay in $^{100}$Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator for CUPID, a next generation 0$ u\beta\beta$ decay experiment. CUPID-Mo was comprised of 20 enriched Li$_2$$^{100}$MoO$_4$ scintillating calorimeters, each with a mass of $\sim$ 0.2 kg, operated at $\sim$20 mK. We present here the final analysis with the full exposure of CUPID-Mo ($^{100}$Mo exposure of 1.47 kg$\times$yr) used to search for lepton number violation via 0$ u\beta\beta$ decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the $^{100}$Mo 0$ u\beta\beta$ decay half-life of $T^{0 u}_{1/2} > 1.8 \times 10^{24}$ year (stat.+syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of $\left < (0.28$--$0.49)$ eV, dependent upon the nuclear matrix element utilized.