Fabrication and characterization of a lithium-glass-based composite neutron detector

A novel composite, scintillating material intended for neutron detection and composed of small (1.5 mm) cubes of KG2-type lithium glass embedded in a matrix of scintillating plastic has been developed in the form of a 2.2 in.-diameter, 3.1 in.-tall cylindrical prototype loaded with $\left( 5.82 \pm 0.02 \right)\%$ lithium glass by mass. The response of the material when exposed to ${}^{252}$Cf fission neutrons and various $\gamma$-ray sources has been studied; using the charge-integration method for pulse shape discrimination, good separation between neutron and $\gamma$-ray events is observed and intrinsic efficiencies of $\left( 1.15 \pm 0.16 \right)\times 10^{-2}$ and $\left( 2.28 \pm 0.21 \right)\times 10^{-4}$ for ${}^{252}$Cf fission neutrons and ${}^{60}$Co $\gamma$ rays are obtained; an upper limit for the sensitivity to ${}^{137}$Cs $\gamma$ rays is determined to be $< 3.70 \times 10^{-8}$. The neutron/$\gamma$ discrimination capabilities are improved in circumstances when a neutron capture signal in the lithium glass can be detected in coincidence with a preceding elastic scattering event in the plastic scintillator; with this coincidence requirement, the intrinsic efficiency of the prototype detector for ${}^{60}$Co $\gamma$ rays is $\left( 2.42 \pm 0.61 \right)\times 10^{-6}$ while its intrinsic efficiency for unmoderated ${}^{252}$Cf fission neutrons is $\left( 4.31 \pm 0.59 \right)\times 10^{-3}$. Through use of subregion-integration ratios in addition to the coincidence requirement, the efficiency for $\gamma$ rays from ${}^{60}$Co is reduced to $\left( 7.15 \pm 4.10 \right) \times 10^{-7}$ while the ${}^{252}$Cf fission neutron efficiency becomes $\left( 2.78 \pm 0.38 \right) \times 10^{-3}$.Comment: Final results, figures, and text; published in Nuclear Instruments and Methods in Physics Research Section

Pulse shape analysis in segmented detectors as a technique for background reduction in Ge double-beta decay experiments

The need to understand and reject backgrounds in Ge-diode detector double-beta decay experiments has given rise to the development of pulse shape analysis in such detectors to discern single-site energy deposits from multiple-site deposits. Here, we extend this analysis to segmented Ge detectors to study the effectiveness of combining segmentation with pulse shape analysis to identify the multiplicity of the energy deposits.Comment: 12 pages, 13 figures, will be submitted to NI

Operation of a 1-Liter-Volume Gaseous Argon Scintillation Counter

We have built a gas-phase argon ionization detector to measure small nuclear recoil energies (< 10 keVee). In this paper, we describe the detector response to X-ray and gamma calibration sources, including analysis of pulse shapes, software triggers, optimization of gas content, and energy- and position-dependence of the signal. We compare our experimental results against simulation using a 5.9-keV X-ray source, as well as higher-energy gamma sources up to 1332 keV. We conclude with a description of the detector, DAQ, and software settings optimized for a measurement of the low-energy nuclear quenching factor in gaseous argon. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory in part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344. Funded by Lab-wide LDRD. LLNL-JRNL-415990-DRAFT.Comment: 29 pages, single-column, double-spaced, 21 figure

Comment on "Evidence for Neutrinoless Double Beta Decay"

We comment on the recent claim for the experimental observation of neutrinoless double-beta decay. We discuss several limitations in the analysis provided in that paper and conclude that there is no basis for the presented claim.Comment: A comment written to Modern Physics Letters A. 4 pages, no figures. Updated version, accepted for publicatio

Project 8 Phase III Design Concept

We present a working concept for Phase III of the Project 8 experiment, aiming to achieve a neutrino mass sensitivity of $2~\mathrm{eV}$ ($90~\%$ C.L.) using a large volume of molecular tritium and a phased antenna array. The detection system is discussed in detail.Comment: 3 pages, 3 figures, Proceedings of Neutrino 2016, XXVII International Conference on Neutrino Physics and Astrophysics, 4-9 July 2016, London, U

Results from the Project 8 phase-1 cyclotron radiation emission spectroscopy detector

The Project 8 collaboration seeks to measure the absolute neutrino mass scale by means of precision spectroscopy of the beta decay of tritium. Our technique, cyclotron radiation emission spectroscopy, measures the frequency of the radiation emitted by electrons produced by decays in an ambient magnetic field. Because the cyclotron frequency is inversely proportional to the electron's Lorentz factor, this is also a measurement of the electron's energy. In order to demonstrate the viability of this technique, we have assembled and successfully operated a prototype system, which uses a rectangular waveguide to collect the cyclotron radiation from internal conversion electrons emitted from a gaseous $^{83m}$Kr source. Here we present the main design aspects of the first phase prototype, which was operated during parts of 2014 and 2015. We will also discuss the procedures used to analyze these data, along with the features which have been observed and the performance achieved to date.Comment: 3 pages; 2 figures; Proceedings of Neutrino 2016, XXVII International Conference on Neutrino Physics and Astrophysics, 4-9 July 2016, London, U

Status of the LUX Dark Matter Search

The Large Underground Xenon (LUX) dark matter search experiment is currently being deployed at the Homestake Laboratory in South Dakota. We will highlight the main elements of design which make the experiment a very strong competitor in the field of direct detection, as well as an easily scalable concept. We will also present its potential reach for supersymmetric dark matter detection, within various timeframes ranging from 1 year to 5 years or more.Comment: 4 pages, in proceedings of the SUSY09 conferenc