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Radford, David C

Publications and source records attributed to Radford, David C.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The Majorana Demonstrator for 0νββ: Current Status and Future Plans

The Majorana Demonstrator will search for neutrinoless-double-beta decay (0νββ) in 76Ge, while establishing the feasibility of a future tonne-scale germanium-based 0νββ experiment, and performing searches for new physics beyond the Standard Model. The experiment, currently under construction at the Sanford Underground Research Facility in Lead, SD, will consist of a pair of modular high-purity germanium detector arrays housed inside of a compact copper, lead, and polyethylene shield. Through a combination of strict materials qualifications and assay, low-background design, and powerful background rejection techniques, the Demonstrator aims to achieve a background rate in the 0νββ region of interest (ROI) of no more than 3cnts/(ROI-t-y). The current status of the Demonstrator is discussed, as are plans for its completion.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Nuclear Structure Studies in the 132 Sn Region: Safe Coulex with Carbon Targets

The collective and single-particle structure of nuclei in the 132 Sn region was recently studied by Coulomb excitation and heavy-ion induced transfer reactions using carbon, beryllium, and titanium targets. In particular, Coulomb excitation was used determine a complete set of electromagnetic moments for the first 2 + states and one-neutron transfer was used to probe the purity and evolution of single-neutron states. These recent experiments were conducted at the Holifield Radioactive Ion Beam Facility at ORNL using a CsI-HPGe detector array (BareBall- CLARION) to detect scattered particles and emitted gamma rays from the in-beam reactions. A Bragg-curve detector was used to measure the energy loss of the various beams through the targets and to measure the radioactive beam compositions. A sample of the Coulomb excitation results is presented here with an emphasis placed on 116 Sn. In particular, the safe Coulex criterion for carbon targets will be analyzed and discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

The MAJORANA DEMONSTRATOR Neutrinoless Double-Beta Decay Experiment

The MAJORANA DEMONSTRATOR will search for the neutrinoless double-beta (ββ(0ν)) decay of the isotope 76 Ge with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate that the neutrino is its own antiparticle, demonstrate that lepton number is not conserved, and provide information on the absolute mass scale of the neutrino. The DEMONSTRATOR is being assembled at the 4850-foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be situated in a low-background environment and surrounded by passive and active shielding. Here we describe the science goals of the DEMONSTRATOR and the details of its design.

Abgrall, N.↗
DOE OSTI2014

High-precision B(E2) measurements of semi-magic 58,60,62,64Ni by Coulomb excitation

High-precision reduced electric-quadrupole transition probabilities B(E2) have been measured from single-step Coulomb excitation of semi-magic 58,60,62,64 Ni (Z = 28) beams at 1.8 MeV per nucleon on a natural carbon target. The energy loss of the nickel beams through the carbon target were directly measured with a zero-degree Bragg detector and the absolute B(E2) values were normalized by Rutherford scattering. The B(E2) values disagree with recent lifetime studies that employed the Doppler-shift attenuation method. The present high-precision B(E2) values reveal an asymmetry about 62 Ni, midshell between N = 28 and 40, with larger values towards 56 Ni (Z = N = 28). The experimental B(E2) values are compared with shell-model calculations in the full pf model space and the results indicate a soft 56 Ni core.

Allmond, James M↗
DOE OSTI2013

The Performance of the Gamma-Ray Energy Tracking In-Beam Nuclear Array GRETINA

The Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) is a new generation high-resolution -ray spectrometer consisting of electrically segmented high-purity germanium crystals. GRETINA is capable of reconstructing the energy and position of each -ray interaction point inside the crystal with high resolution. This enables -ray energy tracking which in turn provides an array with large photopeak efficiency, high resolution and good peak-to-total ratio. GRETINA is used for nuclear structure studies with demanding -ray detection requirements and it is suitable for experiments with radioactive-ion beams with high recoil velocities. The GRETINA array has a 1 solid angle coverage and constitutes the first stage towards the full 4 array GRETA. We present in this paper the main parts and the performance of the GRETINA system.

Paschalis, S.↗
DOE OSTI2013

Electromagnetic properties of the 2+ state in 134Te: Influence of core excitation on single-particle orbits beyond 132Sn

The g factor and B (E2) of the first excited 2+ state have been measured following Coulomb excitation ofthe neutron-rich semimagic nuclide 134Te (two protons outside 132Sn) produced as a radioactive beam. The precision achieved matches related g-factor measurements on stable beams and distinguishes between alternative models. The B(E2) measurement exposes quadrupole strength in the 2+ state beyond that predicted by current large-basis shell-model calculations. This additional quadrupole strength can be attributed to coupling between the two valence protons and excitations of the 132Sn core. However, the wave functions of the low-excitation positive-parity states in 134Te up to 6+ remain dominated by the (g7/2)2 configuration.

Stuchbery, Andrew E↗
DOE OSTI2013

Coherent Scattering Investigations at the Spallation Neutron Source: a Snowmass White Paper

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, Tennessee, provides an intense flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure that is beneficial for background rejection. In this white paper, we describe how the SNS source can be used for a measurement of coherent elastic neutrino-nucleus scattering (CENNS), and the physics reach of different phases of such an experimental program (CSI: Coherent Scattering Investigations at the SNS).

Akimov, D.↗
DOE OSTI2012

Transient field g factor and mean-life measurements with a rare isotope beam of 126Sn

Background: The g factors and lifetimes of the 2+1 states in the stable, proton-rich Sn isotopes have been measured, but there is scant information on neutron-rich Sn isotopes. Purpose: Measurement of the g factor and the lifetime of the 2+1 state at 1.141 MeV in neutron-rich 126Sn (T1/2 = 2.3 105y). Method: Coulomb excitation in inverse kinematics together with the transient field and the Doppler shift attenuation techniques were applied to a radioactive beam of 126Sn at the Holifield Radioactive Ion Beam Facility. Results: g(2+1 ) = 0.25(21) and (2+1 ) = 1.5(2) ps were obtained. Conclusions: The data are compared to large-scale shell-model and quasiparticle random-phase calculations. Neutrons in the h11/2 and d3/2 orbitals play an important role in the structure of the 2+1 state of 126Sn. Challenges, limitations, and implications for such experiments at future rare isotope beam facilities are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Astroparticle physics with a customized low-background broad energy Germanium detector

The Majorana Collaboration is building the Majorana Demonstrator, a 60 kg array of high purity germanium detectors housed in an ultra-low background shield at the Sanford Underground Laboratory in Lead, SD. The Majorana Demonstrator will search for neutrinoless double-beta decay of 76Ge while demonstrating the feasibility of a tonne-scale experiment. It may also carry out a dark matter search in the 1-10 GeV/c² mass range. We have found that customized Broad Energy Germanium (BEGe) detectors produced by Canberra have several desirable features for a neutrinoless double-beta decay experiment, including low electronic noise, excellent pulse shape analysis capabilities, and simple fabrication. We have deployed a customized BEGe, the Majorana Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and shield at the Kimballton Underground Research Facility in Virginia. This paper will focus on the detector characteristics and measurements that can be performed with such a radiation detector in a low-background environment.

dark matter↗
DOE OSTI2011

Search for an Annual Modulation in a p-Type Point Contact Germanium Dark Matter Detector

Fifteen months of cumulative CoGeNT data are examined for indications of an annual modulation, a predicted signature of Weakly Interacting Massive Particle (WIMP) interactions. Presently available data support the presence of a modulated component of unknown origin, with parameters prima facie compatible with a galactic halo composed of light-mass WIMPs.

Aalseth, Craig E.↗
DOE OSTI2011

A Pulse Shape Analysis Technique for the MAJORANA Experiment

In order to achieve background count rates sufficiently low as to allow the observation of rare events such as neutrinoless double beta (0 ) decay, background suppression techniques are routinely employed. In this paper we present details of a novel Pulse Shape Analysis algorithm which allows single-site events such as 0 decay to be distinguished from multi site background events. The algorithm, which is based on the event by event 2 fitting of experimental signals to a basis data set of unique single site pulse shapes, has been developed through simulation studies and tested experimentally using a Broad Energy Germanium detector. It is found experimentally that the technique is able to successfully identify and reject 99% of multi site events in the single escape peak associated with the gamma decay of 208Tl, whilst maintaining a survival probability of 98% for '0 like' double escape peak events.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Coulomb excitation of 124,126,128Sn(Z = 50)

High-precision measurements of <0_1||E2||2_1> matrix elements from the Coulomb excitation of 124,126,128Sn(Z = 50) impinging on a 12C target are presented. The <0_1||E2||2_1> matrix elements and related B(E2) values decrease monotonically as the N = 82 shell closure is approached from N = 74 to 78, despite a near constancy in the first 2+ level energy, E(2_1+). Furthermore, results are presented for the Coulomb excitation of 124,126,128Sn using an enriched 50Ti target, which, combined with the results from the 12C target, provide a measure of the <2_1||E2||2_1> matrix elements and related static quadrupole moments, Q(2_1+) (expected to be ~0 for a spherical shape). These new results indicate that the Sn isotopes have a deformation consistent with zero. The present study marks the first report on measured 2_1+ static quadrupole moments for the unstable Sn isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗