A5070635231- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Quantum, superfluid, helium dynamics
- Radiation Detection and Scintillator Technologies
- Dark Matter and Cosmic Phenomena
- Radiation Therapy and Dosimetry
- Advanced NMR Techniques and Applications
- Nuclear reactor physics and engineering
- Astro and Planetary Science
- Particle physics theoretical and experimental studies
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced MRI Techniques and Applications
- Radioactive Decay and Measurement Techniques
- Particle Detector Development and Performance
- Planetary Science and Exploration
- Quantum Chromodynamics and Particle Interactions
- Solar and Space Plasma Dynamics
- Neutrino Physics Research
- Atmospheric Ozone and Climate
- Calibration and Measurement Techniques
- Radioactivity and Radon Measurements
- Astrophysics and Cosmic Phenomena
- Superconducting Materials and Applications
- High-Energy Particle Collisions Research
- X-ray Spectroscopy and Fluorescence Analysis
Royal Holloway University of London
2024
National Institute of Standards and Technology
2013-2023
NIST Center for Neutron Research
2018
Physical Measurement Laboratory
2018
Ecolab (United Kingdom)
2017
Nalco (Canada)
2014
National Institute of Standards
1996-2013
Dublin Institute For Advanced Studies
1969-2012
European Space Research and Technology Centre
2008-2010
University of Michigan–Ann Arbor
2010
The spin structure function of the neutron gn1 has been determined over range 0.03<x<0.6 at an average Q2 2 (GeV/c)2 by measuring asymmetry in deep inelastic scattering polarized electrons from a 3He target energies between 19 and 26 GeV. integral is found to be F10gn1(x)dx=-0.022±0.011. Earlier reported proton results together with Bjorken sum rule predict F10gn1(x)dx=-0.059±0.019.Received 1 April 1993DOI:https://doi.org/10.1103/PhysRevLett.71.959©1993 American Physical Society
We report on a precision measurement of the neutron spin structure function ${g}_{1}^{n}$ using deep inelastic scattering polarized electrons by ${}^{3}\mathrm{He}$. For kinematic range $0.014<x<0.7$ and $1<{Q}^{2}<17(\mathrm{GeV}/c{)}^{2}$, we obtain $\ensuremath{\int}{0.014}^{0.7}{g}_{1}^{n}(x)dx\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.036\ifmmode\pm\else\textpm\fi{}0.004(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.005(\mathrm{syst})$ at an average...
The neutron longitudinal and transverse asymmetries A1n A2n have been extracted from deep inelastic scattering of polarized electrons by a He3 target at incident energies 19.42, 22.66, 25.51 GeV. measurement allows for the determination spin structure functions g1n(x, Q2) g2n(x, over range 0.03<x<0.6 an average Q2 2 (GeV/c)2. data are used evaluation Ellis-Jaffe Bjorken sum rules. function is small negative within our measurement, yielding integral ∫0.030.6g1n(x)dx=−0.028±0.006 (stat)±0.006...
Water transport is an important consideration in the optimization of polymer electrolyte fuel cell (PEFC) performance, affecting both internal resistance and cathode polarization losses. Novel experiments are described using neutron radiography to measure water gradient profiles within Nafion® operating PEFC. Preliminary intensity gradients show qualitative agreement with expected response membrane content changes feed gas humidification current. Previous experimental measurements similar...
Snow is a critical component of the global water cycle and climate system, major source supply in many parts world. There lack spatially distributed information on accumulation snow land surfaces, glaciers, lake ice, sea ice. Satellite missions for systematic observations will be essential to improve representation cryosphere models advance knowledge prediction variability changes that depend ice resources. This paper describes scientific drivers technical approach proposed Cold Regions...
We have performed a test of Lorentz invariance by searching for time-dependent quadrupole splitting Zeeman levels in $^{21}\mathrm{Ne}$. A component the at twice Earth's sidereal frequency (${\mathrm{\ensuremath{\Omega}}}_{\mathrm{S}}$) would suggest preferred direction which affects local physics $^{21}\mathrm{Ne}$ nucleus. The technique employs polarized and $^{3}\mathrm{He}$ gases produced spin exchange with laser optically pumped Rb. Both species are contained same glass cell, providing...
A hyperon ( XI /sup -/ emitted in the interaction of a 1.5-Bev/c meson (K/sup -/) emulsion was noted to have been absorbed with production double hyperfragment. The ranges and angles involved these subsequent decay processes are given. Analysis ordinary hyperfragment (subsequently emitted) showed captured on light nucleus (C,N,0). Binding energies two DELTA 0/ hyperons were determined. /sub LAMBDA / Be/sup 10-11/ probably formed by capture carbon. (D.C.W.)
Abstract The major bedforms of gravel bed rivers, whether braided, meandering or straight, may be usefully resolved into pool‐riffle units, each comprising a single scour pool together with an associated depositional shoal downstream. At low flow, the latter characterized by emergent bar‐head and submerged riffle, variety remnant braid bars, depending upon type channel. Identification units observation flow structures on small stream in northwest England has demonstrated important links...
The LDEF Ultra-Heavy Cosmic-Ray Experiment (UHCRE) detected Galactic cosmic rays (GCRs) of charge Z ⩾ 70 in Earth orbit with an exposure factor 170 m2 sr yr, much larger than any other experiment. major results include the first statistically significant uniform sample GCR actinides 35 events passing quality cuts, evidence for existence transuranic nuclei one 96Cm candidate event, and a low 82Pb/78Pt ratio consistent experiments. probability component is estimated as 96%, while most likely...
We have measured the neutron structure function g2n and virtual photon-nucleon asymmetry A2n over kinematic range 0.014 ⩽ × 0.7 1.0 Q2 17.0 by scattering 48.3 GeV longitudinally polarized electrons from 3He. Results for are significantly smaller than √R positivity limit most of data generally consistent with twist-2 Wandzura-Wilczek prediction. Using our we obtain results twist-3 reduced matrix element d2n, integral ∫ g2n(x) dx in 1.0. Data this experiment combined existing to an average d2n dx.
We report measurements of asymmetries in quasielastic scattering polarized electrons from ${\mathrm{He}}^{3}$ at ${\mathrm{Q}}^{2}$=-0.2 GeV/c${)}^{2}$. measure ${\mathrm{A}}_{\mathrm{T}\ensuremath{'}}$=(-2.6\ifmmode\pm\else\textpm\fi{}0.9\ifmmode\pm\else\textpm\fi{}0.46)% and ${\mathrm{A}}_{\mathrm{TL}\ensuremath{'}}$=(+1.75\ifmmode\pm\else\textpm\fi{}1.2\ifmmode\pm\else\textpm\fi{}0.31)%. The asymmetry ${\mathrm{A}}_{\mathrm{T}\ensuremath{'}}$ depends predominantly on the previously...
We report the results of an improved determination triple correlation $D P \cdot(p_{e}\times p_{\nu})$ that can be used to limit possible time-reversal invariance in beta decay polarized neutrons and constrain extensions Standard Model. Our result is $D=(-0.96\pm 1.89 (stat)\pm 1.01 (sys))\times 10^{-4}$. The corresponding phase between g_A g_V $\phi_{AV} = 180.013^\circ\pm0.028^\circ$ (68 % confidence level). This represents most sensitive measurement D decay.
The standard model predicts that, in addition to a proton, an electron, and antineutrino, continuous spectrum of photons is emitted the β decay free neutron. We report on RDK II experiment which measured photon using two different detector arrays. An annular array bismuth germanium oxide scintillators detected from 14 782 keV. spectral shape was consistent with theory, we determined branching ratio 0.00335±0.00005[stat]±0.00015[syst]. A second large area avalanche photodiodes directly 0.4...
We have produced 70%–75% 3He polarization by spin-exchange optical pumping in cells ≈100 cm3 volume. The achieved is consistent with known and spin-relaxation rates, but only when the recently discovered temperature dependence of relaxation included. Absolute measurements were performed using two different methods laboratories. results obtained either a spectrally narrowed laser or one type broadband laser. Based on tests several larger at pressures near 1 bar, we find that power required to...
We report a measurement of the asymmetry in spin-dependent quasielastic scattering longitudinally polarized electrons from $^{3}\mathrm{He}$ gas target. This represents first demonstration new method for studying electromagnetic nuclear structure: The measured is good agreement with Faddeev calculation and supports picture as predominantly neutron.
Background: Time-reversal-invariance violation, or equivalently CP may explain the observed cosmological baryon asymmetry as well signal physics beyond Standard Model. In decay of polarized neutrons, triple correlation D<J_{n}>\cdot(p_{e}\timesp_{\nu}) is a parity-even, time-reversal- odd observable that uniquely sensitive to relative phase axial-vector amplitude with respect vector amplitude. The also possible contributions from scalar and tensor amplitudes. Final-state effects contribute D...
Motivated by applications to neutron spin filters and recent advances in spectrally narrowed laser diode arrays (LDAs), we are exploring exchange optical pumping of He3 at pressures near 1 bar. Among our more interesting results has been the production glass cells with extremely long relaxation times. The best these a lifetime T1=840 h [where polarization decays versus time, t, as exp(−t/T1)], dominated dipole–dipole contribution 950 partial pressure 0.85 Using broadband LDA, have obtained...
The first NIST-traceable measurements of environmental thermal neutrons have been completed. average sea level flux is 4 cm/sup 2//hr. This changes less than two times over wide varieties terrain, in all weather conditions and the solar year. neutron normalized to 39N-76.5W. scales with geomagnetic Lat/Long altitude a manner similar incident energetic cosmic rays. shielded has measured under 450 g/cm/sup 2/, residual 0.1 sea-level value. Preliminary shielding studies inside buildings water...
Abstract Conventional nuclear ventilation/perfusion (V/Q) scanning is limited in spatial resolution and requires exposure to radioactivity. The acquisition of pulmonary V/Q images using MRI overcomes these difficulties. When inhaled, hyperpolarized helium‐3 ( 3 He) permits gas distribution. Magnetic labeling blood (arterial spin‐tagging (AST)) provides perfusion. Three normal subjects, two patients who had undergone single lung transplantation for emphysema, one subject with embolism (PE),...
The time dependence of extreme ultraviolet (EUV) fluorescence following an ionizing radiation event in liquid helium is observed and studied the temperature range from 250 mK to 1.8 K. exhibits significant structure including a short $(\ensuremath{\sim}10\mathrm{ns})$ strong initial pulse followed by single photons whose emission rate decays exponentially with $1.6\ensuremath{-}\ensuremath{\mu}\mathrm{s}$ constant. At even longer scale, varies as ``1/time'' (inversely proportional after...