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Measurement of Helium-3/Helium-4 Ratios in Soil Gas at the 618-11 Burial Ground

Description: Seventy soil gas-sampling points were installed around the perimeter of the 618-11 Burial Ground, approximately 400 feet downgradient of well 699-13-3A, and in four transects downgradient of the burial ground to a maximum distance of 3,100 feet. Soil gas samples were collected and analyzed for helium-3/helium-4 ratios from these 70 points. Helium-3/helium-4 ratios determined from the soil gas sampling points showed significant enrichments, relative to ambient air helium-3 concentrations. The highest concentrations were located along the northern perimeter of the burial ground. Helium-3/helium-4 ratios (normalized to the abundances in ambient air) ranged from 1.0 to 62 around the burial ground. The helium-3/helium-4 ratios from the 4 transect downgradient of the burial ground ranged from 0.988 to 1.68. The helium-3/helium-4 ratios from around the burial ground suggest there is a vadose zone source of tritium along the north side of the burial ground. This vadose zone source is likely the source of tritium in the groundwater. The helium-3/helium-4 ratios also suggest the groundwater plume is traveling east-northeast from the burial ground and the highest groundwater tritium value may be to the north of well 699-13-3A. Finally, there appears to be no immediately upgradient sources of tritium impacting the burial ground since all the upgradient helium-3/helium-4 ratios are approximately 1.0.
Date: October 31, 2001
Creator: Olsen, Khris B.; Dresel, P Evan & Evans, John C.
Partner: UNT Libraries Government Documents Department

Low-energy {sup 4}He{sup +} scattering from deuterium adsorbed on stepped Pd(331)

Description: We have taken angle-resolved data for the scattering of low-energy (< I keV) {sup 4}He{sup +} from deuterium adsorbed on a stepped Pd(331) surface. The impact geometry was up the staircase, that is, the {sup 4}He{sup +} beam was perpendicular to and directly incident onto the unshadowed <011>Pd ledge atoms. A strong quasi-elastic scattering signal of {sup 4}He{sup +} from D ({sup 4}He{sup +}/D) was observed at a forward scattering angle of {theta} = 25{degrees} and an incidence angle of {alpha} = 76{degrees} from the (331) normal. The results agree with shadow cone calculations of scattering first from Pd ledge atoms followed by a second event, {sup 4}He{sup +}/D. The resultant adsorption geometry shows D to reside in the quasi- threefold ledge site on the surface directly above the bulk fcc octahedral void. These results are consistent with the previous{sup 4}He{sup +} scattering study of the geometrically related Pd(110)- D(ads) system.
Date: July 1, 1996
Creator: Ellis, W.P. & Bastasz, R.
Partner: UNT Libraries Government Documents Department

Measurements of scattering processes in negative ion - atom collisions. Technical progress report - year 1, April 1, 1995--March 31, 1996

Description: This Technical Progress Report describes the progress made on the research objectives during the past twelve months. The objective of this research project is to provide absolute cross section measurements of various scattering processes which occur in negative ion collisions with atomic (specifically, noble gas and atomic hydrogen) targets at intermediate energies. These processes include: elastic scattering, single- and double-electron detachment, and target-inelastic processes of excitation and ionization. Total cross sections for single- and double-electron detachment were recently published in Physical Review A from this research project. The researchers were successful this past year in acquiring the first cross section measurements of target excitation for H{sup -} impact on helium target atoms.
Date: December 1, 1995
Creator: Kvale, T.J.
Partner: UNT Libraries Government Documents Department

Meson-Exchange Currents and the Strangeness Radius Of <sup>4</sup>He

Description: Meson-exchange current contributions to the strangeness radius of <sup>4</sup>He are computed in the one-boson exchange approximation.It is found that these contributions introduce a <(approx)10% correction to the one-body contribution.They should not, therefore, hamper the extraction of the nucleon strangeness radius from the parity-violating electron-<sup>4</sup>He asymmetry.
Date: September 1, 1993
Creator: Ramsey-Musolf, Michael & Ramsey-Musolf, Michael
Partner: UNT Libraries Government Documents Department

Distributions of Alpha Particles Escaping to the Wall because of Sawtooth Oscillations in TFTR

Description: It has been observed experimentally in deuterium-tritium shots of the Tokamak Fusion Test Reactor (TFTR) that crashes of sawtooth oscillations may result in very inhomogeneous flux of alpha particles to the wall. Namely, measurements with four detectors installed at the wall at 20°, 45°, 60°, and 90° below the midplane of the torus have shown that the alpha flux to the wall is strongly peaked at the 20° and 90° detectors and on the noise level at the 45° detector. To explain this phenomenon, both theoretical analysis and numerical simulation have been carried out. It is concluded that the "crash-induced prompt loss," i.e., the orbital loss of marginally trapped particles arising because of the crash-induced orbit transformation of circulating particles, is responsible for the flux to the 90° and 60° detectors, whereas the crash-induced stochastic diffusion of moderately trapped particles explains the large signal at the 20° detector. The calculated poloidal distributions of the integral alpha flux are in reasonable agreement with experimental data. In addition to the integral flux, the flux of particles with given energy was calculated. The energy spectrum of the escaping particles has also been calculated, which can be used for diagnostics of the crash type.
Date: November 1, 1998
Creator: Kolesnichenko, Ya.I.; Lutsenko, V.V.; White, R.B. & Yakovenko, Yu.V., Zweben, S.J.
Partner: UNT Libraries Government Documents Department

The hep Astrophysical Factor

Description: The S-factor for the {sup 3}He(p,e+ve){sup 4}He reaction has been recently calculated using realistic calculations and currents. The present talk summarizes the main results of that calculation.
Date: April 1, 2001
Creator: Schiavilla, R.
Partner: UNT Libraries Government Documents Department

Measurement of Helium-3/Helium-4 Ratios in Soil Gas at the 618-11 Burial Ground

Description: Seventy soil gas-sampling points were installed around the perimeter of the 618-11 Burial Ground, approximately 400 feet downgradient of well 699-13-3A, and in four transects downgradient of the burial ground to a maximum distance of 3,100 feet. Soil gas samples were collected and analyzed for helium-3/helium-4 ratios from these 70 points. Helium-3/helium-4 ratios determined from the soil gas sampling points showed significant enrichments, relative to ambient air helium-3 concentrations. The highest concentrations were located along the northern perimeter of the burial ground. Helium-3/helium-4 ratios (normalized to the abundances in ambient air) ranged from 1.0 to 62 around the burial ground. The helium-3/helium-4 ratios from the 4 transect downgradient of the burial ground ranged from 0.988 to 1.68. The helium-3/helium-4 ratios from around the burial ground suggest there is a vadose zone source of tritium along the north side of the burial ground.
Date: October 31, 2001
Creator: Olsen, Khris B; Dresel, P Evan & Evans, John C
Partner: UNT Libraries Government Documents Department

Calculation of the {alpha}-particle ground state

Description: The Correlated Hyperspherical Harmonic expansion method is used to calculate alpha-particle properties with a realistic hamiltonian consisting of the Argonne V14 two nucleon and Urbana model VIII three nucleon potentials. The calculated binding energy, mass radius and wave percentages are close to the corresponding quantities obtained with Green's Function Monte Carlo and Faddeev-Yakubovsky techniques.
Date: October 1, 1994
Creator: Viviani, M.; Kievsky, A. & Rosati, S.
Partner: UNT Libraries Government Documents Department

Variational Monte Carlo Calculations of {sup 3}He and {sup 4}He with a Relativistic Hamiltonian - II

Description: In relativistic Hamiltonians the two-nucleon interaction is expressed as a sum of {tilde v}{sub ij}, the interaction in the P{sub ij}=0 rest frame, and the ''boost interaction'' {delta}v(P{sub ij}) which depends upon the total momentum P{sub ij} and vanishes in the rest frame. The {delta}v can be regarded as a sum of four terms: {delta}v{sub RE}, {delta}v{sub LC}, {delta}v{sub TP} and {delta}v{sub QM}; the first three originate from the relativistic energy-momentum relation, Lorentz contraction and Thomas precession, while the last is purely quantum. The contributions of {delta}v{sub RE} and {delta}v{sub LC} have been previously calculated with the variational Monte Carlo method for {sup 3}H and {sup 4}He. In this brief note we report the results of similar calculations for the contributions of {delta}v{sub TP} and {delta}v{sub QM}. These are found to be rather small.
Date: October 1, 1994
Creator: Forest, J.L.; Pandharipande, V.R.; Carlson, J. & Schiavilla, R.
Partner: UNT Libraries Government Documents Department

The {sup 4}He(e,e'p) Cross Section at Large Missing Energy

Description: The (e,e'p) reaction on {sup 4}He nuclei was studied in kinematics designed to emphasize effects of nuclear short-range correlations. The measured cross sections display a peak in the kinematical regions where two-nucleon processes are expected to dominate. Theoretical models incorporating short-range correlation effects agree reasonably with the data.
Date: July 1, 1997
Creator: Leeuwe, J.J. van; Blok, H.P.; Brand, J.F.J. van den; Bulten, H.J.; Dodge, G.E.; Ent, R. et al.
Partner: UNT Libraries Government Documents Department

Coulomb sum rule for {sup 4}He

Description: We determine the Coulomb sum for {sup 4}He using world data on {sup 4}He(e, e') and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment using free-nucleon form factors. The apparent reduction of the in-medium G{sub ep} implied by IA-interpretation of the L/T-ratios measured in {sup 4}He(e,e'p) and {sup 4}He([vec]e, e'p) is not confirmed.
Date: October 1, 2002
Creator: Carlson, J.; Jourdan, J.; Schiavilla, R. & Sick, I.
Partner: UNT Libraries Government Documents Department

A Tutorial on Alpha-channelling

Description: One of the more ambitious uses of intense microwaves in tokamaks or in other magnetic confinement deuterium-tritium (DT) fusion devices would be to divert power from energetic alpha-particles to waves. This so-called "alpha-channelling" would be a large step towards achieving economical fusion power. The intense waves, amplified by the substantial free energy in the alpha-particles, damp on fuel ions, resulting in a hot ion mode, doubling the fusion power of the reactor at the same confined pressure. If the waves damp preferentially on electrons or ions traveling in one direction, current can be driven. This tutorial explains the key concepts and recent advances that lead us to believe in the plausibility of such an effect, at the same time showing how experiments to date give us a measure of confidence in both the simulations themselves, the underlying physical assumptions, and ultimately the reasonableness of the application of these ideas to alpha-channelling in a tokamak reactor.
Date: November 1, 1998
Creator: Fisch, N.J. & Herrmann, M.C.
Partner: UNT Libraries Government Documents Department

Cryogenic design of the liquid helium experiment ``critical dynamics in microgravity``

Description: Although many well controlled experiments have been conducted to measure the static properties of systems near criticality, few experiments have explored the transport properties in systems driven far away from equilibrium as a phase transition occurs. The cryogenic design of an experiment to study the dynamic aspect of critical phenomena is reported here. Measurements of the thermal gradient across the superfluid (He II) -- normal fluid (He I) interface in helium under microgravity conditions will be performed as a heat flux holds the system away from equilibrium. New technologies are under development for this experiment, which is in the definition phase for a space shuttle flight.
Date: October 1, 1995
Creator: Moeur, W.A.; Adriaans, M.J.; Boyd, S.T.; Strayer, D.M. & Duncan, R.V.
Partner: UNT Libraries Government Documents Department

The superfluid Stirling refrigerator, a new method for cooling below 0.5 K

Description: A new subkelvin refrigerator, the superfluid Stirling cycle refrigerator, uses a working fluid of {sup 3}He-{sup 4}He mixture in a Stirling cycle. The thermodynamically active components of the mixture are the {sup 3}He, which behaves like a Boltzman gas, and the phonon-roton gas in the {sup 4}He. The superfluid component of the liquid is inert. Two refrigerators have been built and temperatures of 340 mK have been achieved.
Date: April 9, 1993
Creator: Brisson, J. G.; Kotsubo, V. & Swift, G. W.
Partner: UNT Libraries Government Documents Department

Fusion cross sections and reactivities

Description: Cross section and reactivity data are summarized for several important fusion reactions. Reactivities are included for both Maxwellian plasmas and beam- Maxwellian target fusion. Equations, tabular and also graphical presentations are included for convenience in a variety of applications. (auth)
Date: June 17, 1974
Creator: Miley, G.H.; Towner, H. & Ivich, N.
Partner: UNT Libraries Government Documents Department