563 Matching Results

Search Results

Advanced search parameters have been applied.

Radiative Capture of Protons in Ne²⁰

Description: Abstract: "A preliminary measurement of the Ne²⁰(p,γ)Na²¹ reaction cross section has been made. Targets were prepared by bombarding aluminum targets with neon ions. The neon concentration in the target was determined by elastic scattering of 1.5-Mev-protons. The yield of positrons from the reaction Ne²⁰(p,γ)Na²¹(β)Ne²¹ was identified by the 23-second half life of Na²¹."
Date: October 16, 1957
Creator: Pixley, R. E.; Hester, R. E. & Lamb, W. A. S.
Partner: UNT Libraries Government Documents Department

Dissociative-recombination product states and the dissociation energy D<sub>0</sub> of Ne<sub>2</sub><sup>+</sup>

Description: Final product states of Ne<sub>2</sub><sup>+</sup> dissociative recombination were studied using time-of-flight spectroscopy to determine the kinetic energies released. The dissociative recombination occurred in a sustained discharge in the presence of a variable magnetic field and discharge voltage, at pressures of 5-15 mTorr. Under different conditions various excited states were observed ranging from the lowest 3<i>s</i> metastable states to higher Rydbcrg states within 0.000 54 eV of the dissociation limit. From their narrow widths, it is deduced that these higher states arose from Ne<sub>2</sub><sup>+</sup> ions with subthermal energies. From two of these narrow distributions, we obtain an improved value for the dissociation limit D<sub>0</sub>(Ne<sub>2</sub><sup>+</sup>)= 1.26±0.02 eV.
Date: February 28, 1998
Creator: Hardy, K. A.; Peterson, J. R.; Ramos, G. & Sheldon, J. W.
Partner: UNT Libraries Government Documents Department

Using the thermal Gaussian approximation approximation for theBoltzmann Operator in Semiclassical Initial Value Time CorrelationFunctions

Description: The thermal Gaussian approximation (TGA) recently developed by Mandelshtam et al has been demonstrated to be a practical way for approximating the Boltzmann operator exp(-{beta}H) for multidimensional systems. In this paper the TGA is combined with semiclassical (SC) initial value representations (IVRs) for thermal time correlation functions. Specifically, it is used with the linearized SC-IVR (LSC-IVR, equivalent to the classical Wigner model), and the 'forward-backward semiclassical dynamics' (FBSD) approximation developed by Makri et al. Use of the TGA with both of these approximate SC-IVRs allows the oscillatory part of the IVR to be integrated out explicitly, providing an extremely simple result that is readily applicable to large molecular systems. Calculation of the force-force autocorrelation for a strongly anharmonic oscillator demonstrates its accuracy, and of the velocity autocorrelation function (and thus the diffusion coefficient) of liquid neon demonstrates its applicability.
Date: September 6, 2006
Creator: Liu, Jian & Miller, William H.
Partner: UNT Libraries Government Documents Department

Photo-induced cataphoretic isotope separation. Progress report, June 15, 1978--June 15, 1979

Description: The studies on radiation-induced cataphoretic isotope separation has been associated with the use of a 0.63-..mu.. He:Ne laser as the radiation source in an attempt to obtain separation of /sup 20/Ne and /sup 22/Ne isotopes. A cataphoretic discharge tube containing mixed neon isotopes is within the laser resonator, whereas the laser tube contains only one neon isotope. Cataphoretic separation of the neon isotopes has not been observed, although selective excitation of one isotope has been demonstrated and a very sensitive technique for detecting cataphoretic isotope separation has been developed. Also, it is found that the exchange rate between the two neon isotopes in the excited laser levels is not great enough to significantly reduce the effect of selective excitation. Measurements of the current changes induced by the radiation indicate that the populations of those levels with which the laser radiation interacts is too small.
Date: June 1, 1979
Creator: Carruthers, J.A.
Partner: UNT Libraries Government Documents Department

Mass- and temperature-dependent diffusion coefficients for lightnoble gases for the TOUGH2-EOSN Model

Description: This report describes modifications made to the EOSN module(Shan and Pruess, 2003) of the nonisothermal multiphase flow simulatorTOUGH2 (Pruess, et al., 1999). The EOSN fluid property module simulatestransport of water, brine, air, and noble gases or CO2 in the subsurface.In the standard version of the EOSN module, diffusion coefficients can bespecified by the user, but there is no allowance for liquid-phasediffusion coefficients to change with temperature. Furthermore, usersmust specify radiogenic sources of heat and helium for each element indata block GENER, which can be a time-consuming task for models withlarge numbers of elements. Our modifications seek to increase thefunctionality and efficiency of using TOUGH2-EOSN by allowing for mass-and temperature-dependent liquid-phase diffusion coefficients for heliumand neon and specification of radiogenic heat and helium production as aproperty of a material. The modified version is based on TOUGH2-EOSN andthus requires familiarity with the capabilities and input formats of theTOUGH2 code (Pruess, et al., 1999) and the EOSN module (Shan and Pruess,2003). This report only details our modifications and how to properlyutilize them.
Date: April 13, 2007
Creator: Andrews, J.L.; Finsterle, S. & Saar, M.O.
Partner: UNT Libraries Government Documents Department


Description: The lifetime for the decay of a {pi} meson into {mu} meson and neutral particle was first measured by Richardson and later by Martinelli and Panofsky. The method was the same in both cases: The fraction of {pi} mesons surviving various times of flight is measured by placing photographic detectors at various path lengths from the target. In the experiment reported here we observe the time lag between the two bursts of fluorescence due to mesons decaying in a scintillation crystal. The first burst is due to the stopping of the entering {pi} meson, the second to the {mu}-meson. As is shown in Fig. 1, a particle penetrating the first and into the second crystal starts the sweep (10{sup -8} sec/mm) of an oscilloscope. The pulses in the second crystal are delayed 0.5 x 10{sup -6} sec to allow the sweep to start and brighten and are then photographed. If the responsible particle is a {pi}{sup +} meson which stops in the crystal, it undergoes {pi}-{mu} decay and two pulses appear on the trace. The {mu}{sup +} meson has a range of only 2 mm in the crystal. If its decay electron is detected some time (.5-2.5 x 10{sup -6} sec) later; a neon light flashes and is photographed together with the scope trace. Only such marked traces are measured. Of these marked traces, 650 or roughly one-half, show the two pulses of the {pi}-{mu} event. Five percent are calculated to be due to random delayed coincidences, and another 3 percent due to {pi} mesons which have decayed in flight and come to rest in the second crystal as {mu} mesons. The remaining traces are due to {pi}{mu} decays which are too fast to be resolved. The sweep speed of the oscilloscope is calibrated periodically with an oscillator of known ...
Date: May 10, 1950
Creator: Chamberlain, O.; Mozely, R.F.; Steinberger, J. & Wiegand, C.
Partner: UNT Libraries Government Documents Department


Description: Accelerated heavy particles are candidates for use in cancer therapy. The primary purpose of this investigation was to study the dose-effect relationships for asynchronous human kidney T-1 cells at various values of residual range for monoenergetic beams of carbon 9400 MeV/amu), neon (425 MeV/amu), and argon (570 MeV/amu. The 'track segment' method of exposure was used to minimize variations in the distribution of energy transfer events; secondary fragments produced by the particles in their passage through matter were, however, unavoidably included.
Date: March 1, 1979
Creator: Blakely, E.A.; Tobias, C.A.; Yang, T.C.H.; Smith, K.C. & Lyman, J.T.
Partner: UNT Libraries Government Documents Department

Acceleration of Partially Stripped Ions at the Bevalac

Description: We present results of the first attempts to accelerate partially stripped heavy ions in the Bevatron. Experiments were performed for hydrogen-like argon and neon ions, and, although the survival time of these ions in the 10{sup -7} torr Bevatron vacuum was not sufficient to achieve full energy, valuable charge-changing cross section information was obtained.
Date: October 1, 1977
Creator: Alonso, J.; Force, R.; Tekawa, M. & Grunder, H.
Partner: UNT Libraries Government Documents Department

Proposal to Study Dilepton Neutrino Interactions with the Triplet Quadrupole Beam, the Phase 1 EMI, and the 15' Bubble Chamber Filled with a H-Ne Mixture

Description: The authors propose to study dilepton neutrino events in the 15-foot bubble chamber using the quadrupole beam. The chamber is filled with at least 80% neon (15 ton fiducial target), the EMI is rearranged into 2 planes to give at least 7 absorption lengths for muon identification and give time coincidence, and the beam has a 1 millisecond spill. This will give about 150 dimuon events and 150 muon electron events per 100,000 pictures. They request 200,000 pictures.
Date: January 1, 1975
Creator: Harris, R.; Huson, F.R.; Kahn, S.; Murphy, T.; Smart, W.; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Direct measurement of divertor exhaust neo enrichment in DIII-D

Description: We report first direct measurements of divertor exhaust gas impurity enrichment, {eta}{sub exh}=(exhaust impurity concentration){divided_by}(core impurity concentration), for both unpumped and D{sub 2} puff-with-divertor-pump conditions. The experiment was performed with neutral beam heated, ELMing H-mode, single-null diverted deuterium plasmas with matched core and exhaust parameters in the DIII-D tokamak. Neon gas impurity was puffed into the divertor. Neon density was measured in the exhaust by a specially modified Penning gauge and in the core by absolute charge exchange recombination spectroscopy. Neon particle accounting indicates that much of the puffed neon entered a temporary unmeasured reservoir, inferred to be the graphite divertor target, which makes direct measurements necessary to calculate divertor enrichments. D{sub 2} puff into the SOL (scrape-off layer) with pumping increased {eta}{sub exh} threefold over either unpumped conditions or D{sub 2} puff directly into the divertor with pumping. These results show that SOL flow plays an important role in divertor exhaust impurity enrichment.
Date: June 1, 1996
Creator: Schaffer, M.J.; Wade, M.R.; Maingi, R.; Monier-Garbet, P.; West, W.P.; Whyte, D.G. et al.
Partner: UNT Libraries Government Documents Department

Final state effects and correlation in atomic and molecular systems

Description: This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project`s goals were to experimentally examine phenomena caused by final state interactions of the photo-excited electron with the remaining ionic system. This includes multiple ionization by a single photon, which cannot be described solely within a one-electron framework, but requires explicit incorporation of correlation effects between the second electron and the primary electron. Having only two electrons, helium is one of the simplest systems which exhibits electron correlation and thus is an ideal choice for testing electron correlation models in atoms. The authors measured the double to single ionization ratio in helium and the multiple ionization ratio in several other rare gases to test the recent theories. They found an unexpected ionization channel caused by Compton scattering.
Date: April 1, 1996
Creator: Bartlett, R.J.; Morgan, D.V.; Samson, J.A. & Sagurton, M.
Partner: UNT Libraries Government Documents Department

Neutron and proton therapy in the treatment of cancer

Description: Several decades of clinical research have established that neutron and proton therapy constitute useful and practical additions to the radiation oncologist`s treatment modalities. This paper discusses the rationale for using these therapies and describes practical solutions to their implementation.
Date: August 1, 1996
Creator: Lennox, A.J.
Partner: UNT Libraries Government Documents Department

Electron dynamics in the strong field limit of photoionization

Description: High precision photoelectron energy and angular distributions in helium and neon atoms for a broad intensity range reflect the change in the continuum dynamics that occurs as the ionization process evolves into the pure tunneling regime. Elastic rescattering of the laser-driven free electron from its parent ion core leaves a distinct signature on the spectra, providing a direct quantitative test of the various theories of strong field multiphoton ionization. We show that it takes a relatively complete semi-classical rescattering model to accurately reproduce the observed photoelectron distributions. However, the calculated inelastic rescattering rate fails to reproduce the measured nonsequential double ionization yields.
Date: December 31, 1998
Creator: Sheehy, B.; Walker, B.; Lafon, R. & Widmer, M.
Partner: UNT Libraries Government Documents Department

Disruption Studies in DIII-D

Description: Characteristics of disruptions in the DIII-D tokamak including the current decay rate, halo current magnitude and toroidal asymmetry. and heat pulse to the divertor are described. Neon and argon pellet injection is shown to be an effective method of mitigating the halo currents and the heat pulse with a 50% reduction in both quantities achieved. The injection of these impurity pellets frequently gives rise to runaway electrons.
Date: December 1997
Creator: Kellman, A. G.; Cuthbertson, J. W.; Luckhardt, S.; Zhang, J.; Lee, R. L.; Leuer, J. A. et al.
Partner: UNT Libraries Government Documents Department

Three-body collision contributions to recombination and collision-induced dissociation. 1: Cross sections

Description: Atomic and molecular recombination and collision-induced dissociation (CID) reactions comprise two of the most fundamental types of chemical reactions. They are important in all gas phase chemistry; for example, about half of the 196 reactions identified as important in combustion chemistry are recombination or CID reactions. Many of the current chemical kinetics textbooks and kinetics papers treat atomic and molecular recombination and CID as occurring only via sequences of two-body collisions. Actually, there is considerable evidence from experiment and classical trajectory calculations for contributions by true three-body collisions to the recombination of atomic and diatomic radicals, and that evidence is reviewed. Then, an approximate quantum method treating both two-body and three-body collisions simultaneously and on equal footing is used to calculate cross sections for the reaction Ne{sub 2} + H {rightleftharpoons} Ne + Ne + H. The results provide clear quantum evidence that direct three-body collisions do contribute significantly to recombination and CID.
Date: April 10, 1998
Creator: Pack, R. T.; Walker, R. B. & Kendrick, B. K.
Partner: UNT Libraries Government Documents Department

Inelastic-Collision Cross Sections for Ne

Description: Cross sections for inelastic collisions of slow electrons and the dipole oscillator-strength distribution for the neon atom are given in tabular form. The results are based on experimental data that were checked and adjusted for internal consistency.
Date: 1976
Creator: Soong, S. C. & Kim, Y. K.
Partner: UNT Libraries Government Documents Department

Photo-induced cataphoretic isotope separation. Final report, June 15, 1976-June 15, 1981

Description: The original studies were undertaken to study the feasibility of radiation-induced cataphoretic separation. This part of the work is concerned with laser-induced cataphoretic separation in neon using a He-Ne 6328A laser. The basic concept of radiation-induced caphoretic isotope separation is based on the preferential excitation of one isotope with the result that one isotope is more readily ionized, and relatively more of its ions move toward the cathode in the dc discharge. For the later part of the work a second radiation source was added, a helical Ne/sup 20/ radiation lamp. Radiation-induced cataphoretic isotope separation has not been observed. Selective excitation has been achieved by both the He-Ne/sup 20/ 6328A laser and the Ne/sup 20/ helical radiation lamp in spite of the fact that the isotope shift is comprable with Doppler-broadened linewidths. Collisional excitation exchange between the Ne/sup 20/ and Ne/sup 22/ atoms does not appear to be a problem for the neon partial pressure range involved. The population of the 3S/sub 2/ and 2p/sub 4/ laser levels (6328A) are apparently too low to offer reasonable expectation of inducing observable cataphoretic isotope separation by means of the 6328A laser radiation, even with the high detection sensitivity of the scanning Fabry-Perot spectrometer sytem. The use of the additional radiation source in the form of a helical Ne/sup 20/ radiation lamp has not improved the effectiveness of the laser 6328A laser. It has become clear from these experiments, however, that for isotope separation in neon it is well to concentrate on using radiation sources that interact mainly with the ls population.
Date: March 1, 1981
Creator: Carruthers, J A
Partner: UNT Libraries Government Documents Department