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Dissociation of H₂⁺ by Photons

Description: Abstract: "A measurement was made of the dissociation of vibrationally-excited H2+ ions by photons having quantum energy in the vicinity of 4 e.v. The calculated cross section from theory is 3 x 10-(-18) cm-2. The experimental result is 10-(-17) cm-2; a factor of 10 uncertainty is present because the photon intensity was unknown by that factor."
Date: June 12, 1957
Creator: Linlor, William I., 1915-; Barnett, C. F. & Reinhardt, R.
Partner: UNT Libraries Government Documents Department

Neutral H Atom and Molecular Ion (H₂⁺) Injection into the Mirror Machine at Energies About One Mev

Description: This report presents the best estimate possible on the basis of the available information as to how high an energy would be necessary in order that the gas pressure which could be tolerated would be attainable with present techniques (say 10-(-7) mm Hg.)
Date: May 11, 1956
Creator: Lauer, Eugene J. & Gibson, Gordon
Partner: UNT Libraries Government Documents Department

Cyclotron resonance absorption by a hydrogen plasma

Description: From introduction: "The work described in this report was undertaken as part of an experimental study to determine the effectiveness of radiofrequency field in heating the ions of a hydrogen or deuterium plasma. The ultimate aim is to find a method of heating a deuterium plasma until an appreciable rate of nuclear reaction takes place."
Date: August 30, 1957
Creator: Chambers, Edmund S.
Partner: UNT Libraries Government Documents Department

Scaling of cross sections in ion-atom collisions

Description: Differential electron emission at 15{degrees} is investigated for 50-500 keV/amu hydrogen impacting on He and H targets. From hydrogen particles (H, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}) ratios of cross sections relative to proton impact data, it is shown how bound projectile electrons influence the differential electron emission and where different ionization mechanisms are important. It is demonstrated that the H{sub 2}{sup +} and H{sub 3}{sup +} molecular ions interact as though they are composed of independent nuclei with the appropriate number of bound electrons, the electronic structure of the components appearing to be unimportant.
Date: November 1, 1994
Creator: DuBois, R.D.
Partner: UNT Libraries Government Documents Department

The RHIC Optically-Pumped Polarized H Ion Source.

Description: The depolarization factors in the multi-step spin-transfer polarization technique and basic limitations on maximum polarization in the OPPIS (Optically-Pumped Polarized H{sup -} Ion Source) are discussed. Detailed studies of polarization losses in the RHIC OPPIS and the source parameters optimization resulted in the OPPIS polarization increase to 86-90%. This contributed to increasing polarization in the AGS and RHIC to 65-70%.
Date: September 10, 2007
Creator: Zelenski,A.; Zelenski, A.; Kokhanovski, S.; Kponou, A.; Ritter, J. & Zubets, V.
Partner: UNT Libraries Government Documents Department

H- Enhancement Process in a Multicusp Ion Source Operated with a Barium Insert Structure

Description: It has been demonstrated that the H{sup -} output current from a small multicusp source can be substantially enhanced if the hydrogen plasma is seeded with barium. Operating with a barium washer insert at the extraction aperture, it is found that the extractable H{sup -} current is increased by a factor of three if the insert bias potential is optimized. By use of a mixture of xenon and hydrogen gas, it is further demonstrated that the positive hydrogen ions are responsible for the observed H{sup -} enhancement.
Date: May 1, 1990
Creator: Leung, K.N.; Van Os, C.F.A. & Kunkel, W.B.
Partner: UNT Libraries Government Documents Department

Penning trap and resistive cooling of protons. Final technical report, May 1993--March 1995

Description: Trapped H{sup {minus}} has been produced from trapped H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} in an ICR trap. The initial positive ions collide with a cesiated trap surface and are recaptured as H{sup {minus}} by fast reversal of the trapping potential.
Date: July 1, 1995
Creator: Kenefick, R.A.
Partner: UNT Libraries Government Documents Department

High-intensity sources for light ions

Description: The use of the multicusp plasma generator as a source of light ions is described. By employing radio-frequency induction discharge, the performance of the multicusp source is greatly improved, both in lifetime and in high brightness H{sup +} and H{sup {minus}} beam production. A new technique for generating multiply-charged ions in this type of ion source is also presented.
Date: October 1, 1995
Creator: Leung, K.N.
Partner: UNT Libraries Government Documents Department

Effect of Temperature on the Protonation of the TALSPEAK Ligands: Lactic and Diethylenetrinitropentaacetic Acids

Description: The protonation reactions of two ligands that play important roles in the TALSPEAK process for the separation of trivalent actinides from lanthanides, lactic acid and diethylenetrinitropentaacetic acid (DTPA), have been studied at variable temperatures. The protonation constants at 10-70 C were determined by titration potentiometry and the protonation enthalpies were determined at 25 C by titration microcalorimetry. The protonation constants remain essentially unchanged (25-70 C) within the experimental uncertainties, indicating that the effect of temperature on the protonation of lactate is insignificant. In contrast, the protonation constants of DTPA (log {beta}H's) generally decrease as the temperature is increased. Results from this study indicate that the effect of temperature on the protonation of DTPA could alter the speciation of metal ions (actinides and lanthanides) in the TALSPEAK system, since lower values of log{beta}H at higher temperatures suggest that the hydrogen ions would compete less strongly with the metal ions for the complexation of DTPA at higher temperatures.
Date: October 20, 2009
Creator: Tian, Guoxin & Rao, Linfeng
Partner: UNT Libraries Government Documents Department

Volume- and Caesiated-Volume Negative Ion Sources

Description: H- volume sources and especially caesiated H- volume sources are important ion sources for generating high intensity proton beams, which then in turn generate large quantities of other particles. This paper discusses the physics and technology of the volume production and the caesium enhanced (surface) production of H- ions. Starting with Bacal s discovery of the H- volume production, the paper briefly recounts the development of some H- sources, which capitalized on this process to significantly increase the production of H- beams. Another significant increase was achieved in the 1990s by adding cesiated surfaces to supplement the volume produced ions with surface produced ions as illustrated with other H- sources. Finally the focus turns to some of the experience gained when such a source was successfully ramped up in H- output as well as in duty factor to support the generation of 1 MW proton beams for the Spallation Neutron Source.
Date: January 1, 2013
Creator: Stockli, Martin P.
Partner: UNT Libraries Government Documents Department

Intrabeam stripping in H- Linacs

Description: A beam loss in the superconducting part of the SNS linac has been observed during its commissioning and operation. Although the loss does not prevent the SNS high power operation, it results in an almost uniform irradiation of linac components and increased radiation levels in the tunnel. Multi-particle tracking could neither account for the magnitude of the observed loss nor its dependence on machine parameters. It was recently found that the loss is consistent with the intrabeam particle collisions resulting in stripping of H{sup -} ions. The paper describes experimental observations and corresponding analytical estimates of the intrabeam stripping.
Date: September 1, 2010
Creator: Lebedev, V.; Solyak, N.; Ostigy, J.-F.; /Fermilab; Alexandrov, A.; Shishlo, A. et al.
Partner: UNT Libraries Government Documents Department

Nanostructures from hydrogen implantation of metals.

Description: This study investigates a pathway to nanoporous structures created by hydrogen implantation in aluminum. Previous experiments for fusion applications have indicated that hydrogen and helium ion implantations are capable of producing bicontinuous nanoporous structures in a variety of metals. This study focuses specifically on hydrogen and helium implantations of aluminum, including complementary experimental results and computational modeling of this system. Experimental results show the evolution of the surface morphology as the hydrogen ion fluence increases from 10{sup 17} cm{sup -2} to 10{sup 18} cm{sup -2}. Implantations of helium at a fluence of 10{sup 18} cm{sup -2} produce porosity on the order of 10 nm. Computational modeling demonstrates the formation of alanes, their desorption, and the resulting etching of aluminum surfaces that likely drives the nanostructures that form in the presence of hydrogen.
Date: September 1, 2009
Creator: McWatters, Bruce Ray (Sandia National Laboratories, Albuquerque, NM); Causey, Rion A.; DePuit, Ryan J.; Yang, Nancy Y. C. & Ong, Markus D.
Partner: UNT Libraries Government Documents Department

Progress towards antihydrogen production by the reaction of cold antiprotons with positronium atoms

Description: An experiment aimed at producing antihydrogen atoms by the reaction of cold antiprotons stored in a Penning trap with injected ground state positronium atoms is described. The apparatus developed in an attempt to observe the charge conjugate reaction using proton projectiles is discussed. Technically feasible upgrades to this apparatus are identified which may allow, in conjunction with the PS200 trap, antihydrogen production at LEAR.
Date: March 1, 1995
Creator: Charlton, M.; Laricchia, G. & Deutch, B.I.
Partner: UNT Libraries Government Documents Department

Plasma modified production of high-current, high-purity cw H{sup +}, D{sup +}, and H{sup -} beams from microwave-driven sources

Description: We have recently reported production of cw proton beams from magnetically confined microwave-driven sources, operating under nonresonant (non-ECR) conditions, with proton fractions > 0.95, the remaining fraction consisting of H{sub 2}{sup +} (0.05) with no H{sub 3}{sup +}. We achieve this by adding H{sub 2}O to the plasma at molecular concentrations of 1% and about 700 W 2.45 GHz RF power to the source. High-current (45 mA) high-power (45 kV) beams of >92% proton purity have been produced using this technique. Additional impurity ions O{sup +} at 4ppt and OH{sup +} and H{sub 2}O{sup +} at << 1ppt are produced. We report further progress using this technique and similar results achieved for cw D{sup +} beams with D{sub 2}O and H{sub 2}O additives. Finally, we report progress made in the direct extraction of cw H{sup -} beams from microwave-driven sources in terms of ion source surface material and confining magnetic field configurations. Mechanisms are discussed.
Date: October 1996
Creator: Spence, D.; Lykke, K. R. & McMichael, G. E.
Partner: UNT Libraries Government Documents Department

Intensity limitations in compact H{sup minus} cyclotrons

Description: At TRIUMF, we have demonstrated 2.5 mA in a compact H{sup -} cyclotron. It is worthwhile to explore possibility of going to even higher intensity. In small cyclotrons, vertical focusing vanishes at the center. The space charge tune shift further reduces vertical focusing, thus determining an upper limit on instantaneous current. Limit on average current is of course also dependent upon phase acceptance, but this can be made quite large in an H{sup -} cyclotron. Longitudinal space charge on the first turn can reduce the phase acceptance as well. For finite ion source brightness, another limit comes from bunching efficiency in presence of space charge forces. We present methods of calculating and optimizing these limits. In particular, we show that it is possible to achieve 10mA in a 50 MeV compact H{sup -} cyclotron.
Date: December 31, 1995
Creator: Baartman, R.A.
Partner: UNT Libraries Government Documents Department

Multiphoton processes for atoms in intense electromagnetic fields

Description: Lasers from table-top to giant ICF facilities that produce intense electromagnetic fields (10{sup 14}-10{sup 21} W/cm{sup 2}) have become important tools in probing the intricate nature of matter-radiation interactions. At such intensities, the laser field equals or exceeds that which binds electrons to an atom or molecule, and a new realm of physics opens in which perturbation theory may no longer suffice. We are developing several sophisticated techniques for treating atoms in such a regime, concentrating on two-photon X-ray absorption in intermediate-weight atoms and on laser-assisted electron-atom collisions. We perform most calculations in a time-independent frame in which field-free scattering formalisms can be invoked. We also investigate time-dependent methods in order to study transient effects. This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).
Date: December 31, 1995
Creator: Collins, L.A.; Abdallah, J. & Csanak, G.
Partner: UNT Libraries Government Documents Department

LANSCE linac RF performance for a long pulse spallation source

Description: The present LANL Long Pulse Spallation Source (LPSS) design consists of a 1 MW neutron spallation target fed by a pulsed proton beam from the Los Alamos Neutron Science Center (LANSCE, formerly LAMPF) accelerator. This proton beam would have a repetition rate of 60 Hz and a pulse length of 1 ms for a duty factor of 6%. An average/peak currentof 1.25 mA/21 mA would be required foran 800 MeV beam to provide this power at this duty factor. The spallation target would reside in Area A and use the H+ beam. The LANSCE accelerator would also be required to simultaneoulsy deliver H- beams to the Manual Lujan Jr. Neutron Scattering Center (MLNSC) and Weapons Neutron Research (WNR) facility. Presently LANSCE delivers 16.5 mA peak of H+ beam at 120 Hz, with a 625 {mu}S beam pulsewidth; H- beams are also accelerated for MLNSC and WNR. In Nov. 1995, linac operation shifted to LPSS pulse parameters, except for the peak curent which remained at 16.5 mA. In addition to delivering 800 kW H+ proton beam to physics production targets, H- beams were simultaneously delivered to customers for the PSR feeding MLNSC and to researchers using WNR. Performance of the RF powerplants for the 201.25 MHz drift tube linac 805 MHz side coupled linac, and associated electronics is described. Conclusion of the experiment is that the LANSCE linac can be upgraded through modest improvements to drive a 1 MW LPSS.
Date: September 1, 1996
Creator: Lyles, J.; Regan, A. & Bolme, G.
Partner: UNT Libraries Government Documents Department

Proceedings of the workshop on ion source issues relevant to a pulsed spallation neutron source: Part 1: Workshop summary

Description: The workshop reviewed the ion-source requirements for high-power accelerator-driven spallation neutron facilities, and the performance of existing ion sources. Proposals for new facilities in the 1- to 5-MW range call for a widely differing set of ion-source requirements. For example, the source peak current requirements vary from 40 mA to 150 mA, while the duty factor ranges from 1% to 9%. Much of the workshop discussion centered on the state-of-the-art of negative hydrogen ion source (H{sup {minus}}) technology and the present experience with Penning and volume sources. In addition, other ion source technologies, for positive ions or CW applications were reviewed. Some of these sources have been operational at existing accelerator complexes and some are in the source-development stage on test stands.
Date: October 1, 1994
Creator: Schroeder, L.; Leung, K.N. & Alonso, J.
Partner: UNT Libraries Government Documents Department

Operation of the TFTR Pellet Charge Exchange Diagnostic in the Pulse Counting Mode during H+ RF-minority Heating

Description: The Pellet Charge Exchange technique on TFTR has been used primarily to obtain active charge exchange measurements using a high energy (0.5 - 4.0 MeV) neutral particle analyzer (NPA) in conjunction with impurity pellet injection (Li and B) with the scintillator-photomultiplier detector system operated in the current mode. While passive measurements using pulse counting were also obtained using this instrumentation, operation in this mode was very restrictive with pulse counting rates limited to less than {approximately}10 kHz in the absence of any significant neutron and gamma induced background signal. An upgrade to a specialized pulse counting capability which was developed by the Ioffe Institute was implemented which consisted of CsI(Tl) scintillators having features designed to minimize signals induced by background neutron and gamma rays and 16-channel pulse height analysis electronics on each of the eight NPA energy channels. Passive measurements of RF-driven energetic hydrogen minority ions which served to verify operation of the pulse counting mode are reported. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an RF power of 2 MW to 0.35 MeV at 6 MW.
Date: May 1998
Creator: Medley, S. S.
Partner: UNT Libraries Government Documents Department

The role of implantation damage in the production of silicon-on-insulator films by co-Implantation of He{sup +} and H{sup +}

Description: Recent work has demonstrated that the process of silicon thin film separation by hydrogen implantation, as well as the more basic phenomenon of surface blistering, can occur at a much lower total dose when H and He are co-implanted than when H is implanted alone. Building on that work, this paper investigates the role of implantation damage in this process by separating the contributions of gas pressure from those of damage. Three different experiments using co-implantation were designed. In the first of these experiments, H and He implants were spatially separated thereby separating the damage from each implant. The second experiment involved co-implantation of H and He at a temperature of 77 K to retain a larger amount of damage for the same gas dose. In the third experiment, Li was co-implanted with H, to create additional damage without introducing additional gas. These experiments together show that increasing the implantation damage itself hampers the formation of surface blisters, and that the increased efficiency observed for He co-implantation with H is due to the supplementary source of gas provided by the He.
Date: January 1, 1998
Creator: Venezia, V.C.; Agarwal, A.; Haynes, T.E.; Holland, O.W.; Eaglesham, D.J.; Weldon, M.K. et al.
Partner: UNT Libraries Government Documents Department

State-to-state photodetachment in the negative hydrogen ion

Description: In this final report of a 3-year LDRD project on the fundamental physics of the negative hydrogen ion, new physical phenomena were observed, including the first direct excitation (i.e. without intermediate resonances) of a multiphoton electron detachment resonance in an atomic ion, and the first excess photon detachment of an electron from an atomic species in competition with a single photon process. These new phenomena are relevant to modeling and theory discrimination in 3-body quantum mechanics.
Date: August 1, 1997
Creator: Strauss, C.E.; Funk, D.J.; Zhao, X.M.; Stintz, A.; Rislove, D.; Gulley, M. et al.
Partner: UNT Libraries Government Documents Department

PSR injection-line upgrade

Description: We describe the new injection line to be implemented for the Los Alamos Proton Storage Ring (PSR) in the change from a two-step injection process to direct H{sup -} injection. While obeying all geometrical constraints imposed by the existing structures, the new line has properties not found in the present injection line. bend In particular, it features decoupled transverse phase spaces downstream of the skew bend and a high degree of tunability of the beam at the injection foil. A comprehensive set of error studies has dictated the imposed component tolerances and has indicated the expected performance of the system.
Date: September 1, 1997
Creator: Blind, B. & Jason, A.J.
Partner: UNT Libraries Government Documents Department