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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

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.; Barnett, C. F. & Reinhardt, R.
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

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

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

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

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

The separation of control variables in an H/sup /minus// ion source

Description: This paper describes a successful methodology which was used to classify a series if waveforms taken from a 100 ma H/sup /minus// ion source at Los Alamos. The series of 260 waveforms was divided into a ''training'' set and a ''test'' set. A sequence of mathematical transformations was performed on the ''training'' waveforms data and then it was subjected to discriminant analysis. The analysis generates a set of filters which will allow classification of an unknown waveform in the ''test'' set as being either stable or unstable; if stable, whether optimal or not; if not optimal, which of the six control parameters should be adjusted to bring it to an optimal condition. We have found that the probability of successful classification using this methodology is 91.5%. 3 refs., 4 figs., 2 tabs.
Date: January 1, 1988
Creator: Bowling, P. S. & Brown, S. K.
Partner: UNT Libraries Government Documents Department

H/sup -/ ion source scaling studies at LBL

Description: Four experiments are reported. Constant arc voltage operation was compared with constant arc current operation over a similar range of plasma density. The higher arc voltage required in the constant arc current operation produced more H/sup -/, but it was at the expense of an even larger increase in the accelerated electron current. A comparison of different magnetic filter locations showed the highest accelerated H/sup -/ and the lowest e/sup -/ content at the closest filter location. Beam-forming electrode aperture comparison for round apertures from 2mm to 10mm diameters and a 11 x 27 mm oval slot showed a decreasing H/sup -/ and e/sup -/ with increasing aperture area. Increasing accelerator voltage produced an increasing plasma potential and electron temperature and decreasing electron density in the exit chamber of the plasma source.
Date: October 1, 1986
Creator: Lietzke, A. F. & Hauck, C. A.
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

Plasma ignition schemes for the SNS radio-frequency driven H- source

Description: The H{sup -} ion source for the Spallation Neutron Source (SNS) is a cesiated, radio-frequency driven (2 MHz) multicusp volume source which operates at a duty cycle of 6% (1 ms pulses and 60 Hz). In pulsed RF driven plasma sources, ignition of the plasma affects the stability of source operation and the antenna lifetime. We are reporting on investigations of different ignition schemes, based on secondary electron generation in the plasma chamber by UV light, a hot filament, a low power RF plasma (cw, 13.56 MHz), as well as source operation solely with the high power (40 kW) 2 MHz RF. We find that the dual frequency, single antenna scheme is most attractive for the operating conditions of the SNS H{sup -} source.
Date: September 6, 2001
Creator: Schenkel, T.; Staples, J.W.; Thomae, W.; Reijonen, J.; Gough, R.A.; Leung, K.N. et al.
Partner: UNT Libraries Government Documents Department

Phase-scan analysis results for the first drift tube linac module in the ground test accelerator: Data reproducibility and comparison to simulations

Description: The Ground Test Accelerator (GTA) had the objective of producing a high-brightness, high-current H- beam. The major accelerator components were a 35 keV injector, a Radio Frequency Quadrupole, an intertank matching section, and a drift tube linac (DTL), consisting of 10 modules. This paper discusses the phase-scan technique which was used to experimentally determine the rf operating parameters for the commissioning and routine operation of the first DTL module.
Date: May 1, 1995
Creator: Johnson, K.F.; Sander, O.R. & Bolme, G.O.
Partner: UNT Libraries Government Documents Department

Filament heater current modulation for increased filament lifetime

Description: The surface conversion H-minus ion source employs two 60 mil tungsten filaments which are approximately 17 centimeters in length. These filaments are heated to approximately 2,800 degrees centigrade by 95--100 amperes of DC heater current. The arc is struck at a 120 hertz rate, for 800 microseconds and is generally run at 30 amperes peak current. Although sputtering is considered a contributing factor in the demise of the filament, evaporation is of greater concern. If the peak arc current can be maintained with less average heater current, the filament evaporation rate for this arc current will diminish. In the vacuum of an ion source, the authors expect the filaments to retain much of their heat throughout a 1 millisecond (12% duty) loss of heater current. A circuit to eliminate 100 ampere heater currents from filaments during the arc pulse was developed. The magnetic field due to the 100 ampere current tends to hold electrons to the filament, decreasing the arc current. By eliminating this magnetic field, the arc should be more efficient, allowing the filaments to run at a lower average heater current. This should extend the filament lifetime. The circuit development and preliminary filament results are discussed.
Date: June 1, 1996
Creator: Paul, J.D. & Williams, H.E. III
Partner: UNT Libraries Government Documents Department