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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

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

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

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

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

Summary Report of H- Injection Session II

Description: The H<sup>-</sup> injection was invented many years ago and has since been successfully applied in many machines over the last decades. The challenge to the high intensity machines is how to reduce the injection loss, which is usually the major part of total beam losses in a machine. Painting, both longitudinal and transverse, is an effective way to reduce the space charge e#11;ects and to minimize losses. RF capture of a chopped beam also gives better e#14;ciency than adiabatic capture. To employ a 2nd harmonic rf system to atten the rf bucket shape is another commonly used scheme. To compensate the capacitive space charge impedance by an inductive insert could be a new venture, but which is not discussed at the workshop due to time limitation. The foil physics is well understood. Simulations seem to be able to include all the important e#11;ects in it, including the space charge. The general feeling is that we are in a good position concerning H<sup>-</sup> injection studies. Although there remains a number of design issues, the knowledge, experiences and tools in our hand should be able to address each of them properly.
Date: June 28, 1999
Creator: Chou, Weiren
Partner: UNT Libraries Government Documents Department

Application of a transverse phase-space measurement technique for high-brightness, H{sup {minus}} beams to the GTA H{sup {minus}} beam

Description: The Ground Test Accelerator (GTA) had the objective Of Producing a high-brightness, high-current H-beam. The major components were a 35 keV injector, a Radio Frequency Quadrupole (RFQ), an intertank matching section (IMS), and a drift tube linac (DTL), consisting of 10 modules. A technique for measuring the transverse phase-space of high-power density beams has been developed and tested. This diagnostic has been applied to the GTA H-beam. Experimental results are compared to the slit and collector technique for transverse phase-space measurements and to simulations.
Date: May 1, 1995
Creator: Johnson, K.F.; Garcia, R.C.; Rusthoi, D.P.; Sander, O.R.; Sandoval, D.P.; Shinas, M.A. et al.
Partner: UNT Libraries Government Documents Department

BNL volume H{sup {minus}} source research

Description: At BNL, work is in progress on the development of a volume production H{sup -} ion source having a toroidally shaped plasma generation region and a conical filter field. With the original, 20 cm diameter source, up to 50 mA of H{sup -} was measured at a current density of 25 mA/cm{sup 2} in pulsed operation. In first results with a version of this source scaled down to 9.7 cm diameter, up to 25 mA of H{sup -} at a current density of 50 mA/cm{sup 2} has been obtained. In both sources the extracted electron current is typically 3--10 times the H{sup -} current.
Date: October 1, 1992
Creator: Alessi, J. G.; McCafferty, D. & Prelec, K.
Partner: UNT Libraries Government Documents Department

Enhanced H{sup {minus}} ion source testing capabilities at LANSCE

Description: As part of the on-going beam-current upgrade in the Proton Storage Ring (PSR) at the Los Alamos Neutron Science Center (LANSCE), the current available from the H{sup {minus}} injector will be increased from the present 16 to 18 mA to as much as 40 mA. A collaboration between the Ion Beam Technology Group at Lawrence Berkeley National Laboratory (LBNL) and the Ion Sources and Injectors section of LANSCE-2 at Los Alamos National Laboratory (LANL) has been formed to develop and evaluate a new ion source. A new Ion Source Test Stand (ISTS) has been constructed at LANSCE to evaluate candidate ion sources. The ISTS has been constructed to duplicate as closely as possible the beam transport and ancillary systems presently in use in the LANSCE H{sup {minus}} injector, while incorporating additional beam diagnostics for source testing. The construction and commissioning of the ISTS will be described, preliminary results for the proof-of-principle ion source developed by the Berkeley group will be presented, and future plans for the extension of the test stand will be presented.
Date: December 31, 1998
Creator: Ingalls, W.B.; Hardy, M.W.; Prichard, B.A.; Sander, O.R.; Stelzer, J.E.; Stevens, R.R. et al.
Partner: UNT Libraries Government Documents Department

Atomic physics in strong fields. Final report, September 15, 1990--August 15, 1997

Description: In this final report the author presents a summary of recent research accomplishments. In this grant period (FY90--97), some 36 papers have been published. [See Part 4 for a list of publications]. Significant progress has been made in several areas, both in the development of new theoretical and computational methods, their applications to experimental observations, and in the prediction of some novel new high-intensity phenomena. More detailed discussions on individual research project can be found in previous DOE annual reports and in published articles. Summaries are given of recent research accomplishments in the following areas: (1) time evolution and multiphoton ionization of Rydberg wavepacket in microwave fields; (2) multiphoton detachment of H{sup {minus}}; (3) multiphoton and above-threshold ionization in two-color fields; (4) multiphoton above-threshold ionization by intense laser pulses; and (5) laser-induced chemical bond softening and hardening of H{sub 2}{sup +}, and D{sub 2}{sup +} in intense laser fields.
Date: December 1, 1997
Creator: Chu, S. I.
Partner: UNT Libraries Government Documents Department

Overview and status of the Los Alamos PSR injection upgrade project

Description: An upgrade is in progress to the Los Alamos Proton Storage Ring (PSR) to allow direct injection of the H{sup {minus}} beam into the ring and provide a beam bump system to move the circulating beam off the stripper foil. The primary benefits of this upgrade are matching the transverse phase space of the injected beam to the PSR acceptance and reduction of foil hits by the circulating beam by a factor of ten. Foil thickness is optimized to minimize the combination of circulating-beam losses plus losses due to excited H{sup 0} states produced at injection. An overall factor of five reduction in losses is expected. The project comprises extensive modifications of the injection line, the injection section of the ring, and the waste-beam transport line. The authors will discuss the goals of the project, present an overview of the technical design, and describe the status of the implementation plan.
Date: August 1, 1997
Creator: Fitzgerald, D.H.; Ahn, H. & Blind, B.
Partner: UNT Libraries Government Documents Department

Electronic excitation in transmission of relativistic H{sup {minus}} ions through thin foils

Description: The authors describe a theoretical model to study the transmission of relativistic H{sup {minus}} ions through thin carbon foils. The approach is based on a Monte Carlo solution of the Langevin equation describing electronic excitations of the atoms during the transport through the foil. Calculations for the subshell populations of outgoing hydrogen atoms are found to be in good agreement with recent experimental data on an absolute scale and show that there exists a propensity for populating extreme Stark states.
Date: May 7, 1998
Creator: Reinhold, C.O.; Kuerpick, P.; Burgdoerfer, J.; Yoshida, S. & Gervais, B.
Partner: UNT Libraries Government Documents Department

Multicusp sources for ion beam lithography applications

Description: Application of the multicusp source for Ion Projection Lithography is described. It is shown that the longitudinal energy spread of the positive ions at the extraction aperture can be reduced by employing a magnetic filter. The advantages of using volume-produced H{sup {minus}} ions for ion beam lithography is also discussed.
Date: May 1, 1995
Creator: Leung, K.N.; Herz, P.; Kunkel, W.B.; Lee, Y.; Perkins, L.; Pickard, D. et al.
Partner: UNT Libraries Government Documents Department

Electron energy spectra of H{sup {minus}} autodetaching states resulting from collisions of H{sup {minus}} with He at 1 keV

Description: Electron energy spectra for H{sup {minus}} autodetaching states resulting from collisions H{sup {minus}} with He at 1 keV are rigorously calculated by including couplings between doubly excited states and continuum states and their interference with direct detachment processes. An energy sampling procedure, based on the Gauss quadratures, is used to discretize continuum states. The present theoretical result, for the first time, clarifies mechanisms of excitation to doubly excited states, quantitatively reproduces the experimental spectra first observed by Risley and Geballe in 1974, separates the contributions from each of three autodetaching states, and identifies the cause of the interference between autodetaching and direct-detaching excitation channels.
Date: June 1, 1995
Creator: Kimura, M.; Sato, H.; Hino, K. & Matsuzawa, M.
Partner: UNT Libraries Government Documents Department

The TRIUMF optically-pumped polarized H{sup {minus}} ion source

Description: The TRIUMF dc optically-pumped polarized H{sup {minus}} ion source (OPPIS) produces 200 {micro}A dc H{sup {minus}} current at 85% polarization within a normalized emittance (90%) of 0.8 {pi} mm mrad, for operations at the TRIUMF cyclotron. As a result of development of the ECR primary proton source, 1.6 mA dc polarized H{sup {minus}} current is produced within a normalized emittance of 2 {pi} mm mrad, suitable for high energy accelerators. The OPPIS has also been developed for use in a parity non-conservation experiment which has very severe limits on permissible helicity-correlated changes in beam current and energy.
Date: September 1, 1995
Creator: Levy, C.D.P.; Jayamanna, K. & McDonald, M.
Partner: UNT Libraries Government Documents Department