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Paper Title Other Keywords Page
MOP044 Status of DPIS Development in BNL laser, ion, target, rfq 169
  • M. Okamura
    BNL, Upton, Long Island, New York
  • T. Kanesue
    Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
  • J. Tamura
    Department of Energy Sciences, Tokyo Institute of Technology, Yokohama

Direct injection scheme was proposed in 2000 at RIKEN in Japan. The first beam test was done at Tokyo Institute of Technology using a CO2 laser and an 80 MHz 4 vane RFQ in 2001, and further development continued in RIKEN. In 2006, all the experimental equipment was moved to BNL and a new development program was started. We report on our recent activities at BNL including the use of a frozen gas target for the laser source, low charge state ion beam production and a newly developed laser irradiation system.

MOP045 Design Study of a DPIS Injector for a Heavy Ion FFAG laser, ion, rfq, injection 172
  • M. Okamura, D. Raparia
    BNL, Upton, Long Island, New York
  • K. Ishibashi, T. Kanesue, Y. Yonemura
    Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka

Direct plasma injection scheme has been developed recently for producing and accelerating intense pulsed heavy ion beams with high charge states. This new method uses a combination of a laser ion source and an RFQ linear accelerator and its repetition rate is determined by the laser system. Fixed field alternating gradient (FFAG) accelerator is being focused as a high repetition synchrotron. An integration of these new techniques enables one to produce a large beam power with heavy ion beams. At Ito campus of Kyushu University, a proton FFAG is being installed. We propose to construct a new injector linac for the FFAG. The planned operating parameters are 100 Hz repetition rate, 20 mA of fully stripped carbon beam and 200 MHz operating frequency for the linac.

MOP068 Trains of Sub-Picosecond Electron Bunches for High-Gradient Plasma Wakefield Acceleration wakefield, electron, emittance, simulation 235
  • P. Muggli
    UCLA, Los Angeles, California
  • M. Babzien, K. Kusche, J.H. Park, V. Yakimenko
    BNL, Upton, Long Island, New York
  • M.J. Hogan
    SLAC, Menlo Park, California
  • E. Kallos
    USC, Los Angeles, California

Funding: Work Supported by US Department of Energy
In the plasma wakefield accelerator (PWFA), high quality accelerated electron bunches can be produced by injecting a witness bunch behind a single drive bunch or a train of N bunches. To operate at large gradient the plasma density must be in the 1017/cc range, corresponding to a typical bunch separation of the order of the plasma wavelength or ≈100μm. We have demonstrated that such a sub-picosecond temporal bunch structure can be produced using a mask to selectively spoil the emittance of temporal slices of the bunch*. The bunches spacing, as well as their length can be tailored by designing the mask and choosing the beam parameters at the mask location. The number of bunches is varied by using an adjustable width energy limiting slit. The bunches spacing is measured with coherent transition radiation interferometry. Experimental results will be presented and compared to simulations of the bunch train formation process with the particle tracking code ELEGANT.

*P. Muggli et al., to appear in Phys. Rev. Lett. (2008).

TU301 Positron Beams Propagation in Plasma Wakefield Accelerators positron, emittance, electron, laser 374
  • P. Muggli
    UCLA, Los Angeles, California

Funding: Work Supported by US Department of Energy
Plasma-based accelerators are one of the emerging technologies that could revolutionize e-/e+ colliders, significantly reducing their size and cost by operating at multi-GeV/m accelerating gradients. Proof-of-principle experiments at SLAC have demonstrated the energy doubling of 42 GeV incoming e- in a plasma only ≈85 cm-long,* corresponding to an unloaded gradient of ≈50 GeV/m. Plasma wakes driven by e+ bunches are different from those driven by e- bunches. The acceleration of e+ in plasmas has been demonstrate,** but the acceleration of high-quality e+ beams is challenging. Measurements show that single e+ bunches suffer halo formation and emittance growth when propagating through dense meter-scale, uniform plasmas.*** Advanced schemes, such as hollow plasma channels, or e+ bunch acceleration on the wake driven by a e bunch, may have to be used in a future plasma-based linear collider. Experimental results obtained with e+ beams in plasmas will be reviewed and compared to those obtained with e- beams. Future experiments including a new scheme to produce a drive e bunch closely followed by a witness e+ bunch appropriate for PWFA experiments will also be discussed.

*I. Blumenfeld et al., Nature 445, 741-744 (15 February 2007).
**B.E. Blue et al., Phys. Rev. Lett. 90, 214801 (2003).
***P. Muggli et al., accepted for publication in Phys. Rev. Lett. (2008).


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TU302 Control, Stability and Staging in Laser Wakefield Accelerators laser, controls, linac, wakefield 379
  • D. Panasenko
    LBNL, Berkeley, California

Laser driven plasma wakefields have recently accelerated electron beams with quasi-monoenergetic energy distributions and with gradients of ~100 GV/m. Stabilization and optimization of beam quality are now essential. Recent LBNL experiments have demonstrated control of self trapping, resulting in reproducible bunches at 0.5 GeV. Further optimization has been demonstrated using plasma density gradients to control trapping, producing beams with very low absolute momentum spread at low energies. Simulations indicate that use of these beams as an injector greatly improves accelerator performance and experiments are now underway to demonstrate such staging, which will be a crucial technology for laser driven linacs. This talk will cover recent progress in LWFAs to obtain more reproducible, higher quality beams and also cover staging prospects for high energy laser linacs.


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TUP116 Development of Very Small ECR Ion Source with Pulse Gas Valve ion, ion-source, extraction, ECR 673
  • M. Ichikawa, H. Fujisawa, Y. Iwashita, T. Sugimoto, H. Tongu, M. Yamada
    Kyoto ICR, Uji, Kyoto

We aim to develop a small and high intensity proton source for a compact accelerator based neutron source. Because this proton source shall be located close to RFQ for simplification, ratio of H+ to molecular ions such as H2+ or H3+ must be large. Therefore we select ECR ion source with permanent magnet as a small and high intensity ion source. ECR ion sources can provide high H+ ratio because of their high plasma temperature. Using permanent magnets makes the ion source small and running cost low. Because there is no hot cathode, longer MTBF is expected. Usually, gas is fed into ion sources continuously, even if ion sources run in pulse operation mode. But, continuous gas flow doesn't make vacuum in good level. So, we decided to install pulse gas valve directly to the plasma chamber. Feeding the gas only when the ion source is in operation reduces the gas load to the evacuation system and the vacuum level can be kept high. Recent experimental results will be presented.

TUP119 Ramping Up the SNS Beam Current with the LBNL Baseline H- Source rfq, ion, ion-source, neutron 682
  • M.P. Stockli, B. Han, S.N. Murray, T.R. Pennisi, M. Santana, R.F. Welton
    ORNL, Oak Ridge, Tennessee
  • D.J. Newland
    ORNL RAD, Oak Ridge, Tennessee

Funding: *SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
During the first three years, the Spallation Neutron Source is ramping up the rep rate, pulse length, and beam current to reach 1 to 1.4 MW beam power in 2009. This challenges the Front-end with the H- source designed and built by Lawrence Berkeley National Laboratory. Early in 2007, the low-energy beam transport needed to be modified to improve the availability for duty factors in excess of 0.2%. Late in 2007, the H- source needed to be modified to produce the required 25 mA LINAC beam current during the ~0.4 ms long pulses at 60 Hz. The optimistic 1.4 MW goal requires 38 mA LINAC beam current, which was demonstrated for 4 hours on 12/24/07. LBNL developed a cesium system that uses only 30 mg of Cs to minimize the risk to the adjacent electrostatic LEBT and RFQ. Improved procedures and configuration were needed to generate intense beam currents for long pulses (>0.2 ms). Now optimal beam currents are reached within eight hours of replacing the H- source. The beam decay appears to be as small as 1% per day, which is compensated by a gradual increase in rf power. The peak performance can be restored by slowly re-cesiating the converter without interupting the neutron production.

TH104 An Overview of Linac Ion Sources ion, ECR, ion-source, electron 740
  • R. Keller
    LANL, Los Alamos, New Mexico

Funding: This work was supported by the US Department of Energy under Contract Number DE-AC52-06NA25396
For the purpose of this presentation, the term Linac is narrowed down to comprise rf machines that accelerate ion beams at duty factors between about 5% and continuous operation. This group of Linacs includes proton and H- machines as well as accelerators utilizing multi-charged heavy ions, mostly for nuclear physics applications. Main types of ion sources serving these Linacs include Electron Cyclotron Resonance (ECR) sources, filament and rf driven multi-cusp sources, Penning (PIG) sources and duoplasmatrons. This presentation does not strive to attain encyclopedic character but rather to highlight current trends in performance parameters, major lines of development and type-specific limitations and problems, with emphasis on ECR and multi-cusp sources. The main technical aspects being discussed are ion production and beam formation.


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TH201 Charge State Boosters for Radioactive Ion Acceleration ion, electron, ECRIS, ion-source 745
  • F. Ames
    TRIUMF, Vancouver

For the post acceleration of radioactive ions produced at ISOL facilities the increase of the charge state is essential to reduce the A/q requirements of the accelerators. Many of those existing or proposed facilities are relying on the performance of charge state boosters of EBIS or ECRIS type. Although, in principle both types of sources can be used in pulsed or continuous mode operation an EBIS is better suited for pulsed beams whereas an ECRIS is most efficient in a continuous mode. The present state of the art with respect to existing data of both sources will be presented and potential future developments will be discussed. Latest results from the on line commissioning of a PHOENIX ECRIS charge breeder at ISAC will be presented.


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TH203 Beam Compression in Heavy-Ion Induction Linacs target, ion, solenoid, focusing 754
  • P.A. Seidl, A. Anders, F.M. Bieniosek, A.X. Chen, J.E. Coleman, J.-Y. Jung, M. Leitner, S.M. Lidia, B.G. Logan, P.N. Ni, P.K. Roy, K. Van den Bogert, W.L. Waldron
    LBNL, Berkeley, California
  • J.J. Barnard, R.H. Cohen, D.P. Grote
    LLNL, Livermore, California
  • J.A. Calanog
    UCB, Berkeley, California
  • M. Dorf, E.P. Gilson
    PPPL, Princeton, New Jersey
  • D.R. Welch
    Voss Scientific, Albuquerque, New Mexico

Funding: This work was supported by the Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, DE-AC52-07NA27344, DE-AC02-76CH3073.
The Heavy-Ion Fusion Sciences Virtual National Laboratory is pursuing an approach to target heating experiments in the Warm Dense Matter regime, using space-charge-dominated ion beams that are simultaneously longitudinally bunched and transversely focused. Longitudinal beam compression by large factors has been demonstrated in the LBNL Neutralized Drift Compression Experiment (NDCX) experiment with controlled ramps and forced neutralization. The achieved peak beam current and energy can be used in experiments that generate plasmas of warm dense matter. Using an injected 30 mA K+ ion beam with initial kinetic energy 0.3 MeV, axial compression leading to ~100X current amplification and simultaneous radial focusing to beam radii of a few mm have led to encouraging energy deposition approaching the intensities required for eV-range target heating experiments. We discuss the status of several improvements to the experiment and associated beam diagnostics that are under development to reach the necessary higher beam intensities.


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THP096 Next Generation IGBT Switch Plate Development for the SNS High Voltage Converter Modulator simulation, high-voltage, pulsed-power, diagnostics 1012
  • M.A. Kemp, C. Burkhart, M.N. Nguyen
    SLAC, Menlo Park, California
  • D.E. Anderson
    ORNL, Oak Ridge, Tennessee

Funding: Work supported by the U.S. Department of Energy under contract DE-AC05-00OR22725
The rf source High Voltage Converter Modulator systems installed on the Spallation Neutron Source have operated well in excess of 200,000 hours, during which time numerous failures have occurred. An improved IGBT switch plate is under development to help mitigate these failures. The new design incorporates three significant improvements. The IGBTs are upgraded to 4.5 kV, 1200 A, press-pack devices, which increase the voltage margin, facilitate better cooling, and eliminate explosive disassembly of the package in the event of device failure. The upgrade to an advanced IGBT gate drive circuit decreases switching losses and improves fault-condition response. A common-mode choke is incorporated into the H-bridge to decrease dI/dt during a shoot-through condition, to further improve the circuit response to this fault condition. The upgrade design and development status will be presented.