W. Greenway

Short intense ion pulses for materials and warm dense matter research

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1 mm within 2 ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Finally, we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.

Li+ alumino-silicate ion source development for the neutralized drift compression experiment

We report results on lithium alumino-silicate ion source development in preparation for warm dense matter heating experiments on the new neutralized drift compression experiment II. The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ≈1275 °C, a space-charge limited Li(+) beam current density of J ≈1 mA/cm(2) was obtained. The lifetime of the ion source was ≈50 h while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 μs.

Electron-beam diagnostic for space-charge measurement of an ion beam

An electron beam diagnostic system for measuring the charge distribution of an ion beam without changing its properties is presently under development for Heavy Ion Fusion (HIF) beam physics studies. Conventional diagnostics require temporary insertion of sensors into the beam, but these capture it, or significantly alter its properties. In this new diagnostic a low energy, low current electron beam is scanned transversely across the ion beam; the measured electron beam deflection is used to calculate the line-integrated charge density of the ion beam, assuming at present a circular charge distribution that is functionally dependent only on radius. The initial application of this diagnostic is being made to the Neutralized Transport Experiment (NTX), which is exploring the physics of space charge dominated beam focusing through neutralizing plasma onto a small spot. The diagnostic system is able to scan an ion beam of up to 3 cm radius. Design and performance of this diagnostic system is presented.

Heavy ion fusion science research for high energy density physics and fusion applications

Heavy ion fusion science research for high energy density physics and fusion applications* B G Logan 1 , J J Barnard 2 , F M Bieniosek 1 , R H Cohen 2 , J E Coleman 1 , R C Davidson 3 , P C Efthimion 3 , A Friedman 2 , E P Gilson 3 , W G Greenway 1 , L Grisham 3 , D P Grote 2 , E Henestroza 1 , D H H Hoffmann 4 , I D Kaganovich 3 , M Kireeff Covo 2 , J W Kwan 1 , K N LaFortune 2 , E P Lee 1 , M Leitner 1 , S M Lund 2 , A W Molvik 2 , P Ni 1 ,G E Penn 1 , L J Perkins 2 , H Qin 3 , P K Roy 1 , A B Sefkow 3 , P A Seidl 1 , W Sharp 2 E A Startsev 3 , D Varentsov 4 , J-L Vay 1 , W L Waldron 1 , J S Wurtele 1 , D Welch , G. A. Westenskow 1 and S S Yu 1 Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA Gesellschaft fur Schwerionenforschung mbH, Darmstadt, Germany Voss Scientific, Albuquerque, NM, USA Corresponding Author’s E-mail: bglogan@lbl.gov Abstract During the past two years, the U.S. heavy ion fusion science program has made significant experimental and theoretical progress in simultaneous transverse and longitudinal beam compression, ion-beam-driven warm dense matter targets, high brightness beam transport, advanced theory and numerical simulations, and heavy ion target designs for fusion. First experiments combining radial and longitudinal compression of intense ion beams propagating through background plasma resulted in on-axis beam densities increased by 700X at the focal plane. With further improvements planned in 2007, these results will enable initial ion beam target experiments in warm dense matter to begin next year at LBNL. We are assessing how these new techniques apply to low-cost modular fusion drivers and higher-gain direct-drive targets for inertial fusion energy. 1. Introduction A coordinated heavy ion fusion science program by the Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, and Princeton Plasma Physics Laboratory (the Heavy-Ion Fusion Science Virtual National Laboratory), together with collaborators at Voss Scientific and GSI, pursues research on compressing heavy ion beams towards the high intensities required for creating high energy density matter and fusion energy. Previously, experiments in the Neutralized Drift Compression Experiment (NDCX) and simulations showed increases in focused beam intensities first by transverse focusing [1, 2] and then by longitudinal compression (>50 X) with an induction buncher that imparts increasing ion velocities from the head to the tail of a selected 150 ns slice of beam [3, 4]. Section 2 describes new work on combined radial and longitudinal compression of intense beams within neutralizing plasma. In Section 3 we describe the first joint U.S.-German warm dense matter experiments with porous targets using intense beams from the SIS 18 storage ring at GSI [5], together with plans for initial warm dense matter targets at LBNL next year. Progress in e-cloud research is presented in Section 4, advances in theory and simulations in Section 5, applications to heavy ion fusion in Section 6, and conclusions in Section 7. 2. Combined transverse and longitudinal compression of beams within neutralizing plasma Recent experiments in NDCX have combined neutralized drift compression with a new final focusing solenoid (FFS) and a new target chamber (Figure 1). The FFS was installed with a new beam target chamber, and the plasma density was measured before installing on the NDCX beam line. Two Filtered Cathodic Arc Plasma Sources (FCAPS) streamed aluminum metal plasma upstream toward the exit of the FFS, and a Langmuir probe was driven from the upstream end of the FFS toward the focal plane of the magnet, 18.27 cm downstream of the midplane of the FFS. * This research was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Berkeley and Lawrence Livermore National Laboratories under Contract Numbers DE-AC02-05CH11231 and W-7405-Eng-48, and by the Princeton Plasma Physics Laboratory under Contract Number DE-AC02-76CH03073.

Multiple arc ion sources for heavy ion fusion

Heavy ion fusion requires high current density, low‐emittance ion sources that are reliable and long lived. We report experimental and simulation results on the performance of carbon arc ion sources intended for use in a scaled induction linac experiment. These sources use a planar electrostatic plasma switch to prevent plasma from entering the extraction gap before the extraction voltage pulse is applied. This provides good beam optics for short pulse extraction. Measurements of current density and emittance are presented. Both double‐slit and channel plate‐pepper pot techniques are used for emittance measurement. Data presented are from a compact three‐arc source with plasma coupling of the cathodes. Data on lifetime and multiple arc triggering are also presented. The plasma switch performance has been modeled with a 2D explicit electrostatic particle‐in‐cell code. Results showing plasma shutoff phenomena and behavior during extraction are presented. A 2D steady‐state ion flow model is also used to pred...

Source fabrication and lifetime for Li+ ion beams extracted from alumino-silicate sources

A space-charge-limited beam with current densities (J) exceeding 1 mA/cm(2) have been measured from lithium alumino-silicate ion sources at a temperature of ∼1275 °C. At higher extraction voltages, the source appears to become emission limited with J ≥ 1.5 mA/cm(2), and J increases weakly with the applied voltage. A 6.35 mm diameter source with an alumino-silicate coating, ≤0.25 mm thick, has a measured lifetime of ∼40 h at ∼1275 °C, when pulsed at 0.05 Hz and with pulse length of ∼6 μs each. At this rate, the source lifetime was independent of the actual beam charge extracted due to the loss of neutral atoms at high temperature. The source lifetime increases with the amount of alumino-silicate coated on the emitting surface, and may also be further extended if the temperature is reduced between pulses.

Initial Results on Neutralized Drift Compression Experiments (NDCX-IA) for High Intensity Ion Beam

Ion beam neutralization and compression experiments are designed to determine the feasibility of using compressed high intensity ion beams for high energy density physics (HEDP) experiments and for inertial fusion power. To quantitatively ascertain the various mechanisms and methods for beam compression, the Neutralized Drift Compression Experiment (NDCX) facility is being constructed at Lawrence Berkeley National Laboratory (LBNL). In the first neutralized drift compression experiment, a 280 KeV, 25 mA, K+ion beam is longitudinally 50-fold compressed using an induction core to produce a velocity tilt. This compression ratio is measured using various diagnostics.

Electrical breakdown studies with Mycalex insulators

Insulating materials such as alumina and glass-bonded mica (Mycalex) are used in accelerator systems for high voltage feedthroughs, structural supports, and barriers between high voltage insulating oil and the vacuum beam pipe in induction accelerator cells. Electric fields in the triple points should be minimized to prevent voltage breakdown. Mechanical stress can compromise seals and result in oil contamination of the insulator surface. We have tested various insulator cleaning procedures including ultrasonic cleaning with a variety of aqueous-based detergents, and manual scrubbing with various detergents. Water sheeting tests were used to determine the initial results of the cleaning methods. Ultimately, voltage breakdown tests will be used to quantify the benefits of these cleaning procedures.

HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY 3nd QUARTER 2009 MILESTONE REPORT: Upgrade plasma source configuration and carry out initial experiments. Characterize improvements in focal spot beam intensity

HIFAN 1757 HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY, 3rd QUARTER 2009 MILESTONE REPORT, Upgrade plasma source configuration and carry out initial experiments. Characterize improvements in focal spot beam intensity by S. Lidia, A. Anders, F.M. Bieniosek, A. Faltens, W. Greenway, J.Y. Jung, T. Katayanagi, B.G. Logan, C.W. Lee, M. Leitner, P. Ni, A. Pekedis, M. J. Regis, P. K. Roy, P. A. Seidl, W. Waldron Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA J.J. Barnard, A. Friedman, D. Grote, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA M. Dorf, E. Gilson Princeton Plasma Physics Laboratory Accelerator Fusion Research Division Ernest Orlando Lawrence Berkeley National Laboratory University of California June 2009 This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY 4th QUARTER 2008 MILESTONE REPORT

HIFAN 1667 HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY 4th QUARTER 2008 MILESTONE REPORT Carry out initial target experiment in the new target chamber, using beams compressed and focused by an improved bunching waveform and a final focus solenoid. F.M. Bieniosek, A. Anders, J.J. Barnard, M.R. Dickinson, W. Greenway, E. Henestroza, T. Katayanagi, B.G. Logan, C.W. Lee, M. Leitner, S. Lidia, R. M. More, P. Ni, P. K. Roy, P. A. Seidl, W. Waldron LBNL Accelerator Fusion Research Division Ernest Orlando Lawrence Berkeley National Laboratory University of California Berkeley, California 94720 September 2008 This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.