B.G. Logan

An Updated Point Design for Heavy Ion Fusion

Abstract An updated, self-consistent point design for a heavy ion fusion (HIF) power plant based on an induction linac driver, indirect-drive targets, and a thick liquid wall chamber has been completed. Conservative parameters were selected to allow each design area to meet its functional requirements in a robust manner, and thus this design is referred to as the Robust Point Design (RPD-2002). This paper provides a top-level summary of the major characteristics and design parameters for the target, driver, final focus magnet layout and shielding, chamber, beam propagation to the target, and overall power plant.

Beam dynamics of the Neutralized Drift Compression Experiment-II, a novel pulse-compressing ion accelerator

Intense beams of heavy ions are well suited for heating matter to regimes of emerging interest. A new facility, NDCX-II, will enable studies of warm dense matter at ∼1 eV and near-solid density, and of heavy-ion inertial fusion target physics relevant to electric power production. For these applications the beam must deposit its energy rapidly, before the target can expand significantly. To form such pulses, ion beams are temporally compressed in neutralizing plasma; current amplification factors of ∼50–100 are routinely obtained on the Neutralized Drift Compression Experiment (NDCX) at the Lawrence Berkeley National Laboratory. In the NDCX-II physics design, an initial non-neutralized compression renders the pulse short enough that existing high-voltage pulsed power can be employed. This compression is first halted and then reversed by the beam’s longitudinal space-charge field. Downstream induction cells provide acceleration and impose the head-to-tail velocity gradient that leads to the final neutraliz...

Ion-beam-driven warm dense matter experiments

Author(s): Bieniosek, F.M.; Ni, P.; Leitner, M.; Roy, P.; More, R.; Barnard, J.J.; Covo, M. Kireeff; Molvik, A.W.; Yoneda, H.

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.

Towards a Modular Point Design for Heavy Ion Fusion

Abstract We report on an ongoing study on modular Heavy Ion Fusion (HIF) drivers. The modular driver is characterized by ~20 nearly identical induction linacs, each carrying a single high current beam. In this scheme, one of the full size induction linacs can be tested as an “integrated Research Experiment” (IRE). Hence this approach offers significant advantages in terms of driver development path. For beam transport, these modules use solenoids, which are capable of carrying high line charge densities, even at low energies. A new injector concept allows compression of the beam to high line densities right after the source. The final drift compression is performed in a plasma in which the large repulsive space charge effects are neutralized. Finally, the beam is transversely compressed onto the target, using either external solenoids or current-carrying channels (in the assisted pinch mode of beam propagation). We report on progress towards a self-consistent point design from injector to target. Considerations of driver architecture, chamber environment as well as the methodology for meeting target requirements of spot size, pulse shape and symmetry are also described. Finally, some near-term experiments to address the key scientific issues are discussed.

Induction accelerator technology choices for the integrated beam experiment (IBX)

Abstract Over the next three years the research program of the Heavy Ion Fusion Virtual National Laboratory (HIF-VNL), a collaboration among LBNL, LLNL, and PPPL, is focused on separate scientific experiments in the injection, transport and focusing of intense heavy ion beams at currents from 100 mA to 1 A. As a next major step in the HIF-VNL program, we aim for a complete “source-to-target” experiment, the Integrated Beam Experiment (IBX). By combining the experience gained in the current separate beam experiments IBX would allow the integrated scientific study of the evolution of a single heavy ion beam at high current (~1 A) through all sections of a possible heavy ion fusion accelerator: the injection, acceleration, compression, and beam focusing. This paper describes the main parameters and technology choices of the planned IBX experiment. IBX will accelerate singly charged potassium or argon ion beams up to 10 MeV final energy and a longitudinal beam compression ratio of 10, resulting in a beam current at target of more than 10 Amperes. Different accelerator cell design options are described in detail: Induction cores incorporating either room temperature pulsed focusing-magnets or superconducting magnets.

Simulations for experimental study of warm dense matter and inertial fusion energy applications on NDCX-II

The Neutralized Drift Compression Experiment II (NDCX II) is an induction accelerator planned for initial commissioning in 2012. The final design calls for a {approx}3 MeV, {approx}30 A Li{sup +} ion beam, delivered in a bunch with characteristic pulse duration of 1 ns, and transverse dimension of order 1 mm. The purpose of NDCX II is to carry out experimental studies of material in the warm dense matter regime, and ion beam/hydrodynamic coupling experiments relevant to heavy ion based inertial fusion energy. In preparation for this new machine, we have carried out hydrodynamic simulations of ion-beam-heated, metallic solid targets, connecting quantities related to observables, such as brightness temperature and expansion velocity at the critical frequency, with the simulated fluid density, temperature, and velocity. We examine how these quantities depend on two commonly used equations of state.

A solenoid final focusing system with plasma neutralization for target heating experiments

Intense bunches of low-energy heavy ions have been suggested as means to heat targets to the warm dense matter regime (Temperature ~ 0.1 to 10 eV, solid density ~1% to 100%). In order to achieve the required intensity on target, a beam spot radius of approximately 0.5 mm, and pulse duration of 2 ns is required with an energy deposition of approximately 1 J/cm2. This translates to a peak beam current of 8 A for 0.4 MeV K+ ions. To increase the beam intensity on target, a plasma-filled high-field solenoid is being studied as a means to reduce the beam spot size from several mm to the sub-mm range. A prototype experiment to demonstrate the required beam dynamics has been built at Lawrence Berkeley National Laboratory. The operating magnetic field of the pulsed solenoid is 8 T. Challenges include suitable injection of the plasma into the solenoid so that the plasma density near the focus is sufficiently high to maintain space- charge neutralization of the ion beam pulse. Initial experimental results are presented.

Plans for Warm Dense Matter and IFE Target Experiments on NDCX-II

The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) is currently developing design concepts for NDCX-II, the second phase of the Neutralized Drift Compression Experiment, which will use ion beams to explore Warm Dense Matter (WDM) and Inertial Fusion Energy (IFE) target hydrodynamics. The ion induction accelerator will consist of a new short pulse injector and induction cells from the decommissioned Advanced Test Accelerator (ATA) at Lawrence Livermore National Laboratory (LLNL). To fit within an existing building and to meet the energy and temporal requirements of various target experiments, an aggressive beam compression and acceleration schedule is planned. WDM physics and ion-driven direct drive hydrodynamics will initially be explored with 30 nC of lithium ions in experiments involving ion deposition, ablation, acceleration and stability of planar targets. Other ion sources which may deliver higher charge per bunch will be explored. A test stand has been built at Lawrence Berkeley National Laboratory (LBNL) to test refurbished ATA induction cells and pulsed power hardware for voltage holding and ability to produce various compression and acceleration waveforms. Another test stand is being used to develop and characterize lithium-doped aluminosilicate ion sources. The first experiments will include heating metallic targets to 10,000 K and hydrodynamics studies with cryogenic hydrogen targets.

Meter-long plasma source for heavy ion beam space charge neutralization

Plasmas are a source of unbound electrons for charge neutralizing intense heavy ion beams to allow them to focus to a small spot size and compress their axial pulse length. The plasma source should be able to operate at low neutral pressures and without strong externally- applied electric or magnetic fields. To produce one- meter-long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients have been developed. The source utilizes the ferroelectric ceramic BaTiO3 to form metal plasma. The drift tube inner surface of the neutralized drift compression experiment (NDCX) is covered with ceramic material, and high voltage (~8 kV) is applied between the drift tube and the front surface of the ceramics. A lead- zirconium-titanate prototype ferroelectric plasma source (FEPS), 20 cm in length, has produced plasma densities of 5times1011 cm-3. It was integrated into the neutralized transport experiment (NTX), and successfully charge neutralized the K+ ion beam. A one-meter-long BaTiO3 source comprised of five 20-cm-long sources has been tested and characterized, producing relatively uniform plasma over the one-meter length of the source in the mid-1010 cm-3 density range. This source has been integrated into the NDCX device for charge neutralization and beam compression experiments. Initial beam compression experiments with this source yielded current compression ratios near 100. Future research will develop longer and higher plasma density sources to support beam compression experiments for high energy density physics applications.