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Overview of Theory and Simulations in the Heavy Ion Fusion ScienceVirtual National Laboratory

Description: The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) is a collaboration of Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, and Princeton Plasma Physics Laboratory. These laboratories, in cooperation with researchers at other institutions, are carrying out a coordinated effort to apply intense ion beams as drivers for studies of the physics of matter at extreme conditions, and ultimately for inertial fusion energy. Progress on this endeavor depends upon coordinated application of experiments, theory, and simulations. This paper describes the state of the art, with an emphasis on the coordination of modeling and experiment; developments in the simulation tools, and in the methods that underly them, are also treated.
Date: July 9, 2006
Creator: Friedman, Alex
Partner: UNT Libraries Government Documents Department

Design and simulation of a multi-beamlet injector for a highcurrent accelerator

Description: A multi-beamlet approach to a high current ion injector, whereby a large number of beamlets are accelerated and then merged to form a single beam, offers a number of potential advantages over a monolithic single beam injector. These advantages include a smaller transverse footprint, more control over the shaping and aiming of the beam, and more flexibility in the choice of ion sources. A potential drawback however is a larger emittance. In this paper, we seek to understand the merging of the beamlets and how it determines the emittance. When the constraints imposed by beam propagation physics and practical engineering issues are included, the design is reduced to a few free parameters. We describe the physics design of a multi-beamlet injector, and produce a design for an example set of parameters. Extensive use of 2-D and 3-D particle simulations was made in understanding the injector. Design tolerances and sensitivities are discussed in general and in relation to the example.
Date: February 14, 2002
Creator: Grote, David P.; Henestroza, Enrique & Kwan, Joe W.
Partner: UNT Libraries Government Documents Department

RF gas plasma source development for heavy ion fusion

Description: Presently the Heavy Ion Fusion Virtual National Laboratory is researching ion sources and injector concepts to understand how to optimize beam brightness over a range of currents (50-2000 mA argon equivalent). One concept initially accelerates millimeter size, milliamp beamlets to 1 MeV before merging them into centimeter size, ampere beams. Computer simulations have shown the final brightness of the merged beams is dominated by the emittance growth of the merging process, as long as the beamlets ion temperature is below a few eV. Thus, a RF multicusp source capable of high current density can produce beams with better brightness compared to ones extracted from a colder source with a large aperture and lower current density. As such, experiments have begun to develop a RF multicusp source capable of delivering one amp of extracted beam current. It is expected that it will require 10 kW of 13 MHz RF power delivered via a quartz shielded, one and half turn, four inch diameter antenna. Important considerations in the development of the source include the dependence of current density and beam ion temperature on consumed RF power and gas pressure. A fast rise time ({approx}100 ns) for the extracted beam pulse must also be achieved. Progress on these experiments will be presented.
Date: February 22, 2002
Creator: Ahle, L.E.; Hall, R.P. & Molvik, A.W.
Partner: UNT Libraries Government Documents Department

Efficient computation of matched solutions of the KV envelopeequation for periodic focusing lattices

Description: A new iterative method is developed to numerically calculate the periodic, matched beam envelope solution of the coupled Kapchinskij-Vladimirskij (KV) equations describing the transverse evolution of a beam in a periodic, linear focusing lattice of arbitrary complexity. Implementation of the method is straightforward. It is highly convergent and can be applied to all usual parameterizations of the matched envelope solutions. The method is applicable to all classes of linear focusing lattices without skew couplings, and also applies to parameters where the matched beam envelope is strongly unstable. Example applications are presented for periodic solenoidal and quadrupole focusing lattices. Convergence properties are summarized over a wide range of system parameters.
Date: January 3, 2006
Creator: Lund, Steven M.; Chilton, Sven H. & Lee, Edward P.
Partner: UNT Libraries Government Documents Department

Vlasov simulations of beams with a moving grid

Description: Thanks to the rapid increase of computing power in recent years, simulations of plasmas and particle beams based on direct solution of the Vlasov equation on a multi-dimensional phase-space grid are becoming attractive as an alternative to Particle-In-Cell (PIC) simulations. Their strength lies essentially in the fact that they are noiseless and that all parts of phase space, including the tail of the distribution, are equally well resolved. Their major drawback is that, for inhomogeneous systems, many of the grid points (where no particles are present) are wasted. This is especially the case for beam simulations where the beam moves rapidly through the phase space (due to varying alternating-gradient focusing forces, for example). This inefficiency has made such Vlasov simulations unsuitable for those cases. One of the methods which has proven very efficient for the direct resolution of the Vlasov equation is the semi-Lagrangian method [1, 3]. It consists in updating the values of the distribution function at the grid nodes by following the characteristics ending at these nodes backwards and interpolating the value at the bottom of the characteristics from the known values at the previous time step. In general the interpolation grid is fixed, but this is not mandatory. This paper introduces the concept of a moving grid which is mapped at each time step from a logical uniform grid to the beam, so that it contains the whole beam without needing too many points with vanishing values of the distribution function. In order to implement this new method, we introduce a new time stepping algorithm which does not rely on the time splitting procedure traditionally used in Vlasov solvers.
Date: October 3, 2003
Creator: Sonnendrucker, E.; Filbet, F.; Friedman, A.; Oudet, E. & Vay, J-L.
Partner: UNT Libraries Government Documents Department

A Compact Multi-Beamlets High Current Injector for HIFDrivers

Description: Using curved electrodes in the injector, an array of converging beamlets can produce a beam with the envelope radius, convergence, and ellipticity matched to an electrostatic quadrupole (ESQ) channel. Experimental results were in good quantitative agreement with simulation and have demonstrated the feasibility of this concept. The size of a driver-scale injector system using this approach will be several times smaller than the one designed using traditional single large-aperture beams, so the success of this experiment has significant economical and technical impacts on the architecture of heavy ion fusion (HIF) drivers.
Date: September 6, 2005
Creator: Kwan, J.W.; Bieniosek, F.M.; Grote, D.P. & Westenskow, G.A.
Partner: UNT Libraries Government Documents Department

Initial experiments of RF gas plasma source for heavy ionfusion

Description: The Source Injector Program for the US Heavy Ion Fusion Virtual National Laboratory is currently exploring the feasibility of using RF gas plasma sources for a HIF driver. This source technology is presently the leading candidate for the multiple aperture concept, in which bright millimeter size beamlets are extracted and accelerated electrostatically up to 1 MeV before the beamlets are allowed to merge and form 1 A beams. Initial experiments have successfully demonstrated simultaneously high current density, {approx} 100 mA/cm{sup 2} and fast turn on, {approx} 1 {micro}s. These experiments were also used to explore operating ranges for pressure and RF power. Results from these experiments are presented as well as progress and plans for the next set of experiments for these sources.
Date: May 22, 2002
Creator: Ahle, L.; Hall, R.; Molvik, A.W.; Chacon-Golcher, E.; Kwan, J.W.; Leung, K.N. et al.
Partner: UNT Libraries Government Documents Department

Progress in the Development of Superconducting Quadrupoles forHeavy-ion Fusion

Description: The Heavy Ion Fusion program is developing single aperture superconducting quadrupoles based on NbTi conductor, for use in the High Current Experiment at Lawrence Berkeley National Laboratory. Following the fabrication and testing of prototypes using two different approaches, a baseline design has been selected and further optimized. A prototype cryostat for a quadrupole doublet, with features to accommodate induction acceleration modules, is being fabricated. The single aperture magnet was derived from a conceptual design of a quadrupole array magnet for multi-beam transport. Progress on the development of superconducting quadrupole arrays for future experiments is also reported.
Date: August 19, 2002
Creator: Faltens, A.; Lietzke, A.; Sabbi, G.; Seidl, P.; Lund, S.; Manahan, R. et al.
Partner: UNT Libraries Government Documents Department

Assessment of Potential for Ion Driven Fast Ignition

Description: Critical issues and ion beam requirements are explored for fast ignition using ion beams to provide fuel compression using indirect drive and to provide separate short pulse ignition heating using direct drive. Several ion species with different hohlraum geometries are considered for both accelerator-produced and laser-produced ion ignition beams. Ion-driven fast ignition targets are projected to have modestly higher gains than with conventional heavy-ion fusion, and may offer some other advantages for target fabrication and for use of advanced fuels. However, much more analysis and experiments are needed before conclusions can be drawn regarding the feasibility for meeting the ion beam transverse and longitudinal emittances, focal spots, pulse lengths, and target stand-off distances required for ion-driven fast ignition.
Date: May 1, 2005
Creator: Logan, B. Grant; Bangerter, Roger O.; Callahan, Debra A.; Tabak,Max; Roth, Markus; Perkins, L. John et al.
Partner: UNT Libraries Government Documents Department

Development of superconducting magnet systems for HIFExperiments

Description: The U.S. Heavy Ion Fusion program is developing superconducting focusing quadrupoles for near-term experiments and future driver accelerators. Following the fabrication and testing of several models, a baseline quadrupole design was selected and further optimized. The first prototype of the optimized design achieved a conductor-limited gradient of 132 T/m in a 70 mm bore, with measured field harmonics within 10 parts in 10{sup 4}. In parallel, a compact focusing doublet was fabricated and tested using two of the first-generation quadrupoles. After assembly in the cryostat, both magnets reached their conductor-limited quench current. Further optimization steps are currently underway to improve the performance of the magnet system and reduce its cost. They include the fabrication and testing of a new prototype quadrupole with reduced field errors as well as improvements of the cryostat design for the focusing doublet. The prototype units will be installed in the HCX beamline at LBNL, to perform accelerator physics experiments and gain operational experience. Successful results in the present phase will make superconducting magnets a viable option for the next generation of integrated beam experiments.
Date: July 27, 2004
Creator: Sabbi, Gian Luca; Faltens, A.; Leitzke, A.; Seidl, P.; Lund, S.; Martovets ky, N. et al.
Partner: UNT Libraries Government Documents Department

New simulation capabilities of electron clouds in ion beams withlarge tune depression

Description: The authors have developed a new, comprehensive set of simulation tools aimed at modeling the interaction of intense ion beams and electron clouds (e-clouds). The set contains the 3-D accelerator PIC code WARP and the 2-D ''slice'' e-cloud code POSINST, as well as a merger of the two, augmented by new modules for impact ionization and neutral gas generation. The new capability runs on workstations or parallel supercomputers and contains advanced features such as mesh refinement, disparate adaptive time stepping, and a new ''drift-Lorentz'' particle mover for tracking charged particles in magnetic fields using large time steps. It is being applied to the modeling of ion beams (1 MeV, 180 mA, K+) for heavy ion inertial fusion and warm dense matter studies, as they interact with electron clouds in the High-Current Experiment (HCX). They describe the capabilities and present recent simulation results with detailed comparisons against the HCX experiment, as well as their application (in a different regime) to the modeling of e-clouds in the Large Hadron Collider (LHC).
Date: June 1, 2006
Creator: Vay, J.L.; Furman, M.A.; Seidl, P.A.; Cohen, R.H.; Friedman, A.; Grote, D.P. et al.
Partner: UNT Libraries Government Documents Department

Neutralized Drift Compression Experiments (NDCX) with a HighIntensity Ion Beam

Description: To create high energy density matter and fusion conditions, high-power drivers, such as lasers, ion beams, and x-ray drivers, are employed to heat targets with pulses short compared to hydro-motion. Both high energy density physics and ion-driven inertial fusion require the simultaneous transverse and longitudinal compression of an ion beam to achieve high intensities. We have previously studied the effects of plasma neutralization for transverse beam compression. The scaled experiment, the Neutralized Transport Experiment (NTX), demonstrated that an initially un-neutralized beam can be compressed transversely to {approx}1 mm radius when charge neutralization by background plasma electrons is provided. Here we report longitudinal compression of a velocity-tailored, intense, neutralized 25 mA K+ beam at 300 keV. The compression takes place in a 1-2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity tilt that longitudinally compresses the neutralized beam, enhances the beam peak current by a factor of 50 and produces a pulse duration of about 3 ns. The Physics of longitudinal compression, experimental procedure, and the results of the compression experiments are presented.
Date: July 8, 2006
Creator: Roy, P.K.; Yu, S.S.; Waldron, W.L.; Anders, A.; Baca, D.; Barnard, J.J. et al.
Partner: UNT Libraries Government Documents Department

Recent U.S. advances in ion-beam-driven high energy densityphysics and heavy ion fusion

Description: During the past two years, significant experimental and theoretical progress has been made in the US heavy ion fusion science program in longitudinal beam compression, ion-beam-driven warm dense matter, beam acceleration, high brightness beam transport; and advanced theory and numerical simulations. Innovations in longitudinal compression of intense ion beams by > 50 X propagating through background plasma enable initial beam target experiments in warm dense matter to begin within the next two years. They are assessing how these new techniques might apply to heavy ion fusion drivers for inertial fusion energy.
Date: July 5, 2006
Creator: Logan, B.G.; Bieniosek, F.M.; Celata, C.M.; Coleman, J.; Greenway, W.; Henestroza, E. et al.
Partner: UNT Libraries Government Documents Department

Overview of US heavy ion fusion research

Description: Significant experimental and theoretical progress has been made in the U.S. heavy ion fusion program on high-current sources, injectors, transport, final focusing, chambers and targets for high energy density physics (HEDP) and inertial fusion energy (IFE) driven by induction linac accelerators. One focus of present research is the beam physics associated with quadrupole focusing of intense, space-charge dominated heavy-ion beams, including gas and electron cloud effects at high currents, and the study of long-distance-propagation effects such as emittance growth due to field errors in scaled experiments. A second area of emphasis in present research is the introduction of background plasma to neutralize the space charge of intense heavy ion beams and assist in focusing the beams to a small spot size. In the near future, research will continue in the above areas, and a new area of emphasis will be to explore the physics of neutralized beam compression and focusing to high intensities required to heat targets to high energy density conditions as well as for inertial fusion energy.
Date: June 23, 2005
Creator: Logan, B.G.; Bieniosek, F.M.; Celata, C.M.; Henestroza, E.; Kwan,J.W.; Lee, E.P. et al.
Partner: UNT Libraries Government Documents Department

US Heavy Ion Beam Research for Energy Density Physics Applicationsand Fusion

Description: Key scientific results from recent experiments, modeling tools, and heavy ion accelerator research are summarized that explore ways to investigate the properties of high energy density matter in heavy-ion-driven targets, in particular, strongly-coupled plasmas at 0.01 to 0.1 times solid density for studies of warm dense matter, which is a frontier area in high energy density physics. Pursuit of these near-term objectives has resulted in many innovations that will ultimately benefit heavy ion inertial fusion energy. These include: neutralized ion beam compression and focusing, which hold the promise of greatly improving the stage between the accelerator and the target chamber in a fusion power plant; and the Pulse Line Ion Accelerator (PLIA), which may lead to compact, low-cost modular linac drivers.
Date: September 1, 2005
Creator: Davidson, R.C.; Logan, B.G.; Barnard, J.J.; Bieniosek, F.M.; Briggs, R.J.; D.A., Callahan et al.
Partner: UNT Libraries Government Documents Department

Progress in heavy ion driven inertial fusion energy: From scaledexperiments to the integrated research experiment

Description: The promise of inertial fusion energy driven by heavy ion beams requires the development of accelerators that produce ion currents ({approx}100s Amperesheam) and ion energies ({approx}1-10 GeV) that have not been achieved simultaneously in any existing accelerator. The high currents imply high generalized perveances, large tune depressions. and high space charge potentials of the beam center relative to the beam pipe. Many of the scientific issues associated with ion beams of high perveance and large tune depression have been addressed over the last two decades on scaled experiments at Lawrence Berkeley and Lawrence Livermore National Laboratories, the University of Maryland, and elsewhere. The additional requirement of high space charge potential (or equivalently high line charge density) gives rise to effects (particularly the role of electrons in beam transport) which must be understood before proceeding to a large scale accelerator. The first phase of a new series of experiments in Heavy Ion Fusion Virtual National Laboratory (HIF VNL), the High Current Experiments (HCX), is now being constructed at LBNL. The mission of the HCX will be to transport beams with driver line charge density so as to investigate the physics of this regime, including constraints on the maximum radial filling factor of the beam through the pipe. This factor is important for determining both cost and reliability of a driver scale accelerator. The HCX will provide data for design of the next steps in the sequence of experiments leading to an inertial Fusion energy power plant. The focus of the program after the HCX will be on integration of all of the manipulations required for a driver. In the near term following HCX, an Integrated Beam Experiment (IBX) of the same general scale as the HCX is envisioned.
Date: June 22, 2001
Creator: Barnard, J.J.; Ahle, L.E.; Baca, D.; Bangerter, R.O.; Bieniosek,F.M.; Celata, C.M. et al.
Partner: UNT Libraries Government Documents Department