Download or read book Simulation of Drift Compression for Heavy Ion Fusion written by and published by . This book was released on 2005 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Overview of Theory and Modeling in the Heavy Ion Fusion Virtual National Laboratory written by Ronald C. Davidson and published by . This book was released on 2002* with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Drift Compression Experiments on MBE 4 and Related Emittance Growth Phenomena written by and published by . This book was released on 1991 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have recently conducted a series of experiments on the MBE-4 heavy ion accelerator in which a velocity tilt was placed on the beam in the first accelerating section beyond the injector, followed by drift compression over the remaining 11 meters. Depending upon the magnitude of the velocity tilt and the accompanying mismatch in the focusing lattice, emittance growth was observed, manifested by butterfly'' shapes in x - x(prime) phase space. We discuss various analytical limits on ion beam compression and relate them to these experiments and also to a driver for a heavy ion fusion reactor. We also present numerical simulations which investigate various aspects of compression and consequent emittance growth. 2 refs., 3 figs., 1 tab.

Download or read book Three Dimensional Simulations of Space Charge Dominated Heavy Ion Beams with Applications to Inertial Fusion Energy written by and published by . This book was released on 1994 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavy ion fusion requires injection, transport and acceleration of high current beams. Detailed simulation of such beams requires fully self-consistent space charge fields and three dimensions. WARP3D, developed for this purpose, is a particle-in-cell plasma simulation code optimized to work within the framework of an accelerator's lattice of accelerating, focusing, and bending elements. The code has been used to study several test problems and for simulations and design of experiments. Two applications are drift compression experiments on the MBE-4 facility at LBL and design of the electrostatic quadrupole injector for the proposed ILSE facility. With aggressive drift compression on MBE-4, anomalous emittance growth was observed. Simulations carried out to examine possible causes showed that essentially all the emittance growth is result of external forces on the beam and not of internal beam space-charge fields. Dominant external forces are the dodecapole component of focusing fields, the image forces on the surrounding pipe and conductors, and the octopole fields that result from the structure of the quadrupole focusing elements. Goal of the design of the electrostatic quadrupole injector is to produce a beam of as low emittance as possible. The simulations show that the dominant effects that increase the emittance are the nonlinear octopole fields and the energy effect (fields in the axial direction that are off-axis). Injectors were designed that minimized the beam envelope in order to reduce the effect of the nonlinear fields. Alterations to the quadrupole structure that reduce the nonlinear fields further were examined. Comparisons were done with a scaled experiment resulted in very good agreement.

Download or read book Development of Implicit Kinetic Simulation Methods and Their Application to Ion Beam Propagation in Current and Future Neutralized Drift Compression Experiments written by Stefano Markidis and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ion beams can be accelerated and focused to hit a target thus releasing high density power to achieve nuclear fusion. They can also be used to study phase transition from the solid to the Warm Dense Matter state. The Neutralized Drift Compression Experiment (NDCX) at the Lawrence Berkeley National Laboratory is being used to investigate the possibility of developing drivers for the heavy ion fusion reactors, and for Warm Dense Matter experiments. Because ion beams are positively charged, repulsive forces act on the beam ions. These electrostatic forces defocus the beam, increasing the beam size and degrading the applied compression and focus. Electrons are introduced via a preformed plasma to eliminate the electrostatic forces that defo- cus the beam in the NDCX. The spread of the background plasma electrons inside the beam, and the adjustment of their velocity to the beam propagation velocity is called neutralization process. Because collisions occur on time scales much larger than the time scales for the neutralization process, the plasma can be considered collision-less. Thus, the neutralization process is dominated by plasma-wave interactions instead of collisions, and the kinetic approach is required to model this phenomenon. In this dissertation, the neutralization process in the NDCX configuration is stud- ied. The collision-less kinetic equations of plasma are solved numerically using two implicit Particle-in-Cell methods. The implicit nature of the time-differenced gov- erning equations leads to unconditional numerical stability. The primary numerical scheme is based on an implicit moment Particle-in-Cell approach. It has been devel- oped for the electromagnetic case and implemented in a 3D, parallel code to study the neutralization process. In addition, a fully implicit Particle-in-Cell method to solve the particle and field equations has been also developed and implemented for a simple one dimensional, electrostatic configuration. The goal of the fully implicit scheme was to demonstrate that a fully implicit scheme can indeed converge as it has been a challenge. It has been demonstrated that fully implicit schemes (at least 1D, electrostatic configuration) can in fact converge. The schemes developed and implemented are used extensively to study the neutralization dynamics. The aim of this study is to analyze the dynamics that governs the neutralization process in the NDCX configuration. It has been found that the neutralization is a transient phenomenon, typically occurring on time scales of tens of plasma periods. During this transient, the ion beam undergoes through large electron oscillations. The oscillations are damped by a sheath. This sheath regulates the electron flux into and out of the beam, and because it opposes the electron oscillations, it also oscillates. The forward moving and oscillating sheath persists after the transient, and forms an oscillating shock at the front of the ion beam. The shock is in the form of a moving and oscillating discontinuity in the electric field, the charge density, and the electron average velocity. It has been found that the background plasma and beam densities influence the neutralization process, changing the properties of the sheath at the beam-plasma interface. The damping of the oscillations is important when the background plasma and beam densities are close in value, while it is weaker when the background plasma density is higher than the beam density. Moreover, the magnetic field does not have a significant effect on the ion beam neutralization process in the current and future NDCX configurations, and the simulations can be carried out in the electrostatic limit, achieving the same results as those obtained using electromagnetic simulations. A comparison of the implicit Particle-in-Cell methods with the explicitly time differenced Particle-in-Cell method shows that the implicit moment and the fully im- plicit Particle-in-Cell methods are on average 4 to 40 times computationally more expensive if the same simulation time step is used. Because the ion beam neutral- ization process in the NDCX occurs on the plasma period time scales and on the Debye length spatial scales, these scales need to be resolved to correctly describe the neutralization phenomenon. Because of these constraints on the time step and the grid spacing, the implicit Particle-in-Cell methods are here used on space and time scales where the explicit Particle-in-Cell method is numerically stable, hence denying the advantage that implicit methods have over explicit schemes. However, it is clear that implicit schemes are more efficient for problems that allow large time steps.

Download or read book Drift Compression and Final Focus Systems for Heavy Ion Inertial Fusion written by Michiel Jan Laurens de Hoon and published by . This book was released on 2001 with total page 546 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heavy Ion Fusion Science written by R. C. Davidson and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past two years noteworthy experimental and theoretical progress has been made towards the top-level scientific question for the U.S. program in Heavy Ion Fusion Science and High Energy Density Physics: ''How can heavy ion beams be compressed to the high intensity required to create high energy density matter and fusion conditions''? [1]. New results in transverse and longitudinal beam compression, beam-target interaction, high-brightness transport, beam production, as well as a new scheme in beam acceleration will be reported. Longitudinal and Transverse Beam Compression: The Neutralized Transport Experiment (NTX) demonstrated transverse beam density enhancement by a factor greater than 100 when an otherwise space-charge dominated ion beam was neutralized by a plasma source [2]. This experiment was followed by the Neutralized Drift Compression Experiment (NDCX) in which an ion beam was longitudinally compressed by a factor of 50 [3]. This was accomplished by applying a linear head-to-tail velocity ''tilt'' to the beam, and then allowing the beam to drift through a meter-long neutralizing plasma. In both the transverse and longitudinal experiments, extensive 3-D simulations, using LSP, were carried out, and the agreement with experiments was excellent [4]. A three-dimensional kinetic model for longitudinal compression was developed, and it was shown that the Vlasov equation possesses a class of exact solutions for the problem [5]. Beam-Target Interaction: We have also made significant progress in identifying the unique role ion beams can play in heating material to warm dense matter (WDM) conditions. We have identified promising accelerator, beam, and target configurations, as well as new experiments on material properties. It is shown that the target temperature uniformity can be maximized if the ion energy at target corresponds to the maximum in the energy loss rate dE/dX [6]. Ions of moderate energy (a few to tens of MeV) may be used. The energy must be deposited in times much shorter than the hydrodynamic expansion time (ns for metallic foams at 0.01 to 0.1 times solid density). Hydrodynamic simulations [7] have confirmed that uniform conditions with temperature variations of less than a few per cent can be achieved. High-Brightness Transport: Unwanted electrons can lead to deleterious effects for high-brightness ion beam transport. We are studying electron accumulation in quadrupole and solenoid beam transport systems. Electrons can originate from background gas ionization, from beam-tubes struck by ions near grazing incidence, and from end-walls struck by ions near normal incidence [8]. In parallel with the experimental campaign, we have developed and implemented in WARP 3D a new approach to large time-step advancement of electron orbits, as well as a comprehensive suite of models for electrons, gas, and wall interactions [9]. If sufficient electrons are accumulated within the beam, severe distortion of the beam phase space can result. Simulations of this effect have reproduced the key features observed in the experiments. Beam Production: The merging-beamlet injector experiment recently completed demonstrates the feasibility of a compact, high-current injector for heavy ion fusion drivers. In our experiment, 119 argon ion beamlets at 400 keV beam energy were merged into an electrostatic quadrupole channel to form a single beam of 70 mA. The measured unnormalized transverse emittance (phase space area) of 200-250 mm-mrad for the merged beam met fusion driver requirement. These measurements are in good agreement with our particle-in-cell simulations using WARP3D [10]. We have also completed the physics design of a short-pulse injector suitable for WDM studies. Beam Acceleration: A new concept for acceleration, the Pulse Line Ion Accelerator PLIA [11], offers the potential of a very low cost accelerator for WDM studies. It is based on a traveling wave structure, using a simple geometry with a helical conductor. We have obtained experimental verification of the predicted PLIA beam dynamics. Measured energy gain, longitudinal phase space, and beam bunching are in good agreement with WARP3D simulations. Computational Models and Simulator Experiments: The pioneering merger of Adaptive Mesh Refinement and particle-in-cell methods [12] underlies much of the recent success of WARP3D. BEST, the Beam Equilibrium Stability and Transport code was optimized for massively parallel computers and applied to studies of the collective effects of 3D bunched beams [13] and the temperature-anisotropy instability [14]. Space-charge-dominated beam physics experiments relevant to long-path accelerators were carried out on the recently completed University of Maryland Electron Ring, and on the Paul Trap Simulator Experiment at PPPL.

Download or read book Beam Dynamics of the Neutralized Drift Compression Experiment II NDCX II a Novel Pulse compressing Ion Accelerator written by and published by . This book was released on 2009 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 (almost equal to)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 (almost equal to)50-100 are routinely obtained on the Neutralized Drift Compression Experiment (NDCX) at LBNL. 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 neutralized compression onto the target. This paper describes the discrete-particle simulation models (1-D, 2-D, and 3-D) employed and the space-charge-dominated beam dynamics being realized.

Download or read book Three Dimensional Simulations of Space Charge Dominated Heavy Ion Beams with Applications to Inertial Fusion Energy written by David Peter Grote and published by . This book was released on 1994 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simulations of Ion Beam Neutralization in Support of Theneutralized Transport Experiment written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavy ion fusion (HIF) requires the acceleration, transport, and focusing of many individual ion beams. Drift compression and beam combining prior to focusing result in [approx]100 individual ion beams with line-charge densities of order 10[sup -5] C/m. A focusing force is applied to the individual ion beams outside of the chamber. For neutralized ballistic chamber transport (NBT), these beams enter the chamber with a large radius (relative to the target spot size) and must overlap inside the chamber at small radius (roughly 3-mm radius) prior to striking the target. The physics of NBT, in particular the feasibility of achieving the required small spot size, is being examined in the Neutralized Transport Experiment (NTX) at Lawrence Berkeley National Laboratory. Interpreted by detailed particle-in-cell simulations of beam neutralization, experimental results are being used to validate theoretical and simulation models for driver scale beam transport. In the NTX experiment, a low-emittance 300-keV, 25-mA K[sup +] beam is focused 1 m downstream into a 4-cm radius pipe containing one or more plasma regions. The beam passes through the first 10-cm-long plasma, produced by an Al plasma arc source, just after the final focus magnet and propagates with the entrained electrons. A second, 10-cm-long plasma (produced with a cyclotron resonance plasma source) is created near focus to simulate the effects of a photo-ionized plasma created by the heated target in a fusion chamber. Given a 0.1-[pi]-mm-mrad beam emittance, two and three-dimensional particle-in-cell (PIC) LSP simulations of the beam neutralization predict a

Download or read book Simulations of Ion Beam Neutralization in Support of Theneutralized Transport Experiment written by D. V. Rose and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavy ion fusion (HIF) requires the acceleration, transport, and focusing of many individual ion beams. Drift compression and beam combining prior to focusing result in {approx}100 individual ion beams with line-charge densities of order 10{sup -5} C/m. A focusing force is applied to the individual ion beams outside of the chamber. For neutralized ballistic chamber transport (NBT), these beams enter the chamber with a large radius (relative to the target spot size) and must overlap inside the chamber at small radius (roughly 3-mm radius) prior to striking the target. The physics of NBT, in particular the feasibility of achieving the required small spot size, is being examined in the Neutralized Transport Experiment (NTX) at Lawrence Berkeley National Laboratory. Interpreted by detailed particle-in-cell simulations of beam neutralization, experimental results are being used to validate theoretical and simulation models for driver scale beam transport. In the NTX experiment, a low-emittance 300-keV, 25-mA K{sup +} beam is focused 1 m downstream into a 4-cm radius pipe containing one or more plasma regions. The beam passes through the first 10-cm-long plasma, produced by an Al plasma arc source, just after the final focus magnet and propagates with the entrained electrons. A second, 10-cm-long plasma (produced with a cyclotron resonance plasma source) is created near focus to simulate the effects of a photo-ionized plasma created by the heated target in a fusion chamber. Given a 0.1-{pi}-mm-mrad beam emittance, two and three-dimensional particle-in-cell (PIC) LSP simulations of the beam neutralization predict a

Download or read book Overview of WARP a Particle Code for Heavy Ion Fusion written by and published by . This book was released on 1993 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The beams in a Heavy Ion beam driven inertial Fusion (HIF) accelerator must be focused onto small spots at the fusion target, and so preservation of beam quality is crucial. The nonlinear self-fields of these space-charge-dominated beams can lead to emittance growth; thus a self-consistent field description is necessary. We have developed a multi-dimensional discrete-particle simulation code, WARP, and are using it to study the behavior of HIF beams. The code's 3d package combines features of an accelerator code and a particle-in-cell plasma simulation, and can efficiently track beams through many lattice elements and around bends. We have used the code to understand the physics of aggressive drift-compression in the MBE-4 experiment at Lawrence Berkeley Laboratory (LBL). We have applied it to LBL's planned ILSE experiments, to various ''recirculator'' configurations, and to the study of equilibria and equilibration processes. Applications of the 3d package to ESQ injectors, and of the r, z package to longitudinal stability in driver beams, are discussed in related papers.

Download or read book An Assessment of the Prospects for Inertial Fusion Energy written by National Research Council and published by National Academies Press. This book was released on 2013-08-05 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: The potential for using fusion energy to produce commercial electric power was first explored in the 1950s. Harnessing fusion energy offers the prospect of a nearly carbon-free energy source with a virtually unlimited supply of fuel. Unlike nuclear fission plants, appropriately designed fusion power plants would not produce the large amounts of high-level nuclear waste that requires long-term disposal. Due to these prospects, many nations have initiated research and development (R&D) programs aimed at developing fusion as an energy source. Two R&D approaches are being explored: magnetic fusion energy (MFE) and inertial fusion energy (IFE). An Assessment of the Prospects for Inertial Fusion Energy describes and assesses the current status of IFE research in the United States; compares the various technical approaches to IFE; and identifies the scientific and engineering challenges associated with developing inertial confinement fusion (ICF) in particular as an energy source. It also provides guidance on an R&D roadmap at the conceptual level for a national program focusing on the design and construction of an inertial fusion energy demonstration plant.

Download or read book Simulations for Experimental Study of Warm Dense Matter and Inertial Fusion Energy Applications on NDCX II written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Neutralized Drift Compression Experiment II (NDCX II) is an induction accelerator planned for initial commissioning in 2012. The final design calls for a (almost equal to)3 MeV, (almost equal to)30 A Li ion beam, delivered in a bunch with characteristic pulse duration of 1 ns, and ransverse 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.

Download or read book Toward a Physics Design for NDCX II an Ion Accelerator for Warm Dense Matter and HIF Target Physics Studies written by and published by . This book was released on 2008 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL), a collaboration of LBNL, LLNL, and PPPL, has achieved 60-fold pulse compression of ion beams on the Neutralized Drift Compression eXperiment (NDCX) at LBNL. In NDCX, a ramped voltage pulse from an induction cell imparts a velocity 'tilt' to the beam; the beam's tail then catches up with its head in a plasma environment that provides neutralization. The HIFS-VNL's mission is to carry out studies of warm dense matter (WDM) physics using ion beams as the energy source; an emerging thrust is basic target physics for heavy ion-driven inertial fusion energy (IFE). These goals require an improved platform, labeled NDCX-II. Development of NDCX-II at modest cost was recently enabled by the availability of induction cells and associated hardware from the decommissioned advanced test accelerator (ATA) facility at LLNL. Our initial physics design concept accelerates an (almost equal to) 30 nC pulse of Li ions to (almost equal to) 3 MeV, then compresses it to (almost equal to) 1 ns while focusing it onto a mm-scale spot. It uses the ATA cells themselves (with waveforms shaped by passive circuits) to impart the final velocity tilt; smart pulsers provide small corrections. The ATA accelerated electrons; acceleration of non-relativistic ions involves more complex beam dynamics both transversely and longitudinally. We are using an interactive one-dimensional kinetic simulation model and multidimensional Warp-code simulations to develop the NDCX-II accelerator section. Both LSP and Warp codes are being applied to the beam dynamics in the neutralized drift and final focus regions, and the plasma injection process. The status of this effort is described.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fusion Energy Update written by and published by . This book was released on 1986 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: