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Proposed research on advanced accelerator concepts

Description: This report summarizes technical progress and accomplishments during the proposed three-year research on advanced accelerator concepts supported by the Department of Energy under Contract No. DE-FG02-88ER40465. A vigorous theoretical program has been pursued in critical problem areas related to advanced accelerator concepts and the basic equilibrium, stability, and radiation properties of intense charged particle beams. Broadly speaking, our research has made significant contributions in the following three major areas: Investigations of physics issues related to particle acceleration including two-beam accelerators and cyclotron resonance laser (CRL) accelerators; Investigations of RF sources including the free- electron lasers, cyclotron resonance masers, and relativistic magnetrons; Studies of coherent structures in electron plasmas and beams ranging from a low-density, nonrelativistic, pure electron plasma column to high-density, relativistic, non-neutral electron flow in a high-voltage diode. The remainder of this report presents theoretical and computational advances in these areas.
Date: September 1, 1991
Creator: Davidson, R.C. & Wurtele, J.S.
Partner: UNT Libraries Government Documents Department

Theoretical study of transverse-longitudinal emittance coupling

Description: The effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions is investigated using the generalized Courant-Snyder theory for coupled lattices. Recently, the concept and technique of transverse-longitudinal emittance coupling have been proposed for applications in the Linac Coherent Light Source and other free-electron lasers to reduce the transverse emittance of the electron beam. Such techniques can also be applied to the driver beams for the heavy ion fusion and beam-driven high energy density physics, where the transverse emittance budget is typically tighter than the longitudinal emittance. The proposed methods consist of one or several coupling components which completely swap the emittances of one of the transverse directions and the longitudinal direction at the exit of the coupling components. The complete emittance exchange is realized in one pass through the coupling components. In the present study, we investigate the effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions. A weak coupling component is introduced at every focusing lattice, and we would like to determine if such a lattice can realize the function of emittance exchange.
Date: April 14, 2011
Creator: Qin, H; Davidson, R C; Chung, M; Barnard, J J & Wang, T F
Partner: UNT Libraries Government Documents Department

Calculation Of Change-Changing Cross Sections Of IONS Or Atoms Colliding With Fast IONS Using The Classical Trajectory Method

Description: Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross section. Shortcomings of the CTMC method for multielectron target atoms are discussed.
Date: October 10, 2008
Creator: Kaganovich, I. D., Shnidman, Ariel, Mebane, Harrison, Davidson, R.C.
Partner: UNT Libraries Government Documents Department

Nonlinear and Non-ideal Effects on FRC Stability

Description: New computational results are presented which advance the understanding of the stability properties of the Field-Reversed Configuration (FRC). We present results of hybrid and two-fluid (Hall-MHD) simulations of prolate FRCs in strongly kinetic and small-gyroradius, MHD-like regimes. The n = 1 tilt instability mechanism and stabilizing factors are investigated in detail including nonlinear and resonant particle effects, particle losses along the open field lines, and Hall stabilization. It is shown that the Hall effect determines the mode rotation and change in the linear mode structure in the kinetic regime; however, the reduction in the growth rate is mostly due to the finite Larmor radius effects. Resonant particle effects are important in the large gyroradius regime regardless of the separatrix shape, and even in cases when a large fraction of the particle orbits are stochastic. Particle loss along the open field lines has a destabilizing effect on the tilt mode and contributes to the ion spin up in toroidal direction. The nonlinear evolution of unstable modes in both kinetic and small-gyroradius FRCs is shown to be considerably slower than that in MHD simulations. Our simulation results demonstrate that a combination of kinetic and nonlinear effects is a key for understanding the experimentally observed FRC stability properties.
Date: October 21, 2002
Creator: Belova, E.V.; Davidson, R.C.; Ji, H. & Yamada, M.
Partner: UNT Libraries Government Documents Department

Kinetic description of intense nonneutral beam propagation through a periodic solenoidal focusing field based on the nonlinear Vlasov-Maxwell equations

Description: A kinetic description of intense nonneutral beam propagation through a periodic solenoidal focusing field B{sup sol}({rvec x}) is developed. The analysis is carried out for a thin beam with characteristic beam radius r{sub b} {much_lt} S, and directed axial momentum {gamma}{sub b}m{beta}{sub b}c (in the z-direction) large compared with the transverse momentum and axial momentum spread of the beam particles. Making use of the nonlinear Vlasov-Maxwell equations for general distribution function f{sub b}({rvec x},{rvec p},t) and self-consistent electrostatic field consistent with the thin-beam approximation, the kinetic model is used to investigate detailed beam equilibrium properties for a variety of distribution functions. Examples are presented both for the case of a uniform solenoidal focusing field B{sub z}(z) = B{sub 0} = const. and for the case of a periodic solenoidal focusing field B{sub z}(z + S) = B{sub z}(z). The nonlinear Vlasov-Maxwell equations are simplified in the thin-beam approximation, and an alternative Hamiltonian formulation is developed that is particularly well-suited to intense beam propagation in periodic focusing systems. Based on the present analysis, the Vlasov-Maxwell description of intense nonneutral beam propagation through a periodic solenoidal focusing field {rvec B}{sup sol}({rvec x}) is found to be remarkably tractable and rich in physics content. The Vlasov-Maxwell formalism developed here can be extended in a straightforward manner to investigate detailed stability behavior for perturbations about specific choices of beam equilibria.
Date: August 1, 1997
Creator: Davidson, R.C. & Chen, C.
Partner: UNT Libraries Government Documents Department

TRANSVERSE ELECTRON-PROTON TWO-STREAM INSTABILITY IN A BUNCHED BEAM

Description: This paper is an analytical investigation of the trans-verse electron-proton (e-p) two-stream instability in a pro-ton bunch propagating through a stationary electron back-ground. The equations of motion, including the effect of damping, are derived for the centroids of the proton beam and the electron cloud. An approach is developed to solve the coupled linear centroid equations in the time domain describing the e-p instability in proton bunches with non-uniform line densities. Examples are presented for proton line densities corresponding to uniform and parabolic profiles.
Date: June 1, 2001
Creator: WANG, T.F.; CHANNELL, P.J.; MACEK, R.J. & DAVIDSON, R.C.
Partner: UNT Libraries Government Documents Department

Kinetic Stability of the Field Reversed Configuration

Description: New computational results are presented which advance the understanding of the stability properties of the Field-Reversed Configuration (FRC). The FRC is an innovative confinement approach that offers a unique fusion reactor potential because of its compact and simple geometry, translation properties, and high plasma beta. One of the most important issues is FRC stability with respect to low-n (toroidal mode number) MHD modes. There is a clear discrepancy between the predictions of standard MHD theory that many modes should be unstable on the MHD time scale, and the observed macroscopic resilience of FRCs in experiments.
Date: July 9, 2002
Creator: Belova, E.V.; Davidson, R.C.; Ji, H. & Yamada, and M.
Partner: UNT Libraries Government Documents Department

Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Solenoidal Magnetic Field I: Weak Magnetic Field Limit

Description: Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self- electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite- length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to infuence the self-electric and self-magnetic fields when ωce > ωpeβb, where ωce = eβ/mec is the electron gyrofrequency, ωpe is the electron plasma frequency, and βb = Vb/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.
Date: October 10, 2008
Creator: Kaganovich, I. D., Startsev, E. A., Sefkow, A. B., Davidson, R. C.
Partner: UNT Libraries Government Documents Department

Intense nonneutral beam propagation in a periodic solenoidal field using a macroscopic fluid model with zero thermal emittance

Description: A macroscopic fluid model is developed to describe the nonlinear dynamics and collective processes in an intense high-current beam propagating in the z-direction through a periodic focusing solenoidal field B{sub z}(z + S) = B{sub z}(z), where S is the axial periodicity length. The analysis assumes that space-charge effects dominate the effects of thermal beam emittance, Kr{sub b}{sup 2} {much_gt} {epsilon}{sub th}{sup 2}, and is based on the macroscopic moment-Maxwell equations, truncated by neglecting the pressure tensor and higher-order moments. Assuming a thin beam with r{sub b} {much_lt} S, azimuthally symmetric beam equilibria with {partial_derivative}/{partial_derivative}t = 0 = {partial_derivative}/{partial_derivative}{theta} are investigated. To illustrate the considerable flexibility of the macroscopic formalism, assuming (nearly) uniform axial flow velocity V{sub b} over the beam cross section, beam equilibrium properties are calculated for two examples: (a) uniform radial density profile over the interval 0 {le} r < r{sub b}(z), and (b) an infinitesimally thin annular beam centered at r = r{sub b}(z). The analysis generally allows for the azimuthal flow velocity V{sub {theta}b}(r,z) to differ from the Larmor frequency, and the model is used to calculate the (leading-order) correction {delta}V{sub zb}(r,z) to the axial flow velocity for the step-function density profile in case (a) above.
Date: August 1, 1997
Creator: Davidson, R. C.; Stoltz, P. & Chen, C.
Partner: UNT Libraries Government Documents Department

Statistically-averaged rate equations for intense nonneutral beam propagation through a periodic solenoidal focusing field based on the nonlinear Vlasov-Maxwell equations

Description: This paper presents a detailed formulation and analysis of the rate equations for statistically-averaged quantities for an intense nonneutral beam propagating through a periodic solenoidal focusing field B{sup sol}(x). The analysis is based on the nonlinear Vlasov-Maxwell equations in the electrostatic approximation, assuming a thin beam with characteristic beam radius r{sub b} {much_lt} S. The results are applied to investigate the nonlinear evolution of the generalized entropy, mean canonical angular momentum {l_angle}P{sub {theta}}{r_angle}, center-of-mass motion for {l_angle}X{r_angle} and {l_angle}Y{r_angle}, mean kinetic energy (1/2) {l_angle}X{sup {prime}2} + Y{sup {prime}2}{r_angle}, mean-square beam radius {l_angle}X{sup 2} + Y{sup 2}{r_angle}, and coupled rate equations for the unnormalized transverse emittance {epsilon}(s) and root-mean-square beam radius R{sub b}(s) = {l_angle}X{sup 2} + Y{sup 2}{r_angle}{sup 1/2}. Global energy balance is discussed, and the coupled rate equations for {epsilon}(s) and R{sub b}(s) are examined for the class of axisymmetric beam distributions F{sub b}.
Date: August 1, 1997
Creator: Davidson, R. C.; Lee, W. W. & Stoltz, P.
Partner: UNT Libraries Government Documents Department

Direct numerical solution of Poisson`s equation in cylindrical (r, z) coordinates

Description: A direct solver method is developed for solving Poisson`s equation numerically for the electrostatic potential {phi}(r,z) in a cylindrical region (r < R{sub wall}, 0 < z < L). The method assumes the charge density {rho}(r,z) and wall potential {phi}(r = R{sub wall}, z) are specified, and {partial_derivative}{phi}/{partial_derivative}z = 0 at the axial boundaries (z = 0, L).
Date: July 22, 1997
Creator: Chao, E.H.; Paul, S.F.; Davidson, R.C. & Fine, K.S.
Partner: UNT Libraries Government Documents Department

Confinement of Pure Ion Plasma in a Cylindrical Current Sheet

Description: A novel method for containing a pure ion plasma at thermonuclear densities and temperatures has been modeled. The method combines the confinement properties of a Penning-Malmberg trap and some aspects of the magnetic field geometry of a pulsed theta-pinch. A conventional Penning trap can confine a uniform-density plasma of about 5x1011 cm-3 with a 30-Tesla magnetic field. However, if the axial field is ramped, a much higher local ion density can be obtained. Starting with a 107 cm-3 trapped deuterium plasma in a conventional Penning-Malmberg trap at the Brillouin limit (B = 0.6 Tesla), the field is ramped to 30 Tesla. Because the plasma is comprised of particles of only one sign of charge, transport losses are very low, i.e., the conductivity is high. As a result, the ramped field does not penetrate the plasma and a diamagnetic surface current is generated, with the ions being accelerated to relativistic velocities. To counteract the inward j x B forces from this induced current, additional ions are injected into the plasma along the axis to increase the density (and mutual electrostatic repulsion) of the target plasma. In the absence of the higher magnetic field in the center, the injected ions drift outward until a balance is established between the outward driving forces (centrifugal, electrostatic, pressure gradient) and the inward j x B force. An equilibrium calculation using a relativistic, 1-D, cold-fluid model shows that a plasma can be trapped in a hollow, 49-cm diameter, 0.2-cm thick cylinder with a density exceeding 4 x 1014 cm-3.
Date: December 10, 1999
Creator: Phillips, C.K.; Chao, E.H.; Davidson, R.C. & Paul, S.F.
Partner: UNT Libraries Government Documents Department

US Heavy Ion Beam Research for High Energy Density Physics Applications and 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 19, 2005
Creator: Davidson, R.C.; Logan, B.G.; Barnard, J.J.; Bieniosek, F.M.; Briggs, R.J. & al., et
Partner: UNT Libraries Government Documents Department

Long Plasma Source for Heavy Ion Beam Charge Neutralization

Description: Plasmas are a source of unbound electrons for charge neutralizing intense heavy ion beams to focus them to a small spot size and compress their axial length. The plasma source should operate at low neutral pressures and without strong externally-applied fields. To produce long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients have been developed. The source utilizes the ferroelectric ceramic BaTiO{sub 3} to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) is covered with ceramic material. High voltage ({approx} 8 kV) is applied between the drift tube and the front surface of the ceramics. A BaTiO{sub 3} source comprised of five 20-cm-long sources has been tested and characterized, producing relatively uniform plasma in the 5 x 10{sup 10} cm{sup -3} density range. The source was integrated into the NDCX device for charge neutralization and beam compression experiments, and yielded current compression ratios {approx} 120. Present research is developing multi-meter-long and higher density sources to support beam compression experiments for high energy density physics applications.
Date: June 1, 2008
Creator: Efthimion, P.C.; Gilson, E.P.; Grisham, L.; Davidson, R.C.; Logan, B.G.; Seidl, P.A. et al.
Partner: UNT Libraries Government Documents Department

Physics of Neutralization of Intense High-Energy Ion Beam Pulses by Electrons

Description: Neutralization and focusing of intense charged particle beam pulses by electrons forms the basis for a wide range of applications to high energy accelerators and colliders, heavy ion fusion, and astrophysics. For example, for ballistic propagation of intense ion beam pulses, background plasma can be used to effectively neutralize the beam charge and current, so that the self-electric and self- magnetic fields do not affect the ballistic propagation of the beam. From the practical perspective of designing advanced plasma sources for beam neutralization, a robust theory should be able to predict the self-electric and self-magnetic fields during beam propagation through the background plasma. The major scaling relations for the self-electric and self-magnetic fields of intense ion charge bunches propagating through background plasma have been determined taking into account the effects of transients during beam entry into the plasma, the excitation of collective plasma waves, the effects of gas ionization, finite electron temperature, and applied solenoidal and dipole magnetic fields. Accounting for plasma production by gas ionization yields a larger self-magnetic field of the ion beam compared to the case without ionization, and a wake of current density and self-magnetic field perturbations is generated behind the beam pulse. A solenoidal magnetic field can be applied for controlling the beam propagation. Making use of theoretical models and advanced numerical simulations, it is shown that even a small applied magnetic field of about 100G can strongly affect the beam neutralization. It has also been demonstrated that in the presence of an applied magnetic field the ion beam pulse can excite large-amplitude whistler waves, thereby producing a complex structure of self-electric and self-magnetic fields. The presence of an applied solenoidal magnetic field may also cause a strong enhancement of the radial self-electric field of the beam pulse propagating through the background plasma. If controlled, ...
Date: April 28, 2010
Creator: Kaganovich, I. D.; Davidson, R. C.; Dorf, M. A.; Startsev, E. A.; Sefkow, A. B.; Lee, E. P. et al.
Partner: UNT Libraries Government Documents Department

The Heavy Ion Fusion Program in the U.S.A.

Description: Inertial fusion energy research has enjoyed increased interest and funding. This has allowed expanded programs in target design, target fabrication, fusion chamber research, target injection and tracking, and accelerator research. The target design effort examines ways to minimize the beam power and energy and increase the allowable focal spot size while preserving target gain. Chamber research for heavy ion fusion emphasizes the use of thick liquid walls to serve as the coolant, breed tritium, and protect the structural wall from neutrons, photons, and other target products. Several small facilities are now operating to model fluid chamber dynamics. A facility to study target injection and tracking has been built and a second facility is being designed. Improved economics is an important goal of the accelerator research. The accelerator research is also directed toward the design of an Integrated Research Experiment (IRE). The IRE is being designed to accelerate ions to &gt;100 MeV, enabling experiments in beam dynamics, focusing, and target physics. Activities leading to the IRE include ion source development and a High Current Experiment (HCX) designed to transport and accelerate a single beam of ions with a beam current of approximately 1 A, the initial current required for each beam of a fusion driver. In terms of theory, the program is developing a source-to-target numerical simulation capability. The goal of the entire program is to enable an informed decision about the promise of heavy ion fusion in about a decade.
Date: October 3, 2000
Creator: Bangerter, R.O.; Davidson, R.C.; Herrmannsfeldt, W.B.; Lindl, J.D.; Logan, B.G. & Meier, W.R.
Partner: UNT Libraries Government Documents Department

Numerical Study of the Formation, Ion Spin-up and Nonlinear Stability Properties of Field-reversed Configurations

Description: Results of three-dimensional numerical simulations of field-reversed configurations (FRCs) are presented. Emphasis of this work is on the nonlinear evolution of magnetohydrodynamic (MHD) instabilities in kinetic FRCs and the new FRC formation method by the counter-helicity spheromak merging. Kinetic simulations show nonlinear saturation of the n = 1 tilt mode, where n is the toroidal mode number. The n = 2 and n = 3 rotational modes are observed to grow during the nonlinear phase of the tilt instability due to the ion spin-up in the toroidal direction. The ion toroidal spin-up is shown to be related to the resistive decay of the internal flux, and the resulting loss of particle confinement. Three-dimensional MHD simulations of counter-helicity spheromak merging and FRC formation show good agreement with results from the SSX-FRC experiment. Simulations show formation of an FRC in about 30 Alfven times for typical experimental parameters. The growth rate of the n = 1 tilt mode is shown to be significantly reduced compared to the MHD growth rate due to the large plasma viscosity and field-line-tying effects.
Date: November 12, 2004
Creator: Belova, E.V.; Davidson, R.C.; Ji, H.; Yamada, M.; Cothran, C.D.; Brown, M.R. et al.
Partner: UNT Libraries Government Documents Department

Physics of Neutralization of Intense Charged Particle Beam Pulses by a Background Plasma

Description: Neutralization and focusing of intense charged particle beam pulses by a background plasma forms the basis for a wide range of applications to high energy accelerators and colliders, heavy ion fusion, and astrophysics. For example, for ballistic propagation of intense ion beam pulses, background plasma can be used to effectively neutralize the beam charge and current, so that the self-electric and self-magnetic fields do not affect the ballistic propagation of the beam. From the practical perspective of designing advanced plasma sources for beam neutralization, a robust theory should be able to predict the self-electric and self-magnetic fields during beam propagation through the background plasma. The major scaling relations for the self-electric and self-magnetic fields of intense ion charge bunches propagating through background plasma have been determined taking into account the effects of transients during beam entry into the plasma, the excitation of collective plasma waves, the effects of gas ionization, finite electron temperature, and applied solenoidal and dipole magnetic fields. Accounting for plasma production by gas ionization yields a larger self-magnetic field of the ion beam compared to the case without ionization, and a wake of current density and self-magnetic field perturbations is generated behind the beam pulse. A solenoidal magnetic field can be applied for controlling the beam propagation. Making use of theoretical models and advanced numerical simulations, it is shown that even a small applied magnetic field of about 100G can strongly affect the beam neutralization. It has also been demonstrated that in the presence of an applied magnetic field the ion beam pulse can excite large-amplitude whistler waves, thereby producing a complex structure of self-electric and self-magnetic fields. The presence of an applied solenoidal magnetic field may also cause a strong enhancement of the radial self-electric field of the beam pulse propagating through the background plasma. If ...
Date: September 3, 2009
Creator: Kaganovich, I.D.; Davidson, R.C.; Dorf, M.A.; Startsev, E.A.; Sefkow, A.B; Friedman, A.F. et al.
Partner: UNT Libraries Government Documents Department

Simulation of chamber transport for heavy-ion fusion

Description: Beams for heavy-ion fusion (HIF) are expected to require substantial neutralization in a target chamber. Present targets call for higher beam currents and smaller focal spots than most earlier designs, leading to high space-charge fields. Collisional stripping by the background gas expected in the chamber further increases the beam charge. Simulations with no electron sources other than beam stripping and background-gas ionization show an acceptable focal spot only for high ion energies or for currents far below the values assumed in recent HIF power-plant scenarios. Much recent research has, therefore, focused on beam neutralization by electron sources that were neglected in earlier simulations, including emission from walls and the target, photoionization by radiation from the target, and pre-neutralization by a plasma generated along the beam path. The simulations summarized here indicate that these effects can significantly reduce the beam focal-spot size.
Date: October 4, 2002
Creator: Sharp, W.M.; Callahan, D.A.; Tabak, M.A.; Yu, S.S.; Peterson, P.F.; Rose, D.V. et al.
Partner: UNT Libraries Government Documents Department

Numerical Study of Field-reversed Configurations: The Formation and Ion Spin-up

Description: Results of three-dimensional numerical simulations of field-reversed configurations (FRCs) are presented. Emphasis of this work is on the nonlinear evolution of magnetohydrodynamic (MHD) instabilities in kinetic FRCs, and the new FRC formation method by counter-helicity spheromak merging. Kinetic simulations show nonlinear saturation of the n = 1 tilt mode, where n is the toroidal mode number. The n = 2 and n = 3 rotational modes are observed to grow during the nonlinear phase of the tilt instability due to the ion spin-up in the toroidal direction. The ion toroidal spin-up is shown to be related to the resistive decay of the internal flux, and the resulting loss of particle confinement. Three-dimensional MHD simulations of counter-helicity spheromak merging and FRC formation show good qualitative agreement with results from the SSX-FRC experiment. The simulations show formation of an FRC in about 20-30 Alfven times for typical experimental parameters. The growth rate of the n = 1 tilt mode is shown to be significantly reduced compared to the MHD growth rate due to the large plasma viscosity and field-line-tying effects.
Date: June 6, 2005
Creator: Belova, E. V.; Davidson, R. C.; Ji, H.; Yamada, M.; Cothran, C. D.; Brown, M. R. et al.
Partner: UNT Libraries Government Documents Department

Accelerator and Ion Beam Tradeoffs for Studies of Warm DenseMatter

Description: One approach for heating a target to ''Warm Dense Matter'' conditions (similar, for example, to the interiors of giant planets or certain stages in inertial confinement fusion targets), is to use intense ion beams as the heating source (see refs.[6] and [7] and references therein for motivation and accelerator concepts). By consideration of ion beam phase-space constraints, both at the injector, and at the final focus, and consideration of simple equations of state and relations for ion stopping, approximate conditions at the target foil may be calculated. Thus, target temperature and pressure may be calculated as a function of ion mass, ion energy, pulse duration, velocity tilt, and other accelerator parameters. We connect some of these basic parameters to help search the extensive parameter space including ion mass, ion energy, total charge in beam pulse, beam emittance, target thickness and density.
Date: January 30, 2006
Creator: Barnard, J.J.; Briggs, R.J.; Callahan, D.A.; Davidson, R.C.; Friedman, A.; Grisham, L. et al.
Partner: UNT Libraries Government Documents Department

Toward a physics design for NDCX-II, an ion accelerator for warm dense matter and HIF target physics studies

Description: The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL), a collaborationof 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&quot;tilt&quot; 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 a ~;;30 nC pulse of Li+ ions to ~;;3 MeV, then compresses it 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 analysis, 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.
Date: August 1, 2008
Creator: Friedman, A.; Barnard, J.J.; Briggs, R.J.; Davidson, R.C.; Dorf, M.; Grote, D.P. et al.
Partner: UNT Libraries Government Documents Department

Energy Amplification and Beam Bunching in a Pulse Line Ion Accelerator

Description: In a first beam dynamics validation experiment for a new Pulse Line Ion Acceleration (PLIA) concept, the predicted energy amplification and beam bunching were experimentally observed. Beam energy modulation of -80 keV to +150 keV was measured using a PLIA input voltage waveform of -21 kV to +12 kV. Ion pulses accelerated by 150 keV, and bunching by a factor of four were simultaneously achieved. The measured longitudinal phase space and current waveform of the accelerated beam are in good agreement with 3-D particle-in-cell simulations.
Date: June 8, 2006
Creator: Roy, P K; Waldron, W L; Yu, S S; Coleman, J E; Henestroza, E; Grote, D P et al.
Partner: UNT Libraries Government Documents Department