Three-dimensional particle simulation of heavy-ion fusion beams*

Abstract

The beams in a heavy-ion-beam-driven inertial fusion (HIF) accelerator are collisionless, nonneutral plasmas, confined by applied magnetic and electric fields. These space-charge-dominated beams must be focused onto small (few mm) spots at the fusion target, and so preservation of a small emittance is crucial. The nonlinear beam self-fields can lead to emittance growth, and so a self-consistent field description is needed. To this end, a multidimensional particle simulation code, warp [Friedman et al., Part. Accel. 37-38, 131 (1992)], has been developed and is being used to study the transport of HIF beams. The code’s three-dimensional (3-D) package combines features of an accelerator code and a particle-in-cell plasma simulation. Novel techniques allow it to follow beams through many accelerator elements over long distances and around bends. This paper first outlines the algorithms employed in warp. A number of applications and corresponding results are then presented. These applications include studies of: beam drift-compression in a misaligned lattice of quadrupole focusing magnets; beam equilibria, and the approach to equilibrium; and the MBE-4 experiment [AIP Conference Proceedings 152 (AIP, New York, 1986), p. 145] recently concluded at Lawrence Berkeley Laboratory (LBL). Finally, 3-D simulations of bent-beam dynamics relevant to the planned Induction Linac Systems Experiments (ILSE) [Fessenden, Nucl. Instrum. Methods Plasma Res. A 278, 13 (1989)] at LBL are described. Axially cold beams are observed to exhibit little or no root-mean-square emittance growth at midpulse in transiting a (sharp) bend. Axially hot beams, in contrast, do exhibit some emittance growth.

Experimental investigation of random noise-induced beam degradation in high-intensity accelerators using a linear Paul trap

“…To describe the time evolution of the transverse emittance self-consistently, we make use of particle-in-cell (PIC) simulations. The result of WARP 2D PIC simulations [27] with the same error sample used in the envelope equation demonstrates that the oscillation amplitudes are saturated to some extent, and that the oscillation center increases linearly with the noise duration [ Fig. 2(b)], implying the conversion of free energy available from the envelope oscillations into emittance growth [28].…”

“…(4) necessarily underestimates the actual mean transverse emittance. Particles far away from the beam core ( > ffiffiffi 2 p R b ) are of course weighted more heavily in calculating the emittance in the simulations [12,27].…”

Overview of theory and simulations in the Heavy Ion Fusion Science Virtual National Laboratory

“…In an intense beam, betatron motion can substitute for cyclotron motion, and a Harris-like instability appears. The mode was observed in WARP runs, identified as a possible issue [47], and explored systematically [48]. Detailed understanding has come from BEST δf simulations and analysis.…”

Overview of theory and modeling in the heavy ion fusion virtual national laboratory

“…Examples include: detailed analytical and nonlinear perturbative simulation studies of collective processes, including the electron-ion two-stream instability [2][3][4][5][6][7], and the Harrislike temperature-anisotropy instability driven by T ⊥b T b [8][9][10][11]; development of a selfconsistent theoretical model of charge and current neutralization for intense beam propagation through background plasma in the target chamber [12][13][14][15]; development of a robust theoretical model of beam compression dynamics and nonlinear beam dynamics in the final focus system using a warm-fluid description [16]; development of an improved kinetic description of nonlinear beam dynamics using the Vlasov-Maxwell equations [2,[17][18][19][20], including identification of the class of (stable) beam distributions, and the development of…”

“…Assisted-pinched transport uses a preformed 50-kA channel, created in a gas (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) by a laser and a discharge electrical circuit, to create a frozen magnetic field before the heavy ion beam is injected [43][44][45]. Self-pinched transport uses the ion beam itself to break down a low-pressure gas (1-100 mTorr) [13,46,47], and the net self-magnetic field affords confinement.…”