Beam Equilibrium Stability And Transport Research Articles

Nonlinear δ f simulations of collective effects in intense charged particle beams

A nonlinear δf particle simulation method based on the Vlasov–Maxwell equations has been recently developed to study collective processes in high-intensity beams, where space-charge and magnetic self-field effects play a critical role in determining the nonlinear beam dynamics. Implemented in the Beam Equilibrium, Stability and Transport (BEST) code [H. Qin, R. C. Davidson, and W. W. Lee, Phys. Rev. ST Accel. Beams 3, 084401 (2000); 3, 109901 (2000)], the nonlinear δf method provides a low-noise and self-consistent tool for simulating collective interactions and nonlinear dynamics of high-intensity beams in modern and next generation accelerators and storage rings, such as the Spallation Neutron Source and heavy ion fusion drivers. A wide range of linear eigenmodes of high intensity charged particle beams can be systematically studied using the BEST code. Simulation results for the electron–proton two-stream instability in the Proton Storage Ring experiment [R. Macek et al., in Proceedings of the Particle Accelerator Conference, Chicago, 2001 (IEEE, Piscataway, NJ, 2001), Vol. 1, p. 688] at the Los Alamos National Laboratory agree well with experimental observations. Large-scale parallel simulations have also been carried out for the ion–electron two-stream instability in the very-high-intensity heavy ion beams envisioned for heavy ion fusion applications. In both cases, the simulation results indicate that the dominant two-stream instability has a dipole-mode (hose-like) structure and can be stabilized by a modest axial momentum spread of the beam particles.

δf simulation studies of the ion–electron two-stream instability in heavy ion fusion beams

Ion–electron two-stream instabilities in high intensity heavy ion fusion beams, described self-consistently by the nonlinear Vlasov–Maxwell equations, are studied using a three-dimensional multispecies perturbative particle simulation method. Large-scale parallel particle simulations are carried out using the recently developed Beam Equilibrium, Stability, and Transport (BEST) code. For a parameter regime characteristic of heavy ion fusion drivers, simulation results show that the most unstable mode of the ion–electron two-stream instability has a dipole-mode structure, and the linear growth rate decreases with increasing axial momentum spread of the beam particles due to Landau damping by the axial momentum spread of the beam ions in the longitudinal direction.

Analytical and nonlinear perturbative simulation studies of the equilibrium and stability properties of intense charged particle beams for heavy ion fusion

This paper presents an overview of recent analytical and numerical investigations of collective processes in intense ion beams at the Plasma Physics Laboratory based on the nonlinear Vlasov–Maxwell equations. The topics covered include: (a) nonlinear stability theorem for quiescent beam propagation at high space-charge intensities; (b) development and application of Hamiltonian averaging techniques for intense beam propagation through alternating-gradient field configurations; (c) kinetic studies of the electron–ion two-stream instability which occurs when an (unwanted) component of electrons is present in the beam transport line; (d) application of the newly developed three-dimensional, multispecies, nonlinear perturbative particle simulation scheme, called the Beam Equilibrium, Stability and Transport (BEST) code, to investigate the linear and nonlinear dynamics of intense beam propagation, including the electron–ion two-stream instability; and (e) investigations of the role of collective mode excitations in the expulsion of particles from the beam core and the production of halo particles. Finally, the linear growth properties of instabilities driven by pressure anisotropy are investigated within the framework of a macroscopic warm-fluid model.

Three-dimensional multispecies nonlinear perturbative particle simulations of collective processes in intense particle beams

Collective processes in intense charged particle beams described self-consistently by the Vlasov-Maxwell equations are studied using a 3D multispecies nonlinear perturbative particle simulation method. The newly developed beam equilibrium, stability, and transport (BEST) code is used to simulate the nonlinear stability properties of intense beam propagation, surface eigenmodes in a high-intensity beam, and the electron-proton ($e\ensuremath{-}p$) two-stream instability observed in the Proton Storage Ring (PSR) experiment. Detailed simulations in a parameter regime characteristic of the PSR experiment show that the dipole-mode two-stream instability is stabilized by a modest spread (about 0.1%) in axial momentum of the beam particles.

3D nonlinear perturbative particle simulations of two-stream collective processes in intense particle beams

Collective processes in intense charged particle beams described self-consistently by the Vlasov–Maxwell equations are studied using a 3D multispecies nonlinear perturbative particle simulation method. The newly-developed Beam Equilibrium Stability and Transport (BEST) code has been used to simulate the nonlinear stability properties of intense beam propagation, surface eigenmodes in a high-intensity beam, and the electron–proton (e–p) two-stream instability observed in the Proton Storage Ring (PSR).