Solenoidal magnetic field influences the beam neutralization by a background plasma
An analytical electron fluid model has been developed to describe the plasma response to a propagating ion beam. The model predicts very good charge neutralization during quasi-steady-state propagation, provided the beam pulse duration is much longer than the electron plasma period. In the opposite limit, the beam pulse excites large-amplitude plasma waves. Figure 1 shows the influence of a solenoidal magnetic field on charge and current neutralization. Analytical studies show that the solenoidal magnetic field begins to influence the radial electron motion when {omega}{sub ce} > {beta}{omega}{sub pe}. Here, {omega}{sub ce} is the electron gyrofrequency, {omega}{sub pe} is the electron plasma frequency, and {beta} = V{sub b}/c is the ion beam velocity. If a solenoidal magnetic field is not applied, plasma waves do not propagate. In contrast, in the presence of a solenoidal magnetic field, whistler waves propagate ahead of the beam and can perturb the plasma ahead of the beam pulse. In the limit {omega}{sub ce} >> {beta}{omega}{sub pe}, the electron current completely neutralizes the ion beam current and the beam self magnetic field greatly diminishes. Application of an external solenoidal magnetic field clearly makes the collective processes of ion beam-plasma interactions rich in physics content. Many results of the PIC simulations remain to be explained by analytical theory. Four new papers have been published or submitted describing plasma neutralization of an intense ion beam pulse.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15011639
- Report Number(s):
- UCRL-JRNL-206408; TRN: US0501347
- Journal Information:
- HIF News, Journal Name: HIF News
- Country of Publication:
- United States
- Language:
- English
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