The m=1 diocotron instability in single species plasmas

Journal Article · Fri Dec 10 04:00:00 EST 1999 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.1302120· OSTI ID:21210352

Finn, J M; Castillo-Negrete, D del ^[1]; Barnes, D C ^[2]

---

1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2. Applied Theoretical and Computational Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

According to conventional theory based on the drift-Poisson equations, the m=1 diocotron mode is stable, even for hollow density profiles. However, experiments [C. F. Driscoll, Phys. Rev. Lett. 64, 645 (1990)] show instability for this mode. These results have remained unexplained since 1990. We have found two effects, related to compression parallel to the magnetic field, which lead to instability with growth rates and other properties in good agreement with the experiments. The first is due to curvature of the sheaths at the ends of the trap. The second is the free boundary effect due to the linearized perturbation of the plasma length. These effects are described in terms of the modified drift-Poisson model, which states the conservation of the line integrated density. The modified drift-Poisson equations derived are analogous to the shallow water equations of geophysical fluid dynamics (GFD), with the line integrated density corresponding to the potential vorticity. This is explained in more detail in [del-Castillo-Negrete et al., this volume]. More recent experimental results [A. A. Kabantsev and C. F. Driscoll, this volume] show agreement over a wider range of parameters than the original experiments. We study the m=2 mode and show that curvature and free boundary effects can increase the growth rate, but it is still small compared to that of the m=1 mode for realistic parameters, and the critical hollowness for stability is much greater. Results are also shown for m=1 modes in the analogous GFD system. It is shown that topography variation in cylindrical geometry and free surface effects both lead to instability with properties similar to those in the plasma models.

• OSTI ID: 21210352
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 498; ISSN 0094-243X; ISSN APCPCS
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COMPRESSIBILITY
DISTURBANCES
DRIFT INSTABILITY
ELECTRONS
FLUID MECHANICS
MAGNETIC FIELDS
PLASMA
PLASMA DENSITY
POISSON EQUATION
STABILITY
TRAPS