modes, non-neutral plasma, finite length, cold equilibria, Malmberg-Penning trap
For realistic, cold equilibria of finite length representing a pure electron plasma confined in a cylindrical Malmberg–Penning trap, the mode spectrum for Trivelpiece–Gould, m=0, and for diocotron, m=1, modes is calculated numerically. A novel method involving finite elements is used to successfully compute eigenfrequencies and eigenfunctions for plasma equilibria shaped like pancakes, cigars, long cylinders, and all things in between. Mostly sharp-boundary density configurations are considered but also included in this study are diffuse density profiles including ones with peaks off axis leading to instabilities. In all cases the focus has been on elucidating the role of finite length in determining mode frequencies and shapes. For m=0 accurate eigenfrequencies are tabulated and their dependence on mode number and aspect ratio is computed. For m=1 it is found that the eigenfrequencies are 2% to 3% higher than given by the Fine–Driscoll formula [Phys. Plasmas 5, 601 (1998)]. The "new modes" of Hilsabeck and O'Neil [Phys. Plasmas 8, 407 (2001)] are identified as Dubin modes. For hollow profiles finite length in cold-fluid can account for up to ~70% of the theoretical instability growth rate.
Original Publication Citation
Rasband, Neil S. and Ross L. Spencer."Modes in a non-neutral plasma of finite length, m = ,1." Physics of Plasmas 1 (23): 948-955.
BYU ScholarsArchive Citation
Rasband, S. Neil and Spencer, Ross L., "Modes in a non-neutral plasma of finite length, m = 0,1" (2003). Faculty Publications. 504.
Physical and Mathematical Sciences
Physics and Astronomy
© 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics and may be found at http://link.aip.org/link/?PHPAEN/10/948/1
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