Long-time simulation of the single-mode bump-on-tail instability

Journal Article · Thu Dec 01 04:00:00 EST 1988 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.867008· OSTI ID:6642906

Simon, A; Radin, S; Short, R W

A Vlasov code developed by Denavit (Phys. Fluids 28, 2773 (1985)) was modified and used to study long-time behavior of the single-mode bump-on-tail instability. Large oscillations, which interrupted his original runs at ..omega../sub 0/ Tapprox. =1300 shortly after reaching the O'Neil trapping level (OTL), were identified and controlled by heating the cold background electrons. A run to ..omega../sub 0/T = 30 000 showed growth well beyond the OTL and eventually saturated at about the level predicted by Simon and Rosenbluth (SR) (Phys. Fluids 19, 1567 (1976)), before oscillations set in. A run with warmer background electrons was again interrupted by oscillations. A weakly unstable case was followed to ..omega../sub 0/T = 60 000; it also showed growth well beyond the OTL but saturated at an amplitude that was significantly below that predicted by SR. In all cases, the velocity distribution developed strong ripples near v = 0. These are shown to be caused by a numerical grid effect, and they may be responsible for the eventual development of the large oscillations and for the low level of saturation in the weakly unstable case.

• Research Organization: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299
• OSTI ID: 6642906
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 31:12; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
BEAM-PLASMA SYSTEMS
BUMP-IN-TAIL INSTABILITY
COLLISIONLESS PLASMA
COMPUTERIZED SIMULATION
INSTABILITY
INSTABILITY GROWTH RATES
NONLINEAR PROBLEMS
PLASMA
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA SIMULATION
SIMULATION