Lower hybrid parametric instabilities: Nonuniform pump waves and tokamak applications

Journal Article · Tue Nov 01 04:00:00 EST 1977 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.861804· OSTI ID:7280734

Berger, R L; Chen, L; Kaw, P K; Perkins, F W

Electrostatic lower hybrid ''pump'' waves are often launched into tokamak plasmas by structures (e.g., waveguides) whose dimensions are considerably smaller than characteristic plasma sizes. Such waves propagate in well-defined resonance cones and give rise to parametric instabilities driven by electron E x B velocities. The finite size of the resonance cone region determines the threshold for both convective quasi-mode decay instabilities and absolute instabilities. The excitation of absolute instabilities depends on whether a traveling or standing wave pump model is used; traveling wave pumps require the daughter waves to have a definite frequency shift. Altogether, parametric instabilities driven by E x B velocities occur for threshold fields significantly below the threshold for filamentation instabilities driven by pondermotive forces. Applications to tokamak heating show that nonlinear effects set in when a certain power-per-wave-launching port is exceeded. For sufficiently high powers, these instabilities will occur in the low-density edge region of a tokamak. They are characterized by a daughter wave frequency 10% below the pump wave frequency, in agreement with experimental observations.

• Research Organization: Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08540
• OSTI ID: 7280734
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 20:11; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101 -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
700107* -- Fusion Energy-- Plasma Research-- Instabilities
700108 -- Fusion Energy-- Plasma Research-- Wave Phenomena
CLOSED PLASMA DEVICES
DISPERSION RELATIONS
HEATING
HOMOGENEOUS PLASMA
HYBRID RESONANCE
INSTABILITY
PARAMETRIC INSTABILITIES
PLASMA
PLASMA HEATING
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
RESONANCE
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TRAVELLING WAVES