Fast excitation of geodesic acoustic mode by energetic particle beams

Journal Article · Tue Dec 15 00:00:00 EST 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4938277· OSTI ID:22489989

Cao, Jintao ^[1]; Qiu, Zhiyong ^[2]; Zonca, Fulvio ^[3]

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1. Institute of Physics, Chinese Academy of Science, Beijing (China)
2. Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou (China)
3. ENEA C. R. Frascati, C.P. 65, 00044 Frascati (Italy)

A new mechanism for geodesic acoustic mode (GAM) excitation by a not fully slowed down energetic particle (EP) beam is analyzed to explain experimental observations in Large Helical Device. It is shown that the positive velocity space gradient near the lower-energy end of the EP distribution function can strongly drive the GAM unstable. The new features of this EP-induced GAM (EGAM) are: (1) no instability threshold in the pitch angle; (2) the EGAM frequency can be higher than the local GAM frequency; and (3) the instability growth rate is much larger than that driven by a fully slowed down EP beam.

• OSTI ID: 22489989
• Journal Information: Physics of Plasmas, Vol. 22, Issue 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DISTRIBUTION FUNCTIONS
EXCITATION
GEODESICS
INCLINATION
INSTABILITY GROWTH RATES
LHD DEVICE
MATHEMATICAL SPACE
PARTICLE BEAMS
SOUND WAVES
VELOCITY