Alpha particle destabilization of the toroidicity-induced Alfven eigenmodes
The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped {alpha}-particles through the wave-particle resonances. Satisfying the resonance condition requires that the {alpha}-particle birth speed v{sub {alpha}} {ge} v{sub A}/2{vert bar}m-nq{vert bar}, where v{sub A} is the Alfven speed, m is the poloidal model number, and n is the toroidal mode number. To destabilize the TAE modes, the inverse Landau damping associated with the {alpha}-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the {alpha}-particles and the core electrons and ions. The growth rate was studied analytically with a perturbative formula derived from the quadratic dispersion relation, and numerically with the aid of the NOVA-K code. Stability criteria in terms of the {alpha}-particle beta {beta}{sub {alpha}}, {alpha}-particle pressure gradient parameter ({omega}{sub {asterisk}}/{omega}{sub A}) ({omega}{sub {asterisk}} is the {alpha}-particle diamagnetic drift frequency), and (v{sub {alpha}}/v{sub A}) parameters will be presented for TFTR, CIT, and ITER tokamaks. The volume averaged {alpha}-particle beta threshold for TAE instability also depends sensitively on the core electron and ion temperature. Typically the volume averaged {alpha}-particle beta threshold is in the order of 10{sup {minus}4}. Typical growth rates of the n=1 TAE mode can be in the order of 10{sup {minus}2}{omega}{sub A}, where {omega}{sub A}=v{sub A}/qR. Other types of global Alfven waves are stable in D-T tokamaks due to toroidal coupling effects.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 6508035
- Report Number(s):
- PPPL-2717; ON: DE91000486
- Country of Publication:
- United States
- Language:
- English
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Destabilization of tokamak pressure-gradient driven instabilities by energetic alpha populations
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Related Subjects
700107* -- Fusion Energy-- Plasma Research-- Instabilities
ALFVEN WAVES
ALPHA PARTICLES
CHARGED PARTICLES
CLOSED PLASMA DEVICES
DAMPING
DISPERSION RELATIONS
EQUILIBRIUM
HYDROMAGNETIC WAVES
INSTABILITY
LANDAU DAMPING
MAGNETIC FIELDS
MHD EQUILIBRIUM
PLASMA INSTABILITY
PRESSURE GRADIENTS
THERMONUCLEAR DEVICES
TOKAMAK DEVICES