Author: N. N. GorelenkovPublisher:
ISBN:
Category : Magnetohydrodynamic waves
Languages : en
Pages : 13
Book Description
Fast Particle Destabilization of Toroidicity Induced Alfven Eigenmodes in National Spherical Torus Experiment
Author: N. N. GorelenkovPublisher:
ISBN:
Category : Magnetohydrodynamic waves
Languages : en
Pages : 13
Book Description
Fast Particle Destabilization of Toroidicity Induced Alfven Eigenmodes in National Spherical Torus Experiment
Author: N. N. GorelenkovPublisher:
ISBN:
Category : Magnetohydrodynamic waves
Languages : en
Pages : 13
Book Description
Alpha Particle Destabilization of the Toroidicity-induced Alfven Eigenmodes
Author: C. Z. ChengAlpha Particle Destabilization of the Toroidicity-induced Alfven Eigenmodes
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 28
Book Description
The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped?-particles through the wave-particle resonances. Satisfying the resonance condition requires that the?-particle birth speed v{sub?} ≥ 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?-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the?-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?-particle beta?{sub?},?-particle pressure gradient parameter (?{sub {asterisk}}/?{sub A}) (?{sub {asterisk}} is the?-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 10−4. Typical growth rates of the n=1 TAE mode can be in the order of 10−2?{sub A}, where?{sub A}=v{sub A}/qR. Other types of global Alfven waves are stable in D-T tokamaks due to toroidal coupling effects.
Non-linear Dynamics Of Toroidicity-induced Alfven Eigenmodes On The National Spherical Torus Experiment
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The National Spherical Torus Experiment (NSTX, [M. Ono et al., Nucl. Fusion 40, 557 (2000)]) routinely operates with neutral beam injection as the primary system for heating and current drive. The resulting fast ion population is super-Alfvenic, with velocities 1
Effects of Toroidal Rotation Sshear on Toroidicity-induced Alfven Eigenmodes in the National Spherical Torus Experiment
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 203
Book Description
The effects of a sheared toroidal rotation on the dynamics of bursting Toroidicity-induced Alfven eigenmodes are investigated in neutral beam heated plasmas on the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 557 (2000)]. The modes have a global character, extending over most of the minor radius. A toroidal rotation shear layer is measured at the location of maximum drive for the modes. Contrary to results from other devices, no clear evidence of increased damping is found. Instead, experiments with simultaneous neutral beam and radio-frequency auxiliary heating show a strong correlation between the dynamics of the modes and the instability drive. It is argued that kinetic effects involving changes in the mode drive and damping mechanisms other than rotation shear, such as continuum damping, are mostly responsible for the bursting dynamics of the modes.
Experimental Study of Toroidicity-induced Alfven Eigenmode (TAE) Stability at High Q(0).
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 17
Book Description
Experiments to destabilize the Toroidicity-induced Alfven Eigenmode (TAE) by energetic alpha particles were performed on the Tokamak Fusion Test Reactor using deuterium and tritium fuel. To decrease the alpha particle pressure instability threshold, discharges with an elevated value of q(0)> 1.5 were used. By raising q(0), the radial location of the low toroidal-mode-number TAE gaps moves toward the magnetic axis and into alignment with the region of maximum alpha pressure gradient, thereby (in theory) lowering the value of [beta]{sub {alpha}}(0) required for instability. No TAE activity was observed when the central alpha particle [beta]{sub {alpha}} reached 0.08% in a discharge with fusion power of 2.4 MW. Calculations show that the fusion power is within a factor of 1.5 to 3 of the instability threshold.
Experimental Aspects of Effects of High-energy Particles on Alfven Modes
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 16
Book Description
Global Alfven modes are observed in a number of tokamaks, including DIII-D and TFTR. Instabilities occur during neutral-beam injection and during fast-wave ICRF heating, and may recently have been observed during alpha-particle heating. Identification of toroidicity-induced Alfven eigenmodes (TAE) is based primarily on the scaling of the real frequency of the mode. Other modes, including the beta-induced Alfven eigenmode (BAE), are also observed. The stability threshold of TAE modes agree (to within a factor of two) with theoretical predictions. Toroidal mode numbers of n = 2-6 are usually most unstable, as theoretically expected. Measurements of the poloidal and radial mode structure are consistent with theoretical predictions, but the uncertainties are large. Both TAE and BAE modes can cause large, concentrated losses of fast ions. Phenomenologically, beam-driven Alfven modes usually {open_quotes}saturate{close_quotes} through bursts that expel beam ions, while modes observed during ICPF heating approach a steady saturation amplitude.
Author: D. J. Sigmar
Author: