Author: C.Z. ChengPublisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 10
Book Description
Evolution of the Alpha Particle Driven Toroidicity Induced Alfven Mode
Author: C.Z. ChengPublisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 10
Book Description
Evolution of the Alpha Particle Driven Toroidicity Induced Alfven Mode
Author: C. Z. ChengPublisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 10
Book Description
Nonlinear Evolution of the Alpha Particle Driven Toroidicity-induced Alfven Eigenmode
Author: Yanlin WuPublisher:
ISBN:
Category : Computer simulation
Languages : en
Pages : 34
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.
Energy Research Abstracts
Author: Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 806
Book Description
Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Alpha Particle Losses from Toroidicity Induced Alfvén Eigenmodes
Author: D. J. SigmarNonlinear Interaction of Fast Particles with Alfven Waves in Toroidal Plasmas
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A numerical algorithm to study the nonlinear, resonant interaction of fast particles with Alfven waves in tokamak geometry has been developed. The scope of the formalism is wide enough to describe the nonlinear evolution of fishbone modes, toroidicity-induced Alfven eigenmodes and ellipticity-induced Alfven eigenmodes, driven by both passing and trapped fast ions. When the instability is sufficiently weak, it is known that the wave-particle trapping nonlinearity will lead to mode saturation before wave-wave nonlinearities are appreciable. The spectrum of linear modes can thus be calculated using a magnetohydrodynamic normal-mode code, then nonlinearly evolved in time in an efficient way according to a two-time-scale Lagrangian dynamical wave model. The fast particle kinetic equation, including the effect of orbit nonlinearity arising from the mode perturbation, is simultaneously solved of the deviation, [delta]f= f[minus] f[sub 0], from an initial analytic distribution f[sub 0]. High statistical resolution allows linear growth rates, frequency shifts, resonance broadening effects, and nonlinear saturation to be calculated quickly and precisely. The results have been applied to an ITER instability scenario. Results show that weakly-damped core-localized modes alone cause negligible alpha transport in ITER-like plasmas--even with growth rates one order of magnitude higher than expected values. However, the possibility of significant transport in reactor-type plasmas due to weakly unstable global modes remains an open question.
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.
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.