Thermonuclear Driven Fast Magnetosonic Wave Heating in Tokamak Plasmas
Sutton, William Roy, Iii
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Permalink
https://hdl.handle.net/2142/70885
Description
Title
Thermonuclear Driven Fast Magnetosonic Wave Heating in Tokamak Plasmas
Author(s)
Sutton, William Roy, Iii
Issue Date
1982
Department of Study
Nuclear Engineering
Discipline
Nuclear Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Nuclear
Abstract
A thermonuclear driven fast magnetosonic wave instability is investigated in tokamak plasmas for propagation transverse to the external magnetic field at frequencies of several times the alpha particle gyro rate: (omega)(TURNEQ)L(OMEGA)(, ) =k(,(PERP))v(,A), L(TURN)4 to 8, k(,(PARLL))<<k(,(PERP)). The 2-D differential quasi-linear diffusion equation is derived in circular cylindrical, v(,(PERP))-v(,(PARLL)) geometry. We perform an expansion in the small parameter k(,(PARLL))/k(,(PERP)) of the quasi-linear diffusion coefficients. Examination of the mathematical structure of these coefficents reveals that they are independent of v(,(PARLL)) to zero order in the small parameter k(,(PARLL))/k(,(PERP)) and exhibit the ordering D(,(PERP)):D(,X):D(,(PARLL))(TURN)1:0(k(,(PARLL))/k(,(PERP))):0(k(,(PARLL))('2)/k(,(PERP))('2)) for the perpendicular, cross and parallel terms, respectively. Inherently 2-D phenomena such as loss cone and collisional effects are neglected and the isotropic Gaussian shell source is employed for the initial alpha distribution. These assumptions permit reduction of the problem from 2-D to 1-D by integrating out the v(,(PARLL)) dependence. This reduced system includes the contribution from all alpha particles. We have quantified the instability effect at the microscopic, plasma and system levels for the first time. System level information is available by coupling data produced in production runs of the 1-D formation with a 1 1/2-D tokamak transport code. We have employed a new technique to produce contour plots of the alpha particle threshold fraction to identify the instability regions in the n(,e)-T(,i) plane. Surveys of the n(,e)-T(,i) plane indicate that alpha particle threshold fractions as low as 10('-6)-10('-4) may be possible for the alpha source function in tokamak geometry. Plasma level survey calculations using the reduced 1-D quasi-linear formulation indicate enhancements in the classical alpha-ion energy split by factors of as much as 1.5 for T(,i)=T(,e) at 7 keV. System level effects, however, are less than a 1-2% improvement in fusion power, due to the rapid equilibration of electron and ion temperatures in these plasmas.
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