Efficient Generation of Non-Inductive, Off-axis, Ohkawa Current, Driven by Electron Bernstein Waves in High Beta, Spherical Torus Plasmas

G Taylor G Taylor,M.d Carter M.D Carter,A.p Smirnov A.P Smirnov,C.e Kessel C.E Kessel,R.w Harvey R.W Harvey,C.b Forest C.B Forest,N.m Ershov N.M Ershov,P.c Efthimion P.C Efthimion

doi:10.2172/827839

Efficient Generation of Non-Inductive, Off-axis, Ohkawa Current, Driven by Electron Bernstein Waves in High Beta, Spherical Torus Plasmas

G Taylor G Taylor, M.d Carter M.D Carter + Show 6 more

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https://doi.org/10.2172/827839

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Publication Date: Apr 26, 2004

#Spherical Torus Plasmas #Spherical Torus + Show 8 more

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Abstract

Off-axis rf-driven current can play a critical role in sustaining high Beta spherical torus (ST) plasmas without a central solenoid. Numerical modeling of electron Bernstein wave current drive (EBWCD) for a {Beta} {approx} 40% ST plasma predicts efficient, off-axis, Ohkawa EBWCD. Current can be efficiently driven at r/a greater than 0.5 where the large trapped electron fraction precludes conventional Fisch-Boozer current drive and provides near-ideal conditions for Ohkawa EBWCD. Also, Ohkawa EBWCD efficiency increases with r/a. Enhancement over Fisch-Boozer current drive is a factor of two at r/a {approx} 0.2 rising to over an order of magnitude at r/a {approx} 0.5.

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