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DOE OSTI · 1838250

Doubling off-axis electron cyclotron current drive efficiency via velocity space engineering

Chen, Xi·Petty, C. C.·Lohr, J.·Su, D.·Prater, R.·Cengher, M.·Austin, M.·Gorelov, Y.·Holcomb, C.·Lao, L.·Ponce, D.·Pinsker, R. I.·Victor, B.·Zeng, L.
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Abstract

For the first time, experiments on the DIII-D tokamak have demonstrated electron cyclotron current drive with more than double the conventional efficiency by tailoring the wave–particle interactions in velocity space using a novel ‘top launch’ geometry. Steering the EC waves to propagate nearly parallel to the resonance drives current more efficiently by (1) selective damping on electrons with higher parallel velocity v ||, and (2) longer absorption path to compensate for inherently weaker absorption at higher v ||. Experiments using a fixed-injection top launch system find an optimal velocity space interaction for maximum current drive efficiency at ρ ~ 0.5 where the ease of drawing out a high v || electron tail is balanced by sufficient absorption.

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70 PLASMA PHYSICS AND FUSION TECHNOLOGYECCDNTM controladvanced tokamak scenariocurrent drivehigh qminoff-axisvelocity space

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Chen, Xi, Petty, C. C., Lohr, J., Su, D., Prater, R., Cengher, M., Austin, M., Gorelov, Y., Holcomb, C., Lao, L., Ponce, D., Pinsker, R. I., Victor, B., Zeng, L.. 2022-03-28. Doubling off-axis electron cyclotron current drive efficiency via velocity space engineering. https://doi.org/10.1088/1741-4326%2Fac544a

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