Progress in Icrf Heating Technology and Designs for Future Large Tokamak Heating Systems

Baity, F. W.; Swain, D. W.; Hoffman, D. J.; Becraft, W.R.; Bryan, W.E.; Mayberry, M.J.; Owens, T.L.; Yugo, J.J.

doi:10.1016/b978-1-4832-8376-0.50093-0

Cited by 2 publications

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“…Heating by waves in the ion cyclotron range of frequencies (ICRF) has become the preferred auxiliary heating method for compact ignition experiments [ 1 ] because of its experimental successes in large tokamaks [2][3][4][5][6] and the available low-cost technology [7]. However, ICRF heating also has detrimental effects, among them the generation of metallic impurities from the Faraday screen material [8][9][10][11] and an increased influx of both hydrogen isotopes and carbon from the graphite walls [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Radiofrequency sheaths and impurity generation by ICRF antennas

1989

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In general, Faraday screen elements in an ICRF antenna are not aligned precisely along the combined toroidal and poloidal magnetic fields. When plasma of density n > 2∊0V/eg2 ∼ 109cm−3 (V being the voltage across the gap and g the gap spacing) is present in the gap between the elements, the electron response to the parallel electric field shorts out the electric field over most of the gap, leaving a narrow sheath of positive space charge and an intense electric field. This intense electric field accelerates ions up to an appreciable fraction of the gap voltage (∼1 kV), sufficient to cause physical sputtering of the screen material. Impurities so generated constitute the principal limitationon power density for ICRF antennas. Principles of ICRF antenna and Faraday screen design which minimize sputtering are discussed.

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