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(EX/P2-12) Application of Electron Bernstein Wave Heating and Current Drive to High Beta Plasmas

P.C. Efthimion1), G. Taylor1), B. Jones1), R.W. Harvey4), A.K. Ram3), P. Smirnov5), T. Munsat1), G. Bell2), A. Bers3), J. Decker3), J.C. Hosea1), R. Kaita1), N. Lashmore-Davies6), R. Majeski1), D.A. Rasmussen2), J. Spaleta1), J. Wilgen2), J.R. Wilson1)
1) Princeton Plasma Physics Laboratory, Princeton, USA
2) Oak Ridge National Laboratory, Oak Ridge, TN, U.S.A.
3) Plasma Science and Fusion Center, M.I.T., Cambridge, MA, U.S.A.
4) CompX, Del Mar, CA, U.S.A.
5) Moscow State University, Moscow, Russia
6) Euratom - UKAEA Fusion Assoc., Culham Science Centre, Abingdon, Oxon, U K.

Abstract.  Electron Bernstein Waves (EBW) can potentially heat and drive current in high-beta plasmas. Electomagnetic waves can convert to EBW via two paths. O-mode heating, demonstrated on W-7AS, requires waves be launched within a narrow k-parallel range. Alternately, in high-beta plasmas, the X-mode cutoff and EBW conversion layers are millimeters apart, so the fast X-mode can tunnel to the EBW branch. We are studying the conversion of EBW to the X-mode by measuring the radiation temperature of the cyclotron emission and comparing it to the electron temperature. In addition, mode conversion has been studied with an approximate kinetic full-wave code. We have enhanced EBW mode conversion to $ \sim$ 100% by encircling the antenna with a limiter that shortens the density scale length at the conversion layer in the scrape off of the CDX-U spherical torus (ST) plasma. Consequently, a limiter in front of a launch antenna achieves efficient X-mode coupling to EBW. Ray tracing and Fokker-Planck codes have been used to develop current drive scenarios in NSTX high-beta ($ \sim$ 40%) ST plasmas and a relativistic code will examine the potential synergy of EBW current drive with the bootstrap current.

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IAEA 2003