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Heating and Current Drive Systems for the MST Reversed Field Pinch
| Author: | Goetz J.A. |
| Coauthor: | J.K. Anderson, A.P. Blair, M. Cengher, G. Fiksel, C.B. Forest, B. Hudson, M.C. Kaufman, K.J. McColla |
| Institution : | University of Wisconsin - Madison |
| Abstract text: | Control of the current density profile in MST has led to reduced magnetic fluctuations and transport and much improved confinement. In addition, external heating of the plasma will allow for exploration of the beta limit in the RFP and its effects on transport and confinement. Techniques to apply controlled auxiliary power to the MST plasma and explore these physics issues are now being developed. These methods include oscillating field current drive (OFCD), neutral beam injection (NBI), lower hybrid waves (LH), and electron Bernstein waves (EB). OFCD is a helicity injection method being tested as a way to drive net current or to alter the current density profile. A moderate power system has shown a small amount of current drive [see McCollam, et al., this workshop, for details]. Feasibility tests of NBI as an effective way to heat RFP plasmas are underway. A 1 MW, 1.5 ms beam is being used to perform fast ion confinement studies. Initial results are encouraging and indicate that fast ion confinement is not degraded in the RFP magnetic field. Both LH and EB wave injection are being developed for current drive in the RFP. Antenna design for both techniques poses significant challenges in the MST environment. A traveling wave LH antenna has demonstrated a power handling capability of 50 kW with a good impedance match to the plasma. A rotatable twin waveguide antenna that launches electromagnetic waves that mode convert to EB waves near the plasma boundary has been developed. This antenna has a power handling capability of 150 kW. These antennas will be used to explore the physics issues of current drive in an RFP. The status of the NBI, LH, and EB auxiliary systems and the plans for their extension to higher power will be discussed. |
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