HHFW Heating Efficiency on NSTX versus B{sub {phi}} and Antenna k{sub parallel}
- Princeton Plasma Physics Laboratory, Princeton (United States)
- Johns Hopkins University, Baltimore (United States)
- Oak Ridge National Laboratory, Oak Ridge (United States)
- Columbia University, New York City (United States)
- Nova Photonics, Princeton (United States)
HHFW RF power delivered to the core plasma of NSTX is strongly reduced as the launched wavelength is increased--for B{sub {phi}} = 4.5 kG, heating is {approx}1/2 as effective at k{sub {phi}} = -7 m{sup -1} as at 14 m{sup -1} and {approx}1/10 as effective at -3 m{sup -1}. Measured edge ion heating, attributable to parametric decay (PDI), increases with wavelength but not fast enough to account for the observed power loss. Surface fast waves (FW) may enhance both PDI and also losses in sheaths and structures around the machine--FW fields propagate closer to the wall with decreasing B{sub {phi}} and k{sub parallel} (onset n{sub e}{proportional_to}B{sub {phi}}xk{sub parallel}{sup 2}). A dramatic increase in core heating efficiency is observed at -7 m{sup -1} when B{sub {phi}} is increased to 5.5 kG--central T{sub e} near 4 keV at P{sub RF} = 2 MW. Also, the PDI losses are a weak function of B{sub {phi}} and k{sub parallel}, whereas the far-field RF poloidal magnetic field (at 5.5 kG) increases a factor of {approx}3 when k{sub parallel} is reduced from 14 m{sup -1} to -3 m{sup -1}, suggesting a large increase in wall/sheath power loss and a major effect of surface fast waves on edge losses.
- OSTI ID:
- 21032735
- Journal Information:
- AIP Conference Proceedings, Vol. 933, Issue 1; Conference: 17. topical conference on radio frequency power in plasmas, Clearwater, FL (United States), 7-9 May 2007; Other Information: DOI: 10.1063/1.2800453; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA). NSTX Team; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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