High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experiment
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08540 (United States)
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
- Nova Photon Incorporated, Princeton, New Jersey 08543 (United States)
- Columbia University, New York, New York 10025 (United States)
- Johns Hopkins University, Baltimore, Maryland 21218 (United States)
- Cornell University, Ithaca, New York 14853 (United States)
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
- CompX, Del Mar, California 92014 (United States)
High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency ({eta}) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap {phi}=-90 deg., k{sub {phi}}=-8 m{sup -1}) by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (n{sub onset}{proportional_to}Bxk{sub parallel}{sup 2}/{omega}) away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency (RF) waves propagating close to the wall at lower B and k{sub parallel} can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.
- OSTI ID:
- 21120359
- Journal Information:
- Physics of Plasmas, Vol. 15, Issue 5; Other Information: DOI: 10.1063/1.2837051; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA). NSTX Team; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
High Harmonic Fast Wave Heating Efficiency Enhancemen and Current Drive at Longer Wavelength on the National Spherical Torus Experiment
HHFW Heating Efficiency on NSTX versus B{sub {phi}} and Antenna k{sub parallel}