Full-wave modeling of high harmonic heating and current drive in NSTX
- Oak Ridge National Lab., TN (United States)
- Princeton Plasma Physics Lab., NJ (United States)
The proposed low aspect ratio tokamak experiment, NSTX, provides a totally new and unique environment for ion cyclotron range of frequencies heating and current drive experiments. At the proposed frequency of 41 MHz and magnetic field of 0.3 T, electron beta is high and Landau damping is very strong. Wave energy is rapidly and totally damped between the antenna and plasma center, and the result is a current driven well off axis. High cyclotron harmonic ion resonances also occur in the machine with a ratio of rf frequency to ion cyclotron frequency of 6.0 and above for majority deuterium and 3.0 and above for minority hydrogen. Near the plasma center, the product of perpendicular wave number and ion gyroradius is about 6 for deuterium so that the small Larmor radius expansion clearly breaks down. To calculate ion absorption, it is therefore necessary to use the full modified Bessel functions which are valid for all Larmor radii. We have extended the PICES global wave code to use the modified Bessel functions in evaluating power absorption at the high harmonic ion cyclotron resonances. Results show an ion power fraction of about 0.35 percent at 41 MHz and 3.5 percent at 21 MHz. The question remains as to the validity of the second order Lamor radius expansion is valid. Since the overall wave propagation and absorption is relatively insensitive to ion temperature, it might be argued that the expansion has little effect on the result. However, this conclusion must await more detailed calculations which do not rely on the expansion.
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 489393
- Report Number(s):
- CONF-960354-; TRN: 97:011534
- Resource Relation:
- Conference: International Sherwood fusion theory conference, Philadelphia, PA (United States), 18-20 Mar 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 international Sherwood fusion theory conference; PB: 244 p.
- Country of Publication:
- United States
- Language:
- English
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