HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas

Journal Article · Fri Dec 23 00:00:00 EST 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3664985· OSTI ID:21612497

Taylor, G; Hosea, J C; LeBlanc, B P; Phillips, C K; Valeo, E J; Wilson, J R ^[1]; Bonoli, P T; Wright, J C ^[2]; Green, D L; Jaeger, E F; Maingi, R; Ryan, P M ^[3]; Harvey, R W ^[4]

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1. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2. MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)
3. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
4. CompX, PO Box 2672, Del Mar, California 92014 (United States)

30 MHz high-harmonic fast wave (HHFW) heating and current drive are being developed to assist fully non-inductive plasma current (I{sub p}) ramp-up in NSTX. The initial approach to achieving this goal has been to heat I{sub p} = 300 kA inductive plasmas with current drive antenna phasing in order to generate an HHFW H-mode with significant bootstrap and RF-driven current. Recent experiments, using only 1.4 MW of RF power (P{sub RF}), achieved a non-inductive current fraction, f{sub NI}{approx}0.65. Improved antenna conditioning resulted in the generation of I{sub p} = 650 kA HHFW H-mode plasmas, with f{sub NI}{approx}0.35, when P{sub RF}{>=}2.5 MW. These plasmas have little or no edge localized mode (ELM) activity during HHFW heating, a substantial increase in stored energy and a sustained central electron temperature of 5-6 keV. Another focus of NSTX HHFW research is to heat an H-mode generated by 90 keV neutral beam injection (NBI). Improved HHFW coupling to NBI-generated H-modes has resulted in a broad increase in electron temperature profile when HHFW heating is applied. Analysis of a closely matched pair of NBI and HHFW+NBI H-mode plasmas revealed that about half of the antenna power is deposited inside the last closed flux surface (LCFS). Of the power damped inside the LCFS about two-thirds is absorbed directly by electrons and one-third accelerates fast-ions that are mostly promptly lost from the plasma. At longer toroidal launch wavelengths, HHFW+NBI H-mode plasmas can have an RF power flow to the divertor outside the LCFS that significantly reduces RF power deposition to the core. ELMs can also reduce RF power deposition to the core and increase power deposition to the edge. Recent full wave modeling of NSTX HHFW+NBI H-mode plasmas, with the model extended to the vessel wall, predicts a coaxial standing mode between the LCFS and the wall that can have large amplitudes at longer launch wavelengths. These simulation results qualitatively agree with HHFW+NBI H-mode data that show decreasing core RF heating efficiency and increasing RF power flow to the lower divertor at longer launch wavelengths.

• OSTI ID: 21612497
• Journal Information: AIP Conference Proceedings, Vol. 1406, Issue 1; Conference: 9. topical conference on radio frequency power in plasmas, Newport (United States), 1-3 Jun 2011; Other Information: DOI: 10.1063/1.3664985; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANTENNAS
BEAM INJECTION HEATING
COMPUTERIZED SIMULATION
DIVERTORS
EDGE LOCALIZED MODES
ELECTRIC CURRENTS
ELECTRON TEMPERATURE
H-MODE PLASMA CONFINEMENT
IONS
KEV RANGE
MAGNETIC SURFACES
MHZ RANGE
NSTX DEVICE
PLASMA BEAM INJECTION
PLASMA SIMULATION
SOLENOIDS
THERMONUCLEAR REACTOR WALLS
BEAM INJECTION
CHARGED PARTICLES
CLOSED PLASMA DEVICES
CONFINEMENT
CURRENTS
ELECTRIC COILS
ELECTRICAL EQUIPMENT
ENERGY RANGE
EQUIPMENT
FREQUENCY RANGE
HEATING
INSTABILITY
MAGNETIC CONFINEMENT
MAGNETIC FIELD CONFIGURATIONS
PLASMA CONFINEMENT
PLASMA HEATING
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
SIMULATION
SPHEROMAK DEVICES
THERMONUCLEAR DEVICES
TOKAMAK DEVICES