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

Abstract

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). Ofmore » 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.« less

Authors:
; ; ; ; ;  [1]; ;  [2]; ; ; ;  [3];  [4]
  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)
Publication Date:
OSTI Identifier:
21612497
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 1406; Journal 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); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Taylor, G, Hosea, J C, LeBlanc, B P, Phillips, C K, Valeo, E J, Wilson, J R, Bonoli, P T, Wright, J C, Green, D L, Jaeger, E F, Maingi, R, Ryan, P M, and Harvey, R W. HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas. United States: N. p., 2011. Web. doi:10.1063/1.3664985.
Taylor, G, Hosea, J C, LeBlanc, B P, Phillips, C K, Valeo, E J, Wilson, J R, Bonoli, P T, Wright, J C, Green, D L, Jaeger, E F, Maingi, R, Ryan, P M, & Harvey, R W. HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas. United States. doi:10.1063/1.3664985.
Taylor, G, Hosea, J C, LeBlanc, B P, Phillips, C K, Valeo, E J, Wilson, J R, Bonoli, P T, Wright, J C, Green, D L, Jaeger, E F, Maingi, R, Ryan, P M, and Harvey, R W. Fri . "HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas". United States. doi:10.1063/1.3664985.
@article{osti_21612497,
title = {HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas},
author = {Taylor, G and Hosea, J C and LeBlanc, B P and Phillips, C K and Valeo, E J and Wilson, J R and Bonoli, P T and Wright, J C and Green, D L and Jaeger, E F and Maingi, R and Ryan, P M and Harvey, R W},
abstractNote = {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.},
doi = {10.1063/1.3664985},
journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 1406,
place = {United States},
year = {2011},
month = {12}
}