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Title: Experiments on helicons in DIII-D—investigation of the physics of a reactor-relevant non-inductive current drive technology

Journal Article · · Nuclear Fusion
 [1];  [1];  [1];  [1];  [1];  [2];  [1]; ORCiD logo [1]; ORCiD logo [3];  [4];  [1];  [1];  [5];  [6]
  1. General Atomics, San Diego, CA (United States)
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  5. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  6. Univ. of California, Los Angeles, CA (United States)
+ Show Author Affiliations

Experiments have begun in DIII-D to evaluate a toroidally-directed spectrum of helicon waves (also known as 'very high harmonic fast waves', 'fast waves in the lower hybrid range of frequencies', or 'whistlers') that can generate efficient non-inductive current drive by Landau absorption in a reactor plasma. Modeling has shown (Prater et al 2014 Nucl. Fusion 54 083024) that non-inductive current drive at mid-radius (ρ ~ 0.5) should be achievable in DIII-D with fast waves at 0.5 GHz in high-beta conditions with an efficiency twice that of other non-inductive current drive tools currently available on DIII-D (neutral beams and electron cyclotron current drive). An innovative traveling wave antenna (TWA) of the 'comb-line' type with 12 radiating modules has been constructed, installed in DIII-D, and has been tested at very low power (<0.4 kW) to evaluate the antenna coupling in the linear regime, and to test technological aspects of such structures in the tokamak environment. Results show favorably strong antenna/plasma coupling in several plasma regimes, most significantly in the high-beta ELMing H-mode case with calculated full first-pass absorption of the helicon waves in the desired mid-radius region. No evidence of significant excitation of the undesirable slow wave was found when the total magnetic field adjacent to the structure was approximately aligned with the tilted Faraday screen of the antenna. Finally, the implications of these results for a high-power experiment currently under construction are discussed.

Research Organization:
General Atomics, San Diego, CA (United States); Univ. of California, Los Angeles, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
FC02-04ER54698; FG02-08ER54984; AC05-00OR22725; AC02-09CH11466; AC04-94AL85000
OSTI ID:
1476633
Alternate ID(s):
OSTI ID: 1648977
Journal Information:
Nuclear Fusion, Vol. 58, Issue 10; ISSN 0029-5515
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 17 works
Citation information provided by
Web of Science

References (13)

Application of very high harmonic fast waves for off-axis current drive in the DIII-D and FNSF-AT tokamaks journal June 2014
Physics basis for a reversed shear tokamak power plant journal December 1997
Quasi-linear modeling of lower hybrid current drive in ITER and DEMO
  • Cardinali, A.; Cesario, R.; Panaccione, L.
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conference January 2015
Whistlers, helicons, and lower hybrid waves: The physics of radio frequency wave propagation and absorption for current drive via Landau damping journal September 2015
Review of tokamak experiments on direct electron heating and current drive with fast waves conference January 1994
Fast wave current drive at high ion cyclotron harmonics on DIII-D journal November 2001
Combline antennas for launching traveling fast waves
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conference January 1994
Consideration of neutral beam prompt loss in the design of a tokamak helicon antenna journal November 2016
Measurements of ICRF loading on DIII-D with and without a Faraday shield journal February 1997
Low‐power fast wave antenna loading as a radio‐frequency sheath diagnostic journal January 1996
Comparison of coupling to 5 GHz lower hybrid waves and 0.5 GHz helicon waves
  • Pinsker, R. I.; Porkolab, M.; Petty, C. C.
  • RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 21st Topical Conference, AIP Conference Proceedings https://doi.org/10.1063/1.4936535
conference January 2015
Maximization of ICRF power by SOL density tailoring with local gas injection journal March 2016
Stimulated Mode Conversion at Lower-Hybrid Frequencies journal May 1985

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
helicon
current drive
DIII-D
comb-line
traveling wave antenna