Modeling of electron cyclotron current drive experiments on DIII-D

Conference · Sat May 01 00:00:00 EDT 1999

OSTI ID:353436

Lin-Liu, Y R; Chan, V S; Luce, T C; Prater, R ^[1]; Sauter, O ^[2]; Harvey, R W ^[3]

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1. General Atomics, San Diego, CA (United States)
2. Ecole Polytechnique Federale de Lausanne (Switzerland)
3. CompX, Del Mar, CA (United States)

Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in Advanced Tokamak (AT) operation. Localized ECCD has been clearly demonstrated in recent proof-of-principle experiments on DIII-D. The measured ECCD efficiency near the magnetic axis agrees well with standard theoretical predictions. However, for off-axis current drive the normalized experimental efficiency does not decrease with minor radius as expected from the standard theory; the observed reduction of ECCD efficiency due to trapped electron effects in the off-axis cases is smaller than theoretical predictions. The standard approach of modeling ECCD in tokamaks has been based on the bounce-average calculations, which assume the bounce frequency is much larger than the effective collision frequency for trapped electrons at all energies. The assumption is clearly invalid at low energies. Finite collisionality will effectively reduce the trapped electron fraction, hence, increase current drive efficiency. Here, a velocity-space connection formula is proposed to estimate the collisionality effect on electron cyclotron current drive efficiency. The collisionality correction gives modest improvement in agreement between theoretical and recent DIII-D experimental results.

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States); Swiss National Science Foundation, Bern (Switzerland)
• DOE Contract Number: AC03-99ER54463
• OSTI ID: 353436
• Report Number(s): GA-A23132; CONF-990411-; ON: DE99002584; TRN: AHC29923%%269
• Resource Relation: Conference: 13. topical conference on applications of radio frequency power to plasmas, Annapolis, MD (United States), 12-14 Apr 1999; Other Information: PBD: May 1999
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION
DOUBLET-3 DEVICE
ECR HEATING
NON-INDUCTIVE CURRENT DRIVE
EFFICIENCY
ANALYTICAL SOLUTION
MATHEMATICAL MODELS