Lower Hybrid Current Drive Experiments in Alcator C-Mod

Journal Article · Fri Sep 28 00:00:00 EDT 2007 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.2800491· OSTI ID:21032772

Wilson, J R ^[1]; Bonoli, P; Hubbard, A; Parker, R; Schmidt, A; Wallace, G; Wright, J ^[2]; Bernabei, S

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1. Princeton Plasma Physics Lab, Princeton NJ (United States)
2. MIT PSFC, Cambridge MA (United States)

A Lower Hybrid Current Drive (LHCD) system has been installed on the Alcator C-MOD tokamak at MIT. Twelve klystrons at 4.6 GHz feed a 4x22 waveguide array. This system was designed for maximum flexibility in the launched parallel wave-number spectrum. This flexibility allows tailoring of the lower hybrid deposition under a variety of plasma conditions. Power levels up to 900 kW have been injected into the tokomak. The parallel wave number has been varied over a wide range, n{sub parallel}{approx}1.6-4. Driven currents have been inferred from magnetic measurements by extrapolating to zero loop voltage and by direct comparison to Fisch-Karney theory, yielding an efficiency of n{sub 20}IR/P{approx}0.3. Modeling using the CQL3D code supports these efficiencies. Sawtooth oscillations vanish, accompanied with peaking of the electron temperature (T{sub e0} rises from 2.8 to 3.8 keV). Central q is inferred to rise above unity from the collapse of the sawtooth inversion radius, indicating off-axis cd as expected. Measurements of non-thermal x-ray and electron cyclotron emission confirm the presence of a significant fast electron population that varies with phase and plasma density. The x-ray emission is observed to be radialy broader than that predicted by simple ray tracing codes. Possible explanations for this broader emission include fast electron diffusion or broader deposition than simple ray tracing predictions (perhaps due to diffractive effects)

• OSTI ID: 21032772
• Journal Information: AIP Conference Proceedings, Vol. 933, Issue 1; Conference: 17. topical conference on radio frequency power in plasmas, Clearwater, FL (United States), 7-9 May 2007; Other Information: DOI: 10.1063/1.2800491; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA). Alcator C-Mod Team; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALCATOR DEVICE
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
ELECTRON TEMPERATURE
ELECTRONS
FLEXIBILITY
GHZ RANGE
KEV RANGE
KLYSTRONS
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
PLASMA
PLASMA DENSITY
PLASMA INSTABILITY
PLASMA SIMULATION
RF SYSTEMS
SAWTOOTH OSCILLATIONS
X RADIATION