Lower Hybrid Wave Induced SOL Emissivity Variation at High Density on the Alcator C-Mod Tokamak

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

DOI:https://doi.org/10.1063/1.3664967· OSTI ID:21612483

Faust, I; Terry, J L; Reinke, M L; Meneghini, O; Shiraiwa, S; Wallace, G M; Parker, R R; Schmidt, A E ^[1]; Wilson, J R ^[2]

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1. MIT Plasma Science and Fusion Center, Cambridge, MA (United States)
2. Princeton Plasma Physics Laboratory, Princeton, NJ (United States)

Lower Hybrid Current Drive (LHCD) in the Alcator C-Mod tokamak provides current profile control for the generation of Advanced Tokamak (AT) plasmas. Non-thermal electron bremsstrahlung emission decreases dramatically at n-bar{sub e}>1{center_dot}10{sup 20}[m{sup -3}] for diverted discharges, indicating low current drive efficiency. It is suggested that Scrape-Off-Layer (SOL) collisional absorption of LH waves is the cause for the absence of non-thermal electrons at high density. VUV and visible spectroscopy in the SOL provide direct information on collision excitation processes. Deuterium Balmer-, Lyman- and He-I transition emission measurements were used for initial characterization of SOL electron-neutral collisional absorption. Data from Helium and Deuterium LHCD discharges were characterized by an overall increase in the emissivity as well as an outward radial shift in the emissivity profile with increasing plasma density and applied LHCD power. High-temperature, high-field (T{sub e} = 5keV,B{sub t} = 8T) helium discharges at high density display increased non-thermal signatures as well as reduced SOL emissivity. Variations in emissivity due to LHCD were seen in SOL regions not magnetically connected to the LH Launcher, indicating global SOL effects due to LHCD.

• OSTI ID: 21612483
• 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: 10.1063/1.3664967; (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
ABSORPTION
ALCATOR DEVICE
BREMSSTRAHLUNG
DEUTERIUM
ELECTRON COLLISIONS
ELECTRON TEMPERATURE
ELECTRONS
EMISSION
EMISSION SPECTROSCOPY
EMISSIVITY
EXCITATION
FAR ULTRAVIOLET RADIATION
IONIZATION
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
PLASMA
PLASMA DENSITY
PLASMA SCRAPE-OFF LAYER
X RADIATION
BOUNDARY LAYERS
CLOSED PLASMA DEVICES
COLLISIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ENERGY-LEVEL TRANSITIONS
FERMIONS
HEATING
HIGH-FREQUENCY HEATING
HYDROGEN ISOTOPES
IONIZING RADIATIONS
ISOTOPES
LAYERS
LEPTONS
LIGHT NUCLEI
NON-INDUCTIVE CURRENT DRIVE
NUCLEI
ODD-ODD NUCLEI
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PLASMA HEATING
RADIATIONS
SORPTION
SPECTROSCOPY
STABLE ISOTOPES
SURFACE PROPERTIES
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
ULTRAVIOLET RADIATION