Lower-hybrid current drive and heating experiments up to the 1-MW level in Alcator C

Conference · Sat Jan 01 04:00:00 EST 1983

OSTI ID:6362432

Porkolab, M; Schuss, J J; Lloyd, B

Lower-hybrid current-drive and heating experiments are being carried out on the Alcator C tokamak using two sixteen waveguide array couplers. With the first antenna up to 650 kW of rf power has been injected at 4.6 GHz for time durations up to 200 msec. By applying an rf pulse of duration up to 200 msec, the plasma current decay can be arrested and the current can be maintained at a constant level of 160 kAmp at a maximum electron density of anti n = 5.5 x 10/sup 13/cm/sup -3/ with 600 kW of rf power transmitted into the plasma. The rf current drive is strongly dependent on the phasing of adjacent waveguides, with maximum current drive efficiency obtained at ..delta.. phi approx. = 60/sup 0/ to 980/sup 0/. The flat-top current drive efficiency obtained in these experiments was eta = R(m) n(10/sup 14/cm/sup -3/) I(MA)/P(MW) approx. = 0.12 at B = 10 T and eta approx. = 0.08 at B = 8 T. Current ramping was also observed at a typical value of ..delta..(nI/P)/..delta..t approx. = 0.16 at a density of n approx. = 1.4 x 10/sup 13/cm/sup -3/. Initial measurements of the hard x-ray spectrum indicate photon energies up to 300 keV, and we conclude that the rf current is carried by a high energy electron tail. Bulk electron and ion heating have been observed at densities in the range of 0.8 x 10/sup 14/ less than or equal to n(cm/sup -3/) less than or equal to 2 x 10/sup 14/. The maximum heating efficiency is of the order of n..delta..(T/sub e/ + T/sub i/)/P approx. = (9-11) eV 10/sup 13/ cm/sup -3//kW.

• Research Organization: Massachusetts Inst. of Tech., Cambridge (USA). Plasma Fusion Center; Bell Telephone Labs., Inc., Murray Hill, NJ (USA)
• DOE Contract Number: AC02-78ET51013
• OSTI ID: 6362432
• Report Number(s): DOE/ET/51013-76; CONF-830210-8; ON: DE83009724
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
ALCATOR DEVICE
ANTENNAS
CLOSED PLASMA DEVICES
CURRENT-DRIVE HEATING
EFFICIENCY
ELECTRIC HEATING
ELECTRICAL EQUIPMENT
EQUIPMENT
HEATING
HIGH-FREQUENCY HEATING
HYBRID RESONANCE
JOULE HEATING
PLASMA HEATING
RESISTANCE HEATING
RESONANCE
SPECTRA
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
WAVEGUIDES
X-RAY SPECTRA