Confinement and the safety factor profile
- Fusion Physics and Technology, Torrance, California 90503 (United States)
- Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States)
- Department of Applied Physics, Columbia University, New York, New York 10027 (United States)
The conjecture that the safety factor profile, {ital q}({ital r}), controls the improvement in tokamak plasmas from poor confinement in the Low- (L-) mode regime to improved confinement in the supershot regime has been tested in two experiments on the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Res. {bold 1}, 51 (1987)]. First, helium was puffed into the beam-heated phase of a supershot discharge, which induced a degradation from supershot to L-mode confinement in about 100 ms, far less than the current relaxation time. The {ital q} and shear profiles measured by a motional Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current ramps in supershot plasmas altered the {ital q} profile, but were observed not to change significantly the energy confinement. Thus, enhanced confinement in supershot plasmas is not due to a particular {ital q} profile, which has enhanced stability or transport properties. The discharges making a continuous transition between supershot and L-mode confinement were also used to test the critical-electron-temperature-gradient transport model. It was found that this model could not reproduce the large changes in electron and ion temperature caused by the change in confinement. {copyright} {ital 1996 American Institute of Physics.}
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 282842
- Journal Information:
- Physics of Plasmas, Vol. 3, Issue 4; Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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