Edge gradient and safety factor effects on electrostatic turbulent transport in tokamaks
- Univ. of Wisconsin, Madison, WI (United States)
Electrostatic turbulence and transport measurements are performed on the Tokapole-II tokamak at the University of Wisconsin-Madison, as the safety-factor and the edge equilibrium gradients and varied substantially. Tokapole-II is a poloidal divertor tokamak capable of operating at a wide range of safety factors due to its unique magnetic limiter configuration. It also has retractable material limiters in a large scrape-off region, which permits the study of edge boundary conditions like density and temperature gradients. The turbulence is independent of safety factor, but strongly sensitive to the local density gradient, which itself depends upon the limiter configuration. When a material limiter is inserted in a high discharge, the density gradient is increased locally together with a local increase of the turbulence. On the other hand, limiter insertion in low discharges did not increase the density gradient as much and the turbulence properties are unchanged with respect to the magnetic limiter case. It is conducted then, that electrostatic turbulence is caused by the density gradient. Although the electrostatic fluctuation driven transport is enhanced in the large density gradient case, it is in all cases to small to explain the observed energy confinement times. To explore instabilities with small wavelengths, a 0.5 mm diameter shperical Langmuir probe was constructed, and its power compared with the power measured by larger cylindrical probes.
- Research Organization:
- Univ. of Wisconsin, Madison, WI (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-85ER53198
- OSTI ID:
- 10148194
- Report Number(s):
- DOE/ER/53198-193; ON: DE92014323
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: May 1992
- Country of Publication:
- United States
- Language:
- English
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