Spectroscopic study of edge poloidal rotation and radial electric fields in the DIII-D tokamak (invited)
- General Atomics, San Diego, CA (USA)
Doppler-shift spectroscopy has shown that finite values of poloidal rotation velocity {ital v}{sub {theta}} and of radial electric field {ital E}{sub {ital r}} exist at the edge of a tokamak plasma and that dramatic increases occur in these parameters at an L-H transition. {ital E}{sub {ital r}} is negative in the L mode and becomes more negative in the H mode; {ital v}{sub {theta}} increases in magnitude at the transition. In addition, the radial gradients (shear) of {ital v}{sub {theta}} and {ital E}{sub {ital r}} are large and these gradients also increase at the L-H transition. These results are based on measurements of Doppler shifts of light emitted by He II ions, located in a region about 1--3 cm inside the separatrix. These observations have been made with horizontally viewing and vertically viewing spectrometer systems on the DIII-D tokamak. The nearly orthogonal views of these systems are used to determine the plasma's flow velocity in terms of the orthogonal sets {ital v}{sub {theta}} and {ital v}{sub {phi}} or of {ital v}{sub {perpendicular}} and {ital v}{sub {parallel}}. Knowledge of {ital v}{sub {perpendicular}} is used to calculate {ital E}{sub {ital r}} from the force balance equation for a single ion species. The existing results impose constraints on theories of the L-H transition. More detailed studies of the spatial profiles and temporal evolution of {ital v}{sub {theta}} and {ital E}{sub {ital r}} will be made with upgraded instrumentation, which is now coming on-line.
- DOE Contract Number:
- AC03-89ER51114
- OSTI ID:
- 6309394
- Journal Information:
- Review of Scientific Instruments; (USA), Vol. 61:10; ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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