Spatial distribution of turbulence in the Wendelstein 7-AS stellarator
نویسندگان
چکیده
In this paper measurements of short wavelength electron density fluctuations using collective scattering of infrared light are presented. The Wendelstein 7-AS (W7-AS) stellarator (Renner H et al 1989 Plasma Phys. Control. Fusion 31 1579) and the diagnostic are briefly described. A series of plasma discharges with reproducible confinement transitions was created by ramping up the plasma current. Utilizing the fact that the density fluctuation wavenumber κ is anisotropic in the directions parallel and perpendicular to the local magnetic field, the diagnostic can provide a radial profile of the turbulence during both normal and degraded confinement. The found profiles display an increase of core turbulence for the reduced confinement state. The results are discussed and compared to similar tokamak measurements.
منابع مشابه
On Viscous Damping and Rotation in Low-Shear Stellarators
one of the main results of the Wendelstein 7-AS stellarator (major radius 2 m, average plasma radius 0' l8 m, magnetic field 2.5 T' low shear) is the achievement of the H-mode confinement in ECRand NBl-heated plasmas. The features of the H-mode are similar to those of a tokamak: reduction of the Ho-emission, onset of poloidal rotation anda30vo improvement of the energy confinement time, which i...
متن کاملChanges in density fluctuations associated with confinement transitions close to a rational edge rotational transform in the W7-AS stellarator
At certain values of the edge rotational transform ιa , the confinement quality of plasmas in the Wendelstein 7-AS (W7-AS) stellarator is found to react very sensitively to small modifications of the edge rotational transform ιa . As ιa can be reproducibly changed either by external fields or by a small plasma current, these transitions offer a precise way to systematically analyse differences ...
متن کاملBayesian experimental design of a multichannel interferometer for Wendelstein 7-X.
Bayesian experimental design (BED) is a framework for the optimization of diagnostics basing on probability theory. In this work it is applied to the design of a multichannel interferometer at the Wendelstein 7-X stellarator experiment. BED offers the possibility to compare diverse designs quantitatively, which will be shown for beam-line designs resulting from different plasma configurations. ...
متن کاملDiagnostics development for quasi-steady-state operation of the Wendelstein 7-X stellarator (invited).
The critical issues in the development of diagnostics, which need to work robust and reliable under quasi-steady state conditions for the discharge durations of 30 min and which cannot be maintained throughout the one week duration of each operation phase of the Wendelstein 7-X stellarator, are being discussed.
متن کامل