Main divertor flows in Heliotron E: their distribution and dependence on NBI and ECH
V.V. Chechkin; V.S. Voitsenya; T. Mizuuchi; H. Zushi; K. Nagasaki; M. Nakasuga; H. Okada; S. Besshou; A. Hayakawa; H. Funaba; T. Hamada; K. Kondo; F. Sano; T. Obiki; E.L. Sorokovoj; S. Masuzaki; O. Motojima; V.V. Chechkin; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; V.S. Voitsenya; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; T. Mizuuchi; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; H. Zushi; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; K. Nagasaki; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; M. Nakasuga; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; H. Okada; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; S. Besshou; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; A. Hayakawa; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; H. Funaba; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; T. Hamada; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; K. Kondo; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; F. Sano; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; T. Obiki; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; E.L. Sorokovoj; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; S. Masuzaki; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan; O. Motojima; Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Japan
Журнал:
Nuclear Fusion
Дата:
2000-04-01
Аннотация:
In the l = 2/m = 19 Heliotron E heliotron/torsatron device, with a currentless plasma heated by NBI and ECH, the poloidal distributions were measured of diverted plasma flows near the vacuum chamber wall in eight sections of one helical field pitch. A vertical asymmetry of these distributions was observed, contrary to what had been expected from the helical symmetry of the `ideal' (unperturbed) vacuum divertor magnetic configuration. Under NBI conditions, the density normalized divertor plasma flow J<sub>d</sub>/n̅<sub>e</sub> was a rising function of the density normalized absorbed power P<sub>abs</sub>/n̅<sub>e</sub>. This is considered to be a consequence of the power degradation of confinement. With second harmonic ECH, where the main part of the launched power was absorbed in the central region, a similar power dependence as for the NBI was observed. With fundamental ECH, where a considerable fraction of the microwave power was absorbed at the periphery, J<sub>d</sub>/n̅<sub>e</sub> for some areas of the divertor trace distinctly exceeded those obtained under NBI-only conditions with the same P<sub>abs</sub>/n̅<sub>e</sub>. On the other hand, two different time responses (fast and slow) of J<sub>d</sub> were observed for the perpendicular NBI and fundamental ECH cases in some particular positions. The slow response is considered to be caused by a diffusion-like outflow of the bulk plasma to the divertor. The fast outflow of particles to the divertor might be caused by a loss of locally trapped high energy electrons and ions.
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