Effects of non-vanishing toroidal current densities on stability in the Wendelstein 7-AS stellarator
At the W7-AS stellarator the influence of non-vanishing toroidal current densities on stability is studied over a broad range of externally provided values of the rotational transform. By means of inductive current drive and by varying the heating scenarios, using 1 MW NBI and 0.4 MW ECRH, access is given to a variety of current density radial profiles with significant shear. Disruptive-like events accompanied by fast energy loss are observed as soon as low order major rational resonances appear in the outer region of the plasma in discharges with significant contributions of net toroidal ohmic current in the positive direction (increasing the rotational transform). To some extent the applied loop voltage is able to prevent a total decay of the plasma current. Preceding the partial or total energy loss, a perturbing effect in the equilibrium is observed in the radial profile of the electron temperature, as derived from ECE measurements, and the tearing mode structure is identified by tomographic reconstruction of the emission in the soft X-ray wavelength region.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 40 (2000) No. 8, pp. 1499-1509
Availability: Nuclear Fusion (Journal)
Record Number: 200012378 / Last updated on: 2000-09-08
Original language: en
Available languages: en