Relaxation of plasma potential and poloidal flows in the boundary of tokamak plasmas
The relaxation times of plasma parameters after a sudden change of electrode voltage have been measured in the plasma boundary during polarization experiments on the CASTOR tokamak (R = 0.4 m, a = 75 mm, Bt = 1 T, Ip _ 9 kA, qa _ 10). The time evolution of the floating potential after the biasing voltage switch off can be well fitted by an exponential decay with characteristic time in the range of 10 � 20 µs. The poloidal flow shows a transient behaviour with a time scale of about 10 � 30 µs. These time scales are smaller than the expected damping time based on neoclassical parallel viscosity (which is in the range of 100 µs) and atomic physics via charge exchange (in the range of 100 � 1000 µs). But they are larger than the correlation time of plasma turbulence (about 5 µs). These findings suggest that anomalous damping rate mechanisms for radial electric fields and poloidal flows may play a role in the boundary of tokamak plasmas.
Bibliographic Reference: An oral paper given at: 30th EPS Conference on Controlled Fusion and Plasma Physics Organised by: European Physical Society Held at: St. Petersburg, Russia, 7-11 July 2003 Proceedings available online at: http://eps2003.ioffe.ru/
Availability: Available from Association EURATOM-CEA, Département de Recherches sur la Fusion Contrôlée, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: email@example.com
Record Number: 200317059 / Last updated on: 2003-10-29
Original language: en
Available languages: en