H-mode behaviour induced by edge polarisation in TEXTOR
It was reported recently that the setting up of radial electric fields by means of electrodes in the edge of a tokamak plasma could lead to edge rearrangements which are very similar to L-H transitions. This paper reports on similar experiments in ohmic discharges on TEXTOR. A biasing electrode was introduced up to 6 cm beyond the toroidal belt limiter in full grade TEXTOR plasmas. The probe did not become itself a limiter and was capable of sustaining the heat load from the regular discharge and the extra load connected with the biasing. Clear H-transitions (density rise, profile steepening, D(alpha) drop) were obtained, resulting in improvements of about 1.4 in the energy and 2 to 2.5 in the particle confinement time. This improvement was achieved using positive, i.e. radially outward pointing, fields. Together with the CCT work (negative fields), the experiment appears to favour theoretical models in which confinement improvement depends either on the absolute value of the electric field strength or on a gradient in poloidal rotation speed.
Bibliographic Reference: Paper presented: 17th European Conference on Controlled Fusion and Plasma Heating, Amsterdam (NL), June 25-29, 1990
Availability: Available from (1) as Paper EN 35809 ORA
Record Number: 199011638 / Last updated on: 1994-12-02
Original language: en
Available languages: en