Measurements and Modelling of Electrostatic Fluctuations in the Scrape-Off Layer of ASDEX
In the edge plasma of the ASDEX tokamak, electrostatic fluctuations were observed with Langmuir probes and in H(alpha) light with high poloidal and temporal resolution. These fluctuations contribute a significant fraction to the anomalous radial particle transport in the scrape off layer (SOL). The basis properties and the dependence of the fluctuation parameters on the discharge conditions are documented. A model for an instability mechanism specific to the SOL is introduced and the experimentally observed fluctuation parameters are compared with the predictions of the linearized version of this model. For plasma temperatures above 10 eV in the SOL, the observed parameter dependencies of the fluctuations are well reproduced by the model. By mixing length arguments the radial transport and the resulting density and pressure gradients in the SOL are estimated from the model. Their dependence on plasma temperature and density qualitatively agrees with the behaviour observed in ohmic discharges on ASDEX.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 35 (1995) No. 11, pp. 1307-1339
Record Number: 199610020 / Last updated on: 1996-02-16
Original language: en
Available languages: en