Determination of the two-dimensional distribution of radiation in high-temperature plasmas of the ASDEX tokamak using bolometric measurements and computer tomography
A principal aim of this work was to move from a one- to a two-dimensional determination of the radiative emissivity of a plasma For this purpose the arrangement of metal-film bolometers on ASDEX was greatly expanded, thus enabling a computer-tomography technique to be developed and used to calculate two-dimensional distributions of emissivity. Ohmically heated deuterium discharges are studied. Local areas of increased radiation on the top and bottom of the plasma are emitted from within the plasma and not, as had been surmised, from the X points or the divertor necks. With increasing plasma density, radiation from the bottom of the main-chamber plasma increasingly exceeds that from the top or sides, this asymmetry climbing rapidly as the maximum possible density is approached. With increasing q(a) values, however, it decreases. At q(a) greater than 3 at the density limit, extremely strong inside/outside asymmetries, known as marfes, take its place, which lead to current break after some 10 milliseconds. At q(a) equals 6 with a boron coated wall, marfes remain stable for seconds. On formation, they double radiation loss from the main-chamber plasma.
Bibliographic Reference: Report: IPP III/170 DE (1990) 102 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
Record Number: 199110256 / Last updated on: 1994-12-02
Original language: de
Available languages: de