H-mode discharges with feedback-controlled radiative boundary in the ASDEX Upgrade tokamakFunded under: FP3-FUSION 11C
Puffing of impurities (neon, argon) and deuterium gas in the main chamber is used to feedback-control the total radiated power fraction and the divertor neutral particle density in the ASDEX Upgrade tokamak simultaneously. The variation of P(sep) = P(heat) - P(rad)(core) by impurity radiation during H-mode shows a similar effect on the ELM behaviour as that obtained by a change of the heating power. For radiated power fractions about 90 %, the ELM amplitude becomes very small and detachment from the divertor plates occurs, whilst no degradation of the global energy confinement is observed. Additional deuterium gas puffing is found to increase the radiated power per impurity ion in the plasma core due to the combined effect of a higher particle recycling rate and a lower core penetration probability. The outer divertor chamber, which is closed for deuterium neutrals, builds up a high neutral pressure, and the effective pumping time of neon and argon is considerably accelerated.
Bibliographic Reference: Report: IPP 1/284 EN (1995) 27 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
Record Number: 199510521 / Last updated on: 1995-04-11
Original language: en
Available languages: en