MARFE feedback experiments on TEXTOR-94

This paper reports about the latest developments on feedback control of MARFEs in TEXTOR-94. This technique allows us to avoid most of the density limit disruptions and provides means to create stationary MARFEs. The best signal for MARFE detection is the CII or CIII line radiation from the vicinity of the inner wall. This signal has been used successfully in various feedback loops acting on the deuterium gas how, the external heating power, impurity injection or the horizontal plasma position or a combination of these. The results demonstrate that the proximity to the inner wall can be of major importance for the MARFE development, quite comparable to the average electron density or the plasma current. Recombination becomes significant inside the MARFE at electron densities of about 3 x 10(14) cm(-3) and temperatures of a few eV as is shown by spectroscopy. (C) 1999 Elsevier Science B.V. All rights reserved.