Influence of different heating schemes on high-Z contamination from a tungsten test limiter in TEXTOR
Test limiter experiments have been carried out in TEXTOR under various plasma and heating conditions to broaden the database for the evaluation of the suitability of high-Z materials as plasma facing components in large machines. The heat flux to the test limiter reached values of the order of 20 MW/m2, representative of ITER divertor target conditions. Under OH conditions W-radiation increases with plasma density. Above a critical density, accumulation in the centre leads to an instability characterised by strong central radiation and hollow T(e) profiles. In most discharges heated with NBI(H(0) to D(+)) no strong central radiation was observed although the release of W was comparable with that in OH discharges, and the W-radiation decreases with increasing plasma density. In some discharges with NBI(D(0) to D(+)) a centrally peaked radiation profile was observed. Remarkably, this central radiation decreases as soon as ICRH is added to NBI and disappears afterwards, enabling a sufficiently clean core plasma in a steady state with good confinement to be maintained. A similar RF-induced explusion of W from the centre was also observed in an ohmic target plasma. No accumulation of W in the centre was found in discharges with edge radiative cooling using neon and heated with NBI and/or ICRH.
Bibliographic Reference: Article: 21st EPS Conference on Controlled Fusion and Plasma Physics, Montpellier, 27 June - 1 July, 1994, Vol. 18B (1994) Part II, pp. 1020-1023
Record Number: 199510168 / Last updated on: 1995-02-07
Original language: en
Available languages: en