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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.

Additional information

Authors: TANABE T, Osaka University, Faculty of Engineering, Suita (JP);UEDA Y, Osaka University, Faculty of Engineering, Suita (JP);VAN OOST G ET AL., Ecole Royale Militaire, Bruxelles (BE);PHILIPPS V ET AL., Forschungszentrum Jülich GmbH (KFA) (DE);WADA M, Doshisha University, Department of Electronic Engineering, Kyoto (JP);HAWKES N, AEA Fusion, Culham Laboratory, Abingdon, Oxon. (GB);RUBEL M, Royal Institute of Technology, Physics Department Frescati, Stockholm (SE)
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
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