High-Z Mo-limiter test in TEXTOR : Impurity fluxes, thermal response and post-mortem analysis of Mo-limiter head
In TEXTOR a Mo-limiter has been tested under various conditions of ohmic and NBI heating for about 100 discharges. Maximum power fluxes of 20 MW/m2 have been loaded onto the Mo-limiter without any serious damage, which led to maximal surface temperatures of about 2800 K. The Mo-limiter surface was molten twice with a very thin layer of melting. Local spectroscopy shows that Mo was released predominantly by physical sputtering of the low-Z impurities carbon, oxygen and silicon. The impurity deposition rates in the SOL were measured using collector probes showing a ratio of Si/C and Mo/C of typically 6/100 and 0.1/100, respectively. Post-mortem analyses have revealed no impurity deposition on the Mo surface indicating that the limiter was operated under erosion conditions. The Mo-limiter did not influence the plasma performance very much except for high-density ohmic shots where strong central radiation appeared resulting in a minor disruption or special mode. No serious after-effect due to a possible contamination of the first wall by Mo impurities could be observed.
Bibliographic Reference: Article: Journal of Nuclear Materials, Vols. 212-215 (1994) pp. 1370-1375
Record Number: 199411565 / Last updated on: 1995-01-10
Original language: en
Available languages: en