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On a high density tokamak such as FTU the content of low Z impurities is crucial to assess the plasma operational limits and to determine the ability to recover stable plasma discharges after major disruptions. The optimisation of the surface conditioning is very important and particularly relevant for FTU because of the complexity of the inner wall. The vacuum chamber is completely covered by thermal shields that produce hidden regions that can trap neutral gas and impurities. The only way to clean both the exposed and unexposed surfaces simultaneously is the combined operation of baking plus glow discharge in hydrogen. In this paper, a brief description of the experimental apparatus and the operative procedures is given. A glow discharge was applied to clean the vacuum wall, which was accidentally contaminated by a carbon and oxygen layer. Plasma results obtained before and after this glow discharge are compared.

Additional information

Authors: APICELLA M L ET AL., ENEA, Centro Ricerche Energia Frascati, Roma (IT)
Bibliographic Reference: Paper presented: 20th EPS Conference on Controlled Fusion and Plasma Physics, Lisboa (PT), July 26-30, 1993
Availability: Available from (1) as Paper EN 37545 ORA
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