Effect of beryllium evaporation on the performance of ICRH on JET
Beryllium films (150 to 300Å) have been evaporated on all JET in-vessel components (carbon limiters, nickel screen, inconel walls). Immediate and lasting improvements of the plasma have been observed in all plasma regimes. Results obtained with ICRH and NBI on the density limit and on H-mode plasmas are particularly sensitive to impurity release. Specific effects produced by RF waves are reduced to a negligible level when the following three aspects are combined - beryllium evaporation, dipole phasing, correct screen angle. The density limit obtained with ICRF is now identical to NBI heated cases and substantially higher than the values obtained in the pre-beryllium phase. Long H-modes (1.3 s) have been obtained with RF alone. The H mode confinement is similar to that of NBI cases. In limiter plasmas Z(eff) decreased to 1.2 - 1.4 at high density and 10 MW input power. The results are related to oxygen gettering, suppression of nickel sputtering from the antenna screens and to the use of dipole phasing.
Bibliographic Reference: Report: JET-P(89)85 EN (1989)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199011167 / Last updated on: 1994-12-01
Original language: en
Available languages: en