IMPURITY CONTROL IN JET
JET operated initially with graphite limiters and Inconel walls, later with an inner wall protection (20 m**2) of graphite tiles. The impurity control methods employed were passive, mainly glow discharge cleaning and carbonization. For 4 MA discharges of 5s flat top time, line average densities of 3.5 x 10**19m**-3 and 5 MW of additional heating the Z-eff values achieved were between two and three, mainly resulting from low-Z impurities (about 3% carbon and about 1% oxygen). It seems unlikely that a substantial improvement of Zeff could be achieved with graphite as limiter and wall material. As a consequence JET has initiated and conducted an investigation on the performance of tokamaks with beryllium limiters with the objective to use this material as an alternative to graphite for the new limiter generation (belt limiter) and as an in-situ coating on the inner wall and its graphite protection. This should alleviate some of the problems related to the use of graphite e.g. limiter conditioning, density control and chemical reactions.
Bibliographic Reference: 27TH ANNUAL MEETING OF THE DIVISION OF PLASMA PHYSICS, SAN DIEGO (USA), NOV. 4-8, 1985 PAPER 8F2, P. 1585
Record Number: 1989124124500 / Last updated on: 1987-01-01
Available languages: en