WALL CONCEPTS AND DENSITY CONTROL FOR JET
Only low-Z materials will be used for first wall components of JET. This is particularly important with regard to radiation losses in the outer region of the plasma which can lead to instabilities limiting the plasma density. To avoid implications from redistribution of wall material by erosion and redeposition, the first wall is intended to consist of one material only. Two alternative concepts are being developed. The first employs graphite tiles for limiter and wall protection, with the rest of the wall being carbonised, the second uses beryllium limiters and a thin beryllium layer on the graphite protection and the rest of the wall. Density control will be achieved by Pellet Injection to increase the central density and by pumping at the plasma edge to control the recycling. For the pumping two possibilities are studied. It has been frequently shown that the JET wall acts as an efficient pump. The effect is not understood and if it turns out to be insufficient for full performance conditions in JET, pump limiter modules will be installed in the shadow of the main limiter. As a first step an inertia cooled prototype limiter will be built to find the optimal design parameters for the JET boundary conditions. The final pump limiter will be actively cooled to allow a continuous operation during a JET discharge. For pellet injection JET will start with a single pellet injector followed by a multiple pellet injector with 3 barrels for different pellet sizes repetitive at a rate of 5 pellets per second, both injectors with pellet velocities up to 1.5 km/s. In parallel JET has started a program for developing a high speed injector.
Bibliographic Reference: 14TH SOFT CONFERENCE, AVIGNON (FRANCE), SEPT. 8-12, 1986 VOL. 1, PP. 273-285 1895 P., 1986, VOL. 1 AND VOL. 2, ISBN 0 08 034935 8 WRITE TO PERGAMON PRESS, HEADINGTON HILL HALL, OXFORD, OX3 0BW (UK), PRICE: UKL 220 (FOR BOTH VOLS.)
Record Number: 1989126044501 / Last updated on: 1989-01-01
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