G. Saibene et al., REVIEW OF VACUUM VESSEL CONDITIONING PROCEDURES AT JET AND THEIR IMPACT ON PLASMA OPERATION, Journal of nuclear materials, 222, 1995, pp. 617-622
Citations number
5
Categorie Soggetti
Nuclear Sciences & Tecnology","Mining & Mineral Processing","Material Science
The experience at JET and in other tokamaks shows that the achievement
of reproducible plasma conditions and the improvement on overall plas
ma performance depend crucially on vessel conditioning. The new pumped
divertor, with its coils internal to the vacuum vessel, introduces ne
w elements in the problem of JET wall conditioning the presence inside
the vessel of hidden surfaces not fully exposed to the glow discharge
and of non bakable elements, such as the divertor coils case and heat
shields. The new cleaning and conditioning techniques, adapted to the
changes of the in-vessel configuration, are described in this paper,
and the results of the vessel glow cleaning with an improved GDC syste
m presented. For the first time at JET, the glow discharge cleaning ha
s been extensively diagnosed and the glow current distribution, edge p
otential, density and temperature measured in conjunction with systema
tic scan of the glow gas species current and pressure. A statistical s
urvey of a large number of plasma pulses shows that the ''base level''
impurity content of the plasma is low, and comparable to the 1991 lev
els.