Vacuum vessel and pumping system of the J.E.T. experiment

The vacuum vessel of the J.E.T. (Joint European Torus) experiment has been designed as an all-metal and completely welded composite torus with a noncircular cross section. It consists of thirty-two wedge shaped sectors which take up the external forces, linked together by cylindrical bellows sections which provide for the required electrical resistance in longitudinal direction (i.e. parallel to the induced plasma current). Rigid sectors and bellows sections have a 'double-wall' structure, the interspace between the walls, is used to control the temperature of the vacuum vessel by circulating hot or cold gas. The present state of the design work, related tests, and the manufacture of prototypes is described. Pumping the vacuum vessel will be done by cryo-pumps and turbomolecular pumps, backed by roughing pumps. The feasibility of this scheme has been studied recently by european industries competent in the field of cryo-pumping and cryogenic surroundings