The lower cylinder of the International Thermonuclear Experimental Reactor (Iter) cryostat has been set in its final position in the tokamak pit with the gap between the two cryostat sections reduced to just six millimetres and welding operations ready to start, Iter said.

Lifting of the massive component – about the diameter of the Stonehenge circle in England – began at Iter’s Cadarache site in southern France on 31 August. Welding is expected to take four or five months and will be carried out by specialists from MAN Energy Solution, the same Indian contractor that has been in charge of assembling and welding the various cryostat segments in the cryostat workshop.

Iter said the cryostat base, another part of the cryostat, was inserted into the tokamak pit in May. The ring-shaped lower cylinder, although much taller, was considerably lighter (375 tonnes compared to 1,250 tonnes) and more flexible and likely to deform. Because of its construction its mass was unevenly distributed, which meant a specific rigging arrangement was needed.