76 Scientific American, December 2020EMPTY VESSEL: ITER’s vacuum vessel
will be made of six segments, each built
in South Korea or Italy. The huge steel
sections had to be shipped by boat to the
port of Fos-sur-Mer near Marseille, where
they were transported by road 100 kilo-
meters northeast to the ITER site. Now
that the first pieces have arrived, workers
will connect them with magnets and
thermal shields and then lower them into
the tokamak chamber ( 1 ).DEEP FREEZE: The superconducting magnets in the reactor can work
only at supercold temperatures near absolute zero, which will be main-
tained by liquid helium circulating through cryogenic pumps. Opera-
tors control the system via a complex set of hand valves ( 2 ) based
on local readings of pressure, temperature and flow. The finished cryo -
genic plant, built by contractor Air Liquide ( 3 ), will be the world’s
largest helium-refrigeration unit.1