The Levitated Dipole Experiment (LDX) is a new, innovative magnetic confine
ment fusion experiment being designed and installed in collaboration with C
olumbia University at the Massachusetts Institute of Technology (MIT). The
primary objective of the experiment is to investigate the possibility of st
eady-state, high-beta plasma confinement with near classical transport. The
main component of the experiment is a levitated cryostat with a 5.7 T Nb3S
n superconducting magnet, housed in an Inconel high pressure helium vessel.
The pressure vessel is surrounded by a large thermal mass radiation shield
and an outer vacuum shell, all of which are magnetically levitated inside
a much larger vacuum chamber. The cryostat, now under construction, is desc
ribed in this paper. The cryostat keeps the magnet temperature between 5 an
d 10 K during 8 hours of levitated operation. A low heat leak support syste
m for the helium vessel and the shield is designed to withstand impact forc
es of 10 g in case of a levitating failure. The helium vessel is filled to
125 atm at room temperature with 1.4 kg of helium. The helium vessel and th
e shield are equipped with a tube heat exchanger for initial nitrogen magne
t cooling and daily helium re-cool from a high of 20-25 K back down to 5K.
This cooling system uses hermetically sealed, retractable cryogenic transfe
r lines when the cryostat is resting in the bottom charging station of the
LDX vacuum chamber. The magnet is charged and discharged inductively by an
outer charging magnet.