Helium transfer coupling by use of fluid magnetic seal
has been developed. By use of it, Liq.He can be supplied stably and efficiently from stationary part to rotating
part. Helium of high density in rotor goes to outer part
and that of low density which is warmed in outer part
goes to inner part by centrifugal force. This phenomenon
is called thermal siphon effect. The gaseous helium
in inner part of rotor is reduced pressure. Then it is
very easy to supply Liq.He to rotor. This is called selfpumping
effect. The discoveries of above two effects
make superconducting winding cooled very easily without
complex pipe arrangements. Let us show the
effect by use of Fig. 2. This figure is one of end part of
rotor as shown in Fig. 1. The gaseous helium accumulates
at inner part of rotor. The gas goes through point 1
to 5 in pipe, then cools heat exchanger for torque
tube. In entrance of heat exchanger (2), density of gas is
very high. In the exit (3), it is very low due to heating by
torque tube. This difference of density makes difference
of centrifugal force. Then inner part of rotor is reduced
pressure. Pressure of gas out of generator is atmospheric.
The pressure of Liq.He in rotor can be about
atmospheric.