4He Cryostat assembly
The 4He cryostat is of vapor-cooled design, which eliminates the need
for a separate nitrogen jacket. The outer can has several ports for pumps and
pressure gauges. It also has capton x-ray windows at the bottom. The helium
can is wrapped around with several layers of aluminized mylar. The tail of the IVC
screwes onto the bottom of the helium can. Indium O-ring gasket separates the
IVC from the OVC. Gas evaporating from the helium can passes through a bellows
which is thermally anchored to the copper plate and further to the neck of the
IVC. The aluminum shield is then screwed to the copper plate. This way the
evaporating helium cools the aluminum shield to about 100 Kelvin.
The level of helium in the helium can is measured with a capacitance level
meter which is just a set of concentric thin wall stainless steel pieces of
tubing. The wiring to the gauge as well as to thermometers on the cold copper
plate and at the bottom of the helium can is fed through to the top of the
outer can.
Helium transfer tube port is on the top plate of the OVC, and is fed trough
the copper plate into the helium can.
The cappilary feeding helium from the can into the 1K pot of the insert is
welded into the helium can at the bottom, on the IVC side of the tail.
Several ports and a pressure gauge are located on the IVC neck part of the
assembly.