These ultra low temperature
systems can generate temperatures below 300 mK. He-3 gas is condensed
by bringing it in contact with a He-4 reservoir (1 K pot). Ultra-low
temperatures are achieved by reducing the vapour pressure on top
of the liquid He-3 volume, using an internal sorption pump or an
external pumping system.
Specific designs have
been developed for a variety of optical and non-optical applications
such as: Quantum Hall Effect, X-ray and Neutron studies, de Haas
van Alphen measurements and studies of material surfaces that require
cooling of Scanning Probe, Near Field Optical and Atomic Force Microscopes.
A sample can be placed
in an environment of high and ultra high vacuum, He-3 exchange gas