Monday, October 1, 2012

New dilution refrigerator arriving!

We've been waiting patiently for this for quite some time, but now, it seems, our brand new Oxford Instruments Kelvinox HA400 dilution refrigerator is about to arrive in our lab. Yay! The first two boxes are already there... and another seven, I've been told, are on the way from the UK.
The first picture on the right shows the main insert assembly, which is later dipped into a liquid helium-4 bath for precooling. (Remember, we're going to the millikelvin range, so liquid helium-4 at 4.2K is pretty hot.) The lower, copper-coated part of the insert is a vacuum can, the so-called IVC, and inside there, thermally shielded by the vacuum, all the ultra-low temperature cooling goes on. The lower end of this can finally with a slender tail fits into the 3" central bore of a small superconducting magnet. Some experiments which do not need a magnetic field can be conducted directly at the last cooling stage, others are mounted at the center of this tail, i.e. in the center of the magnet.
The second picture shows the actual main cooling circuit, the so-called dilution unit, which will be mounted into the vacuum can when the system is undergoing final assembly. The cooling process is based on the quantum mechanical properties of liquid helium-3 and helium-4 at temperatures below 0.9K; this particular model can reach temperatures down to 7mK (yes that's 0.007 degrees above the absolute zero of temperature). A simplified description of the process can be found on the dilution refrigerator wikipedia page. We'll post some more and nicer pictures once the final assembly is on the way...

No comments:

Post a Comment

Post a Comment