3 ms·
I worked with NMR about 8 years ago in the uni. We used regular liquid helium to get to about 4.2 degrees K. The next step is He 3 isotope which is an order of
by IgorPartola 9y ago
I worked with NMR about 8 years ago in the uni. We used regular liquid helium to get to about 4.2 degrees K. The next step is He 3 isotope which is an order of magnitude more expensive but gets you an order of magnitude cooler (in degrees K). That usually runs in a closed system (heated He is not vented into the atmosphere) because of its cost.
The way cooking it was explained to me is that you try to slow down atoms with lasers, but I don’t know any of the details.
- beagle3 9y agoFrom memory: you fire a laser at a frequency that is only absorbed if relatvistically shifted the way an electron that goes towards the laser would observe. This, the laser delivers momentum only to atoms coming towards it, and is invisible to those at rest or going away. Do from multiple directions and you’ve reduced absolute momentum in every direction. Claude Cohen danucci received a nobel and a wolf for this (and other things)
- Zaak 9y agohttps://en.wikipedia.org/wiki/Doppler_cooling https://en.wikipedia.org/wiki/Doppler_cooling