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Shakti
05-16-2005, 11:19 AM
I have been looking like heck to find a good site that explains how cryostats work but with no luck. So I was wondering if anybody here can point me to one or two?

Welshy
05-16-2005, 11:51 AM
what the heck is cryostat? lol

Shakti
05-16-2005, 11:54 AM
A cryostat is a machine that, if used with correct helium-types, can cool a substance to temperatures below 1K. I need to know more indepth how it works (but not too much indepth).

Welshy
05-16-2005, 11:57 AM
google (http://www.google.com)

Shakti
05-16-2005, 11:58 AM
I have been looking like heck to find a good site that explains how cryostats work but with no luck
basicly means I have tried google :D

Welshy
05-16-2005, 12:00 PM
in which case im all out of ideas :p

SMurf
05-16-2005, 12:49 PM
Wikipedia (http://en.wikipedia.org/wiki/Cryostat) says that "cryostat" is a synonym for "cryocooler". Try searching for that.

Shakti
05-16-2005, 01:15 PM
Thanks for the tips but I was not able to find anything from that either :(

Jeremy G
05-16-2005, 02:06 PM
I didnt think it was possible to freeze things to less then 1kelvin. Since at 0k there is absolutely no movement.

Govtcheez
05-16-2005, 03:04 PM
But there are numbers between 0 and 1.

Zach L.
05-16-2005, 03:29 PM
But there are numbers between 0 and 1.
Heretic

MadCow257
05-16-2005, 06:48 PM
Does this article help any?
http://liquids.deas.harvard.edu/penanen/workings.html

Shakti
05-17-2005, 03:27 AM
Im sure that will help! Thanks a bunch!

Ken Fitlike
05-17-2005, 04:45 AM
I didnt think it was possible to freeze things to less then 1kelvin. Since at 0k there is absolutely no movement.You're possibly thinking of one statement of the third law of thermodynamics:

Absolute zero cannot be reached in a finite number of stepsBut, as Govtcheez has suggested, it's possible to get within a few hundredths of a degree Kelvin of 0K (if memory serves me correctly). At that stage it's not so much about cooling, as such, but more a precise battle against entropy - for example, aligning the spins of hydrogen nuclei at low temperatures results in a lowering of entropy which equates to a reduction in temperature of that hydrogen. This follows on from a variant statement of the third law of thermodynamics, namely: all perfectly crystalline materials have zero entropy at absolute zero.

Sang-drax
05-17-2005, 01:23 PM
But, as Govtcheez has suggested, it's possible to get within a few hundredths of a degree Kelvin of 0K
Yes, the coolest and warmest temperatures observed by humans in the universe have both been observed on earth.

Govtcheez
05-17-2005, 01:27 PM
> all perfectly crystalline materials have zero entropy at absolute zero.

Doesn't that violate the second law of thermodynamics, though?

Ken Fitlike
05-17-2005, 05:33 PM
No. The second law states that the entropy of the 'Universe' is increasing; the Universe can be regarded as the system under observation (the 'material') plus the surroundings (everything else). A reduction in entropy of the system is bought at the cost of an increase in the entropy of the surroundings such that the total change (system + surroundings) in entropy is positive ie. provided the total entropy increases there is no violation of the second law. In any event, it's a theoretical concept and not practically obtainable since the third law conditions have to be met, namely absolute zero must be attained (which requires an infinite number of steps) and the material in question must also be perfectly crystalline (which is tricky to achieve, to say the least).

Lurker
05-17-2005, 05:49 PM
Yes, the coolest and warmest temperatures observed by humans in the universe have both been observed on earth.

We've had things warmer than the hottest stars here? How? (I'm not disbelieving you, I just don't know).

Govtcheez
05-17-2005, 06:14 PM
Probably created in a lab.

MadCow257
05-17-2005, 06:20 PM
Coldest temp achieved: 450 picokelvin
http://cua.mit.edu/ketterle_group/Projects_2003/450picokelvin.htm

Hottest temp achieved: 10^13 K
http://hypertextbook.com/facts/2003/TiffanyGillyard.shtml

Coldest temp observed: 1 K
http://www.absoluteastronomy.com/encyclopedia/B/Bo/Boomerang_Nebula.htm