Methods of cooling matter to extremely low temperatures

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    Cooling Matter
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Discussion Overview

The discussion focuses on various methods for cooling matter to extremely low temperatures, particularly near absolute zero. Participants explore different cooling techniques applicable to gases and solids, including laser cooling and the use of liquid helium, while also seeking clarity on specific requirements and conditions for cooling.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant mentions laser cooling and evaporative cooling as initial methods found, expressing a desire for more detailed information.
  • Another participant suggests that the type of matter and the desired temperature are crucial for determining cooling methods, highlighting liquid nitrogen and helium for larger solids.
  • A participant clarifies that they are interested in cooling gases and aims to approach absolute zero.
  • Discussion includes a reference to experiments conducted in Finland achieving temperatures around 30 mK by mixing different liquid helium phases.
  • It is noted that dilution refrigerators can reach temperatures down to about 10 mK, with further cooling possible through adiabatic demagnetization.
  • Participants emphasize the importance of specifying the type of gas and its atomic composition for effective laser cooling, as it requires a closed cooling cycle.

Areas of Agreement / Disagreement

Participants generally agree on the importance of specifying the type of matter and the cooling requirements, but multiple competing views on the best methods and their applicability remain unresolved.

Contextual Notes

The discussion lacks specific details on the types of gases being considered for cooling and the exact conditions under which the proposed methods would be effective.

InFlames4ever
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I am trying to find out as many ways of cooling down matter as possible and information on said ways, so far I have found out a bit about laser cooling, evaporative cooling and that's about it. I'm sure there are other ways but I can't find any and the information I can find on these ways is either not in enough detail or too advanced for my level of understanding. I have an A-level in physics but no further so that would be my ability level.
Any help would be appreciated, thanks.
 
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You have to specify more details on what "matter" you want to cool down and how far down you need to go. For larger pieces of matter, like solids, the most common form of cooling is by liquid nitrogen and liquid helium, which can get you down to 1-2 K. Further use of a dilution fridge can get you down to the milikelvin range.

For small samples of trapped atoms or ions, laser cooling (doppler cooling) works, which can be combined with resolved sideband techniques to reach few phonon number states (temperature then depends on level structure).

So, what system are you looking at, annd how cold do you need to be?
 
Well I'm talking about ways of getting near to absolute zero, and I can't believe I didn't put that in the OP. I'm also talking about gases mainly.
 
Hi,
I am not well sure about minimum possible experiments..but some research group in Finland did some experiments in the range of 30 mK..they obtained by mixing two different liquid helium (He I and II if i remember good..)..
 
Rajini said:
Hi,
I am not well sure about minimum possible experiments..but some research group in Finland did some experiments in the range of 30 mK..they obtained by mixing two different liquid helium (He I and II if i remember good..)..

30 mK is the base temperature of a (bad) diliution refrigerator. Commerical diluition refrigerators can reach about 10 mK or so. Once there you can use an adiabatic degmagnetization stage to go lower, below 1mK to say a few hundered microkelvin.
Note that we are talking about cooling large chuncks of matter, several kilograms.

For gases you need laser cooling, look up experiments on Bose-Einstein condensatates.
 
It would also help if you specified what atoms your gas consists of and how it is confined, since for laser cooling for example you are dependent on finding a closed cooling cycle that can be repeated without branching losses and similar.
 

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