Discovering the Secrets of Second Sound: Cooling to 2.5 mK in Superfluid 3He

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SUMMARY

The phenomenon of second sound in superfluid helium-3 (3He) occurs at temperatures as low as 2.5 mK. Achieving such low temperatures requires advanced cooling techniques beyond conventional methods like liquid nitrogen or helium. Key methods include the use of dilution refrigerators and magnetic refrigeration, which are essential for reaching millikelvin temperatures. Understanding these techniques is crucial for exploring quantum phenomena in superfluid systems.

PREREQUISITES
  • Superfluidity in helium-3
  • Dilution refrigerator operation
  • Magnetic refrigeration principles
  • Quantum thermodynamics
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  • Research the design and functionality of dilution refrigerators
  • Explore the principles of magnetic refrigeration in low-temperature physics
  • Study the implications of Pauli pressure in superfluid systems
  • Investigate the behavior of second sound in superfluid helium-3
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Physicists, cryogenics engineers, and researchers interested in low-temperature physics and superfluid phenomena.

fresh_42
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I've just read about the second sound and that this phenomenon can be seen in superfluid 3He at 2.5 mK. How do they manage to come that close to 0?
A short hint about the methods would be nice to read. Normally you hear that things are cooled by fluid nitrogen or helium. But mK are out of reach by those.
 
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