Statistical and Low Temperature Physics - University of Liverpool

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To liquefy Air I shall start with the liquefying of air. The same principles are used in liquefying helium. The cooling of air is achieved by expansion. In an ideal gas, expansion against a moving piston converts internal energy to work, thus cooling it down. In a real gas, work must also be done against the attraction between atoms or molecules. This work is much larger than the work done against the moving piston, and is the principal means of cooling. It is called the Joule-Thomson effect. Statistical Physics 11 Oct - Dec 2009
To liquefy Air Air is first compressed to high pressure. It is then allowed to expand. This cools it down and liquefies it. Note that the tube carrying the cold air out has to be in close contact with the tube carrying the air in. This is an important feature called ”heat exchanger.” It cools down the incoming air first. Liquid nitrogen and oxygen ar ethen obtained from liquefied air by fractional distillation. Statistical Physics 12 Oct - Dec 2009
Page 1 and 2: Statistical and Low Temperature Phy
Page 3 and 4: Aim To understand the basic techniq
Page 5 and 6: Uses of low temperatures The branch
Page 7 and 8: Pobell (2007) The history of low te
Page 9 and 10: Refrigeration techniques Three refr
Page 11: 7.2 Liquids at low temperatures Sta
Page 15 and 16: The Joule-Thomson (or Joule-Kelvin)
Page 17 and 18: A note about liquid hydrogen At roo
Page 19 and 20: http://en.wikipedia.org/wiki/Helium
Page 21 and 22: Helium-3 Helium-3 is only a fractio
Page 23 and 24: Kapitza’s helium liquefier http:/
Page 25 and 26: Liquid helium specific and latent h
Page 27 and 28: 7.3 Solids at low temperatures Stat
Page 29 and 30: Insulators For non-magnetic, crysta
Page 31 and 32: Insulators For T much smaller than
Page 33 and 34: Insulators This is a log-log plot o
Page 35 and 36: Metal Th Pauli principle means that
Page 37 and 38: Superconducting metals Many metals
Page 39 and 40: Magnetic specific heats Recall that
Page 41 and 42: Magnetic specific heats This figure
Page 43 and 44: Magnetic specific heats In the pres
Page 45 and 46: How to measure heat capacity: Calor
Page 47 and 48: A low temperature calorimeter At lo
Page 49 and 50: Superconducting Heat switch The the
Page 51 and 52: Superconducting heat switch In orde
Page 53 and 54: What do we use for storing liquid g
Page 55 and 56: Storing liquid helium is more trick
Page 57 and 58: Pobell (2007) The helium-4 cryostat
Page 59 and 60: The helium-3 evaporation refrigerat
Page 61 and 62: Exercise 1 Show that at room temper
Page 63 and 64:
We can calculate the proportion of
Page 65 and 66:
Exercise 2 At room temperature, nor
Page 67 and 68:
For normal hydrogen at 20 K, 75% wo
Page 69 and 70:
Exercise 3 Calculate the Debye temp
Page 71 and 72:
Exercise 4 At which temperature do
Page 73 and 74:
We can find γ and A from the graph
Page 75 and 76:
On the higher temperature side of p
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Statistical and Low Temperature Physics - University of Liverpool

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