???? What you should pay attention are

1
???? What you should pay attention are
?????? Boring issues

• ?? (Frostbite)
• ?? (Suffocation)
• ?? (Explosion)

???????????? Important issues

• ???? (Apparatus protection)
• ????? (Low-cost experiment)

2
?? Cryogens
LN2 - Tb 77 K - ???????? Relatively large
latent heat - ????? Relatively cheap
LHe - Tb 4.2 K - ????? Small latent heat -
??????????? Large gas enthalpy - ?? Expensive
3
?? Frostbite
LN2 - ????? Mind the liquid! - ??????? Do not
soak! - ???? Socks may be dangerous.
LHe - ????? Mind the gas! ?????????????????????
Large amount of cold gas will be generated in a
short time.
????!! Cold metals are dangerous!!
????? (????????)Do NOT use cloth gloves (Use
loose skin gloves)
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5
?? Suffocation
??!VENTILATION! ??!VENTILATION! ??!VENTILATION! ??
!VENTILATION! ??!VENTILATION!
6
?? Suffocation
LN2 - ??? Open system - ??????? Large
latent heat
LHe - ??? Closed system - ???????
Small latent heat
?????????????Be careful if you are in a small
room
7
?? Explosion

• Tb, oxygen gt Tb, nitrogen

???????? Your LN2 might become LO2

• Vgas 700Vliquid

??????!DONT SEAL OFF!
8
?? Blocking

• ????????????
• When your LHe container is blocked
• ????????????????????????????Wear skin glove.
  Insert a copper pipe slowly to melt the plug.
• ?????!! NEVER poke!!

9
??????? (Check valve safety valve)
??????/??????????? If possible, use multiple
check/safety valves.
10
??????? Helium is expensive
????????????????????????????????????????????????
When you hear music, after it's over, it's gone
in the air. You can never capture it again.
- Last Date by Eric Dolphy