1）cryogenic liquids such as liquid nitrogen and liquid helium can obtain low temperatures of 77K and 4.2k.
The temperature of the liquid pool can be changed by decompressing the space above the liquid level with the pumping system. The lower the pressure, the lower the temperature. The relation between saturated vapor pressure and temperature of liquid nitrogen and liquid helium is given in table 2 and figure 2 respectively. The minimum pressure achieved by decompression depends not only on the pumping speed of the decompression system, but also on the heat flow to the pool. In order to get the lowest possible temperature, it is important to try to reduce heat leakage.
[table 2] the relationship between liquid nitrogen saturated vapor pressure and temperature
[FIG. 2] relation between liquid helium saturated vapor pressure and temperature
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