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How do you get superfluid helium?

It is necessary to obtain superfluid helium in advance before studying the properties of superfluid helium and related techniques. It can be seen from the phase diagram of helium that under different pressures, the experienced way to reach the superfluid helium temperature region from the high-temperature region is different. Therefore, according to the different pressures, the superfluid helium can be divided into the full superfluid helium and the supercooled superfluid helium, and the two methods are also different.

Acquisition of full superfluid helium:

This is the most common method of obtaining superfluid helium in the laboratory. Along the full steam pressure line, decompression for HeI bath when pressure is 5042 pa, the status of the helium in HeI He II, both the condition of superfluid helium, at this time of the temperature of 2.1768 K, the diagram for the full state of superfluid helium test experiment system, which is composed of two double deck glass dewar, in the outer layer of the dewar, participate in liquid nitrogen, form protective screen, to reduce the external incoming to the heat of liquid helium area, and the inner dewar, participate in liquid helium. Both dewar are bilayer, and both dewar walls are now vacuumed between them to reduce heat loss by heat transfer and convection, while both dewar walls are silvered to reduce incoming thermal radiation from dewar walls. The inner diameter of the inner dua is about 9cm and the height of the inner dua is about 1m. The tested parts are installed at the bottom of the inner dewar. Along the body of dewar's bottle there are two silver plated slits through which the interior of dewar can be directly investigated. At the top of the test stand placed in the inner layer of dewar, a number of radiation shields were installed, and helium reflux vapors were used to cool the radiation shields to reduce heat leakage.

The main component for lowering the temperature of the helium bath is one or more vacuum pumps. Because of the heat leaking into the helium bath from the outside of the system, if a lower temperature is required at some point, a vacuum pump set may be required to increase the pumping speed. Since helium is a rare resource, it should be linked to the recovery device after the vacuum pump, which is not shown in the diagram. In the test, it is usually required to control the temperature of the superfluid helium bath. The common methods to control the temperature are to control the opening and closing of the solenoid valve through the reaction of low temperature thermometer or pressure sensor, so as to control the temperature of the superfluid helium bath. A large amount of superfluid helium can be obtained by pumping and decompressing. In some small experimental studies on superfluid helium, cryocooler in the superfluid helium temperature zone can also be used to cool the helium container and obtain a small amount of superfluid helium.

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