Since the cooling coil is immersed in the liquid helium bath, liquid surrounding the coil is also cooled.

A coldplate is placed in thermal contact with the liquid helium bath.

The liquid helium bath is designed to keep the superconducting magnet's bobbin of superconductive wire in its superconductive state.

When this device is immersed in a liquid helium bath both wires become superconducting and hence offer no resistance to the passage of electric current.

Usually it is a few cubic centimeters in size with a pickup-tube extending into the primary liquid helium bath of the dewar.

While this technique is fairly simple to operate, it is inefficient for large helium baths because about 50% of the liquid helium must evaporate to attain to the lowest temperatures.

Only the surface of the small 1-K pot is pumped, leaving the rest of the liquid helium bath at atmospheric pressure.

In the traditional design of a dilution refrigerator (Figure 1a) a liquid helium bath is used.

In a dry dilution refrigerator a cryocooler is integrated in the design of the refrigerator in order to replace the liquid helium bath (see Figure 1 below).

Generally a cryocooler, also known as a coldhead, is used to recondense some helium vapor back into the liquid helium bath.