Economical Liquid Helium Cryostat and other Cryogenic Apparatus

A liquid helium cryostat which is inexpensive and simple to build is described. Its main features originate from the use of spherical metal floats arranged concentrically to form the body of the vessel. The tailpiece used with the cryostat provides for liquid helium to circulate in the sample holder. A mechanical valve allows the flow of liquid to be interrupted so that temperatures above 4.2°K may be maintained. A typical combination of cryostat and tailpiece has a capacity for 2 liters of liquid helium and will store this charge for nearly 4 days. A liquid nitrogen vacuum system cold trap and a liquid helium transfer tube are also described. The former also features the use of metal floats in its construction. The transfer tube has a degree of flexibility and a very small outer diameter.