An optical absorption cell for use at low temperatures

A transmission type cell designed for making optical and electrical measurements on solid specimens, but which could be adapted for liquids or gases, is described. The specimen is immersed in helium gas, which provides the thermal connexion between it and the cooling liquid, and can be kept at a temperature within 1° K of that of the cooling bath between about 330° K and 4.2° K. Operating times of over seventeen hours and one hour per filling of liquid hydrogen and liquid helium respectively are obtained. A simple mechanism enables the cooled specimen to be moved into and out of the radiation beam.