A BAKEABLE, DEMOUNTABLE FIELD ION MICROSCOPE WITH A CONTINUOUS TRANSFER LIQUID HELIUM CRYOSTAT

A stainless field ion microscope head which is bakeable to 250°C and completely demountable is described, and the operational characteristics are presented. The microscope employs the continuous flow technique to cool the specimen cryogenically between 4·2 and 78°K. The liquid helium consumption varies from 0·85 l h-1 to 0·133 l h -1 between 11·7 and 34·8°K, with a pressure of 2·5 mtorr helium inside the microscope. The field ion microscope head is particularly well suited for hydrogen promotion experiments. An example of a gold specimen imaged by the latter technique in the present microscope is given.