A liquid helium cryostat for electron radiation damage and annealing studies

A liquid helium cyostat which has convenient features for studying electron-radiation damage effects in semiconductors is described. The cryostat has two liquid helium dewars and a liquid nitrogen dewar shielding them against thermal radiation. The liquid helium dewars are smoothly rotatable on a vertical axis together with the copper cold finger in order to face the sample with electron beam during irradiation or with magnetic flux in Hall effect measurements. A mechanical valve allows the flow of liquid helium to be interrupted so that the sample may be kept at required higher temperatures for annealing experiments while maintaining liquid helium in the main dewar. (auth.)