JPS6441155A - Supporting device for electron lens - Google Patents

Abstract

PURPOSE:To eliminate troublesome vacuum maintenance, power supply, and water service by arranging an electron lens in a vacuum casing in the condition as accommodated in a vessel of airtight construction, and by coupling a communication pipe with this vessel in such a way as penetrating the vacuum casing. CONSTITUTION:In a vacuum casing 1 an electron lens 2 arranged around a lens barrel 3 is installed with a certain gap to the bore in the condition as accommodated in a vessel 4 of airtight construction, and a communication pipe 5 is coupled with the vessel as penetrating the casing 1, and the vessel is put in communication with outside the casing 1. To exhaust the casing 1, the internal gas is put in communication through a gap 9 formed between the walls of the lens barrel 3 and vessel 4 and the bore of the casing 1, wherein the gas passage resistance is reduced greatly, and gas exhaustion for vacuum maintenance of inside the casing 1 can be made smoothly. Out gas from the electron lens 2 is exhausted directly to outside the casing 1 via the above- mentioned communication pipe 5 without causing discharge inside casing 1, and thus no inconvenience will be generated for vacuum maintenance of the casing 1. Also power supply and water service to the lens 2 are connected the casing 1 via the pipe 5.