CATHODE OPERATION TEMPERATURE SETTING METHOD FOR ELECTRON BEAM MACHINE AND ELECTRON BEAM MACHINE USING THEREOF

摘要

PURPOSE: To improve the stability of emission and the life of a cathode by intermittently introducing a gas containing oxygen into an electron gun chamber made to be vacuum and adjusting the operation temperature with which state change of the electron beam is kept within a desiring range. ;CONSTITUTION: At first a column 1 is made to be at a prescribed vacuum degree and respective voltages are applied to an electron gun to set a WC-LaB₆ cathode 7 at lower temperature than that in a common case. The chamber 2 is made to be at prescribed vacuum degree, a column valve 5 is opened, and electron beam 12 is radiated for 30 seconds. In the case the alteration of bias voltage 10 at the time of radiation is not less than 30%, the valve 5 is closed and the temperature of the cathode 7 is raised to a prescribed temperature and air is introduced into the chamber 2 by a chamber leak valve 18 to produce the same situation of the chamber as that at the time of workpiece change. The chamber 2 is again made vacuum, the valve 5 is opened, and beam is radiated to observe the alteration of the voltage 10. These processes are repeated and at the time when the alteration of the voltage 10 becomes within 30%, the setting of the cathode operating temperature is finished.;COPYRIGHT: (C)1996,JPO