ELECTRON BEAM CONTROL APPARATUS

PROBLEM TO BE SOLVED: To provide an electron beam control apparatus capable of preventing the deformation of a magnetic field, i.e., the deterioration of the positioning error of an electron beam deflected by the magnetic field by promoting the dissipation of heat from a coil generating the magnetic field to prevent the deformation of the coil. SOLUTION: The electron beam control apparatus comprises a coil frame demarcating the passage of an electron beam and carrying a coil operating to generate the magnetic field having an effect on the electron beam passing the passage. The coil frame is formed of a highly strong, nonmagnetic, and electrically insulating ceramic material in an area where at least the coil is present. The ceramic material has thermal conductivity and a thermal expansion coefficient selected so as to dissipate heat at such a speed as to generally stop the thermal expansion of the coil which may cause the deformation of the generated magnetic field on a specified thermal output by the coil during a semi-continuous operation. COPYRIGHT: (C)2004,JPO