| 摘要 |
PURPOSE:For preventing the deterioration of a heating unit and raising the stability of a thermion releasing cathode, to make the both sides of said cathode of the mixture ceramic or thermit of SiC or Al2O3 and Ta. CONSTITUTION:Lower metallic electrodes 108a and 108b having a recess on the upper portion thereof are set up at a distance from each other on the electron gun support table 109 made of an insulating material, and upper Cu or stainless steel electrodes 106a and 106b are fastened on the projecting portion inside of said electrodes 107a and 107b with screws 108a and 108b. Next, the heating units 102a and 102b made by sandwiching a cathode 101 between electrodes 106a and 106b with graphite boards placed therebetween are fastened by graphite boards 105a and 105b. In this construction, said cathode 101 is made of LaB6, and said both side heating units 102a and 102b of the mixture ceramic of SiC or Al2O3 and Ta. Thus, decrease in brightness is avoided. |
