| 摘要 |
PURPOSE:To suppress the influence of local eddy current on a shield body, by forming a window, notch, etc. on the shield body which is in the proximity of a field control element. CONSTITUTION:Field control elements 12a, 12b are arranged in a front cup of electron gun 11 to currect the top aberration. A window 14 is provided at the position near to the field control element 12a of a shield body 11a which is a portion of tubular cup 11. The window 14 is such that it doesn't influence the shield function of the shield body. A notch, punch-out, etc. as well as window may be formed. Consequently the eddy current due to the magnetization near central portion will occur around the window, thereby the concentration of flux due to the eddy current to the field control element 12b is prevented thus the time lag of deflection flux which influence on the central beam is prevented. |
