| 摘要 |
PURPOSE:To enable the distance between electrodes to be set correctly and quickly, by measuring the distance between a first grid and a reference face opposed thereto and the distance between a cathode and the reference face to calculate the distance between the electrodes and moving the electrodes according to the result obtained. CONSTITUTION:The distance (L1) between a first grid G1 and a reference face 18A is measured by a first measuring mechanism 21. A second measuring mechanism 33 is then shifted to the measuring position by rotating an arm 34, and an air micrometer 37 is operated so that the distance (L2) between the micrometer 37 and a cathode K is measured. The distance (L2+l) from the cathode K to the reference face can be thereby determined. A second holding table 28 is shifted by a distance alpha that is obtained by substracting the distance L1 between the first grid G1 and the reference face and the distance X between electrodes from the distance L2+l between the cathode K and the reference face, so that the cathode K held by this holding table can be combined with the first grid G while a desired set distance X between the electrodes being kept. |
