PROBLEM TO BE SOLVED: To make it possible to measure the current value and emittance of a charged particle beam in a vacuum while maintaining a vacuum, and to shorten the length in the beam axis direction. A partial beam blocking device 70 according to the embodiment blocks a part of a charged particle beam b passing through the vacuum chamber 11 in the X direction. The partial beam blocking device 70 is configured to form a gap 21 extending in the Y direction between the first blocking plate 13 that is conductive and extends in the YZ direction and the first blocking plate 13 that is spread in the YZ direction. And a conductive second blocking plate 14, a first blocking plate moving device 15 for moving the first blocking plate 13 in the Z direction, and a second blocking for moving the second blocking plate 14 in the Z direction. And a plate moving device 16. A slit 20 extending in the Y direction is formed on at least one of the blocking plates 13 and 14, and the width of the gap 21 in the Z direction can be changed by moving the blocking plates 13 and 14 by the blocking plate moving devices 15 and 16. is there. [Selection diagram] Figure 1【課題】真空を保持しながら真空中の荷電粒子ビームの電流値およびエミッタンスを測定可能とし、しかもビーム軸方向の長さを短くできるようにする。【解決手段】実施形態に係るビーム部分遮断装置７０は、真空容器１１内をＸ方向に通過する荷電粒子ビームｂの一部を遮断する。ビーム部分遮断装置７０は、ＹＺ方向に広がった導電性の第１の遮断板１３と、ＹＺ方向に広がって第１の遮断板１３との間にＹ方向に延びる間隙２１を形成可能に構成された導電性の第２の遮断板１４と、Ｚ方向に第１の遮断板１３を移動させる第１の遮断板移動装置１５と、第２の遮断板１４をＺ方向に移動させる第２の遮断板移動装置１６と、を有する。遮断板１３、１４の少なくとも一方にＹ方向に延びるスリット２０が形成されていて、遮断板移動装置１５，１６によって遮断板１３，１４を移動させることにより間隙２１のＺ方向の幅が変更可能である。【選択図】図１
