| 摘要 |
PURPOSE:To improve measurement accuracy by arranging the constitution such that each of plural holes formed in a shielding plate cross the range of irradiation of charged particle beams in order so as to enter the charged particle beams passing through each hole into inside of a current detector. CONSTITUTION:The currents of electron beams 9 to be entered into the inside is detected by an electric detector 21 such as, e.g., a Faraday cup or the like mounted on an insulating board 4, and this detector 21 is connected to a signal display being an indication part. At the upper face of the detector 21 is formed a round measuring opening 22, and this opening 22 is made in the diameter larger than an irradiation range 10. The center of a horizontal disc 23, a shielding plate, is mounted to a rotation axis 15, and plural holes 24 are formed on the disc 23, and the holes 24 are arranged at equal intervals on the spiral circumference such that the distance from the rotation center of the disc 23 is different for each. In a current density distribution measuring instrument like this, when the disc 23 is rotated by a rotation driving device 14, the holes 24 cross the irradiation range 10 in order, and an electric signal being output from the current detector 21 when each hole 24 crosses the irradiation hole 10 is indicated on a signal display.
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