| 摘要 |
PROBLEM TO BE SOLVED: To invariably reduce a spurious level by setting the diameter of the tip face of a pair of pole pieces smaller than the inscribed circle diameter of the inner end faces of anode vanes, and setting the angle between the vertical direction of the tube axis of an anode cylinder and the outer peripheral face of the taper shape of a pair of pole pieces to a specific angle or above. SOLUTION: A cathode 2 is arranged at the center of the tube axis of a cylindrical anode cylinder 1, anode vanes 4 are radially arranged at uniform intervals in an acting space 3 around the cathode 2, and a pair of pole pieces 6 are arranged face to face across the cathode 2 and the acting space 3. The diameterϕp of the tip faces of the pole pieces 6 is made smaller than the inscribed circle diameterϕa of the inner end faces of the anode vanes 4. The angleθof a taper formed by a virtual line extended with the tip face of each pole piece 6 in the direction of the anode cylinder 1 and the outer periphery of the pole piece 6 is set to 20 deg. or above, thereby the magnetic flux density at both end sections of the cathode 2 is made 1.1 times the magnetic flux density at the center section of the cathode 2 or above, and a spurious level is improved.
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