PURPOSE: To uniformalize the secondary electron emission ratio and prevent shading from occurring in a pedestal waveform by forming a metal coat that determines a target effective area along the periphery on one surface of a target in a closed loop form and covering the target surface and a part or the whole of the above metal coat.

CONSTITUTION: A ring-type metal coat 13 is formed at the beam scanning side of a pyroelectric material target 11 secured to a support bench 10 so that its inside diameter can be set to 1 and a secondary electron emission coat 12 is formed so that its periphery can be laminated with a part or the whole containing the inner surface of the metal coat 13 and its outside diameter can be set to 2. Where, the relationship between 1 and 2 is 1<2. When the surface of the secondary electron emission coat 12 is scanned with an electron beam, positive surface charge is generated on the surface of the secondary electron emission coat 12 that emits secondary electrons. On the other hand, since the metal coat 13 is kept in zero potential or slightly lower than zero potential, the positive charge generated on the surface of the secondary electron emission coat 12 is coupled through the thickness of the secondary electron emission coat 12 by coulomb force and there can hardly be seen the leak from the surface.