| 摘要 |
PURPOSE:To enable to rapidly perform on-off control of an electron beam by attaching a cooling jacket to a side wall of a scanning tube along a circumference of an irradiation window while providing a deflection means which deflects the electron rays for making the electron rays to be incident to the corresponding inside wall part of the scanning tube. CONSTITUTION:When performing the ordinary electron ray irradiation, the deflection coils 8a and 8b are made to be a constant magnetic field for positioning the electron rays at the center of an irradiation window 6 in the X-direction while the scanning coils 5a and 5b reciprocatingly scan the electron rays in the X-direction. On the other hand, when putting the electron ray irradiation on ''off'', the deflection coils 8a and 8b are made to generate a rectangular wave magnetic field and the electron rays are made to be incident at the part, where the water cooling jackets 7a and 7b of the inside wall of the scanning tube 4 are attached, in the X-direction while the scanning coils 5a and 5b reciprocatingly in the Y-direction. The inside wall of the scanning tube 4 is heated due to the incidence of the electron rays but it offers no problem due to cooling by the water cooling jackets 7a and 7b. Thereby, the on-off response speed is sufficiently quickened. |
