| 摘要 |
PURPOSE:To precisely monitor only the position of the optical axis of an X-ray to be actually utilized without having the influence of an emitted light having a long wavelength. CONSTITUTION:On the upper stream side of a screen 30 arranged in a beam line 9, a filter 31 which transmits the X-ray having a wavelength less than a determined value and arresting the transmission of an emitted light having a wavelength longer than this is provided in such a manner as to be capable of protruding and retreating to the beam line together with the screen. As the filter, an inexpensive aluminium or nickel thin film or thin plate can be adapted. Only the X-ray requiring monitor for actual utilization is transmitted by the filter and reaches the screen, and the emitted light of the long wavelength requiring no monitor never reach the screen.
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