PURPOSE: To take out X ray to be used for an aligner effectively, by providing a absorption membrane which previously absorbs a specific wave length component to be absorbed by an X ray window at the upstream side of the X ray window which permeates a part of a synchrotron radiation beam propagating through an air and a vacuum zones.

CONSTITUTION: A membrane 5 absorbs previously a wave length component which is absorbed by an X ray window. This membrane 5 is located at a upper stream side of the X ray window of a radiation beam pass in a cylinder 1 and the X ray window can be changed to a thin beryllium membrane 6. The membrane 5 is an about 5W50μm thick silicon membrane which absorbs wave length components longer than 10 from the radiation beam 1 before the radiation beam 1 reaches the membrane 6 and consequently an absorbed energy by the membrane 6 is reduced as compared to a conventional case. When a temperature of the membrane 6 goes high to several hundred degrees centigrade, a radiative cooling becomes equivalent to an absorbed energy, therefore, there is on need to cool down, and because the membrane 5 does not separate the inside of the cylinder 2 vacuumwise, the existence of a few number of pinholes or cracks does not cause a problem. Thereby, the membrane 6 can be made more thinner and an X ray used for an aligner can be taken out effectively.