| 摘要 |
PURPOSE:To reduce absorption of X-ray by reducing helium gas supplying pressure in the light path. CONSTITUTION:Pressure difference required for vacuum chuck depends on the conditions but is about 200Torr. When internal pressure of exhaust hole 8 of the chuck 2 is exhausted to vacuum condition, pressure outside the chuck 2 may be 200Torr or so. When light path length is 30cm, X-ray wavelength is 12A and helium pressure is 200Torr, the X-ray absorption coefficient becomes 8.3% and it is reduced to 30% or less in comparison with the case of 1 atmospheric pressure. In case the upper and lower spaces are separated by mask 3, such a pressure difference as not resulting in deformation of mask 3 is allowed. The allowable pressure difference is changed in accordance with the condition of mask 3 but when it is set to 100Torr, an interval between window 4 and mask 3 is almost equal to the light path, absorption of light path is further reduced to 4.2%. |
