Evaluation of an Ultrahigh Precision X-Ray Optics

摘要

We are developing an ultra high precision soft X-ray telescope. The design of the telescope is a normal incident one for 13.5 nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the precision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an X-ray-optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system distortion as a closed loop system. The telescope system is now integrating and checking by optical light. The shape of the primary mirror is an off-axis paraboloid with a focal length of 2m and an effective diameter of 80mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5nm was ranging from 30 to 50%. The secondary mirror is a basically flat mirror but actually an deformable mirror with 31 piezo-actuators. The detector is now a wave front sensor (shack-hartmann type). The closed loop control has been performed and factor of 2.4 improvement of the wave front shape has been performed comparing to the un-control case.