Monochromatic energy multilayer Kirkpatrick-Baez microscope is one of key diagnostic tools for researches on inertial confinement fusion. It is composed by two orthogonal concave spherical mirrors with small curvature and aperture, and produce the image of an object by collecting X-rays in each orthogonal direction, independently. Accurate measurement of radius of curvature of concave spherical mirrors is very important to achieve its design optical properties including imaging quality, optical throughput and energy resolution. However, it is difficult to measure the radius of curvature of spherical optical surfaces with small curvature and aperture by conventional methods, for the produced reflective intensity of glass is too low to correctly test. In this paper, we propose an improved measuring method of optical profiler to accomplish accurate measurement of radius of curvature of spherical optical surfaces with small curvature and aperture used in the monochromatic energy multilayer Kirkpatrick-Baez microscope. Firstly, we use a standard super-smooth optical flat to calibrate reference mirror before each experiment. Following, deviation of central position between measurement area and interference pattern is corrected by the theory of Newton’s rings, and the zero-order fringe position is derived from the principle of interference in which surface roughness has minimum values in the position of zero light path difference. Measured results by optical profiler show the low relative errors and high repeatability. Eventually, an imaging experiment of monochromatic energy multilayer Kirkpatrick-Baez microscope determines the measurement accuracy of radius of curvature.
X-ray Timing and Polarization (XTP) satellite with focusing optics and advanced detectors will study Black Hole, Neutron Star, Quark Star and the physics under extreme gravity, density and magnetism. XTP is about to make the most sensitive temporal and polarization observations with good energy resolution in 1-30 keV. We present the design of XTP Telescope with a larger field of view in this paper. The initial structure design of nested conical Wolter-I telescope in X-rays is determined with the focal length f=4.5m, mirror length L=100mm, thickness t=0.3mm, inner and outer diameter Din-out=100-450mm. To optimize the structure parameters, a self-complied Matlab software is used to maximize the center geometrical collecting are. A constant deviation gap between every two mirrors is introduced, and we calculate geometrical area in on-axis and off-axis. Balancing the performance of the telescope, the final gap value is 0.06 mm. The geometrical collecting area of on-axis decreased by 5%, the average geometrical area of off-axis is increased about 1.7% and the field of view is improved from 22’ to 24’, meanwhile, number of mirrors and total weight of mirrors also are decreased by 5.8%, 5.3% respectively.
The degradation of image quality of the nested conical Wolter-I X-ray telescope mainly results from mirror-position tolerance, alignment-bar tolerance and surface-figure tolerance. The analytical approach of the three kinds of tolerance was presented in this paper. Based on the predetermined initial structure, we analyzed and compared image qualities with different tolerances. Furthermore, we simulated the distribution of the spot diagrams and calculated the spatial resolution of the entire system. Shift along the optical axis (Z axis) and rotation around it have no effects on the image quality for position tolerances. However, shift along X, Y directions and rotation around X, Y axes change the distribution of spot diagrams and decrease the spatial resolution. For higher resolution, we should control the alignment-bar tolerance by placing a displacement sensor at the end of the alignment bar. The angular resolution increases from 1' to 13'' as the alignment-bar tolerance decreased from ±15um to ±3um. With respect to surface-figure tolerance, we simulated image qualities by inserting Zernike polynomial to the surface.