Effective Area Simulation And Measurement Of Wolter-â…  Nested Nicked Surface Gold-plated X-ray Focusing Mirror

An effective tool for astronomical research is the X-ray grazing incidence optical system.Because of its high signal-to-noise ratio,high positioning accuracy,and multi-layer nesting structure,Wolter-Ⅰ focusing mirror in X-ray grazing incidence optical system is widely used in X-ray satellites.This significantly increases the effective area and boosts the quality of astronomical observation data.The Chinese Academy of Sciences proposed the Einstein probe satellite project in 2013.EP is an X-ray detection satellite for high-energy astrophysics and time-domain astronomy.It has a Wide-field X-ray Telescope in a soft X-ray band for wide-field monitoring throughout the day and a Follow-up X-ray Telescope for further in-depth investigation.The 54-layer Wolter-Ⅰ nickel-plated lens nested structure used by the FXT load focusing mirror gives it better depth observation capabilities.The theoretical study of the grazing incidence focusing properties and the effective area of the Wolter-Ⅰ X-ray focusing mirror is presented in this work using the EP-FXT as the research subject.Initially,a thorough discussion of the domestic and international research and development status of X-ray grazing incidence optical systems is presented,followed by an analysis of the common types,examples of applications,benefits,and drawbacks of X-ray optical systems.An study of the typical types,examples of applications,advantages,and disadvantages of X-ray optical systems is offered after a full assessment of the domestic and global research and development status of X-ray grazing incidence optical systems.Second,using ZEMAX optical simulation software,X-ray sources with the characteristic radiation of copper(8.05 ke V),titanium(4.51 ke V),and aluminum(1.49 ke V)were chosen.When calibrated on the ground and in orbit,the54-layer Wolter-Ⅰ focusing mirror with FXT load simulates its effective area.The simulation findings indicate that the focusing mirror’s ground calibration effective area is2.7%,3.0%,and 4.0%greater than the in-orbit effective area,respectively.The in-orbit effective area of the focusing mirror is 448.60 cm~2at 1.49 ke V,82.27 cm~2 at 4.51 ke V,and 30.10 cm~2at 8.05 ke V.The spot intensity distribution of around 40mm of defocusing is obtained that after defocusing simulation of the focusing mirror is accomplished.The distribution of spot intensity at various off-axis angles as well as the curve of the relationship between effective area and off-axis angle are obtained after the focusing mirror’s off-axis simulation at+80 mm position has been completed.The simulation findings reveal that the effective area of the FXT load focusing mirror calibrated on the ground is greater than that in orbit,that the focusing mirror’s off-axis angle gradually increases,and that its effective area drops dramatically.In the 100m X-ray calibration equipment of the Institute of High Energy Physics,Chinese Academy of Sciences,the FXT load-focusing mirror was experimentally proven.The FXT’s focusing mirror has an effective area of 339.80 cm~2 at 1.49 ke V,73.57 cm~2 at4.51 k V,and 29.47 cm~2 at 8.05 k V,while the on-orbit effective area is 330.74 cm~2 at 1.49ke V,71.43 cm~2 at 4.51 k V,and 28.34 cm~2 at 8.00 k V.The light intensity distribution of FXT’s defocused spot and off-axis spot is empirically examined,and the results agree with the theoretical simulation results.The focusing mirror’s angular resolution is also put to the test.When the X-ray energy is 1.49 ke V,the focusing mirror’s spot width(HPD)with 50%photon energy is 22.6",and the focusing mirror’s spot width(W90)with 90%photon energy is 174.4".The focusing mirror performs admirably.We now have a deeper grasp of the calibration of X-ray focusing mirrors’effective areas thanks to the study in this publication.The performance test of more X-ray focusing mirrors in the future,as well as the load calibration of more X-ray astronomy satellites in China,can both benefit from mastering the test method of effective area calibration.