Development of X-ray baffle for the EP-FXT flight spare

Purpose The Einstein Probe (EP) satellite is a science mission of the Chinese Academy of Sciences, which is dedicated to time-domain astronomy and high-energy astrophysics. The X-ray baffle is a crucial component of follow-up X-ray telescope (FXT), which is an important payload onboard EP. It was designed to efficiently reduce stray light, especially single reflection on the hyperboloid of Wolter-I Mirrors.
Methods In this paper, based on the parameters of FXT's mirror module and the detector, the design parameters of the X-ray baffle are optimized through preliminary design and detailed ray-tracing simulation. Fabrication involved precision laser cutting, roll forming, laser welding and integration processes. The thermal stability and mechanical environment adaptability were validated through thermal cycling and mechanical vibration tests. Finally, the X-ray baffle was mounted onto the mirror module with alignment precisely controlled using optical methods.
Results The height of the X-ray baffle ranges from 60 to 120 mm from the outside to the inside; the aperture corresponds to each layer of the mirror module. In order to reduce weight and reduce light occlusion, the thickness of each thin shell is 0.125 mm. The ray-tracing simulation results with X-ray baffle are shown that the stray light is effectively reduced in the effective region of the detector. The Eigen-frequency change of the X-ray baffle after the thermal cycle test and mechanical vibration tests is only 0.52% and 0.77%, respectively. The results proved that X-ray baffle has a high thermo-mechanical reliability. The half power diameter (HPD) of the mirror module remained unchanged on-axis with/without X-ray baffle.
Conclusion The introduction of X-ray baffle is expected to be highly significantly reduce stray light.