Design and alignment of off-axis primary and secondary mirrors system in gravitational wave telescopes

This paper refers to the technical requirements of gravitational wave telescopes and focuses on the design and alignment of the telescope's primary and secondary mirror system. Parameters for the reflective telescope's primary and secondary mirror system are determined based on the design requirements. The materials for the mirror system structure are chosen by analyzing stiffness ratio, thermal expansion coefficient, and surface roughness. The deformation and stress of the support structure under gravitational conditions are analyzed, and its rationality is verified through temperature simulation. Before the alignment, a sensitivity matrix for system aberrations is obtained by introducing maladjustments in different degrees of freedom to guide the alignment. Using the autocollimation method and flat mirror interferometer for system testing, the results show a wavefront error RMS of RMS=0.0316 λ and PV=0.318 λ (λ=632mm). The test results indicate that the primary and secondary mirror system structure meets the initial design requirements.