Precision polishing of the mandrel for X-ray grazing incidence mirrors

Based on chemical-mechanical polishing, a precision polishing method is proposed to accommodate the polishing of the paraboloid surface of the specified mandrel for grazing incidence X-ray mirrors. The influencing factors in the polishing are analyzed to confirm the method complies with the Preston equation and Hertz contact theory. Therefore, the common material removal model based on these two theories is adopted. The effects of processing parameters, such as the force F between the mandrel and the polishing lap, the rotational speed n of the mandrel, and the axial speed v(a) of the polishing lap, on the material removal rate are simulated, respectively. A polishing setup is established to carry out experimental polishing to verify the optimum processing parameters obtained by simulations and previous polishing tests. Besides, the effect of abrasive particle size on the roughness is also verified. The roughness of the polished mandrel is measured at different positions, and the optimum roughness reaches Ra 0.659 nm. The polishing approach can significantly reduce the surface roughness of the replication mandrel, satisfying the low energy band focusing requirement of grazing incidence X-ray mirrors.