Single-Point Diamond-Turned Mirror Performance Before and after Polishing

摘要

The surface finish of a single-point diamond-turned (SPDT) mirror produced in 1977 on the large (2-meter swing) Excello lathe at the Union Carbide Corporation's Y-12 Plant in Oak Ridge, Tennessee, was such that it was not possible to do visible alignment using it. Therefore, it was necessary to polish the mirror by hand. This was done at the University of Arizona. The intent was to remove the high ridges in the SPDT mirror but not to degrade the figure. Both interferometric and encircled energy measurements were made on the mirror before and after polishing. The mirror was an f/2 off-axis parabola 39.37 cm in diameter. The equation describing the generator of the mother parabola is y exp 2 = 309x(cm exp 2 ) and the center of each off-axis sister mirror is at x = 7.64 cm, and y = 48.59 cm. After polishing it was possible to align it using techniques which employed visible light. (ERA citation 04:055852)