Fast optical metrology of the hard x-ray optics for the High Energy Focusing Telescope (HEFT) †

We describe a fast figure metrology system designed for the several thousand mirror quadrants in the High Energy Focusing Telescope (HEFT) balloon experiment. HEFT's multilayer coated hard x-ray optics will have ~ 1 arcminute HEW and operate at 20-80 keV. The optics are a conical approximation to the Wolter-I configuration. Our automated system can measure the axial figure error, in-phase and out-of-phase roundness errors of a mirror quadrant, and output their HEW contribution to the x-ray telescope. An optical laser scans a conical mirror in two cylindrical coordinate axes. A 2-D position sensitive diode (PSD) measures the reflected beam to ~ 4 arcseconds. The conical mirror can have ≥ 3 cm radius. We show the figure measurements of HEFT's aluminum foil and thermally formed glass substrates.