Ion beam figuring of thin glass plates: achievements and perspectives

Abstract

Different hot slumping techniques have been developed in the last decade to shape thin glass plates in Wolter-I configuration for high angular resolution x-ray telescopes. The required high quality surface characteristic, both in terms of figure error and of micro-roughness, is challenging and the best results achieved so far are compatible with an HEW of few arcseconds. In order to push forward the technology enabling x-ray optics with final HEW below 1 arcsec, we investigate the ion beam figuring as a deterministic technology which can correct the low frequency components of the residual error directly on thin glasses. In this paper we present the tests performed so far, giving a first assessment on the deterministic process definition. In particular, we report on the results achieved on flat samples of D263 and Eagle glass, focusing on the removal function characterization, the micro-roughness evolution and the plate shape variation.