Passive doubly curved structures for determining clamping forces applied to X-ray optic assemblies

Clamping of indirectly cryogenically cooled X-ray optics is required to ensure effective heat transfer between the optic and heat exchanger. However, clamping forces can result in distortion of the optical surface of monochromators and mirror systems, which causes angular distortions of the subsequent beam. As such, there is a need for greater understanding of how these optics are assembled and how this affects their performance throughout their life cycle. In this paper, the potential for non-contact, in-process monitoring of the clamping force both during and after assembly using an additively manufactured passive structure based on a doubly curved hyperbolic paraboloid and designed for application to the first crystal for the I20 monochromator at Diamond Light Source is investigated numerically and experimentally. The performance of the passive structure both pre- and post-cryogenic quenching is characterized experimentally. Laser displacement measurements reveal approximately 9 µm total displacement in the passive structure per 100 N of bolt preload, corresponding to an effective magnification of the preload adjustment of approximately 2.5×.