Manufacturing an active X-ray mirror prototype in thin glass

Abstract

Adjustable mirrors equipped with piezo actuators are commonly used at synchrotron and free-electron laser (FEL) beamlines, in order to optimize their focusing properties and sometimes to shape the intensity distribution of the focal spot with the desired profile. Unlike them, X-ray mirrors for astronomy are much thinner in order to enable nesting and reduce the areal mass, and the application of piezo actuators acting normally to the surface appears much more difficult. There remains the possibility to correct the deformations using thin patches that exert a tangential strain on the rear side of the mirror: some research groups are already at work on this approach. The technique reported here relies on actively integrating thin glass foils with commercial piezoceramic patches, fed by voltages driven by the feedback provided by X-rays, while the tension signals are carried by electrodes on the back of the mirror, obtained by photolithography. Finally, the shape detection and the consequent voltage signal to be provided to the piezoelectric array will be determined by X-ray illumination in an intra-focal setup at the XACT facility. In this work, the manufacturing steps for obtaining a first active mirror prototype are described.

Адаптивная И Активная Рентгеновская Оптика

“…Активную оптику следует выбирать так, чтобы она не только улучшала зеркальную форму, но также могла быть включена в зеркальный модуль, не добавляя существенную толщину или структуру в зазоре между соседними вложенными зеркальными оболочками, которая будет перекрывать путь РЛ. Поэтому, по-видимому, предпочтительнее использование поверхностно-касательных актуаторов, обладающих возможностью более гибкой коррекции формы зеркальных оболочек [89][90][91][92][93][94][95].…”

“…Система металлических электродов, нанесенных на обратную сторону стеклянной оболочки. Можно заметить азимутальную кривизну, ранее созданную процессом высокотемпературной формировкой оболочки [93]. Метод Шака−Гартмана является вариацией классического метода Гартмана с той разницей, что для повышения чувствительности вместо маски-диафрагмы используется массив микролинз, разбивающий волновой фронт на множество частей, каждая из которых формирует отдельное фокусное пятно [111] (рис.…”

Technologies for advanced X-ray mirror fabrication

“…The process described above highlights one effort to advance this fabricative methodology. In an alternative approach, electrode patterns have been deposited upon the slumped glass convex surface by photolithography and commercial piezoelectric actuators bonded to the electrodes [44]. In this process, stacking of the active slumped glass substrates was also considered.…”

The X-Ray Surveyor mission concept study: forging the path to NASA astrophysics 2020 decadal survey prioritization

“…In addition to these NASA funded efforts, high-resolution, light-weight X-ray mirrors are also being developed in countries outside of the U.S. These developments include, but are not limited to, active X-ray mirrors in thin glass 4 , thin slumped glass foils 5 and direct polishing of thin SiO 2 substrates 6 . Multiple techniques to further improve mirror performance and reduce residual figure errors and mounting-induced stress are also being developed at various institutions around the globe, and include: differential deposition 7,8 , ion-beam figuring 9,10 , low-stress coating techniques 11 , differential ion implantation 12 , active figure correction 13 and magnetostrictive corrections 14 .…”