Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedback
We provide a technical description and experimental results of the practical development and offline testing of an innovative, closed-loop, adaptive mirror system capable of making rapid, precise and ultra-stable changes in the size and shape of reflected X-ray beams generated at synchrotron light a...
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| Format: | Article |
| Language: | English |
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International Union of Crystallography
2025-01-01
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| Series: | Journal of Synchrotron Radiation |
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| Online Access: | https://journals.iucr.org/paper?S1600577524011007 |
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| author | Ioana-Theodora Nistea Simon G. Alcock Andrew Foster Vivek Badami Riccardo Signorato Matteo Fusco |
| author_facet | Ioana-Theodora Nistea Simon G. Alcock Andrew Foster Vivek Badami Riccardo Signorato Matteo Fusco |
| author_sort | Ioana-Theodora Nistea |
| collection | DOAJ |
| description | We provide a technical description and experimental results of the practical development and offline testing of an innovative, closed-loop, adaptive mirror system capable of making rapid, precise and ultra-stable changes in the size and shape of reflected X-ray beams generated at synchrotron light and free-electron laser facilities. The optical surface of a piezoelectric bimorph deformable mirror is continuously monitored at 20 kHz by an array of interferometric sensors. This matrix of height data is autonomously converted into voltage commands that are sent at 1 Hz to the piezo actuators to modify the shape of the mirror optical surface. Hence, users can rapidly switch in closed-loop between pre-calibrated X-ray wavefronts by selecting the corresponding freeform optical profile. This closed-loop monitoring is shown to repeatably bend and stabilize the low- and mid-spatial frequency components of the mirror surface to any given profile with an error <200 pm peak-to-valley, regardless of the recent history of bending and hysteresis. Without closed-loop stabilization after bending, the mirror height profile is shown to drift by hundreds of nanometres, which will slowly distort the X-ray wavefront. The metrology frame that holds the interferometric sensors is designed to be largely insensitive to temperature changes, providing an ultra-stable reference datum to enhance repeatability. We demonstrate an unprecedented level of fast and precise optical control in the X-ray domain: the profile of a macroscopic X-ray mirror of over 0.5 m in length was freely adjusted and stabilized to atomic level height resolution. Aside from demonstrating the extreme sensitivity of the interferometer sensors, this study also highlights the voltage repeatability and stability of the programmable high-voltage power supply, the accuracy of the correction-calculation algorithms and the almost instantaneous response of the bimorph mirror to command voltage pulses. Finally, we demonstrate the robustness of the system by showing that the bimorph mirror's optical surface was not damaged by more than 1 million voltage cycles, including no occurrence of the `junction effect' or weakening of piezoelectric actuator strength. Hence, this hardware combination provides a real time, hyper-precise, temperature-insensitive, closed-loop system which could benefit many optical communities, including EUV lithography, who require sub-nanometre bending control of the mirror form. |
| format | Article |
| id | doaj-art-780d52e6ba1e485dbf55183c94ec3fc7 |
| institution | Kabale University |
| issn | 1600-5775 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | International Union of Crystallography |
| record_format | Article |
| series | Journal of Synchrotron Radiation |
| spelling | doaj-art-780d52e6ba1e485dbf55183c94ec3fc72025-01-07T14:26:38ZengInternational Union of CrystallographyJournal of Synchrotron Radiation1600-57752025-01-0132113314410.1107/S1600577524011007mo5292Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedbackIoana-Theodora Nistea0Simon G. Alcock1Andrew Foster2Vivek Badami3Riccardo Signorato4Matteo Fusco5Optics and Metrology, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United KingdomOptics and Metrology, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United KingdomObservatory Sciences Ltd, United KingdomZygo Corporation, Middlefield, CT 06441, USAS.RI.Tech, Vigonza, ItalyCAEN, Viareggio, ItalyWe provide a technical description and experimental results of the practical development and offline testing of an innovative, closed-loop, adaptive mirror system capable of making rapid, precise and ultra-stable changes in the size and shape of reflected X-ray beams generated at synchrotron light and free-electron laser facilities. The optical surface of a piezoelectric bimorph deformable mirror is continuously monitored at 20 kHz by an array of interferometric sensors. This matrix of height data is autonomously converted into voltage commands that are sent at 1 Hz to the piezo actuators to modify the shape of the mirror optical surface. Hence, users can rapidly switch in closed-loop between pre-calibrated X-ray wavefronts by selecting the corresponding freeform optical profile. This closed-loop monitoring is shown to repeatably bend and stabilize the low- and mid-spatial frequency components of the mirror surface to any given profile with an error <200 pm peak-to-valley, regardless of the recent history of bending and hysteresis. Without closed-loop stabilization after bending, the mirror height profile is shown to drift by hundreds of nanometres, which will slowly distort the X-ray wavefront. The metrology frame that holds the interferometric sensors is designed to be largely insensitive to temperature changes, providing an ultra-stable reference datum to enhance repeatability. We demonstrate an unprecedented level of fast and precise optical control in the X-ray domain: the profile of a macroscopic X-ray mirror of over 0.5 m in length was freely adjusted and stabilized to atomic level height resolution. Aside from demonstrating the extreme sensitivity of the interferometer sensors, this study also highlights the voltage repeatability and stability of the programmable high-voltage power supply, the accuracy of the correction-calculation algorithms and the almost instantaneous response of the bimorph mirror to command voltage pulses. Finally, we demonstrate the robustness of the system by showing that the bimorph mirror's optical surface was not damaged by more than 1 million voltage cycles, including no occurrence of the `junction effect' or weakening of piezoelectric actuator strength. Hence, this hardware combination provides a real time, hyper-precise, temperature-insensitive, closed-loop system which could benefit many optical communities, including EUV lithography, who require sub-nanometre bending control of the mirror form.https://journals.iucr.org/paper?S1600577524011007adaptive opticsx-ray opticsbimorph deformable mirrorsclosed-loop controlsfibre optic interferometershigh-voltage power suppliesx-ray mirrors |
| spellingShingle | Ioana-Theodora Nistea Simon G. Alcock Andrew Foster Vivek Badami Riccardo Signorato Matteo Fusco Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedback Journal of Synchrotron Radiation adaptive optics x-ray optics bimorph deformable mirrors closed-loop controls fibre optic interferometers high-voltage power supplies x-ray mirrors |
| title | Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedback |
| title_full | Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedback |
| title_fullStr | Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedback |
| title_full_unstemmed | Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedback |
| title_short | Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric feedback |
| title_sort | picometre level surface control of a closed loop adaptive x ray mirror with integrated real time interferometric feedback |
| topic | adaptive optics x-ray optics bimorph deformable mirrors closed-loop controls fibre optic interferometers high-voltage power supplies x-ray mirrors |
| url | https://journals.iucr.org/paper?S1600577524011007 |
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