Development of a glue-free bimorph mirror for use in vacuum chambers

Ichii, Yoshio; Okada, Hiromi; Nakamori, Hiroki; Ueda, Akihiko; Yamaguchi, Hiroyuki; Matsuyama, Satoshi; Yamauchi, Kazuto

doi:10.1063/1.5066105

Cited by 8 publications

(6 citation statements)

References 19 publications

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“…The development of X-ray adaptive optics started in the mid-1990s (Susini et al, 1996). Over the last decade, significant advances (Mimura et al, 2010;Sawhney et al, 2010) have led to the commercial availability of piezo-bimorph mirrors (Alcock et al, 2019a;Ichii et al, 2019) and their successful deployment on several beamlines (Matsuyama et al, 2016;Sutter et al, 2019). A recent review by Cocco et al (2022) summarizes alternative approaches to deformable mirrors.…”

Section: Introductionmentioning

confidence: 99%

Data-driven modeling and control of an X-ray bimorph adaptive mirror

Gunjala¹,

Wojdyla²,

Goldberg³

et al. 2023

J Synchrotron Rad

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Adaptive X-ray mirrors are being adopted on high-coherent-flux synchrotron and X-ray free-electron laser beamlines where dynamic phase control and aberration compensation are necessary to preserve wavefront quality from source to sample, yet challenging to achieve. Additional difficulties arise from the inability to continuously probe the wavefront in this context, which demands methods of control that require little to no feedback. In this work, a data-driven approach to the control of adaptive X-ray optics with piezo-bimorph actuators is demonstrated. This approach approximates the non-linear system dynamics with a discrete-time model using random mirror shapes and interferometric measurements as training data. For mirrors of this type, prior states and voltage inputs affect the shape-change trajectory, and therefore must be included in the model. Without the need for assumed physical models of the mirror's behavior, the generality of the neural network structure accommodates drift, creep and hysteresis, and enables a control algorithm that achieves shape control and stability below 2 nm RMS. Using a prototype mirror and ex situ metrology, it is shown that the accuracy of our trained model enables open-loop shape control across a diverse set of states and that the control algorithm achieves shape error magnitudes that fall within diffraction-limited performance.

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Section: Introductionmentioning

confidence: 99%

Data-driven modeling and control of an X-ray bimorph adaptive mirror

Gunjala¹,

Wojdyla²,

Goldberg³

et al. 2023

J Synchrotron Rad

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“…When the Si substrate is 10 mm thick, and ±500 V is applied to the two layers, a local bending radius of curvature of ∼1 km can be achieved. 4 We find that 1 km is a good target range for local bending radii that will be required in our applications at the Advanced Light Source. Dynamic control and stabilization of a mirror with this form factor have been demonstrated by Gunjala et al 13…”

Section: Article Pubsaiporg/aip/rsimentioning

confidence: 75%

“…One class of adaptive mirrors recently described by Ichii et al has piezoelectric ceramic material bonded symmetrically to the front and back surfaces of the mirror substrate, forming a tri-layer geometry with an open central channel. 4 The piezoelectric strips are segmented longitudinally into channels and wired with thin-film electrodes for actuation. The substrate has a uniform rectangular cross section.…”

Section: Article Pubsaiporg/aip/rsimentioning

confidence: 99%

“…In the field of x-ray optics where ultra-smooth mirrors achieve high reflectivity at glancing angles of incidence, adaptive, bendable mirrors are being deployed to correct and control the wave-front shape, enabling these beamline optical systems to reach diffraction-limited quality. [1][2][3][4][5][6][7] Owing to angles of incidence below 2 ○ , typical x-ray mirrors are hundreds of millimeters long, even for mm-scale beam crosssectional widths. Furthermore, to operate at these short wavelengths, mirrors must be polished-either flat or curved-to nanometerscale shape and surface tolerances, and the required shapes must be preserved during use.…”

Section: Introductionmentioning

confidence: 99%

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Thickness dependence of piezo-bimorph adaptive mirror bending

Goldberg,

La Fleche

2023

Review of Scientific Instruments

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A new generation of adaptive x-ray optics (AXO) is being installed on high-coherent-flux x-ray beamlines worldwide to correct and control the optical wavefront with sub-nm precision. These ultra-smooth mirrors achieve high reflectivities at glancing angles of incidence and can be hundreds of mm long. One type of adaptive x-ray mirror relies on piezoelectric ceramic strips which are segmented into channels and actuated to induce local, longitudinal bending, generating one-dimensional shape changes in the mirror substrate. A recently described mirror model uses a three-layer geometry with parallel actuators on the front and back surfaces of a thicker mirror substrate. By analogy to a solved problem in the thermal actuation of a tri-metal strip, we show that the achievable bending radius varies approximately as the square of the substrate thickness. We provide an analytic solution and simulate bending using a finite-element model.

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“…A boundary would be used to account for the minimum radius that is experimentally reached by M3. The induced shape and height changes depend on the actuator position, as discussed by Ichii et al (2019). It is the combined action of all actuators that produces the minimum radius (all front-side actuators are tuned to the same positive or negative voltage and the back-side actuator has the opposite polarity).…”

Section: Maximum Correctable Deformationsmentioning

confidence: 99%

Compensation of heat load deformations using adaptive optics for the ALS upgrade: a wave optics study

Río

Wojdyla

Goldberg

et al. 2020

J Synchrotron Radiat

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A realistic wave optics simulation method has been developed to study how wavefront distortions originating from heat load deformations can be corrected using adaptive X-ray optics. Several planned soft X-ray and tender X-ray insertion-device beamlines in the Advanced Light Source upgrade rely on a common design principle. A flat, first mirror intercepts the white beam; vertical focusing is provided by a variable-line-space monochromator; and horizontal focusing comes from a single, pre-figured, adaptive mirror. A variety of scenarios to cope with thermal distortion in the first mirror are studied by finite-element analysis. The degradation of the intensity distribution at the focal plane is analyzed and the adaptive optics that correct it is modeled. The range of correctable wavefront errors across the operating range of the beamlines is reported in terms of mirror curvature and spatial frequencies. The software developed is a one-dimensional wavefront propagation package made available in the OASYS suite, an adaptable, customizable and efficient beamline modeling platform.

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Development of a glue-free bimorph mirror for use in vacuum chambers

Cited by 8 publications

References 19 publications

Data-driven modeling and control of an X-ray bimorph adaptive mirror

Data-driven modeling and control of an X-ray bimorph adaptive mirror

Thickness dependence of piezo-bimorph adaptive mirror bending

Compensation of heat load deformations using adaptive optics for the ALS upgrade: a wave optics study

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