ANL, Lemont, Illinois, USA
Deformable optics, including mechanically-bent and bimorph mirrors, are essential optical elements for X-ray beam dynamical focusing and wavefront correction. Existing mechanical bender technology often suffers from poor repeatability and does not include twist compensation. We recently developed an elliptically bent mirror based on a laminar flexure bending mechanism that yielded promising results*,**. In this work, the mirror surface twist was characterized using a Fizeau interferometer under different bending conditions. By applying a shimming correction, the surface twist was successfully reduced from 50 urad to 1.5 urad. The twist angle variation from no bending to the maximum bending is less than 0.5 urad. Our simulation results show that these numbers are significantly lower than the required values to ensure optimum optical performance. The study demonstrates the effectiveness of the twist compensation procedures and validates the mirror bender design parameters.
*Shu, D. et al., AIP Conference Proceedings. Vol. 2054. No. 1, 2019.
**Anton, Jayson WJ et al., Optomechanical Engineering 2019. Vol. 11100, 2019.
ANL, Lemont, Illinois, USA
SLAC, Menlo Park, California, USA
The concept behind the cavity-based X-ray FELs (CBXFELs) such as the X-ray free-electron laser oscillator (XFELO)* and the X-ray regenerative amplifier free-electron laser (XRAFEL)** is to form an X-ray cavity with a set of narrow bandwidth diamond Bragg crystals. Storing and recirculating the output of an amplifier in an X- ray cavity so that the X-ray pulse can interact with following fresh electron bunches over many passes enables the development of full temporal coherence. One of the key challenges to forming the X-ray cavity is the precision of the cavity mechanical system design and construction. In this paper, we present conceptual design of the cavity mechanical system that is currently under development for use in a proof-of-principle cavity-based X-ray free electron laser experiment at the LCLS-II at SLAC.
*Kwang-Je Kim et al., TUPRB096, Proceedings of IPAC2019
**Gabe Marcus et al., TUD04, Proceedings of IPAC2019
ANL, Lemont, Illinois, USA
As part of the Advanced Photon Source Upgrade (APS-U) project, the Coherent Surface Scattering Imaging (CSSI) [1] instrument is currently being developed. One of the most important components of the CSSI instrument at the 9-ID beamline of the APS-U, the Kirkpatrick-Baez (K-B) mirror system, will focus hard X-rays to a diffrac-tion-limited size of 500 nanometers at a working distance of 550 mm. High angular stability (19 nrad for the hori-zontal mirror and 14 nrad for the vertical mirror) is speci-fied no just for the focused beamsize but, more important-ly, to ensure the beam stability at the detector position that is up to 24 m from the K-B mirrors. A large sample-to-detector distance (up to 23 m), one of the beamline’s unique features for achieving a sufficient coherent-imaging spatial oversampling, requires sample angular stability of 50 nrad. In CSSI scattering geometry, the vertically placed sample reflects X-rays in the horizontal direction at an extremely shallow angle. The design in-cludes two high-precision rotary stages for sample pitch (vertical axis) and yaw (horizontal axis). The current design of instrument’s nano-positioning stages [2] and metrology required to satisfy the stability and positioning requirements are discussed in this paper.
*T. Sun et al., Nat. Photonics 6, 586 (2012).
**D. Shu et al., this conference.
ANL, Lemont, Illinois, USA
Kirkpatrick and Baez (K-B) mirror-based nanofocusing optics* will be applied to many beamlines endstation instruments for the APS-Upgrade (APS-U) project. Precision nanopositioning stages with nanometer-scale linear positioning resolution and nanoradian-scale angular stability are needed as alignment apparatus for the K-B mirror hard X-ray nanofocusing optics. For instance, at the APS-U 19-ID In Situ Nanoprobe beamline endstation**, to maintain stability of a 20-nm focal spot on the sample, nanofocusing K-B mirror system with 5-nrad angular stability is required. Similar angular resolution and stability are also required for APS-U 9-ID CSSI***, APS-U 34-ID ATOMIC**** and other beamline endstation instruments. Modular nanopositioning flexure stages have been developed for the K-B mirror nanofocusing optics, which includes: linear vertical and horizontal flexure stages, tip-tilting flexure stages, and flexure mirror benders for bendable nanofocusing K-B mirrors, to overcome the performance limitations of precision ball-bearing-based or roller-bearing-based stage systems. The mechanical design and preliminary test results are described in this paper.
* Kirkpartrick and Baez, JOSA. 1948; 38(9): 766-773.
** S. Kearney et al., this conference.
*** J. Anton et al., this conference.
**** C. Preissner et al., this conference.
ANL, Lemont, Illinois, USA
Wavefront preservation is essential for numerous X-ray science applications. Research is currently underway at the Advanced Photon Source to characterize and minimize Bragg-plane slope errors in diamond crystal optics*. Understanding the effect of cooling the optics to cryogenic temperatures on Bragg-plane slope errors is of interest to this research. Through the use of a finite element model a custom, compact vacuum chamber with liquid nitrogen cooling of samples was designed and manufactured. The design process and initial results are discussed in this paper.
*P. Pradhan et al., J. of Synchrotron Radiation 6, 1553 (2020)