Design of shearing and Hartmann wavefront sensors for

Design of shearing and Hartmann wavefront sensors for diffraction-limited beamlines Antoine Wojdyla 1, Diane Bryant 1, Kenneth A Goldberg 1, Lahsen Assoufid 2, Daniele Cocco 3, Mourad Idir 4 1 ALS, Lawrence Berkeley National Laboratory, Berkeley, California 94710, USA 2 APS, Argonne National Laboratory, Argonne, IL 60439, USA 3 LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94566, USA 4 NSLS-II, Brookhaven National Laboratory, Upton, NY 11973 -5000, USA June 15 th, 2018 – SRI 2018, Taipei, Taiwan SXR wavefront sensor designs - A Wojdyla – SRI 2018

Upgrade of the Advanced Light Source to a diffraction-limited storage ring Soft X-ray + Tender X-ray (260 -1400 e. V, 1 -5 ke. V) Large coherent fraction Diffraction-limited Completion ca 2024 SXR wavefront sensor designs - A Wojdyla – SRI 2018 2

DLSR light sources Diffraction-limited beam σ · σ’ ~ λ/4π Small footprint and small divergence Continuous monitoring of the beam: the wavefront sensor has to be placed before the object (no post-object diverging beam) SXR wavefront sensor designs - A Wojdyla – SRI 2018 3

Perturbations of the wavefront �� High heatload causes deformation 1 mm 1 m phase �� Mirror error figure (older optics, for adaptive correction) �� /16 1 mm COSMIC M 111 �� Fine alignment of optics Misalignments have a signature SXR wavefront sensor designs - A Wojdyla – SRI 2018 tilt +1 mrad defocus astigmatism coma

A zoo of beams ALS/COSMIC LCLS ALS-U/Flagship 1 ALS-U/Flagship 2 NSLS-II ALS-U/Flagship TXR APS-U SXR wavefront sensor designs - A Wojdyla – SRI 2018

Wavefront sensors • Grating-based – Liu E. 1. 2, Wed 13 h 50 • Hartmann grid – Scholze E. 1. 6, Wed 15 h 20 – Plönjes, IWXM • Speckle-based – Wang E. 1. 4, Wed 14 h 30 SXR wavefront sensor designs - A Wojdyla – SRI 2018 6

Wavefront sensors for soft x-ray • No phase gratings and speckle, no crystals • ALS-U SXR Notional beamline(250 -1400 e. V) • “non invasive”: able to work on convergent geometry – After Mono, M 3 – Can be limited to the non-dispersive direction – Stay clear of the beam 4 -m-long undulator beam diagnostics plane mirror elliptical-cylinder monochromator x-focusing mirror WFS z x-y slit SXR wavefront sensor designs - A Wojdyla – SRI 2018

Design of wavefront sensors • Design constraints – beam footprint – detector resolution – beam overlap Beamline (footprint, propagation distance) • Performances – range – sensitivity – efficiency Beam (wavelength, NA) SXR wavefront sensor designs - A Wojdyla – SRI 2018 Optical elements (pitch, pixel size)

Design constraints Lateral shearing interferometry pitch too small pixel size too small shadow regime ZCCD pitch too large Talbot plane too far Hartmann sensor No diffraction (amplitude sensitivity) diffraction regime SXR wavefront sensor designs - A Wojdyla – SRI 2018 ZCCD beam overlap

Distance of operation Wavefront sensors operate in the Fresnel regime: z ≈ a 2/λ The critical dimension a is 10 – 40μm for any reasonable distance of operation (0. 1 -1 m) for most photon energies (0. 2 -10 ke. V) Direct detection (pixel size 15μm) becomes difficult: scintillator-based detection (YAG: Ce) SXR wavefront sensor designs - A Wojdyla – SRI 2018 10

Shearing interferometry with a converging beam d 0 Pattern size: d = d 0 · (z. F-z)/z. F (pitch x demag) Pattern shift: Δ = λ/d 0 · z (divergence x distance) Talbot length: z. T ≜ d 02/λ z. F +1 0 -1 z z. C Converging Talbot distance: d(z. C) = Δ(z. C). . λ/d 0 · z. C = d 0 · (z. F-z. C)/z. F. . λ/d 02 = (z. F-z. C)/z. Fz. C. . . 1/z. T = 1/z. C - 1/z. F 1/z. C = 1/z. T + 1/z. F SXR wavefront sensor designs - A Wojdyla – SRI 2018 11

Typical designs for ALS-U M 3 beamsplitter Maintain 4– 6 mm center-to-center separation pitch SXR wavefront sensor designs - A Wojdyla – SRI 2018 pitch

Soft x-ray shearing interferometer • Currently being assembled and tested SXR wavefront sensor designs - A Wojdyla – SRI 2018

Soft x-ray Hartmann sensor • 20μm holes, 162μm grid, direct detection • Designed by Imagine Optic 500 e. V, FWHM = 50μm data shot-noise limit spot position error [μm] 13. 5 μm pixels counts per spot [ADU] σ[μm]=0. 21 x FWHM[μm] / sqrt(Nph) SXR wavefront sensor designs - A Wojdyla – SRI 2018

Tender x-ray Hartmann sensor • Scintillator-based YAG: Ce • Optimized for 2 -10 ke. V • In collaboration with Imagine Optic SXR wavefront sensor designs - A Wojdyla – SRI 2018

Thank you for your attention! Many thanks to: Lei Huang (BNL) Julia Aquila (LBNL) Walan Grizolli (BNL) Weilun Chao (LBNL) Eric Gullikson (LBNL) Tony Warwick (LBNL) Ruben Reininger (ANL) Howard Padmore (ALS) Valeriy Yashchuck (LBNL) Luca Rebuffi (Sync Trieste) Dietmar Korn (Imagine Optics) Manuel Sanchez del Rio (ESRF) Guillaume Dovillaire (Imagine Optic) Acknowledgments This work is supported under DOE contract DE-FOA-0001414 and performed by the University of California, Lawrence Berkeley National Laboratory under the auspices of the U. S. SXR Department wavefront sensorof designs - A Wojdyla – SRI 2018 Energy, Contract No. DE-AC 02 -05 CH 11231.

We are looking for collaborators, and hiring engineers. We need you at ALS-U! jobs. lbl. gov We are looking for collaborators SXR wavefront sensor designs - A Wojdyla – SRI 2018

6 th International Diffraction Limited Storage Ring (DLSR) Workshop October 29 -31, 2018 – Berkley, CA (USA) Registration open: bit. ly/dlsr 2018 SXR wavefront sensor designs - A Wojdyla – SRI 2018 contact: awojdyla@lbl. gov

Hartmann sensor in converging geometry Toroidal mirror Wavefront sensor Example of reconstructed wavefront projection of the Hartmann grid on the CCD camera 1 mm q=2. 2 m d=0. 7 m We have conducted the experiments on the COSMIC beamline scattering branch, at a photon energy of 490 e. V. We tilted the last toroidal mirror by +/500 urad to observe the change in astigmatism and determine best angle. Wavefront with astigmatism removed (coma-dominated) SXR wavefront sensor designs - A Wojdyla – SRI 2018 Wavefront with defocus removed (astigmatism-dominated)

Fine alignment with WFS Simulations with OASYS/Shadow astigmatism tilt -1 mrad tilt defocus astigmatism coma Zoll index Zernike coefficient [a. u. ] tilt +1 mrad coma Zoll index SXR wavefront sensor designs - A Wojdyla – SRI 2018

Reflection-grating beam-splitter Slide from K Goldberg Duty cycle controls diffraction efficiency. M 3 operate here beamsplitter Example calculated for λ = 1 nm, θ = 1°, SXR wavefront sensor designs - A Wojdyla – SRI 2018 And 5 nm surface relief.

Scintillator efficiency • YAG: ce yield ~10 phvis/ph. SXR • Collection efficiency… (0. 12 NA)^2/2: – 0. 72% incoherent efficiency • 5 x demag • Small distortion (<1 px) • 2 e- dark noise SXR wavefront sensor designs - A Wojdyla – SRI 2018 22