1. 1 BROOKHAVEN SCIENCE ASSOCIATES Coherent Hard X-ray (CHX) Beamline Update Andrei Fluerasu Coherent Hard X-ray Scattering Group Experimental Facilities Division, NSLS-II Experimental Facilities Advisory Committee Meeting April 23-24, 2009

2. 2 BROOKHAVEN SCIENCE ASSOCIATES CHX Team BL scientists : AF, Lutz Wiegart (to join Summer 2009), Lonny Berman, Lin Yang Beamline Advisory Team (BAT) ‏ Robert Leheny, Associate Prof., John Hopkins Univ. (spokesperson) ‏ Karl Ludwig, Professor, Boston University Laurence Lurio, Associate Professor, Northern Illinois University Simon Mochrie, Professor, Yale University Lois Pollack, Associate Professor, Cornell University Aymeric Robert, Instrument Scientist, LUSI/LCLS, SLAC Alec Sandy, Physicist, 8-ID, APS, ANL Oleg Shpyrko, Assistant Professor, University of California San Diego Mark Sutton, Professor, McGill University Management and engineering support : Andrew Broadbent, Qun Shen, Konstantine Kaznatcheev, Mary Carlucci-Dayton Michael Loftus, Lewis Doom, Viswanath Ravindranath, Sushil Sharma

3. 3 BROOKHAVEN SCIENCE ASSOCIATES Outline Scientific Mission and technical requirements Recommendations from recent reviews Beamline Layout Overview Source and front end undulator; requirements for filling modes Optics Enclosure coherence preservation by mirrors and multilayers; focusing with Be CRLs; Pink beam operation; DCM – heat load Experimental Station general layout of the experimental station Summary and Outlook

4. 4 BROOKHAVEN SCIENCE ASSOCIATES Nanoscale dynamics in inorganic materials: WAXS Molecular dynamics in metallic and orientational glasses  -beam SAXS CDI on “large” (e.g. a cell) samples Galssy materials; Driven and out-of-equilibrium systems Nanostructured complex fluids: polymers, colloids Biological systems: proteins in solution, biomembranes Fluid surfaces and interfaces CHX beamline: Technical Requirements and Scientific Mission  Flexible instrument optimized XPCS in SAXS, GI-SAXS and WAXS geometries. Will also provide an excellent instrument for  -beam SAXS & CDI on “large” samples – e.g. cells  Scientific opportunities for XPCS @ NSLS-II P. Falus, S.G.J. Mochrie et al. O.Shpyrko et al.

5. 5 BROOKHAVEN SCIENCE ASSOCIATES  Avoid degrading the source brilliance minimum number of windows; materials chosen carefully Optics – polished to the best figure, manufactured from defect-free Si, Ge or SiC to minimize the disturbance of the wavefronts CHX: Main Design Objectives  XPCS is a signal-starved technique. Every coherent photon must make it to the sample  Stability Vertical focusing minimize vibrations, heat load, etc

6. 6 BROOKHAVEN SCIENCE ASSOCIATES CommentResponse investigate whether accommodation of a microbeam SAXS capability compromises the primary XPCS mission of the beamline... BL design focused on XPCS. However, with a slightly different tuning and sample environment the BL will also be excellent for  -beam SAXS and CDI investigate the possibility to accommodate limited CDI take note of the structure of the electron beam, especially for studies of the fastest time scales, and consider the need to normalize incident beam fluctuations Ongoing interaction with ASD concerning filling mode, bunch structure. take note of the importance of “smart” detectors to ensure the success of the XPCS program at the fastest time scale On-going R&D program - P. Siddons. A first prototype (100 x 100 pix) is in development devote early attention to developing mirror and ML optics specifications, and how to characterize them... Need for 100 nrad optics. R&D - coh. preservation. Recent Recommendations from EFAC and DOE reviews }

7. 7 BROOKHAVEN SCIENCE ASSOCIATES 1 st BAT Meeting – Dec. '08 Main goal of CHX beamline - studies of dynamics by XPCS. Other techniques (  -beam SAXS, CDI) only if possible without compromising performance Detectors are the MOST important (and highest risk) part of the beamline. NSLS-II should advocate for detector development XPCS in a wide angle scattering geometry (WAXS) should be included in the initial scope Limit the power load by a first, high heat load aperture Be CRLs appear as promising for vertical focusing – more studies regarding coherence preservation will be required Role of mulitlayers as a “wider band gap monochromator” was questioned in a layout that includes also a mirror Investigate the option of cryogenically cooling the DCM (with reference to Petra-III which adopted this solution) ‏ BL scientist should be encouraged to remain active in the field and engage into collaborations with other researchers / other facilities Major Recommendations: !

8. 8 BROOKHAVEN SCIENCE ASSOCIATES Beamline Layout Relatively short source-sample distance and vertical focusing allow to use a full coherent mode e.g. 200  m (V) x 20  m (H) by focusing the beam to a 20  m (V) x 20  m (H) spot Large sample detector distance allows to have (relatively) large speckle sizes and resolve them with fast detectors which will, very likely, have relatively large pixels e.g. < 100  m. The WAXS instrument will use additional focusing (H and V) to increase speckle size and resolution.

9. 9 BROOKHAVEN SCIENCE ASSOCIATES Source and Front End Source properties Low-  straight → B=2x10 21 [ph/(s · mrad 2 · mm 2 · 0.1% bw)] U20 IVU (3 m); E=6-15 keV (I c = 2 B/4)

10. 10 BROOKHAVEN SCIENCE ASSOCIATES Source: requirements for filling mode and uniformity  fast XPCS requires a quasi-DC source (uniform filling)  ‏ Need to perform simulations in order to determine how to perform XPCS with the baseline filling mode: ESRF 7/8+1 filling: train of 868 bunches (7/8 of the SR circ.) filled with 200 mA (0.23 mA / bunch). Both edges of the train are filled with 1 mA single bunch. The remaining 1/8 gap is filled in its center with a cleaned 2 mA single bunch. Refill time ~ 5 min. Example of noise in g (2) form a 7/8+1 filling mode at ESRF g (2) = g (2) SR x g (2) sample ~1000 stored bunches; average current stability 1% over all the stored bunches; intensity variation between bunch that was stored for the longest time and the most recently filled – 20 %; single bunch train injection every ~ 1 minute; the injected pulse train “walks” around the bunch patters shifting the boundary between the oldest and the most recently injected bunches; each injection will result in a disturbance to the beam which will damp in 5 to 30 ms; (more DWs – faster damping time)  Slow XPCS @ NSLS-II will benefit of the long lifetime (top-up mode) ‏

11. 11 BROOKHAVEN SCIENCE ASSOCIATES Optics Enclosure (“FOE”) ‏ Primary slits ~100  m(H) x 500  m(V) P<8W (160 W/mm 2 ) note: placed in Front End White beam mirror H deflecting stops bremsstrahlung in OE provides (some) high harmonic rejection heat sink: ~30 mm long footprint P ~ 0.6 W/mm 2 Secondary slits Be Compound Refractive Lenses – vertical focusing White beam stop, pink beam shutter Monochromator: Vertical Si(111) DCM; small offset; cryo-cooling (P/A > 20 W/mm 2, P ~ 6W) Pink Beam: H-deflecting 2 x Multilayer mono, H 2 O cooling,  =1-2 ˚, L~ 5.5 mm, P < 6 W/mm 2

12. 12 BROOKHAVEN SCIENCE ASSOCIATES Mirrors: slope error requirements h(x)=h Sin(  x/L) => h'(x)= h *  / L Cos(  x/L) ‏ Slope error: PV= ‏ 2h  /L=1.25  rad; RMS=h  /L*1/2 1/2 =0.88  rad Max. deflection angle: 2*2h  /L =2.5  rad Smallest speckle size to resolve: s= /D~1 Å / 30  m=3.3  rad Best figure error that manufacturers can guarantee today (3-2 nm) is not optimal for XPCS Some R&D effort is required in order to achieve the desired figure errors Slope errors of 100 nrad will be required for coherence or high resolution applications @ NSLS-II ! Slope errors of 100 nrad will be required for coherence or high resolution applications @ NSLS-II !

13. 13 BROOKHAVEN SCIENCE ASSOCIATES Coherence Preservation by Mirrors & Multilayers on On-going R&D project aiming at evaluating / controlling the effect that mirrors and MLs have on the wavefront of the coherent X-ray beam. E=11 keV (ID06, ESRF), WSi 2 /Si ML, 100  m B fiber, 1 st order reflection (reflectivity ~ 0.7) ‏ A. Fluerasu, O. Chubar, R. Conley, L. Berman, A. Snigirev (ESRF), work in progress

14. 14 BROOKHAVEN SCIENCE ASSOCIATES At wavelength tests - further steps Coherence preservation by multilayers Theoretical work on phase retrieval from in-line holograms O. Chubar, A. Snigirev, A. Fluerasu et al. I. Robinson et al. Phys. Rev. B 52, 9917 (1992) (1D speckle from ML) Aim: retrieve the surface profile, power spectral density function Coherence preservation by mirrors, focusing elements Perform tests on “test” samples purchased from different vendors, polished by different methods Perform test with novel focusing optics: large acceptance Be lenses, linear Be lenses, coherence preservation, etc Perform more “realistic” tests – high heat load in white or pink beam, use the elements under test as “source” as opposed to as “samples”, etc Need for an NSLS-II R&D activity (all BLs) & operating budget A. Madsen et al., ID 10 ESRF

15. 15 BROOKHAVEN SCIENCE ASSOCIATES Focusing with Be CRLs Be compound refractive lenses offer the best and most reliable way to focus the beam for SAXS-XPCS they are in user operation at ID10, ESRF and provide an efficient way of using the full vertical coherent beam without any noticeable loss in contrast - no focusing - V. focusing (CRL) ‏ ID 10, ESRF

16. 16 BROOKHAVEN SCIENCE ASSOCIATES Pink Beam: Double Multilayer Monochromator Pink beam device Natural line width e.g. for 3m long U20 IVU most typically working on the 3 rd or 5 th harmonic  E/E~1/nN<1/450 smaller than the typical bandwith of ML structures (~ 1%) ‏ Multilayers: provide the only practical way to obtain an efficient pink beam operation with good harmonic rejection (e.g. < 10 -3 -10 -4 ) at medium energy SRs ! vs.

17. 17 BROOKHAVEN SCIENCE ASSOCIATES Conclusions of FEA for the DCM: Sharp “thermal bump” if water cooling is used due to small beam ‏. Slope errors are ~ 20  rad irrespective of cooling geometry Cryogenic cooling will be required to maintain the slope error < 0.2 nrad Vibrations issue will be addressed by the mechanical design (seek advice and inspiration from NSLS, 26-ID- APS, Petra-III, …) V. Ravindranath, L. Berman DCM - Heat Load

18. 18 BROOKHAVEN SCIENCE ASSOCIATES Beamline layout – Experimental station Detector for SAXS - maximize sample – detector distance  Local optics on granite block (or optical table) Vert. and Horiz. Focusing (KB, Z. plates...) ‏ Local mirror(s) for GI-SAXS on liquid surfaces BPM (quadrant or 32-ant – P. Siddons) ‏ exit window, slits, etc.  Detector WAXS  -beam SAXS L=0.5-2 m, full 90   Detector SAXS  Detector stage  Beam stop, etc  Sample stage goniometer on-axis microscope guard slits, etc.

19. 19 BROOKHAVEN SCIENCE ASSOCIATES Need for detectors for XPCS Development of a fast (0.1  s) and “smart” (integrated correlators) pixel detector Pete Siddons, NSLS – exploratory study related to detectors that are of importance to NSLS-II, particularly an XPCS detector – First prototype in progress! Other detectors of interest photon-ccounting det. eff~100% @ 8keV Medipix detector : 1kHz, 55  m pixel size Pilatus detector : 100 Hz, 172  m pixel size Pilatus-II detector : ~1 kHz, ~80  m pixel size Array of APDs 'collection' of point detectors - > limitations in stud. non-ergodig systems - > available, possibility to implement with an array of hardware (e.g. FPGA) correlators

20. 20 BROOKHAVEN SCIENCE ASSOCIATES Summary and Outlook Beamline conceptual design is on-track and advancing well towards its completion (09/2009) ‏ Beamline budget ($10.04M) seems adequate even though it was calculated for a beamline (CD-2) which bears little resemblance with the current layout Risk factor: availability of fast (1 MHz) photon-counting pixel detectors with small-enough pixel size. Mitigation: possible use of APD arrays (albeit 0D and not 2D detectors) ‏ On-going research program (not yet funded through an official R&D) aiming at obtaining mirrors and multilayers with required figure errors Future steps: Finalize the comprehensive cost estimate Bremsstrahlung and SR ray tracing (stopping white beam in FOE) ‏ Establish (more) precise requirements for filling modes and bunch to bunch variations