1 BROOKHAVEN SCIENCE ASSOCIATES 0.1-meV Optics Update Yong Cai Inelastic X-ray Scattering Group Experimental Facilities Division, NSLS-II Experimental Facilities Advisory Committee Meeting April 23-24, 2009

2 BROOKHAVEN SCIENCE ASSOCIATES The IXS Group Current Members  Xianrong Huang, 0.1 meV crystal optics  Marcelo Honnicke, multilayer mirrors for analyzer system  Jeff Keister, R&D beamline operation, upgrade and support  Zhong Zhong, NSLS D&I beamline spokesperson (M)  Scott Coburn, engineering design (50%)  Leo Reffi, mechanical design (on loan from design group)  Bill Struble, crystal cutting and lab support  Yong Cai, IXS beamline, group leader Future Members (per staffing plan)  Postdoctoral Fellow (Crystal fabrication, optics testing, etc.) – offer accepted, to start around June 1  Scientific Associate (Crystal fabrication lab) – Searching  Beamline Scientist (IXS beamline) - Searching

3 BROOKHAVEN SCIENCE ASSOCIATES Outline Summary of progress to date, issues & plan Current optical scheme and technical challenges Near-term milestones and longer-term plan Summary

4 BROOKHAVEN SCIENCE ASSOCIATES Summary of Progress to Date, Issues & Plan Major progress in building up the infrastructure to support the R&D program  R&D beamline and optics test end station at NSLS (X16A)  Crystal fabrication labs (Bldg 703) R&D activities have been focused on gaining a better understanding of the technical requirements and challenges of the optics  0.1meV crystal optics  Multilayer mirrors Issues and plan  Crystal fabrication capabilities (equipment & staffing)  Access to more advanced light source(s) for prototyping Since last EFAC Meeting (May 5-7, 2008)

5 BROOKHAVEN SCIENCE ASSOCIATES 0.1meV Crystal Optics CDW CDDW CDW and CDDW optics schemes at 9.1 keV proposed by Yu. Shvyd’ko, verified by our dynamical theory calculations (Xianrong Huang) 0.11 meV Large angular acceptance (>100 µrad) High efficiency (~50%) Sharp tails (Borrmann effect), more important than resolution!

6 BROOKHAVEN SCIENCE ASSOCIATES Beamline and Spectrometer Optics Layout ~20 μrad Divergence ΔE of CDWΔE of CDDW Θ e (= 90˚ – φ) Length of D 2 meV1 meV4.5˚120 mm 0.7 meV0.3 meV1.5˚380 mm 0.2 meV 0.1 meV0.4˚1400 mm! Major parameters determined and verified for E = 9.13 keV, Δ θ e = 5 µrad, and h = 0.5 mm Comb crystal proposed by Yu. Shvyd’ko: a possible solution to the long D crystal length, but a major challenge to fabricate (in progress)

7 BROOKHAVEN SCIENCE ASSOCIATES Comb Crystal Fabrication Current approach employed by APS: o Cut directly from a monolithic crystal. o Polishing the diffraction surface a major challenge. Alternative approach to be explored: o Prepare reference Si(100) surface from a monolithic block o Cut individual fins allowing fine polishing of diffraction surface o Align individual blocks using reference surface on symmetric backscattering Si(800) reflection o Mechanical positioning a challenge, but more solvable As-cut surface roughness 35.4 nm by AFM Reference surface Fine polishing Tilting  (  rad) Reference Si(800) reflection Θ 5mm 100mm

8 BROOKHAVEN SCIENCE ASSOCIATES CDDW for 1meV + Channel Cut Collimated  20  rad 55 No need for long D crystal Switchable between 0.1 and 1 meV Channel-cut (grazing 7  ) Require incident beam collimated to ≤20  rad no problem for mono analyzer needs high-precision mirror. CC causes ~20% efficiency loss Tails sharper than Lorentz

9 BROOKHAVEN SCIENCE ASSOCIATES Lattice homogeneity of the crystal:  d/d = ΔE/E ~ (0.1 meV/10 keV) Temperature uniformity and stability: ΔT ≤ 4 mK (Δd/d = αΔT and thermal coefficient of Si: α=2.56  K -1 ) Surface quality slope errors (straightness of surface): < 10 µrad, crystal bending (due to mounting or gravity sag): < 0.2 µrad, surface roughness (causes diffused scattering): < 2 nm Crystal angular stability: < 0.2 µrad as a result of energy tuning by angular rotation, independent of resolution 0.1 – 1 meV, CDW/CDDW analyzer requires 50~100:1 multilayer focusing mirrors for 5~10 mrad acceptance Other Major Technical Challenges

10 BROOKHAVEN SCIENCE ASSOCIATES Angular Stability Energy Tuning by D crystal rotation  : Tuning rate: 0.07 meV/µrad This implies also: o Angular vibrations of C,W, D all change , must be stable < 0.2  rad (independent of targeted energy resolution  E ) o Lattice bending due to gravity sag or mounting changes , so must be < 0.2  rad, for all C, W, D.

11 BROOKHAVEN SCIENCE ASSOCIATES Laterally Graded Multi-layer Mirror CDW or CDDW 0.2 – 0.3 mm Design Objectives:  Angular acceptance: 5 mrad x 5 mrad  To retain a q resolution of 0.01 nm -1 o Corresponding to ~0.1 mrad in horizontal acceptance at 9.1 keV or 20 µm transverse width at 200 mm from source. Possible solution: use area detector! o Laterally projected source size due to sample thickness may be a limiting factor, but not a severe problem due to lessen q resolution required at higher q. (0.1 mrad = 20 µm projected source size at 200mm) 5 mrad 0.1 mrad Horizontal Scattering Plane Strip Detector

12 BROOKHAVEN SCIENCE ASSOCIATES Ideal Mirror Figure CDW/CDDW Sample Sample – first focus (f 1 ) Parabolic ellipsoid (focusing collimator)  Horizontal collimation to 0.1 mrad or better is required in order to retain the q resolution!  Vertical focusing (up to 0.1 mrad) to minimize D crystal length for analyzer, but may limit the horizontal q resolution at low q.  Vertical collimation to less than 20 µrad may allow the use of 2 nd channel cut for resolution switching between 0.1 and 1 meV for the analyzer, and/or possible energy dispersive and q resolved detection in the vertical direction with an area detector  A real challenge to make!

13 BROOKHAVEN SCIENCE ASSOCIATES Alternative Mirror Configurations A single toroidal mirror to approximate the ideal surface Montel optics: parabolic (collimator) in a double bounce geometry (involving beam inversion of L-R and U-D) KB configuration A single mirror only for vertical focusing/collimating Horizontal angular acceptance of C crystal ~ 3mrad! Horizontal energy dispersion of D crystal: E(φ) = E 0 (1-φ 2 /2) Montel Optics (collimating) 0.2 m 10 m

14 BROOKHAVEN SCIENCE ASSOCIATES Other Works Accomplished Multilayer parameters determined and optimized both for parabolic and elliptical figures. o Mirror specifications for a non-graded flat surface Si or B 4 C layer 1.5 nm, W layer 1.0 nm, 100 bi-layers on Si substrate Theoretical peak reflectivity: 85% o Figure specifications In-house ray-tracing codes developed to examine performance of the multilayer mirrors including effects of slope error, roughness, and interlayer thickness fluctuation (δd/d). Actively in contact with possible vendors for test mirrors Test plan using R&D beamline at NSLS developed. FigureP (mm)Θ m (rad)δx (mm)δy (mm)d 1 (nm)d 2 (nm) Parabolic Elliptical

15 BROOKHAVEN SCIENCE ASSOCIATES First CDW-CDW Test at NSLS C,W D Proof of Principles: o Collimation effect of C crystal o Enhanced Bormann transmission of W crystal o Most importantly, the dispersion effect of the D crystal o  E = 10 meV achieved, possible causes being analyzed Tilting  (  rad) ΔE = 10 meV

16 BROOKHAVEN SCIENCE ASSOCIATES New CDW-CDW Test Aim for a more controlled study of the optics to understand conditions to achieve the targeted energy resolution. Verify sharp tail in resolution function with new optical path New C/W crystal to minimize strain Bill Struble’s first crystal With help from Shu Cheung

17 BROOKHAVEN SCIENCE ASSOCIATES Optics Test End Station 17 Current components designed to test CDW-CDW scheme with temperature control ovens Include a double-crystal diffraction / imaging stage for characterizing crystal quality Flexible and adaptable for other schemes (e.g., CDDW, comb crystals, …) Most components fabricated and assembled, and being installed on R&D beamline C/W crystal D crystal in oven

18 BROOKHAVEN SCIENCE ASSOCIATES Temperature Control Oven Room T Outer Oven, ΔT ≤ 0.5 mK Inner Oven, ΔT ≤ 0.25 mK First oven tests: passive controlling on both inner (~45 C) and outer (~35 C) ovens. Excellent stability; uniformity to be tested. ~15 hr D crystal

19 BROOKHAVEN SCIENCE ASSOCIATES Dedicated R&D Beamline at NSLS An existing PRT beamline, revived after major clean-up and repair effort of shielding, vacuum, safety and user interlock, beamline and endstation control, to allow initial testing of 0.1 meV resolution optics Existing beamline optics (a 1:1 focusing mirror and a DCM) found to be functional but required optimization, to be upgraded within 6-12 months. Beamline granted operation status since April 10, 2009 after beamline review and readiness walkthrough. (took just 1 year from inception to operation, but still a lot of work!) Source Mirror (1:1) Mono R&D beamline assembly Endstation

20 BROOKHAVEN SCIENCE ASSOCIATES Crystal Fabrication Labs EQUIPMENT X-ray Diffractometer / Blade Saw / Diamond Wire Saw Lapping Machine / Spindle Polisher / CMP Polisher Etching Hood High-precision dicing saw for Comb crystal fabrication Two labs being fit out, to be completed in April: Cutting / Lapping Lab major equipments: o Crystal Diffractometer (NSLS equipment) o Mark Blade Saw (NSLS equipment) o Diamond wire saw (delivered) o Lapping machine (delivered) o Strasbaugh Spindle Polisher (rough polishing) Polishing / Etching Lab major equipments: o ADT dicing saw (delivered) o Strasbaugh CMP polisher (superfine ~ 0.1 nm) o Strasbaugh Spindle Polisher (fine polishing) o Chemical etching hood and wet bench Partial operation in April Need to consolidate fabrication equipment and streamline fabrication process Too few staff with expertise in polishing and etching

21 BROOKHAVEN SCIENCE ASSOCIATES Overall Strategy and Near-Term Milestones CDW/CDDW prototypes 1meV  0.5meV  0.1meV Comb crystals fabrication and test Design and Develop collimating multilayer mirrors Overall strategy and timeline: 0.1 meV prototype spectrometer DateItemStatus June 2009 Actual measurement of the resolution function for CDW scheme. Looking for a sharper tail may be more important than the actual resolution. Still on schedule, waiting on completion of end station. Key areas to watch: new control system, ovens test, X16A mirror and mono. Sept 2009 Fabrication and testing of first comb crystal cut for 1meV. Energy resolution and efficiency measured. Still on schedule, need to push for bldg 703 labs. Hire of scientific associate to fill knowhow gap (etching and polishing). Short-term outsourcing Sept 2009 Fabrication and testing of multilayer mirror. Demonstrate required specs can be met. In progress, potential road block – the on-time delivery of mirror Nov 2009 Demonstration of the CDDW/CDDW scheme (beam pass thru all optics) Area to watch, continue investigation of alternative schemes

22 BROOKHAVEN SCIENCE ASSOCIATES Longer-Term Plan & Milestones 2010 Develop a prototype with 1meV resolution Strategy being considered: a Partner User Proposal with APS for Sector 30 Demonstration experiments on Plexiglas with 1meV resolution (real test of energy resolution and tail by scattering rather than diffraction) Full work on CDDW prototype to test 0.5 meV resolution (with comb crystals), including detailed exploration of crystal quality (defects, impurities, inhomogeneities), fabrication issues. Test and improve collimating/focusing multilayer mirrors Seek alternative approaches if encounter unexpected showstoppers 2011 Test and improve analyzer optics with multilayer mirrors Full work on CDDW prototype to test 0.1 meV resolution (with comb crystals) Finalize design

23 BROOKHAVEN SCIENCE ASSOCIATES Summary Excellent progress has been made in establishing the essential infrastructure to support the R&D program. Initial test results of the asymmetric dispersion optics prove the working principles of the optics. Key technical challenges to achieve the 0.1meV resolution for both the monochromator and analyzer are now well understood and being addressed. Need to streamline crystal fabrication capability within the NSLS-II project, and for prototyping a 1meV resolution instrument. A modified approach with intermediate staged goals may be necessary for the development of the IXS beamline.