A Hard X-Ray Coherent Scattering Beamline for NSLS-II

Alec Sandy,

X-Ray Science Division

Argonne National Laboratory

& SAXS?

2

Acknowledgements

Design to be discussed today represents work primarily performed by:

– Scott Coburn, Brookhaven National Laboratory

– Simon Mochrie, Yale University

– Ian Robinson, University College London

Many helpful conversations with:

– Larry Lurio, Northern Illinois University

– Brian Stephenson, Argonne National Laboratory

– Mark Sutton, McGill University

3

Outline

Beamline Mission

Supported Techniques

Lay of the Land

NSLS-II Strengths

Beamline Requirements

Design Philosophy

Conceptual Design

Possible Discussion Items

4

Beamline Mission

Application of hard (7–12 keV) coherent x-rays to the study of nanoscale dynamics and structure of complex materials

– Equilibrium dynamics and fluctuations about the evolution to equilibrium in colloids, polymers, membranes, concentrated proteins, glasses, …

– 3-D imaging of microscopic non-crystalline objects such as catalytically active materials, cavities within steel, defect structures in magnetic multilayers, cellular imaging

Mark A. Pfeifer, Garth J. Williams, Ivan A. Vartanyants, Ross Harder, and Ian K. Robinson, “Three-dimensional mapping of a deformation field inside a nanocrystal,” Nature 442, 63 (2006)

O. G. Shpyrko, E. D. Isaacs, J. M. Logan, Yejun Feng, G. Aeppli, R. Jaramillo, H. C. Kim, T. F. Rosenbaum, P. Zschack, M. Sprung, S. Narayanan, and A. R. Sandy; "Direct measurement of antiferromagnetic domain fluctuations," Nature 447, 68

5

Supported Techniques

Techniques to be employed

– X-ray photon correlation spectroscopy (XPCS) or x-ray intensity fluctuation spectroscopy (XIFS)• X-ray analog of dynamic light scattering

– Coherent x-ray diffraction (CXD)• Coherent x-rays and intensity over-sampling to determine the

nanoscale structure of micron sized crystals via phase retrieval and inversion

– Coherent x-ray diffraction imaging (CXDI)• Coherent x-rays and intensity over-sampling to determine the

nanoscale structure of non-periodic objects via phase retrieval and inversion– Lensless imaging, ptychography, CXDI

– SAXS

– Imaging• Phase contrast imaging• Diffraction enhanced imaging

6

Lay of the Land ESRF (6 GeV)

– General purpose beamline evolving to XPCS and CXD(I) specialization• Small Q XPCS, considerably less large Q XPCS and CXDI: ID-10

APS (7 GeV)– Dedicated XPCS beamline but not (yet) CXD/CXDI

• Small Q XPCS and considerably less large Q XPCS: 8-ID• CXD (large Q) but limited GU program: 34-ID• CXDI (small Q): ?

SPRing 8– Little activity

SLS (2.4 GeV)– SAXS, XPCS, CXDI: cSAXS

• Sophisticated and advanced detector program but lower energy ring and shorter beamlines

Petra III (6.0 GeV)– Tandem endstations: large Q XPCS, CXD and XPCS and CXDI

• Planning phase: 2009–2010 completion—long straights and beamlines Diamond (3.0 GeV)

– USAXS/XPCS branch, CXDI/CXD multiplexed with full-field imaging: I13• 250 m beamline length• Planning phase: 2010–2011 completion

7

NSLS-II Strengths

Unprecedented brightness

– Both XPCS and CXD remain signal starved techniques• CXD “improves” linearly with brightness– Measurement times from hours to minutes

• XPCS “improves” quadratically with brightness– 30× more incident intensity → 1,000× faster dynamics

Existing strong community in soft condensed matter science and a relatively local XPCS community

Soft and hard x-ray coherent x-ray scattering Existing, innovative detector program coupled to activities on the

experiment floor

– Leverage for XPCS and CXD detector development Learn from others’ mistakes and capitalize on several years of operational

experience at other 3rd generation coherence-based beamlines

– ESRF ID10 (XPCS) and APS 8-ID (XPCS) both originally built to satisfy broad scientific mission

8

Beamline Requirements

Coherent flux!

Stability

– Parasitically fluctuating signals contaminate XPCS time autocorrelation analysis

– Parasitically fluctuating signals significantly complicate phase retrieval

Beamtime

– Brilliance-hungry techniques so maximize the beamtime delivered to experimental stations

Long beamline

– High demagnification focusing for CXD and large Q XPCS

– Reduced flux density for radiation sensitive samples

Long small angle XPCS station

– “Smart” detectors likely to have larger pixels than today’s

Minimal energy tunability

– Above energy of large resonant enhancements

9

Design Philosophy

KISS – Keep it simple, stupid!

– Coherent flux• Select the coherent portion of the x-ray beam as far upstream as

possible to eliminate power mitigation issues downstream– Secondary source/pinhole

• Preserve the coherence delivered by the undulator and reduce parasitic scattering– Minimize the number of beamline optics

– Stability– Minimize the number of beamline optics

– Beamtime• Beam comprised of many horizontal coherence lengths—split the

beam and feed independent end stations

– Limited/infrequent energy tunability• Compatible with split beam operations

10

Conceptual Design-Secondary Source/Pinhole

Secondary source or pinhole

– Extract, in the horizontal, only a coherent fraction of the x-ray beam

Undulator

S1 S2

D1 D2

Sample

SecondarySource ( 27 m)

Pixel size = p

11

Conceptual Design-Secondary Source/Pinhole

Coherent diffraction over-sampling

– λD2/S2 > 2p

Far field

– S2/D2 > λ / S2

Coherent illumination

– S2 < λD1/S1

Use entire source

– 2σx < (S1 + S2) D0 / D1

Undulator

S1 S2

D1 D2

Sample

SecondarySource ( 27 m)

Pixel size = p

Item CXD, large Q XPCS Value

XPCS, CXDI Value

Max. sample to detector distance

3 m 10 m

S2 size 100 µm 30 µm

Maximum S1 secondary source size

80 µm 80 µm

Pixel resolution 20 µm 80 µm

12

Conceptual Design-Beam Splitting

2 secondary sources or pinholes in the FOE

– Multiplexed operation creates twice as much beamtime

– Small horizontal-bounce mirrors used to extract coherent fraction of the beam (in the horizontal)

– 2× mirror deflections and long beamline creates sufficient horizontal clearance

CXS FOE Beam Splitting Concept-Plan View

Hi-pass filter

Slit

Mirrors = secondary source or pinhole

½ Slit

WB Stop

ShutterWhite beam (WB)

Power-reducing aperture

Pink beam

12 mrad

13

Conceptual Design-Optical Layout

Simplified version of the optical layout

– Undulator• Future upgrade to tandem devices (rather than canted)

– Standard operating energy goal 12 keV• Low K value → less power• Less sample radiation damage

– High demagnification optics• Kinoform lenses or KB mirrors

14

Conceptual Design-Floor Layout

Stations

– Large Q XPCS and CXD station• High demagnification

optics• Diffractometer

– Small Q XPCS and CXDI station• Pinhole “SAXS”• Vertically focusing

optics

– SOE• Monochromators × 2• Optics?

– FOE

15

Conceptual Design-Small Q XPCS and CXDI Station Requirements

50 m from the source and 15 m long × 4 m wide

– Pinhole SAXS set-up

– 3 or more heavy-duty motorized support tables

1. High demagnification optics and collimating/guard apertures

– Vertical focusing to reduce the vertical coherence length

– Collimating and guard apertures

– All in vacuum where possible

2. Sample environment

– Flow cells

– In vacuum positioning

3. Long flight path and detector support assembly

– Smart detectors

– On-the-fly compression, on-board correlation

16

Conceptual Design-Large Q XPCS and CXD Station

Requirements 100 m from source and 6 m long × 6 m wide

– Optics table• High demagnification nanofocusing optics– KB mirror, kinoform lens, zone plate

– Large load capacity precision diffractometer and/or large load hexapod with ≤ 3 m detector arm

– Optical microscopy/fluorescence detectors for sample alignment and registration

– Small pixel, high dynamic range direct detection area detector

Alio Industries

Silicon kinoform lensK. Evans-Lutterodt et al., Opt. Express

17

Some Possible Issues for Discussion

Long beamline– Conceptual design only but significant rethinking required if not allowed

Mirrors or crystals for beam splitting Split beam vis-à-vis operational support

– Canted versus split beam beamlines Which “imaging” techniques, if any, belong as part of the beamline?

– Lensless imaging/ptychography/coherent diffractive imaging– Phase contrast imaging– Diffraction enhanced imaging

Vertical focusing further upstream– Large vertical correlation can not be used so eliminate from the start?

Energy gap– ≥ 7 keV for hard coherent x-ray scattering versus ≤ 2 keV for soft x-ray

coherent scattering/imaging Sample radiation damage Detectors, detectors, detectors!

– Now is the time to worry about detectors