1. NSLS-II Soft X-ray Undulator Beamlines
Steve Hulberta
Dario Arenaa
Cecilia Sánchez-Hankea
Ruben Reiningerb
aBrookhaven National Laboratory
bScientific Answers & Solutions, Madison, WI
Cylindrical Collimating Mirror
EPU
Elliptical cylinder
KB refocusing mirrors
Exit Slit
Experimental
Station
Plane Mirror
Plane Grating
Beam Chopper

2. NSLS-II source brightness

3. Higher harmonic interference: use QEPU
Source polarization: linear (horiz., vert. or any angle in between), circular, or elliptical

4. Proposed NSLS-II soft x-ray undulator beamlines
High flux
Soft x-ray imaging and coherent scattering
High resolution
Soft x-ray resonant magnetic and inelastic scattering (XRMS, RIXS)
Coherent
XRMS
Imaging
RIXS
Source: Two 2m-long EPUs (EPU42 or EPU45) located in a 5m NSLS-II straight section.
Operating modes: (1) uncanted and phased as a single 4m-long EPU, or (2) canted, by ~0.25 mrad, for fast-switching polarization capability.

5. High resolution soft x-ray undulator beamline : XRS, XRMS
XRS, XRMS (x-ray resonant [magnetic] scattering) endstation
Scientific themes / drivers:
1. Ordering Phenomena in Correlated Electron Materials
2. Magnetic multilayers, superlattices & spintronic materials / devices
3. Nanomagnetism: patterned & self-assembled
4. “Soft” materials (e.g. complex polymers; C, N, O K-edges)
Beamline requirements
- small spot size
>4 mm spot overfills ~100 mm crystal at critical angle of ~4° (h=700eV)
- high energy resolution (select different multiplet states)
- high flux (detect weak, diffuse features in scattered beam)
Comparable endstations (incomplete list)
1. NSLS X1B, X13A, U4B
2. ALS BL 4.0.1
3. APS 4-ID-C
4. ESRF ID-08 (N. Brookes), Rogalev BL, XMaS
5. Diamond: Peter Hatton endstation, BLADE
6. BESSY-II: Helmut Zabel endstation
7. Pohang LS: J-H Park BL
8. Swiss Light Source
9. Spring-8

6. High resolution soft x-ray undulator beamline : RIXS
RIXS (resonant inelastic x-ray scattering) endstation
Scientific themes / drivers:
1. Correlated Electron Materials
low energy excitations (excitions, orbitons, HTc “stripe” formation, etc.)
field- and temperature-driven phase transitions
bulk sensitivity
2. Organic molecules (incl. fullerenes, nanotubes)
Beamline requirements
- Small spot size (collect large solid angle, possibly no entrance slit)
- Very good energy resolution (precise selection of initial state)
- Highest flux possible (very low inelastic cross section)
Comparable endstations (incomplete list)
1. NSLS X1B (commercial Scienta analyzer)
2. MAX-III (J. Nordgren program)
3. ALS beamlines 7.0.1, 8.0.1, MERLIN (lower energy)
4. ESRF: AXES instrument (U. of Milan)
5. Swiss Light Source: SAXES
6. ELETTRA: ComIXS, BACH beam line

7. High flux soft x-ray undulator beamline : Coherent Scattering
Techniques: scattering, diffraction, coherent SAXS, diffraction imaging, holography,…
Scientific themes / drivers:
image the mesoscopic non-crystalline world (few x 10nm resolution), e.g. large cells, magnetic domains, …
measure time-dependent fluctuations in materials (correlated spectroscopy)
3D imaging of granular materials (with grains around 30 nm)
Beamline requirements (with 2013-state-of-the-art optics)
flux > 1013 photons/s on sample
beam size ~few m on pinhole
resolving power ~104
Comparable endstations (incomplete list)
ALS – Cryo-capable Diffraction and Topography (transmission and reflectivity)
ALS – Steve Kevan’s Flange-o-Saurus
SSRL – speckle; EPU
BESSY
ESRF - Goedkoop; Van der Laan
NSLS - CCD based (transmission)
Eisebit & Luening, Nature 432, (2004)

8. High flux soft x-ray undulator beamline : Microscopy
Techniques: STXM, phase contrast scope, full field scope, PEEM, spectro-scopy, …
Scientific themes / drivers:
Imaging nano- and mesoscopic world, simultaneous spectroscopic measurements
Imaging of single nano-elements , nano-contacts, or nano-magnets, to understand isolated behavior (no collective phenomena)
Structural and electronic information, differences between boundaries/interfaces and bulk.
Beamline requirements (with 2013-state-of-the-art optics)
resolving power ~104
STXM: flux > 1012 photons/s on sample, beam size 10m x 10m on Fresnel zone plate (full transverse coherence), <10nm x <10nm on sample
PEEM: flux > few x 1013 photons/s on sample, beam size ~few m on sample
Magnification
Acceleration, focusing
and magnification
Energy and angle selection
Comparable endstations (incomplete list)
NSLS/CFN, ALS, BESSY, ESRF, SLS, Trieste, Spring8, Pohang Light Source, Diamond, Soleil, HASYLAB, …
PEEM

9. Soft x-ray beamline design: VLS PGM illuminated by collimated light
Possible planarM1
Rapid Switching: change M2 and M4
Side View
Beamline
High resolution
High flux
Source to M1
27m
30m
M1 to M2 1m
M2 to M3
PGM design
M2 to grating
~2m
Grating to exit slit
20m
10m
Exit slit to M4
1.85m
M4 to M5
0.5m
M5 to sample
1.0m
Total
53.35m
46.35m
Horizontal Focusing by M :1

10. Sample spot size and divergence Req’d figure error
h=200eV: h=2.3m, v=1.1m
h=1000eV: h=2.1m, v=1.1m
h=200eV: h’=1.1mrad, v’=0.44mrad
h=1000eV: h’=0.8mrad, v’=0.3mrad
100nrad RMS planes
0.5rad RMS Elliptical, cylinder meridional
Req’d figure error

11. Calculated flux & resolving power
Higher resolution beamline
105 rp; 104 rp
Higher flux beamline
2104 rp; 5103 rp
Each soft x-ray undulator beamline would be equipped with at least 3 gratings, interchangeable under computer control

12. 3D schematic of soft x-ray undulator layout
Cylindrical Collimating Mirror
EPU
Elliptical cylinder
KB refocusing mirrors
Exit Slit
Experimental
Station
Plane Mirror
Plane Grating
Beam Chopper

13. Canted undulator optical schematic, polarization switching
Side view
Single beam mode M5 M2 M3
Exit slit M4 M1
Planar
gratings
RCP
LCP
RCP
LCP M5
Exit slit
Top view
Single beam mode M3 M4 M2
Planar
gratings M1
Mechanical
Chopper M5
Top view
Fast switching mode M3 M4
Exit slit M2
RCP
LCP
Planar
gratings M1
RCP
LCP

14. To ensure complete overlap, defocus and/or
Spot sizes on sample, dual (canted) undulator beams
Near, e.g. LCP, beam
Far, e.g. RCP, beam
h=200eV: h=2.2m, v=1.1m
h=1000eV: h=2.4m, v=1.1m
h=200eV: h=2.6m, v=1.1m
h=1000eV: h=2.0m, v=1.1m
To ensure complete overlap, defocus and/or
trim with baffles

15. Comparisons of selected soft x-ray beamlines in the US

16. NSLS-II soft x-ray undulator beamlines
High-resolution, high-flux, polarization-switchable, soft x-ray beamline design, well matched to the high-brightness NSLS-II accelerator design
Example soft x-ray scientific programs well matched to this beamline design: XRMS, RIXS, imaging, coherent scattering
Actual buildout of soft x-ray beamlines will be based on the NSLS-II scientific program, including input from all stakeholders (NSLS-II staff, EFAC, NSLS-II users, …).