1. Coherent X-ray Imaging Instrument
Sébastien Boutet
CXI Instrument Scientist

2. Outline CXI KB Mirrors New CXI Layout Reflective Coating
2 sample chambers in series
45 degree configuration

3. Coherent Diffractive Imaging of Biomolecules
Particle injection
LCLS pulse
Wavefront sensor or second detector
Noisy diffraction pattern
Combine measurements into 3D dataset
Gösta Huldt, Abraham Szöke, Janos Hajdu (J.Struct Biol, ERD-047)

4. CXI Instrument Location
Near Experimental Hall
X-ray Transport Tunnel
AMO
XPP
CXI
Endstation
XCS
Source to Sample distance : ~ 440 m
Far Experimental Hall

5. Far Experimental Hall CXI Control Room Coherent X-ray Imaging
Lab Area
XCS Control Room
Hutch #6
X-ray Correlation Spectroscopy
Instrument
Coherent X-ray Imaging
Instrument

6. Optics and Diagnostics (X-ray Transport Tunnel) Particle injector
0.1 micron
KB system
Optics and Diagnostics
(X-ray Transport Tunnel)
Particle injector
Diagnostics &
Second Detector
Ion Time of Flight
LCLS Beam
1 micron focus
KB system (not shown)
Sample Chamber with raster stage
Detector

7. Kirkpatrick-Baez Mirrors
Mirror pair to focus the X-ray beam
Each mirror focuses in 1 direction with elliptical curvature
CXI will have 2 pairs of KB mirrors
1 micron focus
Focal length = 8 meters
100 nm focus
Focal length = 0.7 meters
Tailor the focal spot to the sample

8. Specifications fully developed Two main issues remain
CXI KB Mirror Status
Specifications fully developed
Reviewed on October
Two main issues remain
Coating
45 degree orientation

9. Coating Requirements Energy range Damage resistance
> 75% reflectivity (for mirror pair) up to at least 8.3 keV
> 86% reflectivity for each mirror
Damage resistance
Capable of withstanding the full beam without any attenuation
Stable over many years
Preserves the figure and roughness of the substrate
Figure is more important than roughness
Flexibility for the future
LCLS could lase, with the current accelerator, up to 10.8 keV if the emmitance is good enough
We require at least some safety margin on the coating so it will still be reflective if the maximum fundamental energy of LCLS is larger then 8.3 keV
Preferably, we should be capable of using a 10.8 keV beam as well
Capable of reflecting the 3rd harmonic up to as high an energy as possible
Reduced radiation damage requirements for 3rd harmonic

10. Coating Options Incidence angle Materials 3.4 mrad B4C SiC Rh or Ru
Excellent reflectivity (>99%)
Light material
High damage threshold
Small energy range at 3.4 mrad incidence
SiC
Reflectivity not as good as B4C
Lower than B4C
Energy range larger than B4C for same incidence
Rh or Ru
High reflectivity over much larger energy range
If it could be used, we could make shorter mirrors with larger incidence
Low damage threshold
Too close for comfort without actual measurements
This approach is too risky
Rh/SiC, Ru/SiC, Rh/B4C Ru/B4C bilayers
Combine the high damage threshold of low Z material with high reflectivity of high Z material
Beam is reflected off top layer for fundamental energy
Reflection off bottom (high Z) layer for 3rd harmonic
Coating stability issues
Requires R&D

11. Coating Material Choice
2 Strips
First Strip
50 nm SiC
Only this strip will be deposited for sure
Second Strip
Choice 1
20 nm Rh
30 nm SiC
Choice 2
50 nm Rh only
Perform early damage experiments at LCLS before choosing second coating strip material
We may choose to leave it blank

12. Coating Underlayer FAC Recommendation, June 2008
“The project is investigating the use of a bilayer mirror with a 40 nm Rh layer capped with a 30 nm B4C layer. The goal would be to get high performance from the B4C layer at low photon energy and high performance from the Rh layer at higher photon energy. The committee was not enthusiastic about this approach. The mirrors are required to perform at an extremely high level to meet the design criteria. Whether the required interfacial roughness can be preserved when creating multiple interfaces between materials that have uncertain wetting characteristics and residual stresses is a significant risk. Even if almost ideal interfaces can be created, there will be subtle thickness variations across the mirror that could lead to complicated interlayer interference and coherence degradation. Finally, the stability of this structure under high instantaneous photon fluxes is uncertain.“
CXI KB System Procurement Review, October 2008
" If appropriate, consider having a Cr underlayer coating (under some or all coating strips). In the case of damage to the coating (due to radiation, etc.), I could remove the damage (lift off) the damaged coating by etching away the Cr underlayer to have the mirror re-coated, instead of the EXPENSIVE and time-consuming alternative of re-polishing / re-figuring. If Cr is unacceptable, other sub layers such as titanium may be considered."
These 2 recommendations are somewhat contradictory
Given the cost of the mirrors, this seems like a valid option to pursue
Does the FAC recommend pursuing the coating underlayer?

13. CXI Focusing Optics (Current Layout)
Be Lenses
1 micron KB
0.1 micron KB
60 m
All 3 focusing optics focus the beam at the same plane
8 m
0.7 m

14. CXI Focusing Optics (Current Layout)
1 micron KB
0.1 micron KB
8 m
0.7 m

15. Issues with Current CXI Layout
Lots of wasted space between the KB mirrors
~ 6 meters of vacuum spools
We need to guarantee the vacuum of the mirror chambers is never compromised by the sample chamber
Beam from 1 micron KB is too small after the second KB system to put a window
Window would not survive the beam
Impossible to “wheel in” a user sample chamber without removing the optics
Large displacement between the 3 focused beams
Most of the photons go through the sample chamber untouched
Can we find a way to reuse them and maximize output?
Project scope involves 2 sample chambers
The first would be temporary and discarded after the second chamber is ready
Can we find a way to continue using this first chamber?

16. CXI Components in the X-ray Transport Tunnel (XRT)
CXI Control Room
FEH Common Room
Beam Direction
FEH H5
Laser Table
2X Double Racks
5X Single Racks
Gas Cabinet
CXI Components in Far Experimental Hall Hutch 5 (FEH H5)
Reference Laser
Focusing Optics
Sample Environment
Diagnostics

17. Beam is Too Small for a Transmissive Window
1 micron focus beam is
15 microns wide
0.1 micron focus beam is
100x200 microns wide
0.1 micron and 1 micron foci

18. Different Beam Direction for Each Optic
Focal Plane
150 mm
1 micron KB
0.1 micron KB
Be Lenses
8 m
0.7 m
20 m
10 m

19. New CXI Layout Solutions
Put both sample chambers in series and have each KB system focus at different planes
Put KB1 system first and focus past the KB0.1 system
Allows differential pumping to protect mirrors and also the possibility to place a very thin (< 1 micron) (removable) window downstream of the KB0.1 system
Allows higher pressure (>10-5 torr) experiments without compromising the mirrors
Place Be lenses between the 2 sample chambers to refocus the 100 nm beam into the second sample chamber
Could get larger focus and also collimated “unfocused” beam in second chamber
All beams are on the same axis and only slightly (<20 mm) offset from each other
Simplifies the mechanics if we choose not to have the ability to move to the direct unfocused beam

20. Proposed CXI Focusing Optics Layout
1 micron focus
1 micron KB
0.1 micron KB
0.1 micron focus
Be Lenses
Refocus of 0.1 micron beam
8 m
0.7 m
Two different focal planes
The first set of mirrors focuses at the second focal plane

21. 1 micron Focus into Second Chamber
1 micron KB
Move the 0.1 micron KB and lenses away to use 1 micron beam in the second sample chamber
0.1 micron KB
Be Lenses
8 m
0.7 m

22. 100 nm Focus into First Chamber
0.1 micron KB
Move the 1 micron KB and lenses away to use 0.1 micron beam in the first sample chamber
1 micron KB
Be Lenses
8 m
0.7 m

23. 100 nm Focus into First Chamber and ~10 micron Focus into Second Chamber
0.1 micron KB
Be Lenses
Move the 1 micron KB away and insert the lenses close to the 0.1 micron focus to refocus into the second sample chamber
Could run two experiments in series by refocusing
1 micron KB
8 m
0.7 m

24. 100 nm Focus into First Chamber and Collimated Beam (~500 microns) into Second Chamber
0.1 micron KB
Be Lenses
Could get a collimated (unfocused) beam on the same axis as the KB0.1 beam with lenses at a different position
1 micron KB
8 m
0.7 m

25. Small Offset Between Focusing Optics

26. Beam would not Destroy a Transmissive Window
0.1 micron focus beam is
100x200 microns wide
0.1 micron focus

27. New CXI Layout Design Beam 1 micron KB Removable Chamber 0.1 micron KB
Differential Pumping
Be Lenses
Differential Pumping

28. Instrument Design Differential KB Mirrors Pumping Differential Pumping
Beam
0.1 micron Sample Chamber
Be Lenses and Diagnostics

29. Instrument Design 0.1 micron Sample Chamber Differential 0.1 micron KB
Pumping
0.1 micron KB
1 micron KB
Beam

30. Instrument Design Detector Stage Be Lenses and Diagnostics
Differential Pumping
Beam
1 micron Sample Chamber
0.1 micron Sample Chamber

31. New Layout Summary Allows serial experiment configuration
Allows separation of mirror vacuum
Allows the use of a thin window to separate KB0.1 mirror vacuum from 0.1 micron sample chamber
Allows the second chamber to be removed without disturbing the mirrors
Allows a user chamber to be attached if needed
Allows all CXI beams to be on the same axis and separated by less than 20 mm
Mechanics are somewhat simplified but we would still need to incline the entire beamline without the 45 degree mirror configuration
Also still need to have x and y motorization on every component

32. 45 degree Orientation Mounting Concept
Beam

33. ANSYS Analysis x y z

34. ANSYS Analysis x y z

35. Surface displacement

36. Wavefront Simulations
With Distortions
Without Distortions
Focal length of mirror is reduced by 0.2 % due to gravitational distortions

37. 45 degree Summary Metrology at 45 degrees is not possible today
Higher risks of not meeting the specs in assembled system
Mechanical simplification of the rest of the beamline is a clear advantage
New layout does not help if we keep the ability to use the direct beam
Early analysis indicates it should be feasible
Vendors are aware of the request and have already started to think about ways to implement it
We will continue to explore this option with more analysis but will set a drop-dead date in early 2009 by which we will make final decision

38. Seeking Advice from the FAC
On the choice of 2 coating strips
On the use of a chromium coating underlayer
On the proposed optical layout
On the risk-reward of the 45 degree mirror arrangement
On the need to maintain the ability to use the direct unfocused beam

39. Summary The CXI KB mirrors will use 2 coating strips
Only the first strip will be deposited until some experiment have occurred
CXI will explore the use of a Chromium coating underlayer which will allow the coatings to be washed off in case of damage
Use 2 sample chambers with each mirror pair producing a focused beam into one of the chambers
Continue to pursue the 45 degree mirror configuration
Maintain the ability to use the direct unfocused beam
With new optical layout, we could choose to abandon the previous 2 points with minimal loss of functionality and minimized increase in complexity
Without ability to use direct beam
Get effectively unfocused beam with the use of Be lenses
Comes at the cost of wavefront distortions from the use of 2 optical elements instead of none
Get a larger focal spot (> 1 micron) on the same axis as the KB beam
Comes at the cost of wavefront distortions from the use of 2 optical elements instead of 1