Coherent X-ray Imaging Instrument Sébastien Boutet CXI Instrument Scientist

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

Coherent Diffractive Imaging of Biomolecules Particle injection LCLS pulse Wavefront sensor or second detector Noisy diffraction pattern Combine 105-107 measurements into 3D dataset Gösta Huldt, Abraham Szöke, Janos Hajdu (J.Struct Biol, 2003 02-ERD-047)

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

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

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

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

Specifications fully developed Two main issues remain CXI KB Mirror Status Specifications fully developed Reviewed on October 8 2008 Two main issues remain Coating 45 degree orientation

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

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

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

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?

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

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

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?

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

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

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

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

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

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

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

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

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

Small Offset Between Focusing Optics

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

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

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

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

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

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

45 degree Orientation Mounting Concept Beam

ANSYS Analysis x y z

ANSYS Analysis x y z

Surface displacement

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

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

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

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