Transcript CXI
SLAC National Accelerator Laboratory Coherent X-ray Imaging Instrument Sébastien Boutet CXI Instrument Scientist Nov 12 2008 Coherent X-ray Imaging 1 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Outline CXI KB Mirrors Reflective Coating New CXI Layout 2 sample chambers in series 45 degree configuration Nov 12 2008 Coherent X-ray Imaging 2 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Coherent Diffractive Imaging of Biomolecules Particle injection LCLS pulse Noisy diffraction pattern Combine 105-107 measurements into 3D dataset Nov 12 2008 Coherent X-ray Imaging 3 Wavefront sensor or second detector Gösta Huldt, Abraham Szöke, Janos Hajdu (J.Struct Biol, 2003 02ERD-047) Sébastien Boutet [email protected] SLAC National Accelerator Laboratory CXI Instrument Location Near Experimental Hall AMO X-ray Transport Tunnel XPP XCS CXI Endstation Source to Sample distance : ~ 440 m Far Experimental Hall Nov 12 2008 Coherent X-ray Imaging 4 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Far Experimental Hall CXI Control Room XCS Control Room Lab Area Hutch #6 X-ray Correlation Spectroscopy Instrument Nov 12 2008 Coherent X-ray Imaging Coherent X-ray Imaging Instrument 5 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Particle injector 0.1 micron KB system Diagnostics & Second Detector Optics and Diagnostics (X-ray Transport Tunnel) Ion Time of Flight 1 micron focus KB system (not shown) Sample Chamber with raster stage Detector Nov 12 2008 Coherent X-ray Imaging 6 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 Nov 12 2008 Coherent X-ray Imaging 7 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory CXI KB Mirror Status Specifications fully developed Reviewed on October 8 2008 Two main issues remain Coating 45 degree orientation Nov 12 2008 Coherent X-ray Imaging 8 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Coating Requirements Energy range > 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 Nov 12 2008 Coherent X-ray Imaging 9 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Coating Options Incidence angle 3.4 mrad Materials B4C Excellent reflectivity (>99%) Light material High damage threshold Small energy range at 3.4 mrad incidence SiC Reflectivity not as good as B4C Light material High damage threshold 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 Nov 12 2008 Coherent X-ray Imaging 10 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 Nov 12 2008 Coherent X-ray Imaging 11 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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? Nov 12 2008 Coherent X-ray Imaging 12 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory CXI Focusing Optics (Current Layout) 1 micron KB Be Lenses 0.1 micron KB 60 m All 3 focusing optics focus the beam at the same plane Nov 12 2008 Coherent X-ray Imaging 8m 0.7 m 13 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory CXI Focusing Optics (Current Layout) 1 micron KB 0.1 micron KB 8m 0.7 m Nov 12 2008 Coherent X-ray Imaging 14 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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? Nov 12 2008 Coherent X-ray Imaging 15 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory CXI Components in the X-ray Transport Tunnel (XRT) Reference Laser Beam Direction Diagnostics CXI Components in Far Experimental Hall Hutch 5 (FEH H5) FEH Common Room CXI Control Room 2X Double Racks Gas Cabinet FEH H5 Laser Table Beam Direction Sample Environment Focusing Optics 5X Single Racks Nov 12 2008 Coherent X-ray Imaging 16 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Beam is Too Small for a Transmissive Window 0.1 micron focus beam is 100x200 microns wide 1 micron focus beam is 15 microns wide 0.1 micron and 1 micron foci Nov 12 2008 Coherent X-ray Imaging 17 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Different Beam Direction for Each Optic Focal Plane 150 mm Be Lenses 8m 0.7 m 20 m 10 m Nov 12 2008 Coherent X-ray Imaging 18 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 Nov 12 2008 Coherent X-ray Imaging 19 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 8m 0.7 m Two different focal planes The first set of mirrors focuses at the second focal plane Nov 12 2008 Coherent X-ray Imaging 20 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 8m 0.7 m Nov 12 2008 Coherent X-ray Imaging 21 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 100 nm Focus into First Chamber 0.1 micron KB 1 micron KB Move the 1 micron KB and lenses away to use 0.1 micron beam in the first sample chamber Be Lenses 8m 0.7 m Nov 12 2008 Coherent X-ray Imaging 22 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 8m 0.7 m Nov 12 2008 Coherent X-ray Imaging 23 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 8m 0.7 m Nov 12 2008 Coherent X-ray Imaging 24 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Small Offset Between Focusing Optics Nov 12 2008 Coherent X-ray Imaging 25 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Beam would not Destroy a Transmissive Window 0.1 micron focus beam is 100x200 microns wide 0.1 micron focus Nov 12 2008 Coherent X-ray Imaging 26 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory New CXI Layout Design 4.5 m 8m 4m 17 m Beam 1 micron KB Differential Pumping Removable Chamber 0.1 micron KB Be Lenses Differential Pumping Nov 12 2008 Coherent X-ray Imaging 27 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Instrument Design KB Mirrors Differential Pumping Differential Pumping Beam Be Lenses and Diagnostics Nov 12 2008 Coherent X-ray Imaging 0.1 micron Sample Chamber 28 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Instrument Design 0.1 micron Sample Chamber Differential Pumping 0.1 micron KB 1 micron KB Beam Nov 12 2008 Coherent X-ray Imaging 29 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Instrument Design Detector Stage Differential Pumping Be Lenses and Diagnostics Beam 1 micron Sample Chamber Nov 12 2008 Coherent X-ray Imaging 0.1 micron Sample Chamber 30 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 Nov 12 2008 Coherent X-ray Imaging 31 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 45 degree Orientation Mounting Concept Beam Nov 12 2008 Coherent X-ray Imaging 32 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory ANSYS Analysis y z x Nov 12 2008 Coherent X-ray Imaging 33 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory ANSYS Analysis z y x Nov 12 2008 Coherent X-ray Imaging 34 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Surface displacement Nov 12 2008 Coherent X-ray Imaging 35 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory Wavefront Simulations Without Distortions With Distortions Focal length of mirror is reduced by 0.2 % due to gravitational distortions Nov 12 2008 Coherent X-ray Imaging 36 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 Nov 12 2008 Coherent X-ray Imaging 37 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 Nov 12 2008 Coherent X-ray Imaging 38 Sébastien Boutet [email protected] SLAC National Accelerator Laboratory 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 Nov 12 2008 Coherent X-ray Imaging 39 Sébastien Boutet [email protected]