Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 1 LUSI Coherent X-ray Imaging Instrument Sébastien Boutet – CXI Instrument Scientist LCLS Facilities Advisory Committee Meeting June 17, 2008 Team Leader: Janos Hajdu Lead Engineer: Paul Montanez Designer: Jean-Charles Castagna Designer: Richard Jackson

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 2 Outline Introduction Instrument Overview Key Components KB Mirrors Sample Environment Summary

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

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 4 CXI Instrument Location XCS AMO (LCLS) CXI Endstation XPP Near Experimental Hall Far Experimental Hall X-ray Transport Tunnel Source to Sample distance : ~ 440 m

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 5 Far Experimental Hall Coherent X-ray Imaging Instrument Control Room Lab Area X-ray Correlation Spectroscopy Instrument High Energy Density Instrument

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 6 X-ray Transport Optics & Diagnostics Soft X-ray Offset Mirror System (SOMS) selects eV range for soft X- ray line Hard X-ray Offset Mirror System (HOMS) selects 2-25 keV range. HOMS periscope located just upstream of the Near Experimental Hall 385 mm clear aperture mirrors  >70% transmission at 2 keV and >98% at 8.3 keV

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 7 CXI Instrument 1 micron focus KB system (not shown) 0.1 micron KB system Sample Chamber with raster stage Detector Diagnostics & Second Detector Optics and Diagnostics (X-ray Transport Tunnel) Particle injector Ion Time of Flight LCLS Beam

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 8 CXI Kirkpatrick-Baez Mirrors KB1 Mirror system Purpose Produce a 1 micron focal spot at sample Located ~8 meters upstream of sample For samples smaller than 1 micron KB0.1 Mirror system Purpose Produce a 100 nm focal spot at sample Located ~0.8 meters upstream of sample For samples smaller than 50 nm KB Mirror Requirements >75% reflectivity over the widest energy range possible At least up to 9keV Accept 5 sigmas or more over the widest energy range possible Match at least the angular acceptance of the Hard X-ray Offset Mirrors (HOMS) Withstand full power of the LCLS beam without damage Preserve coherence Meet the Maréchal criterion at 8.3 keV, the highest fundamental energy Ultra-High vacuum < Torr

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 9 Key Technical Choices Coating material Affects reflectivity Determines maximum incidence angle Damage issues with high Z materials Incidence angle Determines the energy range Determines mirror length Mirror length How long can you make the mirrors and still polish them to the required accuracy?

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 10 Reflectivity of B 4 C at 3.4 mrad 30 nm B 4 C 3.4 mrad incidence Low angle Long mirrors Or poor performance at low energies where the beam is larger Reflective up to ~9 keV Low Z material Damage resistance

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 11 Reflectivity of B 4 C at 5 mrad 30 nm B 4 C 5 mrad incidence Relatively short mirrors Reflective up to ~6 keV Not sufficient Low Z material Damage resistance

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 12 Reflectivity of Rh at 5 mrad 40 nm Rh 5 mrad incidence Relatively short mirrors Reflective up to ~12.5 keV Absorption edge at 3 keV High Z material Possible damage issues

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 13 Reflectivity of Rh/B 4 C at 3.4 mrad Bilayer Top layer: 30 nm B 4 C Bottom layer: 40 nm Rh 5 mrad incidence Relatively short mirrors Reflective up to ~12.5 keV Reflects off B 4 C only up to 6 keV Removes the problem with the Rh edge at 3 keV Peak reflectivity around 8.3 keV No damage problems B 4 C protects Rh at low energies

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 14 Mirror Length needed to match HOMS

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 15 Length to match HOMS and 5 sigma minimum

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 16 Length to match HOMS and 5 sigma maximum

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 17 Acceptance of 350 mm long mirrors 5 sigma minimum target

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 18 Radiation Damage Issues Calculations shown on plots assume normal incidence Grazing incidence reduces dose Lots of uncertainty in the calculations Need to measure damage thresholds under LCLS conditions Melting threshold is independent of incidence angle Rh coating alone can only be used above 4 keV Based on these uncertain calculations Measurements may reveal Rh is safe below the critical angle Other similar material (like Ru which has a higher melting temperature) could be used instead of Rh Thermal fatigue threshold Thermal cycling can lead to cracking Depends on the mechanical properties of the material

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 19 Preferred Solution Bilayer of Rh and B 4 C 40 nm Rh 30 nm B 4 C Mirror usable length 350 mm 8.2 m and 7.8 m focal lengths High damage threshold 5 mrad maximum incidence angle 4.94 mrad average incidence angle

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 20 Mirror Profiles

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 21 Radius of curvature of the surface

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 22 Figure Error Preserve the coherence of the beam Satisfy the Maréchal criterion at 8.3 keV >80% of incident intensity in the central peak at the focal plane h rms = rms height error over entire length of the mirror =wavelength N=number of reflective optics (2 in this case)  =incidence angle At 8.3 keV h rms = 0.75 nm At 25 keV h rms = 0.25 nm Difficult roughness to achieve Nobody has ever done so on such large mirrors 0.56 nm achieved on 100 mm mirrors

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 23 Issues with bilayer for 0.1 micron KB Wide range of incidence angles due to short focal length and high curvature of the surface 3-5 mrad Two reflective surfaces Phase shifts effect on focus? Two beams at focus? Simulations are required

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 24 Proposed Solution Rh/B 4 C Bilayer for 1 micron KB 40 nm Rh 30 nm B 4 C 350 mm usable length 8.2 m and 7.8 m focal length 5 mrad incidence angle 0.75 nm rms height error MUST get early access to soft X-ray beam of LCLS Measure the damage threshold of Rh at grazing incidence Experimental determination of feasibility of using single layer of Rh for 0.1 micron KB If Rh or Ru can survive the beam Single layer Rh for 0.1 micron KB keV range If Rh or Ru cannot survive the beam Single layer B 4 C for 0.1 micron KB Loss of functionality with reduced energy range 4-9 keV

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 25 CXI 0.1 micron KB 100 nm focus is required for imaging small particles Focal length First mirror 900 mm Second mirror 500 mm Focus 68 x 120 nm spot Requires reentrant KB design Closest point of approach to interaction region 300 mm Final sample chamber design cannot occur until we have a final KB design

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 26 Sample Environment - Fixed Targets Sample Environment Requirements Vacuum better than torr Rapid access Multiple apertures Aperture Purpose Clean beam halo Remove slit scatter from upstream slits Aperture Requirements Apodized edges Positional resolution and repeatability : <1 µm Easily replaced if destroyed by the beam Likely made of etched Si wedges Multiple samples held on multiple grids Large area for hit-and-miss with small samples Sample pitch and yaw High resolution telescope for sample viewing Apertures Sample

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 27 Sample Environment - Injected Particles Sample stage can be translated and used as an aperture Utilize the same setup for fixed samples and particle injection Particle beam comes in from the top Particle beam aperture Particle beam diagnostics Charge detectors Particle Beam Aperture

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 28 CXI Detector Stage Detector Stage Purpose Center the detector hole on the direct beam Position the detector at the appropriate distance from the interaction region Detector Stage Requirements Range along the beam : mm Non-continuous Vacuum better than torr Diagnostics behind the detector for alignment Valve to isolate the detector vacuum Detector Sample Detector

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 29 Temporary Chamber Build a first chamber decoupled from the KB0.1 system Full chamber functionality Fixed targets Injected particles Ion time-of-flight Compatible with detector stage May not be compatible with KB0.1 system Reuse the interior components Build a second chamber Temporary stand May not be reusable with KB0.1 Pros Ready for beam sooner Can learn from the first chamber to design a better final chamber Cons Costs more $$$$

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 30 “Early Science” CXI Instrument

Sébastien Boutet LCLS FAC June Coherent X-Ray Imaging 31 Summary Proposed solution for 1 micron KB Use Rh/B 4 C bilayer Measure damage thresholds at LCLS to determine solution for 0.1 micron KB Bilayer will likely not work Could possibly use heavy metal coating alone Design and fabrication can proceed with temporary chamber decoupled from KB systems Early operations with only 1 micron KB Full functionality included in temporary chamber