Imaging Update to LCLS SAC, June 2006 Henry Chapman, LLNL LLNL: Uppsala: UC Davis: SLAC: DESY: TU Berlin: LBNL: ASU: Sasa Bajt, Anton Barty, Henry Benner, Micheal Bogan, Henry Chapman, Matthias Frank, Stefan Hau-Riege, Richard Lee, Richard London, Stefano!Marchesini, Tom McCarville, Alex Noy, Urs!Rohner, Eberhard!Spiller, Abraham!Szöke, Bruce Woods Janos Hajdu, Gösta Huldt, Carl Caleman, Magnus Bergh, Nicusor Timeneau, David!van!der!Spoel, Florian Burmeister, Marvin!Seibert David Shapiro Keith Hodgson, Sebastien Boutet Thomas Tschentscher, Elke Plönjes, Marion Kulhman, Rolf Treusch, Stefan Dusterer, Jochen Schneider Thomas Möller, Christof Bostedt Malcolm Howells, Congwu Cui John Spence, Uwe Weierstall, Bruce Doak
Single particle diffraction offers many challenges One pulse, one measurement One measurement Particle injection 10 fs pulse Noisy diffraction pattern Combine 10 5-10 7 measurements Classification Averaging Orientation Reconstruction
The diffraction imaging interaction chamber and detector arrangement Electrostatic trap Particle injection Pixel detector 1 Pixel detector 2 Intelligent beam-stop XFEL beam (focussed, Compressed) Particle orientation beam To mass spectrometer Optical and x-ray diagnostics (veto and determine position of particle in beam) Readout and reconstruction
We are developing the first experiments for LCLS at FLASH The FLASH experiments are essentially a dry-run for LCLS Diffraction imaging with a single pulse, to surpass radiation damage limits Determine if there is any change in structure of particles during the pulse Measure the dynamics of the FEL-particle interaction to validate models Develop and demonstrate particle injection and alignment techniques Develop optics and instrumentation
We have carried out experiments at the first soft-x-ray FEL in the world The VUV-FEL at HASYLAB, DESY User facility, FEL radiation to 6 nm wavelength Initial FEL Operation August 2005 at 32 nm and <30 fs pulses, 10 13 photons Now lasing at 13 nm
Our diffraction camera can measure forward scattering close to the direct soft-x-ray FEL beam Soft edge prevents any scatter from the hole Multilayer reflectivity is uniform across the 30 to 60 gradient
The VUV-FEL diffraction experiment is designed to measure forward scattering with high SNR 15 o 60 multilayer mirror 2 cm sample shield -15 o 30 CCD with transmission filter 60 d = 32 nm 30 d = 18 nm Reflectivity 1 0.5 32nm mirror 16nm mirror 0 10 100 1000 Photon energy (ev) Shadow mask Sasa Bajt, Eberhard Spiller, and Jennifer Alameda
Image reconstructed from an ultrafast FEL diffraction pattern 1 micron SEM of structure etched into silicon nitride membrane 2nd shot at full power Reconstructed Image achieved diffraction limited resolution! Wavelength = 32 nm 1st shot at full power Edge of membrane support also reconstructed 1 micron
The reconstruction is carried out to the diffraction limit of the 0.26 NA detector SEM Single pulse FEL 1 micron Phase-retrieval transfer function gives an estimate of the resolution of the reconstructed image 1.0 0.8 0.6 0.4 0.2 60 nm 0.0 0 2 4 6 8 10 q (1/µm) 32 nm, one wavelength! / NA
The sample is quite damaged by the FEL pulses FIB cowboy sample after FEL exposure before 10 micron Pulse energy: 10 µj or 1 J/cm 2 Dose in Si 3 N 4 : 10 5 J/g or 22 ev/atom Temperature of 6"10 4 K, or 5.2 ev, ionization/atom of 2.5 Surfaces will expand at sound speed: 1.3"10 6 cm/s In 25 fs, material will not move more than 3 Å
We will perform 3D imaging of identical objects at FLASH and high-resolution imaging of cells Silicon nitride pyramid Hit one pyramid, then rotate and move up sample 1 µm High-resolution imaging will be carried out at the third harmonic, e.g. a wavelength of 4.5 nm. Requires 2 µm focus Silicon nitride membrane with pyramids Silicon
XFEL diffraction of molecules is modified (damaged) by photoionization and motion of atoms Ion density (10 22 /cm 3 ) 3 2 1 (2,4) (2,3) (2,2) Carbon (1,2) (2,0)(1,0) (2,1) (1,1) 0 0 5 10 15 20 (1,4) (1,3) time (fs) (k,l) =(# K-shell, # L-shell) electrons black = neutral carbon blue = valence ionization red = inner shell ionization electron escapes if E > 3eQ 2R neutralized hot core Stefan Hau-Riege, Richard London, Abraham Szoke We have developed a hydrodynamic continuum model for the atomic motion and the ionization processes that can treat large and small molecules Allows for trapping and secondary effects (such as inverse Bremsstralung, 3-body recombination) Damage is dominated by ionization at short times A tamper reduces motion e- e- charged layer R/R 0 1.0 0.5 ionization ionization + motion 0.0 0 10 20 Time (fs)
By repairing ionization damage, the imaging is limited by the inertia of the atoms resolution (Å) 10 8 6 4 Electron damage 6fs 9fs 5fs 4fs 3fs 2fs with repair Ion damage (estimated) 20fs 30fs 60fs 50fs 40fs 2 1fs 10fs 0 100 200 Molecule Radius (A) 0 100 200 Molecule Radius (A) (Hau-Riege et al., PRE 2005) Even longer pulses can be tolerated if a tamper is used, but image classification will be more difficult
Particle explosion experiments were performed on latex particles on membranes The particle size is determined by Mie scattering of the VUV-FEL pulse by the particles (FEL pulse is both pump and probe) To see a 5% change in radius during pulse, require size distribution of ~1%. 100 µm 15º 50 mm 20 nm thick silicon nitride 357 windows per chip 1µm SEM of particles 25 mm Mounted on piezo x-y stage to move each window into beam Half beam diameter (10 µm) - 220 particles
Scattering from balls demonstrates that they retain their shape throughout the duration of the pulse
Our VUV hydrodynamic code shows that latex spheres start exploding in ~ 2 ps Density y (nm) Incident pulse direction z (nm) Color scale: 0 g/cm 3 2 g/cm 3
The substrate is a high-resolution detector (at low enough fluence) z Electric field intensity at z=0 150nm Ø polystyrene R 20nm Si 3 N 4 150nm sphere 4 0 1 2 3 Intensity 0 (I ) 1.5 1.0 0.5!=32nm, D=145nm!=32.5nm, D=145nm!=32nm, D=155nm 1 2 3 4 100nm 0,1,2,3,4: depression rings 0.0 0 50 100 150 200 250 300 R (nm)
We invented a new method called femtosecond timedelay holography Prompt diffraction Delayed diffraction #z Time delay 2 #z / c Multilayer Mirror 30 fs pulse (9 µm long) Detector Unfolded geometry reference object
First demonstration of time-delay holography with 30 fs time resolution indicates the particle explosion Intensity (counts) 1000 100 raw smoothed 2.5 5.0 7.5 10.0 q (µm -1 ) 8 Single shot ultrafast time-delay X-ray hologram, with 300 fs delay Log (Intensity) 6 4 2 0-2 0.5 ps 3.8 ps 7.2 ps 10.5 ps 2.5 5.0 7.5 q (µm -1 ) 10.0
First EUV-FEL experiments show that structural information can be obtained before destruction During 30 fs pulse (10 14 W cm -2 ) 32 nm wavelength Reflectivity unchanged Multilayer d spacing not changed by more than 0.3 nm After pulse Si/C multilayer Reflectance (%) Plasma forms, layers ablate 4 3 2 1 30 fs pulse reflectivity at 32nm 16% 100% increasing fluence Low-fluence 0 35 40 45 50 Angle of incidence (degrees) Nomarski micrograph of crater 400 nm 40 micron Peak Brightness Collaboration, R. Lee et al J. Kryzwinski, R. Sobierajski, H. Chapman et al 5 µm 10 µm 5 µm 10 µm
The multilayer structure can test our hydrodynamic models Temperature profile in the multilayer Reflectivity (%) 3 2 1 fit simulation 96 ev/atom 0 0 2 4 6 8 Motion occurs after the pulse 2 Fluence (J/cm ) 100 nm TEM (before FEL exposure) -100 z position (nm) 0 100 200 300 0 10 20 Time (fs) 0 2 4 6 8 10 Time (ps)
HIGH FIELD EFFECTS At 32 nm, the high field regime starts at around 10 17 W/cm 2, At 6 nm, the high field regime starts at around 2.5 x 10 18 W/cm 2. We expect to approach 10 19 W/cm 2 with submicron focusing this year. This wiil be needed. It also gives access to a new field of science: - Studies on non-linearity and multiphoton processes (multiple inner shell ionisations, two-electron ejections) - Access to hot dense matter regime and to high pressure states - Magnetic field effects could appear at 10 18 W/cm 2 at 32 nm - Relativistic effects above 10 19 W/cm 2 at 32 nm
Sub-micron focusing optics could provide ~10 19 W/cm 2 y z 10 cm 1/e beam width at optic is 10.4 mm Oversize optic to 2 diam = 50.8 mm Mount: must have much better than 50 nm steps (1 microrad over 5 cm) 25 cm Optic is not sensitive to x, y displacement (since beam is nearly parallel and optic is a parabola. Optic is sensitive to tilts as shown below. Need better than microradian alignment (use wavefront sensor, but need fine adjustments) Spot size x misalignment y misalignment With diffraction Geometric Optic must have <0.5 waves abberration (at 32 nm). That is 16 nm RMS, or 8 nm RMS in surface figure error. i.e.!/80 (or!/100 better) surface error at HeNe
SAMPLE INTRODUCTION AND MANIPULATION The Basic Concept: 1. Take molecules of interest from sample solution 2. Introduce them into the beam XFEL pulse 0.1-1 um diameter ~20-100 fs Challenges: 1. Particle concentration 2. Keeping molecules in native conformation 3. Diagnostics: How do we know if a pattern is good? 3. Hit them with the XFEL pulse and record diffraction pattern 4. Repeat to get sufficient number of patterns for averaging & image reconstruction.
Introducing Large Molecules into the Beam Using Electrospray Ionization (ESI) ESI Capillary http://www.newobjective.com/electrospray/index.html Liquid sample Charged droplets Charged ions HV Taylor cone Controlled evaporation! ESI is widely used to bring macromolecules or viruses into the gas phase, e.g., for mass spectrometry! ESI can create large number of droplets and molecular ions (~10 10 /sec at 1 µl/min)! ESI droplet size adjustable from nm to µm (compared to ~1-50 µm for ink jet droplet generator)! Both ESI and ink jet can be pulsed as desired! Droplets / ions can be sucked into vacuum of mass spectrometer or beam line - differential pumping and skimmers
Particle injection system developed at LLNL (Henry Benner, Matthias Frank, Mike Bogan) First tests with a pulsed visible laser beam pulsed XFEL beam Fragment Detector TOF MS Interaction point Scattered x rays Detector Beam Stop
Aerodynamic lens for precision injection of particles into the FEL beam Aerodynamic lens: stack of concentric orifices with decreasing openings. Can be used to introduce particles from atmosphere pressure into vacuum Near 100% transmission Creates a tightly focused particle beam. Final focus can be as small as ~10 µm diameter 1 µm polystyrene balls sprayed from a distance of 25 cm for 10 minutes. Diameter of particle spot deposited on the target: ~500 µm The lens can be aimed just like a gun
We will test such an injector at FLASH later this year FEL Focused particle beam aperture CCD Unfocused particle beam Alignment
Laser alignment will help establish molecular imaging at XFELs and synchrotrons Equipartition of rotational potential energy with thermal energy gives!" 2 = T 3 #10 $8 I!% T - temperature in K I - laser power in W/cm 2!" - polarizability anisotropy in nm 3 Resolution is limited by the degree of alignment: d = (L/2)!# J.C.H. Spence and R.B. Doak, Phys. Rev. Lett. 92, 198102 (2004) J.C.H. Spence et al., Acta Cryst. A 61, 237 (2005) D. Starodub et al. J. Chem Phys 123, 244304 (2005) Larsen, J. Chem Phys 111, 7774 (1999).
We are testing aligned-particle X-ray diffraction at the ALS Water-protein solution 100 W IPG Fiber Laser X-rays CCD D. Shapiro, J. Spence et al
A Ceramic Soller collimator can filter out parastic scattering Can be manufactured to conical shapes with tapered channels (diameters down to ~10 micrometer) CERAMIC CHANNEL COLLIMATOR AREA DETECTOR 2$ = 30º Reduces background. May allow us to take many shots from a pulse train until a hit is recorded.
Laue multilayer pulse compressor #% " % H!L = H!" " (1 + b)2 tan 2 # B 1 cos$ E=8 kev, $ B =1.7157 o, w=5.0 µm, b=1 Experiments at APS: W/SiC 3280 bilayers, d-spacing = 2.58 nm Hyon Chol Kang, Brian Stephenson, Sa!a Bajt
SINGLE PARTICLES, CLUSTER AND BIOMOLECULES: SCHEMATIC LAY OUT OF THE INSTRUMENT OPTICS AND BEAM CONDITIONING Optional monochromator and pulse compressor (beam displacement!) SAMPLE HANDLING - INJECTION SYSTEM - LASER FOR PARTICLE ORIENTATION (10 9-10 12 W/cm 2 ) - CRYO EM GONIOSTAT (FLUORESCENCE IMAGE) - INSPECTION MICROSCOPE Pressure < 10-6 mbar, ideally 10-8 mbar AREA DETECTORS 1 µm K-B 0.1 µm K-B Adjustable 20-500 mm Gas attenuator and foils Apodising apertures Beam profile monitor Apodising apertures Beam profile monitor BEAM DIAGNOSTICS - WAVEFRONT SENSOR - SPECTROMETER (Total pulse energy, image of the beam, SAMPLE DIAGNOSTICS intensity distribution) - TOF MASS SPECTROMETER - BEAM STOP - ELECTRON SPECTROMETER - POSITION-SENSITIVE FLUORESCENCE DETECTOR (to locate/characterise hits)
Initial experiments at LCLS Follow on from the FLASH experiments Diffraction imaging of a cell with a single pulse, to surpass radiation damage limits Measure the extent of the Coulomb explosion during the pulse Measure the dynamics of the FEL-particle interaction to validate models (pumpprobe measurements) Diffraction of injected and aligned particles TMV Photosystem 1 nanocrystals and particles Unknown structures Single particle diffraction as optics commissioned and injection improved start with Symmetric objects