sébastien boutet [email protected] lcls fac meeting oct 30, 2007 coherent x-ray imaging1...

Sébastien [email protected]

LCLS FAC Meeting Oct 30, 2007Coherent X-ray Imaging 1

Coherent X-ray Imaging InstrumentSébastien Boutet

Coherent X-ray Imaging InstrumentSébastien Boutet

Coherent Imaging ExperimentsInstrument OverviewInstrument LayoutSystem Description

X-ray opticsSample environmentsDetectorDiagnostics

Technical ChoicesSummary

Coherent Imaging ExperimentsInstrument OverviewInstrument LayoutSystem Description

X-ray opticsSample environmentsDetectorDiagnostics

Technical ChoicesSummary



Molecular Structure Determination by Protein CrystallographyMolecular Structure Determination by Protein Crystallography

Molecular structure is crucial for medical applications.Inability to produce large high quality crystals is the main bottleneck.Radiation damage is overcome by spreading it over 1010 or more copies of the same molecule.

Molecular structure is crucial for medical applications.Inability to produce large high quality crystals is the main bottleneck.Radiation damage is overcome by spreading it over 1010 or more copies of the same molecule.



Coherent Diffractive Imaging of BiomoleculesCoherent Diffractive Imaging of Biomolecules

Combine 105-107 measurements into 3D dataset

Noisy diffraction pattern

XFEL pulse

Particle injection

One pulse, one measurement

Gösta Huldt, Abraham Szöke, Janos Hajdu (J.Struct Biol, 2003 02-ERD-047)

Wavefront sensor or second detector



Particle injection

LCLS beam

(focused, possibly optically compressed)

Optical and x-ray

diagnostics

Pixel detector

Intelligent beam-stop (wavefront

sensor)

To Time Of Flight (TOF) mass

spectrometer

Conceptual Design of CXI InstrumentConceptual Design of CXI Instrument

Readout and reconstruction



CXI Science at LCLSCXI Science at LCLS

Unique Characteristics of LCLSShort pulses (100 fs)

Instantaneous snapshots with no thermal fluctuations.Limited radiation damage during the exposure.

Organic samples

Time-resolved imaging experimentsTime evolution after laser excitation

High brightness (1012 photons all at once)Perform experiment in a single shot

Flash imaging of radiation sensitive samples

Large Spatial coherence (~400 µm transversely for unfocused beam in the Far Experimental Hall)

Coherent Imaging of larger samplesLCLS has fundamental limitations in the longitudinal coherenceObject size limited to 1000 x resolution unless a monochromator is used

Unique Characteristics of LCLSShort pulses (100 fs)

Instantaneous snapshots with no thermal fluctuations.Limited radiation damage during the exposure.

Organic samples

Time-resolved imaging experimentsTime evolution after laser excitation

High brightness (1012 photons all at once)Perform experiment in a single shot

Flash imaging of radiation sensitive samples

Large Spatial coherence (~400 µm transversely for unfocused beam in the Far Experimental Hall)

Coherent Imaging of larger samplesLCLS has fundamental limitations in the longitudinal coherenceObject size limited to 1000 x resolution unless a monochromator is used



CXI Instrument LocationCXI Instrument Location

XCS

AMO(LCLS)

CXIEndstation

XPP

Near Experimental Hall

Far Experimental Hall

X-ray Transport Tunnel

Source to Sample distance : ~ 440 m



System SpecificationsSystem Specifications

Item Purpose Specification

Focusing optics

Produce required flux. Focal spot sizes of 10,1, 0.1 micron

Slits/Apertures Beam halo cleaning0.1 m stability1 m repeatability

X-ray pulsecompressor

Reduce pulse length < 20 fs pulse length

Attenuators Control incident x-ray flux Up to 107 reduction at 1.5Å

Slits/Apertures Beam halo cleaning0.1 m stability1 m repeatability

Sample chamber

Vacuum sample env., reduced background

Vacuum below 10 -7 torr

Particleinjector

Deliver single particles inthe gas phase

Particle size range : 10 – 1000 nmParticle beam focus < 150 microns

DetectorMeasurement of diffraction pattern

2-D, 760 x 760 pixels, 120 Hz readout110110 µm pixel size, with central hole

Samplediagnostics

Analysis of samplefragments after Coulombexplosion

Ion TOF : resolution of one mass unit up to 100 AMU

Wavefront Sensor

Measure the wavefront on every shot

Resolution: 10% of the beam waist

X-ray DiagnosticsIntensity monitorBeam position/profile monitor

0.1% relative intensity measurement< 5% incident x-ray attenuation

Photon Shutter

Guard Slits

Focusing Lenses

Attenuators

Pulse Picker

Diagnostics

Sample EnvironmentParticle InjectorIon TOF-MS

KB Mirrors

FE

H H

utch

5

Wavefront Sensor

Detector Stage

Compressor

Beam Dump

Guard Slits

Guard Slits

KB Mirrors

Aperture

Aperture

X-ray T

ransp

ort T

un

nel



1 micron focusKB system

0.1 micron focusKB system

Sample Chamber with raster stage

Detector

Wavefrontsensor

10 micron focus Be lens (X-ray Transport Tunnel)

Particle injectorIon Time of Flight



X-ray OpticsX-ray Optics

Slit systemsVariable horizontal and vertical gap from 5 μm – 5 mmCan withstand full LCLS flux – unfocusedMinimal background scatterUsed as cleanup slits only

Slit systemsVariable horizontal and vertical gap from 5 μm – 5 mmCan withstand full LCLS flux – unfocusedMinimal background scatterUsed as cleanup slits only

D. Le Bolloc’h et al., J. Synchrotron Rad., 9, 258-265 (2002).




AttenuatorsVariable, up to 10 7 reduction at 8.3 keVCoherence preservingHigh damage threshold

AttenuatorsVariable, up to 10 7 reduction at 8.3 keVCoherence preservingHigh damage threshold




Pulse pickerPermit LCLS operation at 120 hzMillisecond shutter.

Allows any pattern of pulses to be selected.

Single pulses for samples supported on substratesHigh damage threshold

Pulse pickerPermit LCLS operation at 120 hzMillisecond shutter.

Allows any pattern of pulses to be selected.

Single pulses for samples supported on substratesHigh damage threshold

http://www.azsol.ch/




Beryllium Compound Refractive Lenses

Produce 10 m focusFor large particles

> 40% throughput

Positioning resolution and repeatability to 1 µm

Beryllium Compound Refractive Lenses

Produce 10 m focusFor large particles

> 40% throughput

Positioning resolution and repeatability to 1 µm

B. Lengeler et al., J. Synchrotron Rad., 6, 1153-1167 (1999).

-40 m

0 m



Kirkpatrick-Baez MirrorsKirkpatrick-Baez Mirrors

KB Mirror system (1 µm and 0.1 µm KB)

KB mirrors have demonstrated <50 nm focus with SRAchromatic focusing.Use B4C as coating

Damage resistantClose to 100% reflectivity

KB Mirror system (1 µm and 0.1 µm KB)

KB mirrors have demonstrated <50 nm focus with SRAchromatic focusing.Use B4C as coating

Damage resistantClose to 100% reflectivity

0 m

-0.4 m

-4 m

H. Mimura et al, Japanese Journal of Applied Physics 44, L539-L542 (2005)

-40 m



Sample environmentSample environment

Sample chamber Vacuum better than 10-7 torrSample raster stageAperture raster stagesOptical diagnosticsSample diagnostics (Time-of-Flight Mass Spectrometers)

Sample chamber Vacuum better than 10-7 torrSample raster stageAperture raster stagesOptical diagnosticsSample diagnostics (Time-of-Flight Mass Spectrometers)

FEL



Sample Environment - Fixed TargetsSample Environment - Fixed Targets

Detector

SampleAperture

Particle Injector

FEL



Sample Environment - Injected ParticlesSample Environment - Injected Particles

Aperture

The entire assembly is translated upstream to let the particle beam passThe last aperture is close to the particle beam to minimize background

The entire assembly is translated upstream to let the particle beam passThe last aperture is close to the particle beam to minimize background

Particle Beam

Particle Injector

FEL



Apodized Edge AperturesApodized Edge Apertures

If 1 part in 106 of the LCLS beam gets scattered off the slits onto the detector, there is on average 1 photon per pixel and the background is too high!Soft edge apertures, such as etched Silicon minimize scattering.Use extra apertures to remove the scatter from the upstream apertures.

If 1 part in 106 of the LCLS beam gets scattered off the slits onto the detector, there is on average 1 photon per pixel and the background is too high!Soft edge apertures, such as etched Silicon minimize scattering.Use extra apertures to remove the scatter from the upstream apertures.

LCLS Beam



Particle InjectorParticle Injector

Aerodynamic lens: stack of concentric orifices with decreasing openings. Can be used to introduce particles from atmosphere pressure into vacuum Near 100% transmission achievableCreates a tightly focused particle beam. Final focus can be as small as ~10 m diameterParticle size range : 10 – 1500 nm

Aerodynamic lens: stack of concentric orifices with decreasing openings. Can be used to introduce particles from atmosphere pressure into vacuum Near 100% transmission achievableCreates a tightly focused particle beam. Final focus can be as small as ~10 m diameterParticle size range : 10 – 1500 nm



A

B

C D

E F

G

A. Aerodynamic lensB. Particle beam steering C. Charge detectorD. Particle beam skimming apertureE. Particle beam alignment aperturesF. Time-of-flight mass spectrometerG. Faraday cup

Atmospheric pressure droplets evaporate

1-10 Torr ~1 Torr ~0.05 Torr<1x10-7 Torr

Particles in

Aerodynamically Focused Particle BeamAerodynamically Focused Particle Beam

Aerodynamic lens

FEL out of page



Sample DiagnosticsSample Diagnostics

Ion TOF3 x1012 photons in 100 nm spot

(a) 2 fs pulse(b) 10 fs pulse(c) 50 fs pulse

Provide diagnostics to understand the ‘explosion’

Ion ToF detectorsable to resolve single atom fragments (1 AMU)

Ion TOF3 x1012 photons in 100 nm spot

(a) 2 fs pulse(b) 10 fs pulse(c) 50 fs pulse

Provide diagnostics to understand the ‘explosion’

Ion ToF detectorsable to resolve single atom fragments (1 AMU)

Particle Injector TOF-MS

Aperture



DetectorDetector

Tiled detector, permits variable ‘hole’ size<1 photon readout noise110x110 m2 pixels760x760 pixels103 dynamic range120 Hz readoutSample-detector distance : 50-3000mm

Tiled detector, permits variable ‘hole’ size<1 photon readout noise110x110 m2 pixels760x760 pixels103 dynamic range120 Hz readoutSample-detector distance : 50-3000mm

‘Hole’ in detector to passIncident beam



2D Pixel Array Detector2D Pixel Array Detector

High resistivity Silicon (500 µm) for direct x-ray conversion.Reverse biased for full depletion.Bump-bonding connection to CMOS ASIC.ASIC limit on size, 21 mm2

Collaboration with

the Gruner Group

at

Cornell University



Hartmann Wavefront SensorHartmann Wavefront Sensor

Focal PlaneFocusing Optic

2D Detector

FEL Beam

Hartmann Plate

Variable Description Value Value Value

f Focal length 0.4 m 4 m 40 m

D Focus to Hartmann plate distance 5 m 15 m 15 m

w0 Focal spot size 0.1 m 1 m 10 m

W Beam size at Hartmann plate 5 mm 1.5 mm 0.15 mm*

f D L

Ww0

* Requires a defocusing optic

Detector



Diffractive Wavefront ReconstructionDiffractive Wavefront Reconstruction

The oversampled diffraction pattern of the focus is measured.The focal spot is iteratively reconstructed using phase retrieval methods by propagating the wave from the optic to the focus and then to the detector plane.

The constraints are applied at the optic and detector planes.

The oversampled diffraction pattern of the focus is measured.The focal spot is iteratively reconstructed using phase retrieval methods by propagating the wave from the optic to the focus and then to the detector plane.

The constraints are applied at the optic and detector planes.

Focal PlaneFocusing Optic

2D Detector

FEL Beam

f L

Ww0

Attenuator

Detector



X-ray DiagnosticsX-ray Diagnostics

Pop-in diodes to check alignment of different opticsPop-in fluorescent screens for beam position monitoringNon destructive Be foil backscattering can monitor intensity during measurement.

95% transmission0.1% accuracy

Pop-in diodes to check alignment of different opticsPop-in fluorescent screens for beam position monitoringNon destructive Be foil backscattering can monitor intensity during measurement.

95% transmission0.1% accuracy

Pop-in diode

Thin Be backscattering beam monitor



Key Technical ChoicesKey Technical Choices

Nanoparticle InjectorShotgun versus pulsed triggered approach

Focusing OpticsKB mirrors versus Be lenses or zone plates

Pulse PickerFlipping blade versus rotating disks

Wavefront SensorHartmann plate versus diffractive imaging

Apertures versus slits

Nanoparticle InjectorShotgun versus pulsed triggered approach

Focusing OpticsKB mirrors versus Be lenses or zone plates

Pulse PickerFlipping blade versus rotating disks

Wavefront SensorHartmann plate versus diffractive imaging

Apertures versus slits



SummarySummary

Instrument designed for imaging of submicron particles at near atomic resolution.Sample environments

Fixed targetsInjected samples

X-ray optics can tailor FEL parameters for users 3 focal spot size : 0.1, 1 and 10 micronsVariable attenuationSingle pulse selection with pulse picker

Instrument designed for imaging of submicron particles at near atomic resolution.Sample environments

Fixed targetsInjected samples

X-ray optics can tailor FEL parameters for users 3 focal spot size : 0.1, 1 and 10 micronsVariable attenuationSingle pulse selection with pulse picker

sébastien boutet [email protected] lcls fac meeting oct 30, 2007 coherent x-ray imaging1...

Documents

lcls fac meeting

detector slide

organic samples time

limited radiation damage

reconstruction slide

experimental hall xra

unfocused beam

fundamental limitations