Transcript CXI Instrument - Stanford Synchrotron Radiation Lightsource

Coherent X-ray Imaging Instrument
Sébastien Boutet
Coherent Imaging Experiments
Instrument Overview
Instrument Layout
System Description
X-ray optics
Sample environments
Detector
Diagnostics
Technical Choices
Summary
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Molecular 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.
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Coherent Diffractive Imaging of Biomolecules
One pulse, one measurement
Particle
injection
XFEL
pulse
Noisy diffraction
pattern
Combine 105-107 measurements into 3D dataset
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Wavefront
sensor or
second
detector
Gösta Huldt, Abraham
Szöke, Janos Hajdu
(J.Struct Biol, 2003 02ERD-047)
Sébastien Boutet
[email protected]
Conceptual Design of CXI Instrument
Particle injection
Pixel
detector
Intelligent beam-stop
(wavefront sensor)
LCLS beam
(focused, possibly
optically compressed)
To Time Of Flight
(TOF) mass
spectrometer
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Optical and
x-ray
diagnostics
Readout and
reconstruction
Sébastien Boutet
[email protected]
CXI Science at LCLS
Unique Characteristics of LCLS
Short pulses (100 fs)
Instantaneous snapshots with no thermal fluctuations.
Limited radiation damage during the exposure.
Organic samples
Time-resolved imaging experiments
Time 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 samples
LCLS has fundamental limitations in the longitudinal coherence
Object size limited to 1000 x resolution unless a monochromator is used
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
CXI Instrument Location
Far Experimental Hall
X-ray Transport Tunnel
CXI
Endstation
XCS
AMO
XPP
(LCLS)
Source to Sample distance : ~ 440 m
Near Experimental Hall
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
System Specifications
Photon Shutter
X-ray Transport Tunnel
Guard Slits
Item
Purpose
Specification
Compressor
Focusing
optics
Produce required flux.
Focal spot sizes of 10,1, 0.1 micron
Attenuators
Slits/Apertures
Beam halo cleaning
0.1 m stability
1 m repeatability
X-ray pulse
compressor
Reduce pulse length
< 20 fs pulse length
Attenuators
Control incident x-ray flux
Up to 107 reduction at 1.5Å
Diagnostics
Slits/Apertures
Beam halo cleaning
0.1 m stability
1 m repeatability
KB Mirrors
Sample
chamber
Vacuum sample env.,
reduced background
Vacuum below 10 -7 torr
Particle
injector
Deliver single particles in
the gas phase
Particle size range : 10 – 1000 nm
Particle beam focus < 150 microns
Detector
Measurement of diffraction
pattern
2-D, 760 x 760 pixels, 120 Hz readout
110110 µm pixel size,
with central hole
Analysis of sample
fragments after Coulomb
explosion
Ion TOF : resolution of one mass unit up to
100 AMU
Focusing Lenses
Pulse Picker
Guard Slits
Guard Slits
FEH Hutch 5
KB Mirrors
Aperture
Aperture
Sample Environment
Particle Injector
Sample
Ion TOF-MS
diagnostics
Detector Stage
Wavefront
Sensor
Measure the wavefront on
every shot
Resolution: 10% of the beam waist
Wavefront Sensor
X-ray Diagnostics
Intensity monitor
Beam position/profile monitor
0.1% relative intensity measurement
< 5% incident x-ray attenuation
Beam Dump
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Ion Time of Flight
10 micron focus
Be lens
(X-ray Transport
Tunnel)
Particle injector
Wavefront
sensor
1 micron focus
KB system
0.1 micron focus
KB system
Sample Chamber
with raster stage
Detector
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
X-ray Optics
D. Le Bolloc’h et al., J. Synchrotron Rad., 9, 258-265 (2002).
Slit systems
Variable horizontal and
vertical gap from 5 μm – 5 mm
Can withstand full LCLS flux –
unfocused
Minimal background scatter
Used as cleanup slits only
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
X-ray Optics
Attenuators
Variable, up to 10 7 reduction at 8.3 keV
Coherence preserving
High damage threshold
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
X-ray Optics
Pulse picker
Permit LCLS operation
at 120 hz
Millisecond shutter.
Allows any pattern of
pulses to be selected.
Single pulses for
samples supported on
substrates
High damage threshold
http://www.azsol.ch/
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
X-ray Optics
-40 m
B. Lengeler et al., J. Synchrotron Rad., 6, 1153-1167 (1999).
Beryllium Compound Refractive
Lenses
0m
Produce 10 m focus
For large particles
> 40% throughput
Positioning resolution and
repeatability to 1 µm
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Kirkpatrick-Baez Mirrors
KB Mirror system
(1 µm and 0.1 µm KB)
-40 m
-4 m
KB mirrors have
demonstrated <50 nm focus
with SR
Achromatic focusing.
Use B4C as coating
-0.4 m
Damage resistant
Close to 100% reflectivity
0m
H. Mimura et al, Japanese Journal of Applied
Physics 44, L539-L542 (2005)
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Sample environment
Sample chamber
Vacuum better than 10-7 torr
Sample raster stage
Aperture raster stages
Optical diagnostics
Sample diagnostics (Time-of-Flight Mass Spectrometers)
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Sample Environment - Fixed Targets
Detector
Particle Injector
Sample
Aperture
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Sample Environment - Injected Particles
Particle Injector
Particle Beam
Aperture
The entire assembly is translated upstream to let the particle beam pass
The last aperture is close to the particle beam to minimize background
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Apodized 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.
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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LCLS Beam
Sébastien Boutet
[email protected]
Particle Injector
Aerodynamic lens: stack of concentric orifices with decreasing
openings.
Can be used to introduce particles from atmosphere pressure
into vacuum
Near 100% transmission achievable
Creates a tightly focused particle beam.
Final focus can be as small as ~10 m diameter
Particle size range : 10 – 1500 nm
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Aerodynamically Focused Particle Beam
Particles in
Atmospheric pressure
droplets evaporate
B
Aerodynamic
lens
FEL out of page
E F
C
D
G
A
1-10 Torr
A.
B.
C.
D.
E.
F.
G.
~1 Torr
~0.05 Torr
<1x10-7 Torr
Aerodynamic lens
Particle beam steering
Charge detector
Particle beam skimming aperture
Particle beam alignment apertures
Time-of-flight mass spectrometer
Faraday cup
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Sample Diagnostics
Ion TOF
3 x1012 photons in 100 nm
spot
(a) 2 fs pulse
(b) 10 fs pulse
(c) 50 fs pulse
Provide diagnostics to
understand the ‘explosion’
Particle Injector
TOF-MS
Ion ToF detectors
able to resolve single atom
fragments (1 AMU)
Aperture
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Detector
Tiled detector,
permits variable ‘hole’
size
<1 photon readout
noise
110x110 m2 pixels
760x760 pixels
103 dynamic range
120 Hz readout
Sample-detector
distance : 50-3000mm
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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‘Hole’ in detector to pass
Incident beam
Sébastien Boutet
[email protected]
2D Pixel Array Detector
Collaboration with
the Gruner Group
at
Cornell University
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
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Hartmann Wavefront Sensor
Focusing
Optic
Focal Plane
Detector
FEL Beam
2D Detector
W
w0
f
Hartmann
Plate
D
L
Variable
Description
Value
Value
Value
f
Focal length
0.4 m
4m
40 m
D
Focus to Hartmann plate distance
5m
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*
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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* Requires a
defocusing
optic
Sébastien Boutet
[email protected]
Diffractive Wavefront Reconstruction
Attenuator
Focal Plane
Focusing
Optic
2D Detector
Detector
FEL Beam
W
w0
f
L
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.
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
X-ray Diagnostics
Pop-in diode
Thin Be
backscattering
beam monitor
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Pop-in diodes to
check alignment of
different optics
Pop-in fluorescent
screens for beam
position monitoring
Non destructive Be
foil backscattering
can monitor intensity
during measurement.
95% transmission
0.1% accuracy
Sébastien Boutet
[email protected]
Key Technical Choices
Nanoparticle Injector
Shotgun versus pulsed triggered approach
Focusing Optics
KB mirrors versus Be lenses or zone plates
Pulse Picker
Flipping blade versus rotating disks
Wavefront Sensor
Hartmann plate versus diffractive imaging
Apertures versus slits
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]
Summary
Instrument designed for imaging of submicron
particles at near atomic resolution.
Sample environments
Fixed targets
Injected samples
X-ray optics can tailor FEL parameters for users
3 focal spot size : 0.1, 1 and 10 microns
Variable attenuation
Single pulse selection with pulse picker
LCLS FAC Meeting Oct 30, 2007
Coherent X-ray Imaging
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Sébastien Boutet
[email protected]