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Keith A. Nugent

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Coherent X-ray Science: Coherence, Imaging & Molecules Keith A. Nugent ARC Centre of Excellence for Coherent X-ray Science & School of Physics The University of Melbourne – PowerPoint PPT presentation

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Title: Keith A. Nugent


1
Coherent X-ray Science Coherence, Imaging
Molecules
  • Keith A. Nugent
  • ARC Centre of Excellence for Coherent X-ray
    Science School of Physics
  • The University of Melbourne
  • Australia

2
Plan of presentation
  • Develop a view of coherent diffractive imaging
    including partial coherence.
  • Describe CDI and identify three limits within the
    framework of partial coherence
  • Coherent
  • Partially coherent illumination
  • Time varying object
  • Describe the method
  • Essential developments
  • Applications in biology
  • Applications in materials science
  • Partial coherence in CDI
  • How important is it?
  • How can coherence be measured
  • Building partial coherence into the
    reconstruction
  • Time varying objects as partially coherent
    diffraction
  • Some thoughts

3
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4
Formalism for CDI
  • In far-field

The far-field intensity is therefore
5
Three limits
  • 1. CDI with coherent light static object
  • Harmonically varying (ie. coherent) incident
    field static object

2. CDI with partially-coherent light static
object
  • Random variation in incident field static object

3. CDI with coherent light dynamic object
  • Coherent incident field variation in object

6
Plan of presentation
  • Develop a view of coherent diffractive imaging
    including partial coherence.
  • Describe CDI and identify three limits within the
    framework of partial coherence
  • Coherent
  • Partially coherent illumination
  • Time varying object
  • Describe the method
  • Essential developments
  • Applications in biology
  • Applications in materials science
  • Partial coherence in CDI
  • How important is it?
  • How can coherence be measured
  • Building partial coherence into the
    reconstruction
  • Time varying objects as partially coherent
    diffraction
  • Some thoughts

7
Conventional coherent diffractive imaging
  • 1. CDI with coherent light static object
  • Harmonically varying (ie. coherent) incident
    field static object

8
Coherent imaging methods are being developed.
Coherent Field
Impose Measured Intensity, Keep Phase
z
Impose support
Guess Phase
9
First Demonstration
  • Assumes complete coherence
  • Object must be finite in extent

10
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11
The Shrinkwrap Algorithm
12
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13
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14
Fresnel diffraction imaging
15
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16
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18
Biological Applications
19
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21
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22
Materials Applications
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27
Plan of presentation
  • Develop a view of coherent diffractive imaging
    including partial coherence.
  • Describe CDI and identify three limits within the
    framework of partial coherence
  • Coherent
  • Partially coherent illumination
  • Time varying object
  • Describe the method
  • Essential developments
  • Applications in biology
  • Applications in materials science
  • Partial coherence in CDI
  • How important is it?
  • How can coherence be measured
  • Building partial coherence into the
    reconstruction
  • Time varying objects as partially coherent
    diffraction
  • Some thoughts

28
Conclusion Algorithms implicitly assume a very
high degree of spatial coherence. A very high
degree of spatial coherence is required for
reliable, high-resolution image recovery.
29
Including partial coherence
30
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32
z
33
The Complex Degree of Coherence
34
S Flewett, HM. Quiney, CQ Tran and KA. Nugent,
Extracting Coherent Modes from Partially Coherent
Wavefields, Optics Letters, submitted
Three coherent modes
35
The effects of partial coherence can be included
in the analysis and provide a significantly
greater degree of stability in the reconstruction
36
Plan of presentation
  • Develop a view of coherent diffractive imaging
    including partial coherence.
  • Describe CDI and identify three limits within the
    framework of partial coherence
  • Coherent
  • Partially coherent illumination
  • Time varying object
  • Describe the method
  • Essential developments
  • Applications in biology
  • Applications in materials science
  • Partial coherence in CDI
  • How important is it?
  • How can coherence be measured
  • Building partial coherence into the
    reconstruction
  • Time varying objects as partially coherent
    diffraction
  • Some thoughts

37
Three limits Limit Three
3. CDI with coherent light dynamic object
  • Coherent incident field variation in object

Studies have been predicated on the need for the
condition
38
The need for short pulses
39
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41
Summary
  • Coherent x-ray imaging techniques are well
    developed.
  • Methods are emerging that allow the inclusion of
    the effects of partial coherence.
  • The imaging of a system that is effected by the
    pulse can be formulated as a problem of partial
    coherence.
  • The recovery of structure in this way might be
    possible is suitable models can be developed.
    This will be a challenge.

42
Major Collaborators
  • Garth Williams (UM)
  • Andrew Peele (La Trobe)
  • Ian McNulty (APS)
  • Harry Quiney (UM)
  • Lachlan Whitehead (UM)
  • David Vine (UM)
  • Rueben Dilanian (UM)
  • Bo Chen (UM)
  • Brian Abbey (UM, now at Oxford)
  • Sam Flewett (UM)
  • Chanh Tran (La Trobe)
  • Jesse Clark (La Trobe)
  • David Paterson (APS, now Australian Synchrotron)
  • Martin de Jonge (APS, now Australian Synchrotron)
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