Transcript Zone Plate Scanning Microscopes and Applications at the APS

Measurement of x-ray coherence
Cairns, QLD Australia
Monday, 30 June 2003
Ian McNulty
Argonne National Laboratory
APS
Summary
Motivation
Recent work
Experiments at APS
Future directions
APS
Why bother?
•
Synchrotron sources produce highly brilliant, partially
coherent x-ray beams; x-ray lasers are around the corner
•
High resolution x-ray experiments require more complex
beamline optics -- coherence "degradation"?
•
Unique coherence-based experiments now possible
•
Aim: develop means to quantify spatial coherence and
wavefront quality of high brilliance x-ray beams
 Cohereometer
APS
Source degeneracy
 = B3/4c = Fcc
Photons per temporal and spatial mode
LC LS
10
9
10
7
TTF
LEUTL
APSU 3.3
N SLS U8 .0
AL SU 3.9
AL SU 8.0
PEPU 7.7
10 5
AL SW13 .6
ave
AL Sb en d
10
3
10
1
10
N SLS be nd
-1
10 -3
10 -5
10
-7
10
-9
10
-11
10 0
10 1
10 2
10 3
Ene rgy [e V]
10 4
10 5
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Peak degeneracy
Photons per temporal and spatial mode, per pulse
LC LS
TTF
LEUTL
10 16
APSU 3.3
N SLS U8 .0
10
14
10
12
10
10
AL SU 3.9
AL SU 8.0
PEPU 7.7
AL SW13 .6
AL Sb en d
N SLS be nd
10 8

p
10 6
10
4
10
2
10 0
10
-2
10
-4
10
-6
10 -8
10
0
10
1
10
2
10
Ene rgy [e V]
3
10
4
10
5
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Applications of coherent x-rays
•
Micro/nano-focusing
•
Holography
•
Interferometry
•
Quantitative phase contrast
•
Coherent scattering (speckle, XIFS, diffraction, microdiffraction)
•
Novel coherent optics
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TiO2-DNA nanocomposites in mammalian cells
• Cell is transfected with TiO2-DNA nanocomposites
Map Ti distribution with x-ray induced K
fluorescence to quantify success rate of
TiO2-DNA transfection and visualize target
• DNA targets specific chromosomal region
• TiO2 photocleaves DNA strands upon illumination
Affinity of transfected DNA to ribosomal
DNA causes nanocomposites to localize
to the nucleolus
• Potential use in gene therapy
g/cm2
Ti
2.2
5 m
g/cm2
Zn
0.0
S. Vogt, J. Maser, I. Moric, D. Legnini (ANL)
G. Woloschak, T. Paunesku, N. Stojicevic
(Radiation Biology Dept., Northwestern Univ.)
5.8
0.0
APS
Full-field coherent phase imaging
Full-field image of
~2 µm spider silk
Difference between infocus, defocused images
Reconstructed phase
B. Allman et al., JOSA A17, 1732 (2000)
APS
Phase nanotomography of Si AFM tip
3D reconstructions of real part of refractive index of projections.
(a, b) Horizontal slices through tip. (c) Vertical slice. (d-f) Volume
renderings. Measured  = 5.0 ± 0.5 x 10-5 , calculated  = 5.1 x 10-5.
P. McMahon et al., Opt. Commun., 217, 53 (2003)
APS
X-ray speckle
Magnetic speckle observed with
circulary polarized x-rays tuned to
the Gd M5 resonance at 1183.6 eV.
Radius of ring corresponds to ~115
nm domain size.
J.F. Peters et al., ESRF Newsletter
34, 15 (2000)
•
•
Access to high momentum transfer at short wavelengths
Scatter from core electron, magnetic, and nuclear charge
•
•
Study physics of nanoscale structure and disorder
Study fluctuations in domain position, size, and orientation
APS
Definitions
Temporal (longitudinal) coherence:
Degree to which waves have well defined phase.
Temporal coherence of beam is function of source bandwidth.
lc
2
~

c
2
~
c
Spatial (transverse) coherence:
Degree to which wave front has well defined phase.
Spatial coherence of beam is function of source size.
wc ~
z
a
Coherent beam does not necessarily imply coherent source!
APS
Coherent field from incoherent source
van Cittert-Zernike theorem
Fourier-invert to obtain source size
and shape (assumes symmetry)
12,  ei
ik xy/ z
 I (x,y) e
dxdy
 I (x,y) dxdy
I (x, y)  FT 1 12
P.H. van Cittert, Physica 1, 201 (1934)
F. Zernike, Physica 5, 785 (1938)
APS
Partially coherent field
I par r    Gr / zI cohr  r dr 
I par  GI coh
g 
where
G  FT 
g
 
FT 1 I par
FT 1I coh
K. Nugent, J. Opt. Soc. Am. A8, 1574 (1991)
APS
Undulator radiation
•
VCZ assumes incoherent, quasi-homogeneous source where
wavefront is assumed to be spherical
•
Undulator source interesting when photon emittance not
dominated by electron emittance:  ~ (sin Nx)/Nx
•
SR sources (except FEL) are incoherent, but are highly
forward directed due to relativistic effects:  ~ 1/
 Dependence of µ12 on ?
Electrons
R. Coisson, Appl. Opt. 34, 904 (1995)
Y. Takayama, Phys. Rev. E59, 7128 (1999)
APS
How to measure it?
Temporal (longitudinal) coherence
Measure fringe visibility off-axis (count fringes)
Measure spectral width directly
Spatial (transverse) coherence
Measure fringe visibility on-axis
Measure wavefront phase
Spatial methods
Diffraction by aperture/object
Amplitude interferometer (Young, Shack-Hartmann)
Intensity interferometer (Hanbury Brown-Twiss)
Time-domain (A. Baron, Phys. Rev. Lett. 77, 4808 (1996))
Speckle contrast (D. Abernathy, J. Synchr. Rad. 5, 37 (1998))
Non-intermerometric (K. Nugent, Phys. Rev. A61, 063614 (2000))
 Desire complete 2D coherence function, µ12(x,y)
APS
Amplitude interferometer (Young)
Sensitive to 1st-order coherence
gr1 ,r2  
r1 ,r2
r1 ,r1r2,r2
 r1,r2  Er1 , E* r2 , 
S
 12 
N
APS
Intensity interferometer (Hanbury Brown - Twiss)
Sensitive to 2nd-order coherence
S
2
T
 12 
N
r
g r1 ,r2 
2
I r1I r2
I r1 I r2 
 1
APS
EUV laser and undulator experiments
– Collisionally excited laser (20.7 nm)
• URA
J. Trebes et al., Phys. Rev. Lett. (1991)
– Undulator beamline (13.4 nm )
• Youngs
C. Chang et al., Opt. Commun. 182, 25 (2000)
– Capillary discharge laser (46.9 nm)
• Youngs
R. Bartels et al., Opt. Lett. 27, 707 (2002)
• Shack-Hartmann
S. Le Pape et al., Phys. Rev. Lett. 88, 183901 (2002)
Full measurement of field amplitude and phase
APS
Single-aperture method
V. Kohn et al., Phys. Rev. Lett. 85, 2745 (2000)
APS
Young's experiment (hard x-rays)
Young's interferograms at 10 keV for two
secondary source sizes M at 23 m.
Measured and calculated coherence profile at
10 keV as a function of Youngs slit spacing
W. Leitenberger et al., Opt. Lett. 191, 91 (2001)
APS
2-ID-B beamline (1-4 keV)
Source degeneracy
0.001 - 0.01
Monochromaticity
40 - 4000
Coherence time
0.1 - 10 fs
Long. coherence length
0.025 - 2.5 µm
Transverse coherent area
5 - 100 m (H)  50 m (V)
Coherent intensity
2  105 ph/m2 /s/0.1% BW
Coherent flux
1  109 ph/s/0.1% BW
APS
Young's experiment (1.1 keV)
Experiment geometry (top view)
Young's slits (1.6 µm Au, 3 µm wide, 10 µm apart)
20 µm slit separation
50 µm slit separation
APS
Coherence function at 2-ID-B
Horizontal degree of spatial coherence |µ12|
measured 8 m from monochromator exit slit.
|µ12| is dominated by beamline optics.
Energy
= 1.1 keV
Entrance slit = 50 µm
Exit slit
= 220 µm

2
2

wc  wslit  wsource
1
2
|µ12| measured with 120 µm exit slit. |µ12| is
dominated by exit slit, producing sinc profile.
D. Paterson, et al., Opt. Commun. 195, 79 (2001)
APS
How to speed up? parallelize measurement
1D
2D
Uniformly redundant array:
All possible aperture separations occur with same frequency
1D URA equivalent to many simultaneous Young’s experiments
K. Nugent et al., Rev. Sci. Instrum. (1992)
APS
Experiments at APS
•
Fast measurement of 1D and 2D
coherence functions with URAs
and CCDs (< 1 min exposures)
•
Performed at APS 2-ID-B (soft) and
2-ID-D (hard x-ray) beamlines
•
Measured with 8, 2.5 nm-rad
electron beam emittance
•
Obtained |µ12| by Fresnel inversion
1D URA (1.18 µm Au, 2.5 µm min. width)
APS
Spatial coherence function by phase URA (8 keV)
Coherence function measured 43.4 m from source slits of size
(a) 10 µm, (b) 50 µm, © 90 µm, and (d) 170 µm
J.J.A. Lin, et al., Phys. Rev. Lett. 90, 074801 (2003)
APS
Intensity interferometry
•
Soft and hard x-ray experiments
Y. Kunimune et al., J. Synchrotron Rad. 4, 199 (1997)
E. Gluskin et al., J. Synchrotron Rad. 6, 1065 (1999)
•
But ... few data points, long acquisition time (days!),
large uncertainty in |µ12|
APS
Recent HBT experiment (14.4 keV)
M. Yabashi et al., Phys. Rev. Lett. 87, 140801 (2001)
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Coherence "degradation"?
CCD image of Young's interference pattern with 10 µm slit separation at 1.07 m,
using 1.5 keV x-rays. Image is 820 µm by 420 µm and fringe spacing is 90 µm.
Condition for full utilization of coherence by experiment:
daperture < dspeckle
APS
Future directions
•
Measure wavefront, phase by TIE method to obtain complete
determination of (complex) µ12
•
Spatial coherence mapping of lasers, other "flash" x-ray sources
–
•
Intensity interferometry with XFEL ( >> 1) ?
–
•
Hard x-ray XFEL pulse (unseeded) contains ~ 102 temporal modes
Noise in correlation signal > Poisson noise
With sufficiently high , can we prepare nonclassical photon
number (Fock) states?
–
Novel correlations, multiphoton interference (Mandel, Ghosh, Zhou, …)
 Interesting x-ray quantum optics problems addressable soon
APS
Acknowledgements
Ercan Alp
Joe Arko
Efim Gluskin
Barry Lai
Derrick Mancini
Mike Moldovan
David Paterson
Cornelia Retsch
Wolfgang Sturhahn
John Sutter
APS, Argonne National Laboratory
Chris Chantler
Tom Irving
Jon Lin
Phil McMahon
Keith Nugent
Andrew Peele
School of Physics University of Melbourne
Brendan Allman
Iatia Corp.