X-ray Imaging and Spectro-microscopy:
the Present and the Future
Stanford Synchrotron Radiation Laboratory
October 8-9, 2002
Organizers: John Miao & Keith Hodgson

A workshop on "X-ray Imaging and Spectro-microscopy: the Present and the Future" was held on October 8-9, 2002. This workshop, organized by John Miao (SSRL) and Keith Hodgson (SSRL) provided a forum to discuss the scientific applications of a variety of imaging and spectro-microscopic techniques, including photoemission electron microscopy (PEEM), angle resolved photoemission spectroscopy (ARPES), coherent diffraction imaging, x-ray microscopy, micro-tomography, holographic imaging, and x-ray micro-probe. Twelve invited speakers discussed the important scientific applications of these techniques, and also predicted the future scientific directions with the advance of instrumentation and x-ray sources. The workshop was well attended with over fifty registered attendees.

Keith Hodgson opened the workshop with welcome remarks and pointed out the future x-ray imaging and spectro-microscopy opportunities at SSRL with the SPEAR3 upgrade and the LCLS project. The first scientific talk was given by Jo Stöhr who presented the scientific results from PEEM - imaging ferromagnetic and antiferromagnetic structures by means of x-ray magnetic linear/circular dichroism, and further emphasized that the future instruments will not only greatly improve the real space resolution, but also provide both imaging and dynamics capability. Janos Kirz (Stony Brook) turned the audience's attention to a different kind of microscopy - scanning transmission x-ray microscopy. This zone plate based microscope can obtain both the structure information and chemical mapping of a variety of samples from biology to environmental science. Chuck Fadley (LBNL & UC Davis) gave an overview of holographic imaging of local atomic structure. With the development of better detector systems, he concluded that this imaging technique will find much broader applications.

The following session focused on coherent x-ray diffraction imaging and the phase retrieval techniques. Ian Robinson (UIUC) discussed the principle of the oversampling method, and showed the experimental results of phasing 3D diffraction patterns from gold nanocrystals. Keith Nugent (Melbourne) explained his pioneering work on the transport of intensity approach, and illustrated its applications in light microscopy, electron microscopy and x-ray imaging. The last talk of this session was given by John Miao (SSRL) on 3D structure determination of nanostructured materials by using the oversampling method and the potential of imaging single biomolecules by using X-FELs. The next session, chaired by Hiro Tsuruta (SSRL), focused on biology and polymers. Carolyn Larabell (LBNL & UC San Francisco) compared fluorescence, electron and x-ray microscopy for imaging cellular structures, and concluded that, while cell biology needs all three, x-ray microscopy has the advantages of imaging the 3D structures of thick samples at their natural environment. Adam Hitchcock (McMaster) further discussed the unique capability of soft X-ray microscopy for the imaging and chemical mapping of polymers and biofilms. Barry Lai (APS) reported the powerful capability of combining the micro-probe technique with x-ray fluorescence for tracing heavy elements in biological cells.

The last session of the workshop was chaired by Ingolf Lindau (SSRL). Kyle Shen (Stanford) summarized the science conducted at Zi-Xun Shen's group of studying highly correlated materials, such as the high-temperature superconductors, by using ARPES. This momentum space microscope will be even more powerful with better spectrometers and x-ray sources. Ian McNulty (APS) then brought the audience's attention back to real space imaging by discussing soft x-ray microscopy activity at APS. This intermediate range x-ray microscope covers the absorption edge of more elements than its counterpart in the soft x-ray region. By using magnetic x-ray microscopy, Paul Evans (Wisconsin-Madison) reported the results of imaging antiferromagnetic domains in chromium with spatial resolution at the micron scale, an improvement by orders of magnitude in comparison with previous experiments.


Tuesday, October 8, 2002
Morning Session Chair: J. Miao

K. Hodgson Stanford Synchrotron Radiation Laboratory
Welcome Remarks
J. Stöhr Stanford Synchrotron Radiation Laboratory
Real Space Imaging by Means of X-Ray Photoemission Electron Microscopy
J. Kirz State University of New York at Stony Brook
STXM and diffraction-imaging - the view from the NSLS
C. Fadley UC, Davis & Lawrence Berkeley National Laboratory
Holographic Imaging of Local Atomic Structure: Where Is It and Where Can It Go?
Afternoon Session Chair: K. Hodgson
I. Robinson University of Illinois at Urbana-Champaign
Phasing of Three Dimensional Diffraction Patterns from Finite-Sized Objects
K. Nugent University of Melbourne
Approaches to the Recovery of Complete Wavefield Information
J. Miao Stanford Synchrotron Radiation Laboratory
Single Particle X-ray Diffraction: the Present and the Future
Discussion  What can bright X-ray sources (i.e. high flux, coherence and ultrashort pulses) do for imaging and spectro-microscopy?
Wednesday, October 9, 2002
Morning Session Chair: H. Tsuruta
C. Larabell UC, San Francisco & Lawrence Berkeley National Laboratory
Cryo X-ray tomography of whole cells at 50 nm resolution
A. Hitchcock McMaster University
Soft X-ray microscopy of polymers and biofilms
B. Lai Argonne National Laboratory
X-Ray Fluorescence and Spectro-Microscopy for Biomedical Applications
Afternoon Session Chair: I. Lindau
K. Shen Stanford University
High-resolution photoemission studies of many-body effects in the solid state - "The story from Einstein's electrons"

I. McNulty

Argonne National Laboratory
Soft x-ray microscopy at APS
P. Evans University of Wisconsin-Madison
Imaging antiferromagnetic domains in chromium with magnetic x-ray microscopy