Colloquium: Dr. Bennett C. LarsonDr. Bennett C. Larson Materials Science and Technology Division, Emeritus Oak Ridge National Laboratory, Oak Ridge, TN 37830
Synchrotron Adventures in Space and Time
The use of synchrotron x-ray radiation for x-ray diffraction experiments began in the 1970’s with the realization that the parasitic x-rays generated by bend magnets associated with high-energy physics synchrotron accelerators produced highly collimated x-ray beams with pulsed intensities exceeding laboratory x-ray sources by many orders of magnitude. During the 1980’s and succeeding decades, dedicated synchrotron x-ray beamlines were constructed at the Stanford Synchrotron Radiation Laboratory (SSRL), the Cornell High Energy Synchrotron Source (CHESS), the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory and others around the world. Previously impossible experimental measurements ensued immediately as did the development of advanced x-ray monochromator optics, both of which have continued apace up to the present time.
In this presentation I will recall seminal single synchrotron x-ray pulse investigations of pulsed-laser melting in silicon performed with nanosecond resolution at CHESS in 1981 and contrast these experiments with present ~10 femtosecond measurement capabilities at the free-electron laser facilities such as the Linear Coherent Light Source (LCLS) at SLAC. I will further recall the mid 1980’s development of millimeter resolution sagitall focusing monochromators at the NSLS and contrast this with the ~2000 time-frame development of submicron resolution polychromatic x-ray focusing mirrors. These mirror optics coupled with differential-aperture (knife-edge) depth resolution have enabled the development of a submicron resolution three-dimensional x-ray microscopy (3DXM) dedicated beamline at the Advanced Photon Source (APS) at Argonne National Laboratory. The development of 3DXM has in turn made it possible to obtain full diffraction information on materials from submicron voxels with submicron point-to-point 3D spatial resolution over mesoscopic length scales of hundreds of microns. The information includes local crystal structure, orientation, strain and strain gradients from single crystals, polycrystals, composites, and functionally graded materials. Examples of the application of 3DXM to fundamental aspects of deformation of single crystals will be discussed.
*Research supported by the Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division and by the Center for Defect Physics an Energy Frontier Research Center. The Advanced Photon Source is supported by the Department of Energy, Scientific Users facility Division.