http://xray1.physics.sunysb.edu/
Professors Jacobsen and Kirz and their groupiwork on the development and applications of X-ray optics. This includes electron beam microfabrication of zone plates, construction of soft X-ray microscopes and their applications to biological and environmental problems, and the development of high resolution soft X-ray imaging based on the recording and numerical reconstruction of diffraction patterns or holograms. Professor Jacobsen and some of his students collaborate with Dr. Don Tennant of Bell Labs in the fabrication of state-of-the-art phase zone plates for the focusing of soft and hard X-rays. This work makes use of the latest electron beam writing tools, and results in zone plates that can form the finest focus of electromagnetic waves of any wavelength - about 30 nm.
X-ray microscope group photo
Toby Beetz It is these zone plates that are used in scanning soft X-ray microscopes recently upgraded at the National Synchrotron Light Source (NSLS) where the group operates a pair of undulator beamlines. The NSLS, located at Brookhaven National Lab just 30 minutes from campus, provides the bright soft X-ray beams that makes efficient imaging possible. The sample is mechanically scanned in the focus and transmitted X-rays are detected to form the image under computer control. Imaging can be extended to a third dimension in two ways: One can generate what amounts to a CAT scan by collecting a set of these images as the specimen is rotated around an axis perpendicular to the beam. A three dimensional image of the specimen is then reconstructed from the data. Alternatively the third dimension can be the beam energy. A series of images is collected as the wavelength is swept across an X-ray absorption edge. The resulting data provides local chemical information in the image through the chemical sensitivity of absorption spectra near edges.
Work on the recording and reconstruction of diffraction patterns is based on the ideas of Dr. David Sayre, who is a collaborator in this work. The scheme was first shown to work in 1999 on a simple test pattern, and work is now in progress to extend it to higher resolution, to three dimensions, and to specimens of biological interest. An alternative scheme involving the recording of a series of holograms is also being pursued. All these techniques and instrumentation for scanning microscopy and diffraction-imaging were developed by the group and its collaborators, and these developments continue to be an important activity.
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