Dietbert Rudolph

PHASE CONTRAST STUDIES OF BIOLOGICAL SPECIMENS WITH THE X-RAY MICROSCOPE AT BESSY (INVITED)

The transmission x‐ray microscope at the BESSY storage ring is being used for investigations in the fields of biology, biophysics, medicine, colloid chemistry, and soil sciences. The system has been instrumented for phase contrast studies with the possibility of quick change between imaging in amplitude and phase contrast mode. Phase contrast has the advantage of considerable higher image contrast and reduced radiation dosage compared to amplitude contrast. A cryogenic object chamber has been implemented on the x‐ray microscope. First experiments have shown that at cryogenic temperatures the structural stability of biological specimens is increased by three orders of magnitude in comparison with unfixed wet specimens at room temperature.

X-ray microscopy.

Owing to the short wavelengths of X-radiation X-ray microscopes allow higher resolution than optical microscopes. In contrast to electron microscopes, X-radiation can be used to study relatively thick aqueous specimens in their natural environment. X-ray microscopes require intense X-radiation, which is best provided by electron storage rings, as well as efficient X-ray optics. X-ray microscopes with zone plate optics are installed at the storage ring BESSY in Berlin for studies in the fields of biology, medicine, biophysics, colloid chemistry, and soil sciences.

V Holographic Diffraction Gratings

Publisher Summary This chapter discusses the holographic diffraction gratings and describes the basic method of making gratings holographically, to describe the results obtained and compare these results with those obtained from gratings produced by traditional means. The first experiments with grating like structures have been probably made by the American astronomer. There was a use of parallel hairs laid in a fine screw and observed diffraction effects of light. Because of the severe mechanical problems of ruling gratings many alternative methods of production are considered. Holographic plane and concave gratings with high groove densities and sinusoidal groove profiles have only been widely used up to now. These gratings have efficiency values comparable to those of classically ruled gratings but have less scattered light and are completely free of ghosts. Holographic gratings with sawtooth profiles will, therefore, only be used widely in the future when replica gratings in large series are available. The holographic methods allow the production of scales of high accuracy, especially by use of identical wavefronts, as discussed in the chapter.

Concept and Design of the SMART Spectromicroscope at BESSY II

The concept of a new spectromicroscope (SMART = spectromicroscope for all relevant techniques) currently under construction for an undulator beam line at BESSY II is discussed. The design of the optical system is described as well as the modes of operation and the experiments that can be performed. Monochromatic XUV-radiation (tunable within the energy range 20 to 2000 eV) will be provided by a planegrating monochromator and focussed onto the sample by means of an ellipsoidal mirror. In addition, an electron gun will be installed allowing LEEM, MEM and other forms of microscopy as well as small spot LEED to be performed. With an aberration corrector we expect to achieve a lateral resolution better than 5 nm and to increase considerably the transmission of the optical system compared to previous instruments. An imaging band pass filter corrected to second order will select the energy and the energy band width for the image-forming electrons. The instrument will also allow spectroscopy of photoelectrons from selected small areas of the sample (5–500 nm) with an energy resolution of 0.1 eV.