Synchrotron radiation (SR) is having a very large impact on interdisciplinary science and has been tremendously successful with the arrival of third generation synchrotron x-ray sources. But the revolution in x-ray science is still gaining momentum. Even though new storage rings are currently under construction, even more advanced rings are under design (PETRA III and the ultra high energy x-ray source) and the uses of linacs (energy recovery linac, x-ray free electron laser) can take us further into the future, to provide the unique synchrotron light that is so highly prized for today's studies in science in such fields as materials science, physics, chemistry and biology, for example. All these machines are highly reliant upon the consequences of Einstein's special theory of relativity. The consequences of relativity account for the small opening angle of synchrotron radiation in the forward direction and the increasing mass an electron gains as it is accelerated to high energy. These are familiar results to every synchrotron scientist. In this paper we outline not only the origins of SR but discuss how Einstein's strong character and his intuition and excellence have not only marked the physics of the 20th century but provide the foundation for continuing accelerator developments into the 21st century.

Tapered glass capillaries have successfully condensed hard x-ray beams to ultrasmall dimensions providing unprecedented spatial resolution for the characterization of materials. A spatial resolution of 50 nanometers was obtained while imaging a lithographically prepared gold pattern with x-rays in the energy range of 5 to 8 kiloelectron volts. This is the highest resolution scanning x-ray image made to date with hard x-rays. With a beam 360 nanometers in diameter, Laue diffraction was observed from the smallest sample volume ever probed by x-ray diffraction, 5 x 10(-3) cubic micrometers.

Structural information on an atomic scale has been obtained for a Langmuir-Blodgett (LB) trilayer system by means of long-period x-ray standing waves. The LB trilayer of zinc and cadmium arachidate was deposited on a layered synthetic microstructure (LSM) consisting of 200 tungsten/silicon layer pairs with a 25 A period. A 30 A thermally induced inward collapse of the zinc atom layer that was initially located in the LB trilayer at 53 A above the LSM surface has been observed. The mean position and width of the zinc atom layer was determined with a precision of +/- 0.3 A.

A confocal x-ray fluorescence microscope was built at the Cornell High Energy Synchrotron Source (CHESS) to determine the composition of buried paint layers that range from 10-80 µm thick in paintings. The microscope consists of a borosilicate monocapillary optic to focus the incident beam and a borosilicate polycapillary lens to collect the fluorescent x-rays. The overlap of the two focal regions is several tens of microns in extent, and defines the active, or confocal, volume of the microscope. The capabilities of the technique were tested using acrylic paint films with distinct layers brushed onto glass slides and a twentieth century oil painting on canvas. The position and thickness of individual layers were extracted from their fluorescence profiles by fitting to a simple, semi-empirical model.

Practically all synchrotron x-ray sources to data are based on the use of storage rings to produce the high current electron ͑or positron͒ beams needed for synchrotron radiation ͑SR͒. The ultimate limitations on the quality of the electron beam, which are directly reflected in many of the most important characteristics of the SR beams, arise from the physics of equilibrium processes fundamental to the operation of storage rings. It is possible to produce electron beams with superior characteristics for SR via photoinjected electron sources and high-energy linacs; however, the energy consumption of such machines is prohibitive. This limitation can be overcome by the use of an energy recovery linac ͑ERL͒, which involves configuring the electron-beam path to use the same superconducting linac as a decelerator of the electron beam after SR production, thereby recovering the beam energy for acceleration of new electrons. ERLs have the potential to produce SR beams with brilliance, coherence, time structure, and source size and shape which are superior to even the best third-generation storage ring sources, while maintaining flexible machine operation and competitive costs. Here, we describe a project to produce a hard x-ray ERL SR source at Cornell University, with emphasis on the characteristics, promise, and challenges of such an ERL machine.

In conventional x-ray diffraction experiments on single crystals, essentially monochromatic x-rays are used. If polychromatic x-rays derived from a synchrotron radiation spectrum are used, they generate a Laue diffraction pattern. Laue patterns from single crystals of macromolecules can be obtained in less-than 1 second, and significant radiation damage does not occur over the course of an exposure. Integrated intensities are obtained without rotation of the crystal, and individual structure factors may be extracted for most reflections. The Laue technique thus offers advantages for the recording of diffraction patterns from short-lived structural intermediates; that is, for time-resolved crystallography.

Otoliths, the carbonate earstones of fishes, take up minor and trace amounts of elements as they accrete through a fish's life. We apply synchrotron microbeam x-ray fluorescence methods to establish a breakthrough in high-resolution, simultaneous area mapping of multiple trace elements in otoliths, with spatial resolution down to 20 µm and trace element detection down into the part per million range for multiple elements. Concentration maps of Ca, Sr, Zn and, for the first time, Ba, Mn, and Se are obtained simultaneously. Combinations of these elemental maps provide new insights into the environmental history of fishes and their lifetime movements, illustrated by several case studies. This method helps pave the way toward improved spatial analysis of otolith microchemistry.

X-ray test results from a prototype 92 Â 100 pixel array detector (PAD) for use in rapid time-resolved X-ray diffraction studies are described. This integrating detector is capable of taking up to eight fullframe images at microsecond frame times. It consists of a silicon layer, which absorbs the X-rays, bump-bonded to a layer of CMOS electronics in which each pixel has its own processing, storage and readout electronics. Tests indicate signal performance characteristics are comparable with phosphorbased CCD X-ray detectors, with greatly improved time resolution, comparable linearity and enhanced point spread. This prototype is a test module en route to a larger detector suitable for dedicated operation. Areas of needed improvement are discussed.