Donald H. Bilderback

Review of third and next generation synchrotron light sources

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 todays 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 Einsteins 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 Einsteins 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.

X-ray Laue Diffraction from Protein Crystals

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.

Single-bounce monocapillaries for focusing synchrotron radiation: modeling, measurements and theoretical limits

Single-bounce hollow glass capillaries with ellipsoidal shapes have been used at the Cornell High Energy Synchrotron Source recently for various microbeam experiments, with focal spot sizes from 12 to 23 microm, divergences from 2 to 8 mrad, intensities up to 450 times the intensities of incident X-rays, and working distances up to 55 mm. Simple formulae are developed in this paper to explain capillary performance given the X-ray source size, capillary dimensions and slope errors. Capillary length is optimized for best focusing performance. Capillary fabrication accuracy is reported and capillary X-ray tests confirm the focusing properties expected from formulae. The application of capillaries to third-generation X-ray sources and future energy-recovery linac X-ray sources are discussed.

Submicron concentration and confinement of hard X-rays

Abstract High-intensity hard X-ray beams of submicron diameters were generated using a tapered glass capillary as a concentrator. A complete description of the fabrication and characterization of such capillary optics is given. A new method for producing submicron X-ray collimators is also described.

Kinetics of the main phase transition of hydrated lecithin monitored by real-time X-ray diffraction.

A method is described for observing and recording in real-time x-ray diffraction from an unoriented hydrated membrane lipid, dipalmitoylphosphatidylcholine (DPPC), through its thermotropic gel/liquid crystal phase transition. Synchrotron radiation from the Cornell High Energy Synchrotron Source (Ithaca, New York) was used as an x-ray source of extremely high brilliance and the dynamic display of the diffraction image was effected using a three-stage image intensifier tube coupled to an external fluorescent screen. The image on the output phosphor was sufficiently intense to be recorded cinematographically and to be displayed on a television monitor using a vidicon camera at 30 frames X s1. These measurements set an upper limit of 2 s on the DPPC gel----liquid crystal phase transition and indicate that the transition is a two-state process. The real-time method couples the power of x-ray diffraction as a structural probe with the ability to follow kinetics of structural changes. The method does not require an exogenous probe, is relatively nonperturbing, and can be used with membranes in a variety of physical states and with unstable samples. The method has the additional advantage over its static measurement counterpart in that it is more likely to detect transiently stable intermediates if present.

Real-time X-ray diffraction using synchrotron radiation: System characterization and applications☆

Abstract Time resolved X-ray diffraction can provide information about temporal aspects of structural changes as they occur in a sample. The advent of powerful synchrotron radiation sources and the development of various fast detection systems make it possible to explore this developing area. The dynamics of wide and small angle X-ray diffraction have been recorded in real-time with a two-dimensional electro-optical detector. Performance characteristics of the detection system [3-stage image intensifier with ZnS(Ag) fluorescent screen] and read-out devices (video camera, cassette recorder/player, and monitor) are presented. Quantitative intensity information was obtained by interfacing the video recorder with a Grinnell digital image processing system. We have demonstrated the applicability of this real-time diffraction method for investigating the dynamics and mechanism of structural changes induced in a variety of materials. Samples were selected to (1) cover a range of material types representative of the various applied and basic sciences, (2) provide examples of materials that scatter well enough to investigate their wide or small angle diffraction patterns in live time, and (3) illustrate the type of perturbations that can be applied and the range of processes that can be examined.

Design of doubly focusing, tunable (5–30 keV), wide bandpass optics made from layered synthetic microstructures

Abstract Layered Synthetic Microstructures (LSMs) show great promise as focusing, high-throughput, hard X-ray monochromators. Experimental reflectivity vs. energy curves have been obtained on carbon-tungsten and carbon-molybdenum LSMs of up to 260 layers in thickness. Reflectivities for three flat LSMs with different bandppasses were 70% with ΔE E = 5.4%, 66% with ΔE E = 1.4%, and 19% with ΔE E = 0.6% . A new generation of variable bandwidth optics using two successive LSMs is proposed. The first element will be an LSM deposited on a substrate that can be water cooled as it intercepts direct radiation from a storage ring. It can be bent for vertical focusing. The bandpass can be adjusted by choosing interchangeable first elements from an assortment of LSMs with different bandpasses (for example, ΔE E = 0.005, 0.01, 0.02, 0.05, 0.1 ). The second LSM will consist of a multilayered structure with a 10% bandpass built onto a flexible substrate that can be bent for sagittal focusing. The result will be double focusing optics with an adjustable energy bandpass that are tunable from 5 to 30 keV.

Microbeam generation with capillary optics (invited)

Grazing incidence x‐ray optics for microbeam generation can be classified into five types: ellipsoidal mirror, Wolter mirror, monocapillary concentrator, microchannel array, and polycapillary concentrator. These components each have their own properties, yet they are closely related. Each optical component is at a different stage of development. Ellipsoidal mirrors are based on a mature technology and at 1/10 magnification should yield 10‐μm‐diam beams. Optics based on replicate Wolter mirrors are capable of producing beams on a 1–10 μm scale with high gain. Monocapillary concentrators are producing beam sizes of less than 0.1 μm. On a larger scale, polycapillary concentrators, and microchannel arrays are promising microbeam components. Ray tracing programs exist in different forms for some of these components. Prototype capillary optics have been tested, but as a whole, the manufacturing methods could be significantly improved with further investments in time and effort. All of these optical designs show...

Focusing of synchrotron radiation using tapered glass capillaries

Abstract A simple technique for focusing synchrotron radiation and thereby providinghigh intensity x-ray beams as small as 0.1 micron in diameter is described. Gradually tapered glass capillaries serve as the focusing elements. The first measurements of gain in the intensity of x-rays using focusing capillaries have been made.

X-ray Applications with Glass-Capillary Optics

Glass capillaries have unique properties for guiding X-rays in experiments with micrometer precision. Design considerations of such optics are presented for X-ray applications involving macromolecular crystallography, tomography and high-pressure experiments at the Cornell High Energy Synchrotron Source. The authors propose that crystallography with protein crystals is feasible on a 50 mum or smaller scale using capillary optics along with a cold gas stream and precision rotation stages. For computed tomography experiments, capillary optics can produce X-ray beams on a submicrometer scale. The distribution of X-rays passing through the sample can then be blown up in size with a secondary capillary optic to match the ~10 mum pixel size of CCD detectors. For high-pressure experiments in diamond-anvil cells, mono- and polycapillary optics may provide 1-50 mum diameter beams for diffraction or X-ray absorption fine-structure applications.