We report the results of our research and development in techniques for producing elliptical x-ray mirrors by controlled bending of a flat substrate. We review the theory and technique of mirror bending with emphasis on the optical engineering issues and describe our design concepts for both metal and ceramic mirrors. We provide analysis of the various classes of error that must be addressed to obtain a high quality elliptical surface and a correspondingly fine focus of the x-ray beam. We describe particular mirrors that have been built, using these techniques, to meet the requirements of the scientific program at the Advanced Light Source at Lawrence Berkeley National Laboratory. For these examples, we show optical metrology results indicating the achievement of surface accuracy values around and, in some cases, below 1 rad as well as x-ray measurements showing submicrometer focal spots.

The x-ray exposure at which significant radiation damage occurs has been quantified for frozen crystals of bacteriorhodopsin. The maximum exposure to approximately 11-keV x-rays that can be tolerated for high-resolution diffraction experiments is found to be approximately 10(10) photons/microm(2), very close to the value predicted from limits that were measured earlier for electron diffraction exposures. Sample heating, which would further reduce the x-ray exposure that could be tolerated, is not expected to be significant unless the x-ray flux density is well above 10(9) photons/s-microm(2). Crystals of bacteriorhodopsin that contain approximately 10(11) unit cells are found to be large enough to give approximately 100 high-resolution diffraction patterns, each covering one degree of rotation. These measurements are used to develop simple rules of thumb for the minimum crystal size that can be used to record x-ray diffraction data from protein microcrystals. For work with very small microcrystals to be realized in practice, however, it is desirable that there be a significant reduction in the level of background scattering. Background reduction can readily be achieved by improved microcollimation of the x-ray beam, and additional gains can be realized by the use of helium rather than nitrogen in the cold gas stream that is used to keep the protein crystals frozen.

A new beam line (beam line 11.0) at the Advanced Light Source has been designed to employ a Variable-Included-Angle Plane-Grating-Monochromator. The extended range available from a specific grating is exploited to cover energies from the carbon 1s absorption edge to the oxygen 1s absorption edge with two different gratings (150l/mm and 1200l/mm) with dispersion different by a factor of three. The phase space of a zone plate microscope can then be efficiently filled either at low or high resolution (R=2500 and R=7500).At the same time the monochromator is designed to cover the energy range from 75eV to 1500eV using the same two gratings at high resolution for spectroscopy. A deformable mirror pair will re-focus to a monochromatic spot 5 x 10 microns, matched into the acceptance of a fluorescence spectrometer.The monochromator will operate in vertically collimated light and the free choice of focussing parameter provides a guarantee of high resolution even when the power loading is high. However, we will provide a thermally engineered pre-mirror so that the high resolution requirement at low photon energy can be met without loss of efficiency.

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