Development of high throughput multilayer x-ray beam conditioning optics for hard x-ray.

摘要

Graphite monochromator and total reflection mirror (TR) systems have been widely used as x-ray beam conditioning optics for diffractometers and many other kinds of instruments. These optics serve as collimating tools, intensity enhancement tools, and band pass filters. A graphite monochromator is a Bragg reflector and delivers monochromatic beam. But the collimating and enhancement capability is poor. In some cases, for example protein crystallography, TR with Ni filter can deliver 2.5 to 5 times more flux than a graphite monochromator. However, the background is noisy.; A new family of graded d-spacing multilayer optics have been designed, fabricated, and tested for several different applications. X-ray multilayer has a larger reflection angle, resulting in high collection efficiency. A multilayer also serves as a monochromator. No additional filtration is necessary. Utilizing a variation of Kirkpatrick-Baez scheme called the "side-by-side" scheme enables the placement of both mirrors at the most optimized location. Protein diffraction experiments have shown that the intensity is increased by about 5 to 6 times over a total reflection setup. There is also improved spectrum purity. The Cu Kbeta component is reduced by about 100 times compared to a 15mum Ni filter. Small angle x-ray diffraction tests have proven that the beam size on the detector (resolution) is reduced by three times compared to a graphite monochromator system. Meanwhile, flux is increased by about one order.; The new optics have also been used for a microfocusing application. Comparing with other optics, the new optics offer larger numerical aperture, controllable band pass, and compact size. Preliminary tests indicates a focal size of about 10 micrometers and an intensity gain of more than three orders.; This thesis will present an overall picture about these developments. The characteristics of multilayers are first discussed. Several commonly used optics are then studied. Theoretical investigation of the possible improvement on the performance of diffractometers, while using the new optics, is presented. Finally the possibility of using the optics for a microfocusing application is studied.