Designing X-ray Microbeam Experiments with Glass
Capillaries - Present and Future Opportunities
Don Bilderback and Rong Huang
CHESS
Hollow glass monocapillaries can be drawn into useful shapes for making precision x-ray microbeams for applications in crystallography (protein, high-pressure, etc.), fluorescence, imaging, etc.. We discuss how to design a capillary shape given the properties of the CHESS source, microbeam size and divergence desired. We will give specific examples of design and performance for the CHESS F1 protein crystallography station where a 14 x 18 micon beam size with 1.7 mrad divergence has been used for microcrystallography. Another application is to have a higher gain in flux/micron2 for x-ray fluorescence where 10 mrad of divergence can be tolerated.
We will discuss the performance limits of the current DB2 glass pulling machine and talk about the plans for upgrading to even higher performance. Currently, we can make single-bounce focusing capillaries with figure errors of 1 to 2 microns and slope errors of order 70 microradians for parts that are 20 to 100 mm in length. Flux gains of 10 to 1000 have been observed depending on the amount of divergence tolerable for the application. Beam sizes can be in the range of sub-micron to 30 micron in diameter.
We will also mention longer range efforts to construct the ultimate microbeam source of x-rays based on the Cornell proposed Energy Recovery Linac source of x-rays that could be demagnified down to perhaps a 1 nm beamsize where even single-atom x-ray experiments could be performed some 10 or more years into the future.