X-ray tests of microfocusing mono-capillary optic for protein crystallography

A single, borosilicate-glass capillary was drawn into a 30.5 cm long elliptical shape. The inside diameter was 0.40mm at the large base end and 0.13mm at the tip. With 12 keVX-rays from the CHESS D1 bending magnet, the single-bounce capillary produced a focus of better than 18mm in diameter (FHWM) at a 3 cm distance from the capillary tip. A flux gain of 110 in the focus position was observed along with a total flux in the spot of 4 1010X-rays/s (conditions: 5.3GeV, 182mA, 1.5 % bandwidth multilayer, 12 keV X-rays). A measurement of the far field focus ring diameter yielded a divergence of 3.8mrad, in good agreement with the 4mrad design of the optic for protein crystallography. Using a small 25mm square beam, we measured the local reflectivity to be greater than 95 % and the inner slope errors of the capillary to average about 150mrad, both from raw and elliptically shaped tubing. Our conclusion is that more perfect starting tubing (i.e. one with lower slope errors) is needed to make even more perfect elliptically figured optics i