Using refractive lenses to provide a variable spot size for Kirkpatrick-Baez mirrors.

For many X-ray microprobe experiments it is desirable to be able to vary the beam size: using large beams for survey scans and a small beam for the final measurements. Beryllium refractive lenses were found to be a simple and controllable method for enlarging the focus in a Kirkpatrick-Baez-based microprobe. They can provide variable spot size, can be quickly inserted or removed and do not move the beam center on the sample.