Using refractive optics to broaden the focus of an X-ray mirror.

David Laundy,Vishal Dhamgaye,Kawal Sawhney

doi:10.1107/s1600577517006038

David Laundy, Vishal Dhamgaye + Show 1 more

Open Access

https://doi.org/10.1107/s1600577517006038

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Abstract

X-ray mirrors are widely used at synchrotron radiation sources for focusing X-rays into focal spots of size less than 1 µm. The ability of the beamline optics to change the size of this spot over a range up to tens of micrometres can be an advantage for many experiments such as X-ray microprobe and X-ray diffraction from micrometre-scale crystals. It is a requirement that the beam size change should be reproducible and it is often essential that the change should be rapid, for example taking less than 1 s, in order to allow high data collection rates at modern X-ray sources. In order to provide a controlled broadening of the focused spot of an X-ray mirror, a series of refractive optical elements have been fabricated and installed immediately before the mirror. By translation, a new refractive element is moved into the X-ray beam allowing a variation in the size of the focal spot in the focusing direction. Measurements using a set of prefabricated refractive structures with a test mirror showed that the focused beam size could be varied from less than 1 µm to over 10 µm for X-rays in the energy range 10-20 keV. As the optics is in-line with the X-ray beam, there is no effect on the centroid position of the focus. Accurate positioning of the refractive optics ensures reproducibility in the focused beam profile and no additional re-alignment of the optics is required.

Highlights

X-ray optical elements such as X-ray mirrors or refractive lenses are commonly used on synchrotron radiation beamlines to focus X-ray beams down to the sub-micrometre level for high-spatial-resolution microprobe experiments and for X-ray diffraction measurements from small crystalline samples
This should be done with no significant reduction in the overall beam intensity in the focal spot and the change should be fast in order to meet the demands of rapid data collection at modern synchrotron radiation sources
In a second publication we presented the use of hybrid optics in order to reduce the focus size of the optics of an X-ray beamline (Sawhney et al, 2016)

Summary

Introduction

X-ray optical elements such as X-ray mirrors or refractive lenses are commonly used on synchrotron radiation beamlines to focus X-ray beams down to the sub-micrometre level for high-spatial-resolution microprobe experiments and for X-ray diffraction measurements from small crystalline samples. It is frequently desirable to be able to broaden the focus size in order, for example, to allow larger sample areas to be imaged more rapidly at lower spatial resolution or to allow the beam size to be matched to a diffracting crystal in order to reduce the sample radiation dose and minimize radiation damage during a measurement This should be done with no significant reduction in the overall beam intensity in the focal spot and the change should be fast in order to meet the demands of rapid data collection at modern synchrotron radiation sources. By applying the modification in separate parallel lanes running along the length of the mirror, we were able to demonstrate that the beam size could be reproducibly changed by translating the mirror laterally This concept has recently been used to specify a seven-lane mirror for the VMXm macromolecular crystallography beamline at the Diamond Light Source, UK (Trincao et al, 2015). The LIGA process allows large numbers of devices made from the polymer SU8 to be made on a single silicon wafer substrate

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