High Precision Lens Alignment for Macromolecular Crystallography

Researchers of the PSI have developed an innovative solution based on a two-stage demagnification microfocus module for hard X-rays based on a hybrid reflective-diffractive approach [1].
A prefocusing of the undulator source of the X10SA beamline at the Swiss Light Source (SLS) is achieved with a pair of reflective and diffractive optics which creates a secondary source. A second demagnification stage refocuses the beam to the sample position utilizing a pair of high-efficiency kinoform diffractive lenses.
Two SmarPods are used to precisely align the kinoform lenses within the X-ray beam. Per dimension, three chips containing four lenses each are mounted on top of two of the hexapod-like SmarPods. Due to the long travel ranges of these customized positioning systems an array of lenses can be mounted at once, whereas each lens combination can be positioned and precisely aligned in the X-ray beam. All mechanical units including the lenses are placed in a high-vacuum chamber. Thus, a single lens can be selected and aligned in all six degrees of freedom with nanometer precision in high-vacuum. Both SmarPods glide on a 1 meter SLLV42 rail for coarse positioning along the X-ray axis.
Macromolecular crystallography often requires focused high-intensity X-ray beams for solving challenging protein structures from micrometer-sized crystals using synchrotron light sources. The design of optical focusing schemes for hard X-rays showing high efficiency and flexibility in beam size is therefore continuously pursued.

^[1] High-intensity x-ray microbeam for molecular crys-tallography using silicon kinoform diffractive lenses, Maxime Lebugle et al., Applied Optics, Vol. 57, No. 30, 20 October 2018, doi: 10.1364/AO.57.009032