The combined requirements of small beam size and narrow convergence angle required for either selected-area X-ray microdiffraction analysis of large specimens or maximimum possible intensity for diffractometry of microcrystal specimens dictate the use of a focussing monocapillary optic. Our optics uniquely offer narrow beam convergence angles suitable for resolution of either large unit cells or stress/strain/pressure/temperature superlattice structure, with excellent spectral characteristics. Long output focal lengths permit the unobstructed use of complex specimen cells and environments.

Focussing monocapillary optics offer greatly enhanced beam intensity for low-divergence microbeam production compared to any other X-ray optics. Importantly, although other optics (e.g. polycapillaries) may offer greater total beam flux, the larger beam divergences employed result in a low flux per unit incident solid-angle at the specimen and a short focal depth-of-field. The resulting diffraction pattern is then 'smeared' across the detector plane within the mosaic spread acceptance of the specimen, and whilst a greater total diffracted flux is recorded, the greater detector area used results in no nett gain in signal-to-noise ratio. In fact, where the specimen mosaicity is much less than the incident beam convergence angle, the majority of the incident flux only produces incoherent scatter background from the specimen.

Contact us to advise on a combination of optical stage and optic to suit your choice of X-ray source and specimen platform. We can provide either a standard assembly or custom-made system to satisfy the constraints of your specification.

Applications

The huge variety of X-ray sources used for microdiffraction analysis invariably requires us to produce custom-made optics and housings for the majority of applications. Please see our Optical design criteria for the information you may need to specify an optical solution to your application, and contact us for an evaluation.

Microdiffraction image from a 10-micron-diameter small-molecule crystallite within a larger matrix produced using a high-gain focussing monocapillary optic
(AXCO labs)

Microbeam-Laue analysis system using W-target microfocus tube and ellipsoidal monocapillary optic, with Laue pattern produced from Si-wafer

(Courtesy CSIRO Manufacturing Technologies)