In parallel beam X-ray diffraction analysis, a multi-capillary collimating optical crystal can be used to form a high-intensity parallel X-ray excited beam, resulting in a very high X-ray intensity on the sample surface. The definition of X-ray diffraction is

For the parallel beam geometry, the sample position can change, and the XRD system is no longer limited by making the distance between the X-ray source and the sample equal to the distance between the sample and the detector. The flexibility of the geometry can be adapted to existing manufacturing conditions and can be used for a wider range of sample shapes and sizes. Parallel beam XRD is not only insensitive to errors related to sample displacement; Virtually all other well-known instrumental error functions are also eliminated.

Parallel beam XRD using X-ray optical crystals has been successfully applied in thin film analysis and sample texture evaluation.