Apertures with finely adjustable blades enable a sharp limitation of X-ray cross-sections with various geometries.
The materials used for the blades are heavy metals such as W or Ta. The adjustment of the blades is either via a manual or motorised spindle drive (step or DC motor). The movement of opposite blades is either symmetrical or asymetrical depending on the type of aperture.
The length of slit apertures can be limited by large cross aperture gates.
Soller slits (segment slits, Venetian blinds) reduce the divergence of the beam in slit direction behind slit apertures.
Collimators are pinhole apertures used for generating point-shaped beam cross-sections with lowest possible divergence.