An X-ray optical system with an X-ray source (Q) and a first graded multi-layer
mirror (A), wherein the extension Qx of the X-ray source (Q) in an x
direction perpendicular to the connecting line in the z direction between the X-ray
source (Q) and the first graded multi-layer mirror (A) is larger than the region
of acceptance (F) of the mirror (A) at a focus (Oa) of the mirror (A)
in the x direction, is characterized in that a first collimator (bl) is disposed
at a focus of the first graded multi-layer mirror (A) between the X-ray source
(Q) and the mirror (A) whose opening in the x direction corresponds to the region
of acceptance of the first graded multi-layer mirror (A) and the separation qzA
between first collimator (bl) and X-ray source (Q) is:
wherein x is the angle subtended by the first graded multi-layer
mirror (A) in the x direction, as viewed from the first collimator (bl). This permits
reduction of the disturbing radiation on the sample for constant useful X-radiation
power from the source Q.
