Focusing compound refractive Beryllium lenses

A set of four compound refractive x-ray lenses (CRL), made out of Beryllium, is installed in OH2 at an optical distance of 94 m from the source point. Their role is to provide a better vertical focus as the one obtained by the toroidal mirror. This is achieved thanks to the larger demagnification M (M = q/p = 0.085) with respect to the standard optical setup, using the toroidal mirror (M = 0.33). The use of the focusing CRL is optional and intended for experiments which need a very small spot size on the sample. In order to ensure the highest throughput, the focusing CRL has to be used in conjunction with the collimating CRL. If one assumes a perfect vertical collimation of the X-ray beam (s_z’ = 0), the equation for the focusing lens becomes:

R/N=2 q

where R is the radius of the hole, N the number of holes, d is the refractive index decrement, and q the distance between the lens and the focal plane.

Table X summarises the characteristics of the focusing CRL’s.

The web thickness in the center axis of the lens is 0.1 mm. The focusing lens system is currently being commissioned.

Picture 1 : View of the CRL Be lenses vacuum chamber.	Picture 2 : Be lenses installed on the goniometer head.
Picture 3 : View of the CRL Be lenses inside the vacuum chamber.