Compound Refractive Lens Systems (CRL Systems)

Our CRL systems are divided into three main categories:

  • Water cooled; for white, or pink, beams
  • Braid cooled; for pink or multilayer-monochromatic beams
  • Uncooled; for monochromatic beams 

Compound Refractive Lenses are used as collimating or focusing elements in X-ray beamlines on FELs and synchrotrons. A CRL is typically used on a hard X-ray line with the lens material being Be, Al or Ni as the energy increases. The refractive lenses can either be a shaped as a rotated parabola, and focus in 2D, or as a cylindrical parabola, and focus in 1D. The standard available lenses are listed on the RXOPTICS homepage from where we source Be, Al and Ni lenses.

A key feature of CRL focusing is that it is significantly less sensitive to vibrations than for instance mirror focusing: The moment transfer of a reflective mirror and a refractive CRL is given as below, where k is the is the wave vector,  ϑ is the incidence angle (or angular vibration), N is the number of lenses (typically between 10 and 100 lenses are used) and δ is the real part of refractive index (which is material and energy dependent number, but typically it is in the order of 10-6), see figure for visual representation of the moment transfer:

Mirror                 Q = 2k sin ϑ

CRL                       Q = N½ k δ

By this it can be deduced that lenses are in the order of at least, for all practical purposes, 100 times less sensitive to vibrations. The same principle can be applied to surface contaminations, so CRLs are basically insensitive to for instance carbon depositions.    

Momentum transfer for mirror and CRL (figure taken from that also gives further details).

    Images of the three CRL types are given below. As seen in the pictures the CRL systems are typically delivered with a five-way transfocator system offering; pitch, yaw, lateral, vertical and longitudinal motion of the CRL vessel.

    The systems are generally modular in design and can be scaled relatively freely. We also have smaller setups that are typically used for beam collimation, see the bottom most picture.   

    Water cooled CRL transfocator system. The showed system is deployed on the European XFEL.

    Braid cooled CRL transfocator system. The showed system is deployed on the NLSL II synchrotron. 

    Uncooled CRL transfocator system. The showed system is deployed on the NSRRC synchrotron.

    Single arm water cooled CRL setup for whitebeam collimation (designed by JJ X-Ray; developed and tested extensively at ESRF).

    See also our poster with CRL systems.