Single Crystal Diamond Compound Refractive Lenses

JJ X-Ray and the Danish Technical University have over the last two years been developing Compound Refractive Lenses (CRL) of Single Crystal Diamonds (SCD´s) and will continue the development in foreseeable future.

The lens shape is carved using a short-pulsed laser and subsequently, the surface roughness is improved by various wet and dry etches. The dry etches can also be used to minimize the web of the dual lens in a diamond. The shape of the lens can be made relatively freely and thus be tailored to the parameters of the specific beamline, they will be deployed for. It is also possible to make more lenses in one diamond, e.g. a 2D and a 1D lens can be positioned next to each other, see Figure 1. This means that both focusing types could be available in one CRL system and selected between by simply translating the whole system.

Figure 1 2D and 1D lenses in the same diamond.

While diamonds do absorb more than Be, they have a comparatively higher refractive index at high energies yielding an overall higher available flux, see Figure 2.

Figure 2 Normed flux availability for a 1D lens made in Be vs Al vs Diamond when focusing with p=46.7m, q=56.5m and a lens number N between 1-95. By courtesy of Mati Meron APS, 2018

The SCD lenses can be packaged in Cu disks. The Cu disks give a thermal path with a low resistance ideal for white beam applications.

The current Generation II, GII, SCD lenses have been characterized on the 1BM beamline at APS where a CRL consisting of seven dual SCD lenses was found to focus an 8keV beam up to 2.1 times the theoretical beam size. The individual SCD lenses were characterized by Talbot interferometry and found to have a residual standard height deviation below 3µm, see Figure 4 and Figure 5. The height error was generally driven by a systematic error that we expect to eliminate in the GIII lenses which we are working on now. An article on the GII data is in the making and will be linked to when it is published.

We are continually working on improving the lenses and discounts are given to customers wishing to upgrade their SCD lenses to a later generation. GII is available now, see table below for the projected availability of the coming generations.

Generation  Projected availability Residual height error [σ µm]
II Now < 3.0
III February 2020 < 2.2
IV November 2020 < 1.6

Figure 4 Talbot reconstructed shape measurement of a single SCD dual lens.

Figure 5 Residual height error of a SCD lens. The doughnut like height error is systematic for the GII lenses.