Crystal Science

Crystal Scientific specialize in producing diffraction crystals for second and third generation synchrotron sources. Third generation synchrotrons and new sources with enhanced performance such as Free Electron Lasers (FEL), place high demands on diffraction optics. The severe heat loads imposed mean that the crystals must be cooled to minimise scattering. We specialise in using low thermal expansion materials such as single crystal silicon for just this purpose. Our diffraction crystals are principally used in x-ray monochromators both single, channel cut, and double crystal designs. A number of cooling systems can be applied to the crystals which can require precise machining of channels or holes in the crystal. Precise orientation of the crystal is vital in order to produce high quality characteristics. X-ray crystallographic techniques are used to orientate the crystal for machining to an accuracy of 0.05 degrees. All crystals are supplied with full x-ray characterisation data. Diffraction crystals from Crystal Scientific are now in operation in sychrotron beamlines in all the new facilities worldwide.

Many synchrotron research techniques are pushing for smaller focused spot sizes. The major technical barrier to producing KB pairs with the required performance has been the difficulty in reproducibly achieving the extremely high specifications in both slope error and micro-roughness required for the elliptical mirrors. Crystal Scientific utilises a unique methodology to overcome this barrier. Super high quality spherical surfaces with state-of-the-art slope errors and micro-roughness (better than 0.4 µradian and

Using a channel cut crystal is the simplest way of achieving a "double crystal" monochromator set up. Fabricating the "first" and "second" crystals from a single piece of silicon ensures parallelism between the refracting planes without the necessity of mechanisms to maintain the alignment. The main disadvantage of channel cut crystals is that the beam position cannot be maintained during an energy scan. Bragg angle ranges are also limited by the length of the "second crystal" part.

Crystal Scientific specialize in producing mirrors for second and third generation synchrotron sources. Third generation synchrotrons and new sources with enhanced performance such as Free Electron Lasers (FEL), place high demands on reflection optics. The severe heat loads imposed mean that the mirrors must be cooled to ensure their geometric shape is preserved and slope errors minimised. We specialise in polishing high heat conductivity and low thermal expansion materials such as single crystal silicon for just this purpose. We have developed sophisticated techniques in machining, lapping and polishing to achieve high accuracy. Our extensive suite of metrology tools allows frequent checks of slope and roughness during the polishing process to ensure the highest possible quality.

The latest generations of synchrotrons place high demands on diffraction optics. The severe heat loads imposed mean that the crystals must be cooled to minimise scattering. Cooling can involve boring holes through the crystal for water cooling or cutting cooling fins. We have the precise tools available to machine the crystal to your specification. An example is shown here.

Sagittal focusing crystal systems were primarily developed to focus broad x-ray fans from bending magnet sources. The sagittal focusing crystal is used as the second crystal in a double crystal monochromator. As well as acting as the second crystal, bending the crystal into a cylindrical shape results in horizontal focusing of the beam. Bend radii can be quite extreme (5 to 1m radius of curvature) and so careful mechanical design of the crystal, together with precision manufacturing, is critical for performance. A wide variety of designs exist with the rib dimensions and repeat distances being optimised for different applications.

Cylindrical mirrors can be produced to the following specifications: Length up to 1.4m Slope errors as low as 1.25 microradians over 900mm Roughness

The quality of x-ray mirrors that are produced today is significantly better (slope error and surface roughness) than that which was available 5-10 years ago. Thus there are many large optics installed world wide with slope and roughness characteristics that can be improved. In addition mirror coatings degrade (surface contamination) over time resulting in a reduction in performance. In order to provide customers with an optics upgrade path that doesn't require a complete new mirror purchase, we offer a refurbishment service for x-ray mirrors. At a basic level this involves stripping off old coatings and replacing the coating. This can be done for any mirror shape. Furthermore we offer to repolish, and then recoat, existing mirrors to improve slope errors and surface roughness. This is especially attractive for plano mirrors as our plano polishing techniques are rapid, allowing us to achieve high quality results in a few weeks. This makes it a practical proposition to consider refurbishing a mirror during a short shutdown.

Plano mirrors can be produced to the following specifications: Length up to 1.2m physical, 1.1m optical Slope errors as low as