Precision Johansson Monochromators

Along with creating near perfect crystal surfaces, RIT also developed technology for controlling an induced quasimosaicity in a crystal’s surface. The mosaicity of a Ge crystal was increased by one order of magnitude to improve the crystal axial acceptance for an application requiring a large and uniform field of irradiation.

Advanced crystal machining

Traditional bent crystal techniques for making diffractive optics induce residual stress and dislocations in the crystal lattice. Our technology results in an ultra-thin crystal that virtually eliminates lattice distortions and produces a monochromator with exceptional full field illumination and precise focus.

Applications include:

• Uniform large field illumination
• High-resolution X-ray diffraction as a beam conditioning element
• High-resolution X-ray fluorescence as an analyzer
• Advanced new edge techniques such as X-ray Absorption Near Edge Spectra (XANES) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) benefit from the high selectivity, even illumination and intensity that these new optics provide. A crystal pre-test executed by one potential customer had shown a resolution of 0.2 eV for the photons with the energy around 8 keV using the Si<444> reflection.
• Electron Beam Microprobe Analysis benefits from the higher crystal resolution

Beam uniformity

At left is a typical image from RIT’s precision Johansson Monochromator. On the right is an image from a typical Monochromator with poor surface quality where a large portion of the surface does not satisfy the Bragg condition. The images are taken near the monochromator.