Thermomechanical Analysis and Development of a Novel Monochromator First Crystal Using an Interference Fit: A complete redesign of first crystal assemblies from first principles
Synchrotrons are particle accelerators that generate high intensity X-ray light, which is used in various disciplines including medicine (for protein sequencing), engineering (for strain analysis) and archaeology (for examination of fragile artefacts). These processes require monochromatic X-ray radiation, leading to the need for synchrotron monochromator devices. These devices are subject to demands of greater beam power and smaller footprints, such that higher resolutions can be achieved and more beamlines can be installed, as higher beam powers boost the signal to noise ratio of the experiments. This has exposed limitations in current, conventional first crystals assembly, as the heat dissipation required is very high; the first crystal receives the full beam power, and only 5-10 % is diffracted to the second crystal with the rest absorbed as heat. Through a focus on five key areas of weakness in first crystal design philosophy, a novel monochromator assembly has been constructed. The novel assembly is unconstrained at room temperature and through the use of mechanical properties is held in a firm grip at cryogenic temperatures. The deformations caused by clamping and cooling in the novel design and in a conventional design were compared experimentally; the novel design was found to exhibit surface deformations an order of magnitude lower when clamped and cooled than those observed in the conventional design due to cooling alone. The novel design had the temperature of both the crystal and heat exchanger monitored and was found to be in excellent thermal contact at cryogenic temperatures
