Diamond Annual Review 2023/24

67 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 3 / 2 4 lens can move the focal plane. It can also correct the astigmatism and coma of a KB mirror system and compensate chromatic aberrations in a compound refractive lens (CRL). Inserting an Alvarez lens is easy because it does not disturb the beam path. In tests at B16, the focal plane of an elliptical mirror with focal distance 235 mmwas displaced by ±2 mmwith minimal aberration by a combination of mirror pitch rotation and correction with the Alvarez lens. The Alvarez lens also kept the focal position of the CRL constant while the X-ray energy was varied from 13.8 keV to 16.2 keV. Assessment of cryo-cooled Si monochromator crystals for Diamond-II Si double crystal monochromators (DCMs) are key optical components in Diamond’s hard X-ray beamlines. Thermal deformation of the first DCM crystal degrades the performance. A cooling scheme that minimises this deformation must be developed when a DCM is designed or when the power of the incident beam is substantially increased. The latter is true for Diamond-II; therefore, the beamline performance of all Diamond’s DCMs must be reassessed. Finite element analysis (FEA), the usual tool for predicting thermal deformation, is time-consuming, and for each DCM, multiple cooling schemes may need to be trialled. The Optics and Metrology group has therefore developed a simple theoretical model to evaluate and assess the DCM cooling schemes. For each cooling scheme, a curve of critical power versus power density is generated by heat transfer equations. If the expected incident power and power density on the DCM’s first crystal lie below this curve, the cooling scheme passes and may be considered further. Experimental data and FEA simulations on DCMs at several undulator beamlines at Diamond have validated this model (Figure 8) . Publications 1. Dhamgaye, V. et al. Alvarez varifocal X-ray lens. Nature Communications 14 (1), 4582 (2023). https://doi.org/10.1038/s41467-023-40347-1 2. Sutter, J. P. et al. Developments in X-ray optics modelling at Diamond Light Source. Synchrotron Radiation News 36 (5), 28-32 (2023). https://doi.org/10. 1080/08940886.2023.2274754 3. Hu, L. et al. Research on the beam structures observed from X-ray optics in the far field. Opt. Exp. 31 (25), 41000-41013 (2023). https://doi.org/10.1364/ OE.499685 4. Morrow, K. et al. Correcting retrace and system imaging errors to achieve nanometer accuracy in full aperture, single-shot Fizeau interferometry. Opt. Exp. 31 (17), 27654-27666 (2023). https://doi . org/10.1364/OE.498043 5. Nistea, I.-T. et al. Diamond-VeNOM: a high-speed slope profiler for characterising X-ray mirrors. Proc. SPIE 12695 , 126950A (2023). https://doi. org/10.1117/12.2688134 6. Sutter, J. P. et al. X-ray topography of diffracting crystal optics at the Diamond Light Source. Proc. SPIE 12694 , 1269409 (2023). https://doi. org/10.1117/12.2675894 7. Sutter, J. P. et al. PyCSFex: an extensible Python 3 package for calculating X-ray structure factors in complex crystals. Proc. SPIE 12697 , 126970A (2023). https://doi.org/10.1117/12.2676361 8. Bainbridge, E. V. et al. Passive doubly curved structures for determining clamping forces applied to X-ray optic assemblies. J. Synchrotron Rad. 30 (6), 1143-1148 (2023). https://doi.org/10.1107/S1600577523007579 9. Yacoot, A. et al. Measuring sub-nanoradian angles. Presented at Sensor and Measurement Science International (SMSI) 2023, Chapter D6 “Nanomeasurements and Nanofabrication.” https://doi.org/10.5162/ SMSI2023/D6.2