Diamond Annual Review 2023/24

65 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 theoretical tool for evaluating optics cooling designs rapidly. The Optics and Metrology group is also leading the procurement of all new optics for Diamond-II. New optics metrology lab The OML in Zone 12 was decommissioned and rebuilt in Zone 4. The new OML required special measures to shield the sensitive metrology instruments from the vibrations and acoustic noise produced by the multiple beamlines, peripheral labs, the loading bay, and the plant equipment surrounding it. Wall panels and doors with improved sound absorption were installed, the speed of the fans was lowered, and the ductwork was supplied with vibrational and acoustic damping. In collaboration with the Engineering group, enclosures (Figure 1) were developed to shield the instruments from fluctuations in the surrounding air, and platforms were developed to provide passive and active vibration damping to the instruments mounted on them (Figure 2) . Overall, despite stronger external disturbances, the lab achieves exceptional stability in temperature (< 0.01°C) and humidity (<5%), and the metrology instruments are performing better than in the old OML. The Diamond-NOM now achieves a repeatability ~ 9 nrad rms and a high-speed Diamond-VeNOM optical profiler has been developed to speed up the optics metrology measurements. The new OML is now fully operational. Reconstruction of B16 The planned construction of the CSXID beamline also required the control room of the B16 Test Beamline to be moved to a new location at the end of its experimental hutch (Figure 3) . The experimental hutch therefore also had to be modified with new doors, new chicanes, a reconfigured Personal Safety System, and an altered search route. Contractors managed by the Diamond Installation and Facilities Management group, in collaboration with the B16 technical working group, completed the design and planning stage in December 2023. The reconstruction of B16 began in January 2024 and is scheduled for completion in June 2024. During this period, B16 is not available to users, but other upgrades such as the replacement of several motion axis controllers will be done to prepare for Diamond-II. Ion beamfiguring of X-ray mirrors State-of-the-art X-ray mirrors demand height errors below 1 nm and micro-roughness of several Å over lengths of tens of centimetres. These stringent specifications present a formidable challenge. The application of ion beam figuring (IBF) to remove excess material over selected areas on a pre-polished surface shows promise. An in-house IBF system has now been developed at Diamond (Figure 4a ). It consists of a large-diameter DC gridded ion source, a four-axis motion stage equipped with a uniquely designed holder, and a high-resolution camera for precise workpiece alignment. The ion beam remains stationary as the workpiece moves. An onboard laser speckle angular measurement (SAM) system provides real-time metrology feedback. An aperture plate passes ion beams of various shapes and sizes, thus enabling both coarse and fine figure corrections. This IBF apparatus has been used to correct flat Si mirrors of 50 × 20 mm 2 area. The rms height error of a plane mirror was reduced to below 1 nm and the rms slope error was reduced below 100 nrad (Figure 4b and c). The combination of sub-nanometre rms Figure 2: (Left) Accelerometer scans showing vibrational velocity over time during Diamond-NOM fly scans with and without the new active damping. (Right) The closed-loop geophone/voicecoil active damping system. Figure 3: Layout of the new control room (K16 CC) at the end of the experimental hutch (K16 EH). Figure 4: (a) Inside view of the IBF system. (b) Height error map of a Si X-ray mirror before IBF figure correction. (c) Height error map of the same mirror after one iteration of IBF figure correction. Figure 5: Photograph of Diamond’s multilayer deposition system.