Annual Review 2024-2025

A N N U A L R E V I E W 2 0 2 4 / 2 5 34 O P T I C S A N D M E T R O L O G Y A comparison of the flux transmitted through the PGM using the ML-coated grating or a single-layer Pt-coated grating shows up to a 14-fold intensity enhancement in X-ray photoelectron spectroscopy (XPS, Figure 1b) and near-edge X-ray absorption fine structure (NEXAFS) measurements. In addition, the PGM with the multilayer stripe exhibits high flux transmission, even when it deviates from the Bragg equation. This suggests that, in some cases, strict adherence to the Bragg equation may not be necessary to achieve high flux transmission. The improved spectral resolution and flux demonstrate the potential of such gratings to enhance the performance of beamline monochromators. By extending the photon energy range, it will help many soft X-ray beamlines address additional scientific applications. The Optics & Metrology (O&M) group’s preparations for Diamond-II are now well advanced. The versatile optics test beamline B16 was reopened to users in September 2024 after remodelling to accommodate the new Diamond-II CSXID beamline at I17. The rebuilt optical metrology laboratory OML2, which had been moved to make room for CSXID, has also resumed operation. The recently established in-house multilayer fabrication lab and ion-beam figuring machine have been fully commissioned and have started to produce niche optics to go on to Diamond beamlines. The upgrade of B16 for Diamond-II has moved to the implementation phase after the successful completion and sign-off of the B16 Technical Design Report and a new double multilayer monochromator and double crystal monochromator are being designed. O&M continues its active involvement in the design and procurement of new optical components for Diamond-II. This includes the development of new software tools for simulations, such as PGMweb for plane-grating monochromators and MLgrating for multilayer gratings, as well as more streamlined procedures for writing tender documents for optical systems. Development of a high-performance multilayer grating in the tender X-ray regime Laminar and blazed gratings are commonly used in plane-grating monochromators (PGM) for soft X-ray beamlines. However, the efficiency of conventional single-layer coated gratings is poor in the tender X-ray range. Multilayer-coated gratings offer significantly higher efficiency for tender X-rays. We have designed and developed a multilayer grating for the B07 beamline (Figure 1a) in our recently established multilayer fabrication facility. After installation on the beamline, the grating demonstrated an efficiency in the energy range 1500 to 2800 eV that was significantly superior to that of a grating coated with a single layer. Optics and Metrology Figure 1: (a) Photo of multilayer grating with Pt-coated grating stripe and Cr/C multilayer-coated grating stripes. (b) The measured photoelectron spectral intensity (Au 4f) with the Cr/C multilayer stripe (black) and Pt-coated stripe (red) at a photon energy of 2800 eV. B A 40mm x 200mm Binding Energy (eV) Intensity