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Abstract: A new Optics Metrology Laboratory for assembling and characterizing beamline x-ray optical systems has been built. This replaces the old laboratory, which was demolished to make space for construction of a new flagship beamline for the forthcoming Diamond-II facility upgrade. The new cleanroom laboratory is located between several beamlines and laboratories, which intermittently generate significantly higher levels of acoustic noise and floor vibrations. A threefold design strategy was employed to create an ultra-stable environment for the sensitive, optical metrology instruments. First, the walls, ceiling and doors of the laboratory were constructed to attenuate acoustic noise. Second, the air handling systems were designed to minimize self-production of noise and vibrations. Finally, engineering solutions were developed to further isolate the metrology instruments from environmental fluctuations. Overall, despite higher levels of external disturbances, this strategy enables nano-metrology to be successfully conducted in the new laboratory. The shielded environment around each instrument achieves noise rating NR30, which is 5–25 dB quieter than the old laboratory. Over 60-h, the temperature inside the Diamond-NOM’s enclosure varied by only 0.004 °C rms, and humidity changed by <1% RH. All optical metrology instruments are now performing better than in the old laboratory: the slope error repeatability of Diamond-NOM is improved from 15 to 9 nrad rms; the GTX micro-interferometer has measured super-polished substrates with micro-roughness <40 pm rms; the new gantry for Speckle Angular Measurement is commissioned; and the HDX Fizeau interferometer has measured mirrors with slope errors <50 nrad.

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Abstract: Additive manufacturing (AM; 3D Printing), a process which creates a part layer-by-layer, has the potential to improve upon conventional lightweight mirror manufacturing techniques, including subtractive (milling), formative (casting) and fabricative (bonding) manufacturing. Increased mass reduction whilst maintaining mechanical performance can be achieved through the creation of intricate lattice geometries, which are impossible to manufacture conventionally. Further, part consolidation can be introduced to reduce the number of interfaces and thereby points of failure. AM design optimisation using computational tools has been extensively covered in existing literature. However, additional research, specifically evaluation of the optical surface, is required to qualify these results before these advantages can be realised. This paper outlines the development and metrology of an AM mirror for a CubeSat platform with a targeted mass reduction of 60% compared to an equivalent solid body. This project aims to incorporate recent developments in AM mirror design, with a focus on manufacture, testing and evaluation. This is achieved through a simplified design process of a Cassegrain telescope primary mirror mounted within a 3U CubeSat chassis. The mirror geometry is annular with an external diameter of 84 mm and an internal diameter of 32 mm; the optical prescription is flat for ease of manufacture. Prototypes were printed in AlSi10Mg, a low-cost aluminium alloy commonly used in metal additive manufacturing. They were then machined and single-point diamond turned to achieve a reflective surface. Both quantitative and qualitative evaluations of the optical surface were conducted to assess the effect of hot isostatic pressing (HIP) on the optical surface quality. The results indicated that HIP reduced surface porosity; however, it also increased surface roughness and, consequently, optical scatter.

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Abstract: Multilayer (ML) monochromators are essential components in synchrotron radiation facilities, widely used for X-ray imaging and X-ray diffraction, as well as select X-ray spectroscopy techniques. However, ML monochromators introduce stripe artefacts to the reflected beam, which degrade the quality of the X-ray images. These stripe artefacts originate from figure errors on the monochromator’s surface, which are challenging to minimise for most manufacturers. In this study, we demonstrate stripe-free imaging from ultra-high-quality ML monochromators. We employed a state-of-the-art ion beam figuring (IBF) technique to produce multilayer substrates with a cutting-edge slope error of less than 30 nrad root mean squared (rms). These substrates were coated in an advanced multilayer deposition system, enabling the production of uniform multilayer coatings. The performance of the ML monochromators was tested at the B16 test beamline at the diamond light source. Speckle-based metrology was used to verify the theoretical link between wavefront curvature and the appearance of stripe artefacts. We obtained stripe-free X-ray images from the newly fabricated ML monochromators in both single-bounce and double-bounce configurations, with excellent image clarity and flat field uniformity. This represents a breakthrough in the production of ML monochromators.

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Abstract: The plane grating monochromator (PGM) is an optical instrument used in the majority of soft X-ray beamlines. Despite its ubiquity, the PGM efficiency can easily be overestimated, because the geometry of many modern PGMs can lead to unexpected blocking of the beam. We have developed a new workflow in Python for simulating PGMs, thus extending the capabilities of SHADOW3, a well established ray tracing software tool. We have used our method to simulate the flux on branch C of the Versatile Soft X-ray (VerSoX) beamline B07 at Diamond Light Source. The simulation results demonstrate qualitative agreement with the experimental measurements, confirming the robustness of the proposed methodology.

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Abstract: Contamination or damage to X-ray optics is becoming increasingly problematic for beamlines at 3rd and 4th generation storage-rings and FEL sources. Carbon contamination, induced by ultra-intense photon-beams, can cause a major loss in flux, focusing power, and specific absorptions which are detrimental to spectroscopy. For new light sources, with higher coherence, intensity, and repetition rates, contamination and accumulated damage will occur more rapidly. Replacing damaged optics is a time-consuming, risky, and expensive task. Production times are typically >6 months, and sometimes exceed 1 year. Costs per optic are typically tens of thousands of Euro, and can exceed 100k Euro. If several optics need to be replaced on a beamline, the overall cost can be hundreds of thousands of Euros. It is not sustainable or cost effective to replace optics on a yearly basis. Most facilities have independently investigated optical contamination over many years, but coordinated action is now required before the problem gets out of control. These issues motivate two-fold action: find practical methods to slow down the rate of contamination and damage; and develop protocols to safely remove contamination and return the optic to a pristine condition. High-quality metrology and surface science techniques are required to quantify the topography and chemical nature of the contamination, and assess the effectiveness of methods to reduce or remove it. To achieve these challenging goals requires a community effort. We propose an extensive collaboration, including experts from a range of scientific disciplines at various synchrotron and XFEL labs. X-ray optic community projects have recently delivered improvements in the quality X-ray mirrors via enhanced optical metrology. It is hoped that a concerted group effort will deliver similar major advancements, thereby helping to provide beamlines with cleaner, better-performing, X-ray optics.