Novel Instrumentation for X-ray and Neutron Facilities

The Basic Energy Sciences (BES) program invites applications for development of technologies to support its X-ray and neutron scattering scientific user facilities and advance BES missions in designing and building next-generation facilities. As science-driven X-ray and Neutron beam performance requirements increase, new technologies in accelerators, optics, instrumentation, and detectors are needed to generate, shape, and use these beams.

Areas of Interest Specific areas of interest include the following:

a. Permanent magnet-based accelerator elements: A promising future upgrade path for DOE BES light sources and accelerator facilities is a new “Complex Bend” (CB) lattice that requires combined-function permanent magnet quadrupoles (PMQs). These PMQs integrate both bending (dipole) and strong focusing (quadrupole) magnetic fields within a single

magnet assembly. Their compact design saves longitudinal space, addressing a common constraint in low-emittance lattice design.

Goals and Metrics • The magnetic field strength requirements for these combined-function magnets are 0.5 Tesla for the dipole component and 130 Tesla per meter (T/m) for the quadrupole component. Additionally, the magnetic field must maintain a low level of higher-order multipoles (harmonics), specified as 10 units (1000 ppm) within a 3 mm good field region. Meeting this requirement is particularly challenging given the small magnet aperture (16 mm diameter), which increases sensitivity to mechanical and magnetic material errors. • Proposals are sought for the development of two types of combined-function permanent magnet quadrupoles (PMQs): o A hybrid PMQ design that combines PM with soft iron pole materials. o A Halbach-type PMQ that uses only PM and offers more compact design geometry than the hybrid design. • Further research and development (R&D) are needed to address key challenges associated with both designs and to meet the following requirements: o Magnetic field correction after assembly o Tunability of the magnetic field (± 2 %) o Precise alignment within 15 μm o Enhanced radiation resistance of permanent magnet materials enabling a lifecycle exceeding 30 years

References 1. Halbach, K., Design of Permanent Multipole Magnets with Oriented Rare Earth Cobalt Materials, Nuclear Instruments and Methods, vol. 169, p. 1, 1980. Available at https://doi.org/10.1016/0029-554X(80)90094-4. 2. Shaftan, T., Smaluk, V., and Wang, G., The Concept of Complex Bend, Brookhaven National Laboratory, NSLS-II Tech Note 276, 2018. Available at https://technotes.bnl.gov/PDF?publicationId=211211. 3. Brooks, S., et al., Permanent Magnets for the Return Loop of the Cornell-Brookhaven Energy Recovery Linac Test Accelerator, Physical Review Accelerators and Beams, vol. 23, 112401, 2020. Available at https://doi.org/10.1103/PhysRevAccelBeams.23.112401. 4. N'Gotta, P., et al., Hybrid High Gradient Permanent Magnet Quadrupole, Physical Review Accelerators and Beams, vol. 19, 122401, 2016. Available at https://doi.org/10.1103/PhysRevAccelBeams.19.122401. 5. N'Gotta, P., et al., Development of Permanent Magnets Dipole-Quadrupole for NSLS- IIU, Invited talk at Low Emittance Ring – Permanent Magnet Workshop, Trieste, Italy, November 14–15, 2023. Available at https://indico.cells.es/event/1373/contributions/2340/attachments/1631/3352/Low_Emitta nce_Ring_PM_Workshop_Ngotta.pptx.

b. In situ X-ray optics cleaning methods: An X-ray optical system typically consists of one or more mirrors or gratings housed in an ultra-high vacuum (UHV) chamber, along with in-vacuum and/or out-of-vacuum precision motion and mechanical systems. The optical and mechanical requirements for X-ray optics at diffraction-limited synchrotron light sources and free-electron laser facilities are extremely demanding, as they must preserve the source's wavefront and intensity. These optics are often made from single-crystal silicon, polished to a shape with subnanometer figure errors, and typically coated with transition metals and/or boron carbide to improve X-ray reflectivity and/or diffraction efficiency.

The fabrication, characterization, assembly, and installation of these X-ray optical systems are extremely challenging and costly due to the stringent requirements for cleanliness, precision, and stability. Unfortunately, carbonaceous buildup on the optical surfaces during operation is inevitable. This contamination worsens the figure error and, in turn, degrades the X-ray beam. An in-situ method for servicing these optics to restore their original high-quality figure is therefore required to reduce the effort for maintenance or performance recovery and minimize operational downtime.

Goals and Metrics Proposals are sought for the design of an instrument/apparatus that applies a verified method for cleaning highly precise X-ray optics in-situ that meet the following criteria/requirements: • The method must demonstrate the following properties: o Applicability for substrates made of common materials for X-ray optics, such as single crystal silicon and fused silica, up to 1 meter in length o Applicability to substrates with common coating thin-film materials, such as Au, Ru, Pt, SiC, B4C, Mo/Si, and Ni. Note that cleaning different coatings may require different approaches. Approaches that can address multiple coatings are strongly encouraged. o Preservation of the quality and property of the polished surface, i.e., micro roughness and figure error, without oxidation and/or degradation of the optic mechanics, mounting components, or vacuum chamber o Permanent device installation, or on a per-cleaning-need on the vacuum chamber o Utilization of a non-toxic gas or cleaning agent that does not require special handling of the source gas or the exhaust gas • The instrument/apparatus and cleaning method must be UHV compatible • All necessary mechanics, electronics, and controls components must be provided as part of the design package. • A proven and repeatable cleaning recipe for each type of addressable coating is provided with the method.

Note: Applicants are further encouraged to study literature in the following areas: • Plasma Cleaning Techniques for synchrotron mirrors. • Atomic Hydrogen Cleaning • In-Situ Cleaning and Prevention • Advanced Cleaning Technologies [as applied to Extreme Ultraviolet (EUV) lithography] • Mirror Lifetime and Degradation Studies

References 1. Oxford University Press, Coherent X-ray Optics, D. Paganin, 2007, https://academic.oup.com/book/doi/10.1093/acprof:oso/9780198528606.001.0001. 2. Carbon contamination of soft X-ray beamlines: dramatic anti-reflection coating effects observed in the 1 keV photon energy region, C. Chauvet, F. Polack, M. G. Silly, B. Lagarde, M. Thomasset, et al., Journal of Synchrotron Radiation, vol. 18, p. 761, 2011. Available at https://doi.org/10.1107/S0909049511023119.

c. Strain-engineered optics for next-generation X-ray spectroscopy: X-ray spectroscopy is a critical tool for detailed characterization of advanced materials relevant to quantum information, chemical catalysis, and biological processes, particularly in the hard X-ray regime (~6 keV to 15 keV). A key limitation of current instruments is the trade-off between energy

resolution, measurement sensitivity, and instrument compactness [1,2], which limits their broader applicability and overall throughput. Throughput can be increased by enlarging the solid angle of collection, which is typically achieved by tiling many analyzers, resulting in bulky and high-maintenance spectrometers [3]. An alternative way to improve the solid angle is to reduce the distance between a sample and the crystal analyzer. This, in turn, requires the crystal to be bent to a correspondingly smaller radius of curvature (e.g., 80% for a 2.0 Å neutron at grazing angle of 0.8 deg (m = 4)). o Resilience: High thermal and radiation resilience to withstand harsh accelerator or reactor environments, with an operating lifetime of 5–15 years. o Dimensions: Substrate thickness of 5–10 mm; minimum dimensions of 5 cm wide by 100 cm long. • Novel Monochromator Developments: Development of bi-layer nano-composite structures to resolve thermal and cold neutron beam energies with higher efficiency and finer resolution. o Efficiency: Scattering efficiency > 80% of 1.5 Å neutrons with bandwidth ≤0.15 Å. o Polarization: If polarizing, polarization efficiency > 95% at 2.0 Å.

References 1. Saxena, A. M. and Schoenborn, B. P., "Multilayer neutron monochromators." Acta Cryst. A33, 805 (1977). International Union of Crystallography, Multilayer neutron monochromators, Acta Cryst. A33, 805 (1977), https://doi.org/10.1107/S056773947700196X. 2. Hayter, J. B. and Mook, H. A., "Discrete thin-film multilayer design for X-ray and neutron supermirrors." Journal of Applied Crystallography 22, 35 (1989). International Union of Crystallography, Discrete thin-film multilayer design for X-ray and neutron supermirrors, Journal of Applied Crystallography 22, 35 (1989), https://doi.org/10.1107/S0021889888010003. 3. Elsenhans, O., et al., "Development of Ni/Ti multilayer supermirrors for neutr