X-ray and extreme ultraviolet optics

Researchers at Lawrence Livermore develop and deploy coating technologies to enable novel observations in the x-ray and extreme ultraviolet wavebands.

Developing multilayer coating technologies

Multilayer interference coatings are an enabling element of optical components for extreme ultraviolet (EUV) and x-ray observatories, providing capabilities for solar physics, planetary physics, and astrophysics. Multilayers consist of stacks of alternating thin film layers of two or more materials deposited on an optical substrate. The constructive interference between the layers results in high reflectance.

In the EUV and soft x-ray region (1–100 nanometers [nm]), multilayers can provide high reflectance at near-normal incidence, a regime where a single layer of any material would have zero reflectance. In the hard x-ray, multilayers are used to create high efficiency optics that operate at extremely shallow grazing incidence angles (hundredths of a degree) and require coating layers with sub-nanometer thicknesses, corresponding to just a few atoms of material.

Researchers at LLNL develop state-of-the-art multilayer coatings and implement them for space missions. Using capabilities including advanced metrology and in-band characterization techniques, materials science and modeling, and optical design, we can identify and study limitations of multilayer technologies and provide robust solutions for improving optics from the EUV to gamma-ray wavebands.

Optics team behind the Mag-1

From left: Jennifer Alameda, Regina Soufli, Jeff Robinson, Marie-Anne Descalle, and Catherine Burcklen in front of the Mag-1 deposition system with its lid open. Four sputtering sources (materials) used in thin film depositions are inside the Mag-1. Two sources are 100 mm in diameter and the other two are rectangular, 127x250 mm2 in size.

X-ray and EUV optics development at LLNL falls into several overlapping areas:

Multilayer coating development to enable normal-incidence EUV and soft x-ray optics with compact geometries

Multilayer coating development to enable grazing-incidence hard x-ray and gamma-ray optics

Metrology and photometric calibration for research activities and flight optic quality assurance

Large-area coating capability to produce coatings with precise thickness control on curved optics for space telescopes

Leveraging state-of-the-art modeling capabilities, deposition facilities, and measurement facilities

The topmost layers of a coating for the EUV spectral region
This cross-sectional transmission electron microscopy image shows the topmost layers of a corrosion-resistant magnesium (Mg)/silicon carbide (SiC) multilayer for the EUV spectral region. The aluminum (Al)-Mg corrosion barrier layer is underneath the top SiC layer and has been formed by two individual Al and Mg layers that interdiffused spontaneously.

Designing and fabricating multilayer coatings involve many challenges:

  • Determining multilayer systems with high reflectance, appropriate spectral selectivity, and stable performance over time, for the specific wavelength region of operation.
  • Addressing the sensitivity of materials to degradation mechanisms such as contamination, oxidation, and corrosion.
  • Determining accurate refractive index values, including near absorption edges, which are essential for the reliable design of multilayer coating systems.
  • Meeting stringent requirements for surface figure and surface roughness on optical substrates with various shapes and geometries (planar, curved, nested).

We address these challenges by studying the physics of periodic (narrowband) and aperiodic (broadband) multilayer coatings with nanoscale layers, including the crucial interfaces between layers, and by developing new multilayer material systems with improved properties. For hard x-ray applications, we improve performance by developing multilayer coatings with the thinnest achievable layers. We advance multilayer design algorithms, deposition methodologies, characterization methodologies, and corrosion barriers for extended lifetime stability.

Accurate substrate specification and metrology are an integral part of the development of these optical systems and represent one of the key competencies at LLNL. We implement state-of-the-art metrologies for measurements of surface figure and roughness of optical substrates for space applications.

Using these techniques, we have:

  • Identified the corrosion mechanisms for magnesium-based multilayer coatings and developed corrosion barriers. These aluminum-based barriers address the issue of catastrophic corrosion, enabling magnesium multilayer use for space-borne instruments that require long-term stability.
  • Developed new multilayer coatings for use in the EUV, including triple-wavelength magnesium-based multilayers and aluminum/scandium-based multilayers.
  • Established accurate measurement methodologies for the refractive index of several important materials for EUV and x-ray optics: molybdenum, silicon, beryllium, iridium, yttrium, boron, strontium, silicon monoxide, boron carbide, platinum, chromium, and aluminum.
  • Demonstrated narrowband multilayer optics that can operate at photon energies up to the soft gamma-ray spectral range. This is the highest photon energy where multilayers have been experimentally shown to work.
  • Demonstrated efficient broadband multilayer coatings for photon energies from a few keV to more than 100 keV.
  • Provided the multilayer coatings and calibration for the Atmospheric Imaging Assembly (AIA) instrument aboard NASA’s Solar Dynamics Observatory. We led the design, deposition, metrology, and photometric calibration of the four AIA telescopes, providing seven EUV narrowband channels ranging from 9.4 to 33.5 nm, each tuned to corresponding emission lines from the Sun’s ionized plasma.
  • Provided the multilayer coatings and calibration for the Solar Ultraviolet Imager (SUVI) telescopes aboard NASA/NOAA’s Geostationary Operational Environmental Satellites (GOES). Each mirror was coated in six spatial (60-degree) segments, providing six EUV narrowband channels on each mirror. We delivered twelve flight mirrors for six SUVI telescopes, launched in 2017 aboard GOES-16 and in 2018 aboard GOES-17. The remaining four telescopes are expected to launch in 2022 and into the late 2020s or early 2030s.
  • Provided silicon-carbide coatings for the mirror and grating for the far-ultraviolet imaging spectrometer on the United Arab Emirates-led Hope Mars mission that launched in 2020. The Emirates Ultraviolet Spectrometer is studying the Martian atmosphere from 100–170 nm, and it has captured detailed images of auroras in the Martian sky. The silicon carbide coating allows imaging at shorter wavelengths than other Mars orbiting spectrometers, enabling observations of emission produced by the extended hydrogen exosphere at 102.6 nm.
  • Developed beam splitters for astrophysics mission concepts. In a collaboration with the University of Iowa, we deposited multilayer coatings on a 2-micron-thick polyimide membrane to reflect 0.5 keV x-rays to a Bragg polarimeter and transmit 2–10 keV x-rays to the primary polarimeter for the Gravity and Extreme Magnetism Small Explorer Mission concept.

Techniques and tools serving a dual purpose

Optics developments that enable these studies of high-energy phenomena in space also enable diagnostic instrumentation for ground-based experiments. Advances in multilayer coating technologies and optics system design for space science applications have been key to enabling new capabilities such as the Wolter microscope developed for Sandia’s Z machine—the world’s strongest pulsed-power facility—and mirrors for K-shell fluorescence of plutonium and uranium.

Other applications enabled by multilayer optics include plasma diagnostics, radiation detection, attosecond physics, and EUV/x-ray laser sources. LLNL also pioneered and advanced EUV photolithography for semiconductor manufacturing, which was deployed to power the latest smartphones.


Name Title Discipline


Name Department Institution
Eric Gullikson Center for X-ray Optics, PI for beamline 6.3.2 Advanced Light Source Lawrence Berkeley National Laboratory
Farhad Salmassi Center for X-ray Optics Lawrence Berkeley National Laboratory
Patrick Naulleau Center for X-ray Optics Lawrence Berkeley National Laboratory
    European Synchrotron Radiation Facility
    Lockheed Martin Corporation
  Advanced Photon Source Argonne National Laboratory
Franck Delmotte Group Laboratoire Charles Fabry, Institut d’Optique Graduate School University Paris-Saclay
Juan Larruquert Group Instituto de Óptica Consejo Superior de Investigaciones Científicas
    Harvard-Smithsonian Center for Astrophysics
    NASA Marshall Space Flight Center
    Sandia National Laboratories
    Idaho National Laboratories
    Oak Ridge National Laboratory
    Los Alamos National Laboratory
    DTU-Space (Denmark)
Eberhard Spiller Consultant Lawrence Livermore National Laboratory
Yurii Platonov   Rigaku Corporation
    Reflective X-ray Optics, LLC
Phil Kaaret Group   University of Iowa
  Laboratory for Atmospheric and Space Physics University of Colorado Boulder

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