Beam power meter for x-ray free-electron lasers is compact, durable

Dec. 1, 2017
Researchers at the Free-Electron Laser in Hamburg have come up with a bolometric radiometer that is only 26 mm on a side, enabling easy measurement of a free-electron laser beam at many locations along the beam.
Content Dam Lfw Print Articles 2017 12 1712lfw Nb F1

A number of large free-electron lasers (FELs) emitting in the extreme-ultraviolet (EUV) and x-ray ranges have come online within the past decade or so, including the Free-Electron Laser in Hamburg, Germany, the SPring-8 Compact SASE Source and the SPring-8 Angstrom Compact Free-Electron Laser (SACLA; both in Hyogo, Japan), and the Linac Coherent Light Source (Menlo Park, CA). Others, including the European x-ray FEL, the SwissFEL, and the Pohang Accelerator Laboratory XFEL, are under development. These powerful light sources share something in common: the need for a beam power measurement system that is not only accurate, but can stand up to peak powers up to the gigawatt range.

Researchers at the Free-Electron Laser in Hamburg have come up with just such a device-a bolometric radiometer that is only 26 mm on a side, enabling easy measurement of a FEL beam at many locations along the beam. The room-temperature device includes a vacuum-chamber housing and thermal shields—within the chamber is a 1-mm-thick gold plate inside a cylindrical copper shell that has a 5 mm aperture. The absorptance is >99.7% over the 1–60 keV photon energy range. Heaters within the chamber maintain an even temperature of about 300 K to within 40 μK. When a beam strikes the device and the temperature is maintained, the heaters require less current—it is this current that is monitored to determine beam power. Experiments of half a year's time confirmed the bolometer's efficacy and durability. Reference: T. Tanaka et al., Opt. Lett. (2017); https://doi.org/10.1364/ol.42.004776.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Achromatic Lenses: High-Quality Custom Optics

March 13, 2025
Ensure clarity and accuracy in your optics systems with Lacroix’s achromatic lenses. Explore how our custom solutions minimize chromatic aberration for perfect results.

Manufacturing Considerations for Tolerancing Aspheres

March 13, 2025
Understand the critical factors in manufacturing aspheres and how Lacroix Optics ensures precise tolerancing in every optical component.

Explore Our Videos: Insights into Precision Optics

March 13, 2025
Get an inside look at Lacroix Optics with our collection of informative videos showcasing our capabilities, innovations, and processes.

Optical Assemblies: Reliable and Precise Solutions

March 13, 2025
Ensure your optical system works seamlessly with Lacroix Optics' custom optical assemblies. Discover the precision and reliability we bring to every project.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!