Novel Intermediate Energy X-ray Beamline Opening for Researchers

Estimated reading time: 8 minutes

Superconductors with transition temperatures above the temperature of liquid nitrogen hold the promise of practical applications, such as the efficient production and transport of electricity. However, how those moderate- to high-temperature superconductors function is not well understood.

When Campuzano and Abbamonte joined forces to develop the IEX beamline, their shared interest in high-temperature superconductivity became the focal point for the design of its two scientific endstations. Years of collective work in photoemission spectroscopy and X-ray scattering, respectively, would culminate in a powerful combination of tools located in one place.

Campuzano was already using ultraviolet ARPES and was considered one of the leading experts in the field when he set his sights to building a new APS beamline.

"We already knew that low-energy photons released electrons mostly from the surface of a material, which is not necessarily representative of what's going on inside it," said Campuzano. "The way to get around that was to build a beamline that had much higher-energy photons, soft X-rays."

The IEX ARPES experimental station, designed and built by Campuzano's team at UIC, uses photons in a relatively high-energy range of 1000 eV to probe electrons deeper within a solid. As electrons absorb incoming photons, they are ejected from the structure. This lets users better analyze the dynamics of electron, the electronic excitations, in a sample.

By understanding what happens to the electronic structure when macroscopic properties are changed, scientists get a better idea of how they can manipulate those properties to their advantage, whether it's finding the best remnant magnetic fields for spintronics or determining transition temperatures in superconductors.

Where ARPES lets researchers know how electrons propagate in a material, the RSXS endstation lets them know where those electrons are located. Designed and built by Abbamonte's team at UIUC, resonant soft X-ray scattering is a photon-in-photon-out technique that yields real-space information about electronic ordering and information about correlation lengths.

For Abbamonte, the technique is central to his research in determining whether heterogeneity is relevant for optimizing superconductivity.

"Set the beam energies to the right resonance value, and when the photons hit the sample, they'll scatter in all different directions because of this heterogeneity that we're interested in," he explained. "Then you use an angle-resolving detector to scan and measure the angle dependence of the light to back out what the form of that heterogeneity is."

In addition to the traditional microchannel plate angle-resolving detector, the RSXS endstation is equipped with a two-dimensional energy-resolving detector, another of the highly unique applications on this beamline. Considered among the most sensitive energy-resolving detectors in the world, it is based on transition-edge sensor (TES) technology pioneered by the National Institute of Standards and Technology (NIST) for cosmology applications, such as research in cosmic microwave background radiation.

This is the first time TES technology has been used for scattering, and could prove 1000 times more sensitive to heterogeneity than any previous technology.

The development of IEX was jointly funded by DOE and NSF.

About Argonne National Laboratory

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