Tag: superconducting

Milestone for superconducting undulator

Milestone for superconducting undulator

A EUROPEAN XFEL TEAM AT THE KARLSRUHE INSTITUTE FOR TECHNOLOGY HAS TESTED A MOCK-UP COIL OF THE SUPERCONDUCTING UNDULATOR PRE-SERIES MODULE (S-PRESSO) DESIGNED FOR AN UPGRADE OF THE EUROPEAN XFEL. IT REACHED A WORLD RECORD MAGNETIC FIELD.

Undulators are one of the most important devices for a free-electron laser like the European XFEL in Schenefeld near Hamburg. With the help of a series of strong magnets an undulator creates an extremely brilliant light by forcing fast-moving electrons onto a slalom course. Furthermore, the undulators stimulate the electrons to emit laser-like electromagnetic radiation.

The strength of the magnets of an undulator determines the tunability of the photon energy range available for experiments. The Undulator Systems Group of European XFEL has started different activities in collaboration with Deutsches Elektronen-Synchrotron DESY to allow the implementation of superconducting undulators into the European XFEL in the upcoming years. The contract for superconducting undulator pre-series module (S-PRESSO) consisting of two pair of coils and a phase shifter has been assigned to Bilfinger Noell GmbH. Now, a European XFEL team at the Karlsruhe Institute for Technology has tested a 30-centimeter-long mock-up superconducting coil designed and build by Bilfinger Noell GmbH. The magnetic field of the S-PRESSO mock-up has reached 2 Tesla, which is larger ever reached before in such undulators.

Read more on the European XFEL website

Image: Undulators like this one cause highly accelerated electrons to emit intense and brilliant X-ray light. European XFEL is currently testing superconducting undulators in order to be able to offer users even better conditions for their research in the future.

The fourth signature of the superconducting transition in cuprates

The fourth signature of the superconducting transition in cuprates

The results cap 15 years of detective work aimed at understanding how these materials transition into a superconducting state where they can conduct electricity with no loss.

When an exciting and unconventional new class of superconducting materials was discovered 35 years ago, researchers cheered.

Like other superconductors, these materials, known as copper oxides or cuprates, conducted electricity with no resistance or loss when chilled below a certain point – but at much higher temperatures than scientists had thought possible. This raised hopes of getting them to work at close to room temperature for perfectly efficient power lines and other uses.

Research quickly confirmed that they showed two more classic traits of the transition to a superconducting state: As superconductivity developed, the material expelled magnetic fields, so that a magnet placed on a chunk of the material would levitate above the surface. And its heat capacity – the amount of heat needed to raise their temperature by a given amount – showed a distinctive anomaly at the transition. 

But despite decades of effort with a variety of experimental tools, the fourth signature, which can be seen only on a microscopic scale, remained elusive: the way electrons pair up and condense into a sort of electron soup as the material transitions from its normal state to a superconducting state.

Now a research team at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University has finally revealed that fourth signature with precise, high-resolution measurements made with angle-resolved photoemission spectroscopy, or ARPES, which uses light to eject electrons from the material. Measuring the energy and momentum of those ejected electrons reveals how the electrons inside the material behave.

In a paper published in Nature, the team confirmed that the cuprate material they studied, known as Bi2212, made the transition to a superconducting state in two distinct steps and at very different temperatures.

Read more on the SLAC website

Image: How can you tell if a material is a superconductor? Four classic signatures are illustrated here. Left to right: 1) It conducts electricity with no resistance when chilled below a certain temperature. 2) It expels magnetic fields, so a magnet placed on top of it will levitate. 3) Its heat capacity – the amount of heat needed to raise its temperature by a given amount – shows a distinctive anomaly as the material transitions to a superconducting state. 4) And at that same transition point, its electrons pair up and condense into a sort of electron soup that allows current to flow freely. Now experiments at SLAC and Stanford have captured this fourth signature in cuprates, which become superconducting at relatively high temperatures, and shown that it occurs in two distinct steps and at very different temperatures. Knowing how that happens in fine detail suggests a new and very practical direction for research into these enigmatic materials.

Credit: Greg Stewart, SLAC National Accelerator Laboratory