100 million X-rays in one

Scientists at the US Department of Energy's Argonne National Laboratory have devised a 'next generation' X-ray light source many times brighter than current technologies.

"The free electron laser oscillator (X-FELO) we are proposing can create X-rays up to one hundred million times brighter than currently operating machines," Argonne distinguished fellow Kwang-Je Kim said.

Current technology uses undulators to create bright X-ray beams of spontaneous emission at the Advanced Photon Source (APS) at Argonne.

In an X-FELO, the electron pulse enters an undulator and generates an X-ray that is reflected back into the undulator entrance by crystals and connects with the next electron bunch and again travels back along the undulator.

This pattern is repeated indefinitely with the X-ray intensity growing each time until equilibrium is reached.

The spectral brightness is proportional to the intensity of coherent photons per unit spectral bandwidth. It is a standard figure of merits for the strength and purity of an X-ray source.

The intensity of individual X-ray pulse from an X-FELO is lower by about three orders of magnitude. However, the X-FELO pulse has extremely narrow bandwidth — three to four orders of magnitude narrower than other technologies — and the pulses come with repetition rates higher by two to four orders of magnitudes.

"Collaborators from around the world are working to develop the high-quality electron beam necessary for the oscillator," Kim said.