In bright news for the scientific world, the world's biggest X-ray laser has generated its first light in Hamburg, Germany. The 3.4 km (2.1 mi) long European X-ray Free Electron Laser (XFEL) produced a pulsing laser light with a wavelength of 0.8 nm at one pulse per second as part of the last major development milestone ahead of its September official opening. When up and running properly, it will generate up to 27,000 pulses per second – a considerable improvement over the previous maximum of 120 per second.

A free electron laser operates on the principle of a synchrotron, an atomic accelerator that generates high-intensity electromagnetic radiation by accelerating electrons to relativistic speeds, then directing them through special magnetic structures. Only in this case, the XFEL is a billion times more brilliant than conventional synchrotron light sources and can capture images at atomic resolution.

The key component is a 2.1 km (1.3-mi) long superconducting linear accelerator that came online in April. Here electron pulses are accelerated to near the speed of light and to very high energies before entering a photon tunnel containing 210-m (689-ft) of X-ray-generating devices consisting of 17,290 permanent magnets called "undulators" with alternating poles above and below the electron stream. These twist the electrons out of their straight line, and every time they curve they give off energy like an overloaded truck losing its cargo, only this is in the form of extremely short-wavelength X-rays.

First Laser Light at the European XFEL, recorded by an X-ray detector at the end of the tunnel(Credit: DESY)

The result is a laser of short pulses of hard X-ray light of extremely high luminosity. This laser can then be beamed into several experiment stations in an underground experimental hall, where different experiments can be carried out at the same time. This means that more projects can be handled more quickly with each researcher given more "beamtime" than is currently available at other, overbooked facilities.

Because the XFEL has a wavelength the diameter of an atom, the developers say it will provide new insights into the nanocosmos as well as a better understanding of organic molecules, leading to more advanced medical diagnosis and treatments. In addition, the laser could be used to produce more efficient chemical process and even simulate conditions of planetary interiors.

The undulators generate the bright X-ray light(Credit: European XFEL/Heiner Müller-Elsne)

"This is an important moment that our partners and we have worked towards for many years," says European XFEL Managing Director Professor Robert Feidenhans'l. "The facility, to which many countries around the world contributed know-how and components, has passed its first big test with flying colors. The colleagues involved at European XFEL, DESY, and our international partners have accomplished outstanding work. This is also a great success for scientific collaboration in Europe and across the world. We can now begin to direct the X-ray flashes with special mirrors through the last tunnel section into the experiment hall, and then step by step start the commissioning of the experiment stations. I very much look forward to the start of international user operation, which is planned for September."

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