First electrons accelerated in the European XFEL

The first component of the most powerful X-ray laser is the premiere

This is the next step: the superconducting accelerator part of the XFEL © DESY
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On the way to a new dimension of X-ray flashes: An important part of the X-ray laser European XFEL in Hamburg has successfully completed its premiere: The so-called injector, the 45 meter long foremost part of the free electron laser has accelerated the first electron. The rest of the facility is also expected to be completed by 2017. It will then generate the hitherto most energy-rich and shortest X-ray laser pulses.

Already we owe X-ray lasers completely new insights into the micro world: With the help of only few femtoseconds short light pulses researchers already shot shock waves in the diamond, shot a first group picture of free molecules and cracked the "Grail" of the chemistry, by atoms at the moment of the chemical Binding recorded.

Electrons on a rolling course

Even deeper insights should, however, be provided by the X-ray laser European XFEL at DESY in Hamburg from 2017 onwards. It produces 27, 000 X-ray flashes per second and a brightness billions of times higher than the best conventional X-ray sources. The system consists of a two kilometer superconducting electron linear accelerator followed by a series of high-precision magnetic structures.

As soon as the electrons have reached almost the speed of light, the magnets force them into a slalom ride on the last third of the way. In this course, the electrons in the curves are braked again and again and emit energy in regular pulses: the x-ray pulses. The principle is similar to circular synchrotrons, but the slalom course produces pulses of coherent X-rays - a pulsed X-ray laser.

View into the main accelerator tunnel of the European XFEL, in which 100 superconducting accelerator modules are mounted Dirk N lle / DESY

First test successful

The injector, the foremost part of the linear accelerator, has now successfully mastered its premiere. In it, several billion electrons are knocked out of an electrode made of cesium telluride and bombarded with UV laser pulses. This creates an electron packet, the display

is initially pre-accelerated in a normal-conducting cavity resonator. Subsequently, two superconducting, helium-cooled accelerator modules ensure further energy increase.

In the first test, the injector successfully generated and accelerated the first series of high-energy electron bunches. The electrons needed 0.15 microseconds for the 45-meter path from the beginning to the end of the injector, approaching the speed of light.

"The first electrons in the injector are a milestone for this ambitious discovery machine - congratulations to all the physicists and engineers who built and assembled the various components with great commitment, " said Helmut Dosch, Chairman of the DESY Board of Directors. "More than half of the superconducting modules in the main accelerator have already been tested and assembled, and I'm sure we can start putting them into service soon."

Over the next few weeks and months, the injector will be tested intensively, while the rest of the linear accelerator will be built. The next big milestone is the acceleration of electrons over 2.1 kilometers planned for the end of 2016. The user enterprise is to begin 2017.

(DESY, 22.12.2015 - NPO)