Particle accelerators can fire all kinds of particles, from protons to electrons and even whole atomic nuclei — and now an enormous linear photon accelerator is about to join the mix. Deutsches Elektronen-Synchrotron (DESY) has been working for years toward this single monumental achievement: It’s about to fire up the world’s biggest X-ray laser.
The 3.4-km-long European XFEL is the largest and most powerful of the five great X-ray lasers worldwide. And it’s an upgrade in terms of speed, not just intensity. With more than 27,000 hard X-ray pulses per second, instead of the previous maximum of 120 Hz, plus the ability to work in parallel thanks to several experiment stations, it will be possible for scientists to do their work much faster — good news for both evanescent experimental substrates and time between experiments.
The laser’s accelerator tunnel is 2.1 km long, and takes an undulating “slalom” course. The why and wherefore of this is because radiation moves faster than electrons. To create the X-ray beam, scientists fire a beam of high-energy electrons through an undulating course of extremely precise dimensions. The electrons are on a high enough energy level that they emit EM radiation in the X-ray band. As the radiation overtakes the electrons flying ahead and interacts with them along the way, it accelerates some electrons and slows others down. As a result, the electrons “gradually organize themselves into a multitude of thin disks.”
What makes this desirable is the fact that all of the electrons in a given disk emit their X-rays “in sync.” (Is it just me, or does this sound a bit like a Fourier transform done on particles?) Organizing the electrons into discrete discs makes it possible for a continuous beam of electrons to produce short, extremely intense flashes of hard X-ray light.
Helmut Dosch, chairman of the DESY Directorate, said: “The European X-ray laser has been brought to life! The first laser light produced today with the most advanced and most powerful linear accelerator in the world marks the beginning a new era of research in Europe. This worldwide unique high-tech facility was built in record time and within budget. This is an amazing success of science…The European XFEL will provide us with the most detailed images of the molecular structure of new materials and drugs and novel live recordings of biochemical reactions.”
Beyond its utility as a photon accelerator, the laser will be useful for X-ray crystallography. Because there’s a range of achievable wavelengths that corresponds to the sizes of atoms, X-ray lasers like the European XFEL can produce extremely precise images of hard-to-capture molecules. But more than that, its extreme operating speed means that even unstable compounds are subject to X-ray imaging.
DESY waxes poetic about the options afforded by this crazy new laser on their site. “Films of chemical reactions that take place in fractions of a second; images of proteins in which every atom can be seen; pictures of nanomaterials that show the tiniest details; insights into the states of matter inside giant planets or stars – up until now, scientists could only dream of conducting such experiments.”
European XFEL Managing Director Prof. Robert Feidenhans’l said, “The European XFEL has generated its first X-ray laser light. The facility, to which many countries around the world contributed know-how and components, has passed its first big test with flying colors…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.”
The European XFEL is scheduled to go online for international operation in September.
source : https://www.extremetech.com/extreme/249059-largest-x-ray-laser-ever-turn