SLAC Lab Hard X-ray Free Electron Laser Successfully Upgraded

July 27, 2020

In April 2009, the world's first hard X-ray free electron laser (XFEL) produced the first light at the SLAC National Accelerator Laboratory of the US Department of Energy. The Linac Coherent Light Source (LCLS) produces X-ray pulses that are one billion times brighter than any previous light source. Since then, its performance has brought new insights in many scientific fields, from creating chemical "molecular movies" to studying the structure and movement of proteins of a new generation of drugs and simulating the "diamond rain" in the giant planets of our solar system. ".

The SLAC National Accelerator Laboratory launched the LCLS-II project in 2013 to increase the power of X-ray lasers by thousands of times and generate one million pulses per second. At present, only 120 pulses can be generated per second. The project upgrade is expected to be completed within two years.

The working principle of hard X-ray free electron laser is divided into two steps. First, it accelerates the powerful electron beam to nearly the speed of light. The beam is then passed through a series of precisely tuned magnets in a device called a waver, which converts electron energy into intense pulses of X-rays.

These pulses are only one millionth of a second in length, so that they can capture the birth of chemical bonds and produce images with atomic resolution. The LCLS-II project plans to install a new accelerator for the laboratory that can use cryogenic superconducting technology to achieve an unprecedented repetition rate, and install a new waver that can precisely control the X-ray beam.

In the past year and a half, the original LCLS pulsator in the laboratory was replaced by two brand new systems with brand new functions. Each wave device contains thousands of magnets that extend more than 100 meters; the magnetic field they produce together is tens of thousands of times stronger than the earth's magnetic field, and the force generated is equivalent to a few tons of weight. At the same time, the structure of the magnet will not twist more than one hundredth of the width of a human hair.

The new wave device was designed by the Argonne National Laboratory in the United States and built by the Lawrence Berkeley National Laboratory, and installed at the SLAC National Accelerator Laboratory in the past year. Scientists at the SLAC Accelerator Laboratory are able to guide the electron beams of existing LCLS accelerators through the magnet array in the new "hard X-ray" undulator. In just a few hours, they generated the first X-ray signal and then precisely adjusted the configuration to maximize X-ray laser performance.

Henrik von der Lippe, director of engineering at Berkeley Laboratories, said: "The generation of the first light is a long-awaited milestone. This scientific facility will enable new scientific research."