China develops 'world's brightest' VUV free-electron laser research facility

A group of scientists from numerous institutions in China has developed a vacuum-ultraviolet (VUV) free-electron-laser (FEL) light source called the Dalian Coherent Light Source (DCLS) that can deliver what the scientists call the world's brightest FEL light in the energy range from 8 to 24 eV. This would make the DCLS the world's premier coherent light source operating in the VUV region.

The participating institutions include the University of Science and Technology of China (USTC), Tsinghua University, and the Institute of High Energy Physics. The project was funded by National Natural Science Foundation of China and Chinese Academy of Sciences.

VUV light sources are useful for sensitive detection of atoms, molecules, and molecular clusters, and can also probe valence electronic structures for all kinds of materials.

The development of high-gain FELs has captured great attentions in the scientific community in the last decade, as these sources can provide the brightest light sources in the VUV to x-ray regions where conventional laser technology cannot reach.

Recently, a series of high gain FEL light source facilities in the x-ray and soft x-ray regions have been successfully launched across the world (LCLS, USA; SACLA, Japan; FLASH, Germany; and FERMI, Italy), with a few others currently under development. The LINAC based Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC) has helped scientists to make discoveries in frontier research areas, including the study of biomolecules.

Previously, however, no dedicated high-gain VUV FEL light source facility for basic research had been developed. Led by Yang Xueming (Dalian Institute of Chemical Physics, DICP) and Zhao Zhentang and Wang Dong (Shanghai Institute of Applied Source, SINAP), the Chinese team of scientists and engineers developed the DCLS.

In the last two months the team commissioned the new FEL facility, which operates in both high-gain harmonic generation (HGHG) and self-amplified spontaneous emission (SASE) modes. By applying undulator tapering technology in the HGHG mode, a flux of 1.4x10¹⁴ photons per pulse was achieved.

"VUV FEL light sources have wide applications in the study of basic energy science, chemistry, physics, and atmospheric sciences," says YANG Xueming, one of the researchers.

Source: https://www.eurekalert.org/pub_releases/2017-01/caos-cdw011217.php