In 2021, breakthroughs have been made continuously for debugging of Shanghai soft X-ray free electron laser, and has pushed the shortest wavelength of free electron laser of China to 2nm, and firstly realized full band coverage of the "water window" among the 3 soft X-ray free electron laser facilities around the world.

The "water window" refers to a soft X-ray with a wavelength that has a range between 2.3 and 4.4 nanometers. Water is relatively transparent to X-rays but other essential life elements, such as carbon, still interact strongly with X-rays. As such, the "water window" soft X-rays provide a unique opportunity for investigating biological materials, added the researchers.

Scientists said that this achievement means that X-ray FEL research in China has advanced from the facility research and development phase to user operation phase. Within the "water window", SXFEL can generate high-intensity free electron laser pulses, which are 1 billion times brighter than those of synchrotron radiation light sources. Such ultrabright, ultrafast and coherent pulses enable scientists to take X-ray snapshots of atoms and molecules at work, revealing fundamental processes in materials, technology and living organisms.

Researchers said that the research result this time will be applied in microscopic imaging of living cells, and may provide a revolutionary research tool for multiple disciplines, including physics, biology and chemistry. The SXFEL facility is scheduled to begin user operation next year and will be open to both users at home and abroad.