[Reading Science] US Completes World's Most Powerful 'Giant Microscope'

Completed Upgrade of Synchrotron Accelerator LCLS
8000 Times Faster and 10000 Times Brighter than Before
"Capturing Electron Movements in Chemical Reactions Instantly"

The United States has completed and started operating the world's most powerful X-ray laser (linear synchrotron accelerator). It has the capability to capture and image the movement of atoms occurring at the moment of chemical reactions, promising to bring innovation to related research.

The LCLS, a synchrotron light source operated by the Stanford Linear Accelerator Center (SLAC) at Stanford University, USA. Photo by SLAC website

The SLAC National Accelerator Laboratory at Stanford University in the U.S. announced on the 12th that it successfully produced the first beam after completing a performance upgrade project for the LCLS-I (Linac Coherent Light Source) synchrotron accelerator, which had been underway for over a decade with an investment of 1.1 billion dollars. Through this upgrade, the improved LCLS-II increased the number of X-ray pulses per second from 120 to an astonishing 1 million, more than 8,000 times higher. As a result, it can shoot videos at 100,000 frames per second. The brightness of the laser has also increased by more than 10,000 times on average. Scientists expect to capture molecular motion with unprecedented clarity and to observe the interiors of rare molecular phenomena that were impossible with other equipment.

The international academic journal Nature reported, "It will be possible to image the extremely fast movements of materials, including electrons orbiting atoms during chemical reactions," adding, "This could help uncover the secrets of photosynthesis or develop new electronic devices for computing systems."

Before the upgrade, LCLS-I, installed in 2009, already boasted remarkable performance. It was the world's first synchrotron accelerator capable of shooting X-rays at laser speed to study atoms. The principle involves accelerating electrons through about 3 km of copper wire and then disturbing them using magnetic fields to emit X-rays. It can simultaneously produce high-energy hard X-rays (short wavelength with strong penetration) and low-energy soft X-rays.

The laboratory replaced part of the copper wire in the accelerator with superconducting niobium (Nb) wire cooled to an ultra-low temperature of 2 Kelvin (around -271.5 degrees Celsius), achieving zero electrical resistance. This allowed X-ray pulses to be produced much faster, while the remaining copper wire sections produce only soft X-rays (long wavelength with weaker penetration). The lab had planned to complete the upgrade in 2020, but due to various reasons including the COVID-19 pandemic, it was finalized this time.

South Korea has also been utilizing the 3rd and 4th generation Pohang synchrotron accelerator since 1994. Synchrotron accelerators accelerate electrons close to the speed of light and use the resulting light to capture images at the atomic and molecular level, serving basic science, medicine, and applied sciences. The light from synchrotron accelerators is much brighter than the sun, enabling observation at the atomic and molecular scale, earning them the nickname "ultra-high-performance giant microscopes." Currently, a 4th generation multipurpose synchrotron accelerator is being constructed in Ochang, Chungbuk, with an investment of 1 trillion won. It will accelerate electrons to 4 GeV (4 billion electron volts) at the picometer scale and produce light about 1 trillion times brighter than the sun.