Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL)

PAL-XFEL, operated by the Pohang Accelerator Laboratory in Pohang, South Korea, is an X-ray free-electron laser — a machine that produces ultrashort, ultra-intense pulses of coherent X-rays, letting researchers film chemical reactions and atomic motion as they unfold.

Construction of PAL-XFEL began in 2011, and in November 2016 the machine achieved saturation of a 0.144 nm beam — making it the world’s third hard X-ray free-electron laser, after LCLS in the United States and SACLA in Japan. User operations began in June 2017. The facility is built to host up to five undulator lines — three for hard X-rays and two for soft X-rays — with one hard and one soft line in service.

At a glanceFacility profile

Location

Pohang, South Korea

Operator

Pohang Accelerator Laboratory (PAL)

Type

X-ray free-electron laser (XFEL)

Linac energy

Up to about 11 GeV

Wavelength

0.1–6 nm (hard and soft X-rays)

Beamlines

Capacity for five undulator lines; hard and soft X-ray lines in operation

First lasing

2016; user operations from 2017

Website

pal.postech.ac.kr

The scienceWhat researchers do here

Unlike a storage ring, a free-electron laser concentrates its X-rays into pulses lasting only femtoseconds — short enough to capture the making and breaking of chemical bonds, the folding of proteins, and the response of materials to light. PAL-XFEL is used for ultrafast chemistry and catalysis, time-resolved structural biology, and studies of matter under extreme conditions. Its coherent beam also enables single-particle imaging and the study of fragile samples before radiation damage sets in.

Where a synchrotron takes a photograph, a free-electron laser makes a film — revealing atomic motion on the timescale of chemistry itself.

PAL-XFEL shares its campus with the PLS-II synchrotron, so researchers in Pohang can pair the ultrafast, coherent pulses of the laser with the steady high brilliance of a storage ring.