HEPS starts taking beamtime proposals

On 20 March the High Energy Photon Source, or HEPS, opened its first round of beamtime proposals, the formal step that moves Asia’s first fourth-generation synchrotron light source from construction into the beginning of real operation. Scientists from any institution can now apply for time at the facility’s beams, and the opening of the proposal round, announced by the Institute of High Energy Physics of the Chinese Academy of Sciences, marks the point at which a machine that has been under construction near Beijing since 2019 begins to earn its keep.

Synchrotron light sources are, in effect, giant microscopes. Electrons accelerated to near the speed of light in a storage ring emit extremely bright X-rays as they are bent by magnets, and those X-rays allow researchers to see the structure of matter at atomic scale: the folds of a protein, the defects in a semiconductor, the reactions inside a working battery. Generations of the technology have each brought brighter and more coherent beams, and fourth-generation sources, built on a design that uses carefully arranged magnet arrays to shrink the electron beam’s emittance, offer a jump in brilliance and coherence that opens experiments which were previously impossible.

HEPS is the first such source in Asia and, at the design stage, the brightest synchrotron in the world, a status that earned it the nickname of a super microscope. It is also a large engineering project in its own right: roughly seven years of construction in the Huairou district, north of Beijing, with the accelerator complex, the experimental halls and the beamline instrumentation built and tested together. The announcement of the first proposal round follows the completion of the machine’s key commissioning milestones, and it comes with the caveat typical of a new facility: early users will be debugging as much as measuring, and the first experiments will help the machine mature as much as they will answer questions.

The timing is not accidental. HEPS was one of the headline items in the batch of twenty-one frontier achievements presented at the closing of the 2026 Zhongguancun Forum in late March, alongside results from other major facilities. For Chinese science the facility sits in a larger pattern: a suite of large instruments, from the spallation neutron source to the hard X-ray free-electron lasers, coming online in the same years, each designed to be shared across disciplines. The beamtime queue is the real test of whether the pattern works, because a facility of this scale is only as good as the experiments it enables.

The practical consequences will be felt most immediately in fields that live on X-ray characterisation. Materials scientists building next-generation batteries and catalysts, structural biologists who need to solve protein structures, condensed-matter physicists studying quantum materials, and archaeologists and conservation scientists analysing pigments and corrosion will all be applying for time in the coming rounds. For those communities the message of 20 March is simple: the machine exists, the light is on, and the queue is open. The seven years of building are over; the years of questions are just beginning.