China Spallation Neutron Source Opens 200 kW Operations as Upgrade Advances Toward 500 kW

Dongguan facility doubles its original design power

The China Spallation Neutron Source in Dongguan, Guangdong province, has begun serving researchers at a beam power of 200 kilowatts, twice the level specified in its original design. The Institute of High Energy Physics of the Chinese Academy of Sciences announced on October 24 that the facility reached the milestone on October 20 after nearly a month of accelerator tuning.

The achievement brings an immediate increase in capability at a facility whose 11 neutron instruments are open to users. It also tests equipment and operating methods needed for the second phase of construction, known as CSNS-II, which aims to raise beam power to 500 kW.

The institute said accelerator specialists reduced beam loss even as they increased power. Keeping more particles on their intended path matters because particles escaping the beam can deposit energy in surrounding equipment and complicate reliable operation.

The latest work extends beyond the accelerator. A new target, designated T8, was installed and tested on September 25 with cooling designed for operation at 200 kW. Maintenance teams also serviced the instruments that researchers use to examine materials.

For scientists studying batteries, alloys, biological materials and other samples, the practical value lies in the neutrons reaching their experiments. A stronger source can collect useful measurements more quickly and support investigations that need smaller samples or finer detail. The facility has now reached twice its original power, while further accelerator construction remains necessary to reach the full second phase target.

How a proton beam becomes a research tool

CSNS produces neutrons by accelerating protons and directing them into a target. The collisions release neutrons through a process called spallation. Instruments guide those neutrons toward samples and measure how they scatter.

Scientists examine changes in the direction, energy and momentum of the scattered neutrons to work out how atoms are arranged and how they move. In simple terms, the particles act as probes of structures too small to see with an ordinary microscope.

Beam power describes the energy delivered by the proton beam each second. Raising it allows the source to produce more neutrons, giving researchers more information to collect. The benefit for an individual experiment also depends on its instrument, sample and measurement method.

What researchers stand to gain

Wang Sheng, deputy director of the Institute of High Energy Physics and general director of the upgrade project, described the expected scientific gains when construction of the second phase began in March 2024.

"After completion of the phase II, the source can generate more neutrons at the same time, which means the time of the experiments could be shortened, and the resolution of the experiments could be improved, enabling the measurement of smaller samples and the study on faster dynamic processes," Wang said.

Shorter measurements can free instrument time for more projects. Better resolution allows researchers to distinguish details that would otherwise blend together, while faster measurements help them follow changes taking place inside a material.

The facility already supports research on lithium-ion batteries, solar cells, aerospace components, magnetic materials, superconductors, thin films and strong alloys. Zhang Junrong, who oversees user experiments and applications at CSNS, identified these areas when describing its work at the second phase launch.

Those subjects connect the accelerator to practical problems. Battery studies can examine changes in materials during use, while investigations of alloys and aerospace components can help researchers understand how their internal structures relate to performance. The upgrade is also intended to broaden work in life sciences, drug development and catalyst design.

Summer shutdowns make room for construction

The CSNS-II team uses the annual summer shutdown to install equipment while limiting interruptions to scheduled research. This creates a demanding sequence: construction, equipment tests and accelerator tuning must fit around the operation of an existing scientific facility.

During the latest shutdown, workers installed and tested equipment at the front of the linear accelerator, all the solid state modulators and a third magnetic alloy cavity in the rapid cycling synchrotron. The modulators provide controlled electrical pulses, while the cavity helps supply the energy needed to accelerate the beam.

The linear accelerator sends particles along a straight path before they enter the synchrotron, where they circulate and gain further energy. Equipment in both parts must operate together so that the beam reaches the target in the required condition.

According to the institute, all accelerator equipment planned for CSNS-II is now installed except the superconducting section. That remaining section is part of the work needed to increase the linear accelerator beam energy to 300 million electronvolts, or 300 MeV.

Keeping a denser beam under control

Higher power made the accelerator harder to tune. Changes in equipment settings interacted with forces inside the beam and with the beam's surroundings, creating conditions in which groups of particles could become unstable.

One challenge was space charge, the electrical repulsion between particles carrying the same charge. Another involved interactions between the beam and accelerator structures, described as beam impedance effects. Together, such effects can disturb the beam and increase the number of particles lost along its path.

The accelerator team adjusted key sections of the upgraded linear accelerator, including the radio frequency quadrupole, or RFQ, and the medium energy beam transport section, or MEBT. These sections prepare, accelerate and guide the beam before its next stage.

The institute said major changes to the operating mode resolved collective beam instability. It also said the beam density index exceeded the highest level reported for comparable accelerators internationally. The announcement did not provide a numerical value for that index or the amount by which beam loss fell.

The reported reduction in losses gives the project a useful result beyond reaching a power figure: the team has demonstrated a way to operate a more demanding beam while keeping more of its particles under control.

A new target and serviced instruments

The T8 target sits where the accelerated protons strike to release neutrons. Its cooling design is built for operation at 200 kW, and new temperature monitoring tracks conditions in the target plates.

Heat management becomes more demanding as beam power rises. Measurements from T8 will feed into the design of the more powerful target required for CSNS-II, giving engineers operating experience before the facility advances toward 500 kW.

The 11 instruments open to users also underwent summer maintenance. Work covered scattering chambers, choppers, detectors and sample environments, all of which affect how an experiment is conducted and measured.

Choppers control which parts of a neutron pulse pass through an instrument. Detectors record the scattered neutrons, while sample environments allow scientists to study materials under selected conditions, such as different temperatures. Servicing these systems prepares the experimental end of the facility to use the stronger source.

How the 500 kW plan expands capacity

The Institute of High Energy Physics set out the scale of CSNS-II in its project launch announcement. The launch meeting took place in Dongguan on March 30, 2024, and the stated construction period was five years and nine months.

The official plan raises beam power from 100 kW to 500 kW and increases the number of neutron spectrometers from 11 to 20. It also lists two additional experimental terminals, including one for experiments using high energy protons. The construction programme includes user laboratories as well as new instruments and terminals.

The planned increase from 11 to 20 spectrometers adds nine instruments, an expansion of about 82 percent. The power target is five times the original 100 kW design. At 200 kW, the facility is operating at 40 percent of the planned final power, although construction progress depends on much more than that single measure.

The latest update describes the project as about halfway through construction. Building work was completed at the end of September, and a helium refrigerator capable of approximately 1 kW of cooling at 2 kelvin was installed on October 15. Two kelvin is about minus 271 degrees Celsius, a temperature used for superconducting accelerator systems.

The dates behind the upgrade

CSNS has moved from its original construction programme to an expansion carried out alongside user operations. The main dates show how the latest milestone fits into that longer effort.

• 2011: Construction began on the original CSNS project, with an investment of 2.3 billion yuan.
• August 2018: The facility entered service.
• March 30, 2024: The CSNS-II launch meeting was held in Dongguan, with a stated construction period of five years and nine months.
• September 25, during the latest upgrade work: The T8 target was installed and tested.
• End of September: Building work for the second phase was completed.
• October 15: The helium refrigerator for operation at 2 kelvin was installed.
• October 20: The facility reached the 200 kW milestone after nearly a month of beam tuning.
• October 24: The Institute of High Energy Physics announced user operation at the higher power.

The next accelerator step identified by the institute is to raise the linear accelerator beam energy to 300 MeV. Experience from the latest commissioning will guide that work and the subsequent increase in power.

Demand extends beyond the accelerator

The institute's 2024 launch announcement recorded more than 6,000 registered users and more than 1,500 completed experimental projects since CSNS entered operation in 2018. Those figures describe the facility at the time of the launch announcement.

More than 100 completed projects involved users from Hong Kong, Macao, Taiwan and abroad, according to the institute. The user community spans energy, physics, materials and engineering, creating demand for both instrument access and a wider choice of experimental conditions.

Zhang Junrong, the official responsible for user experiments and applications, described the pressure for expansion at the launch.

"There is an urgent need to upgrade the CSNS to meet the increasing demand of the users," said Zhang.

The second phase addresses that demand in two connected ways. More powerful beams can make some measurements faster, while additional instruments give researchers more places and methods to conduct experiments. For users, the outcome depends on both parts working together: a stronger source and enough experimental capacity to turn its neutrons into results.

Key Points

• CSNS reached 200 kW on October 20 and began user operations at twice its original design power.
• The institute says beam loss fell as power increased following equipment tuning and changes to the operating mode.
• A new T8 target and maintenance of all 11 user instruments support operation at the higher power.
• CSNS-II aims for 500 kW and an increase from 11 to 20 neutron spectrometers, alongside additional experimental terminals.
• The superconducting accelerator section remains to be installed, with a linear accelerator energy increase to 300 MeV among the next steps.
• The expansion is intended to support faster measurements, smaller samples and a broader range of research.