Fusion world

Collaborative research intensifies on China's HL-3 tokamak

In the framework of a deepened collaboration between the Southwestern Institute of Physics (SWIP), China and the ITER Organization, the HL-3 tokamak has become a satellite device of ITER. A campaign dedicated to deuterium-tritium plasma experiments in support of ITER's physics research and operation is planned. 

Recent progress in the development of high-performance scenarios is essential for successful deuterium-tritium operation in HL-3 and for burning plasma research. Photo courtesy of SWIP.

In December 2023, the ITER Organization signed an agreement for academic, scientific and technical cooperation with the Southwestern Institute of Physics (SWIP) in Chengdu, China. SWIP has built more than 20 experimental devices for controlled nuclear fusion research, including medium-sized tokamaks HL-1 (1984) and HL-1M (1994), divertor-based tokamak HL-2A (2002), and the advanced-divertor tokamak HL-3 (formerly called HL-2M) that achieved first plasma in 2020 and high-confinement operation (H-mode) in August 2023

Collaboration is now intensifying in areas such as integrated operation scenarios simulation, disruption physics, and plasma control. The spring 2025 experimental campaign has attracted international research teams from the United States, France, Japan, South Korea, Portugal, and Thailand for joint investigations that will target key challenges for high-fusion-power-production deuterium-tritium (DT) plasmas in ITER such as high-beta plasma sustainment, disruption mitigation techniques, isotope mixing effects, and advanced heat exhaust solutions.

A prototype tri-band spectrometer system for ITER's charge-exchange recombination spectroscopy diagnostics has completed its initial technical validation on HL-3, demonstrating the capabilities for simultaneous ion temperature measurements and impurity monitoring which will improve ITER measurement capabilities. The HL-3 team has also successfully commissioned two self-developed plasma heating systems—a high-power electron cyclotron heating system and a 7 MW neutral beam injection system—during recent facility upgrades. 

HL-3 is a research device located at the Center of Fusion Science/Southwestern Institute of Physics (SWIP) in Chengdu, China. Its construction was a decade-long project that cumulated with the completion of first plasma in December 2020. Photo courtesy of SWIP.

Recent experiments have achieved stable 1.6 MA plasmas in diverted configuration and developed a novel tripod divertor magnetic configuration demonstrating enhanced heat flux handling. Operation scenarios with electron or ion internal transport barriers have achieved HL-3 record electron temperatures exceeding 160 million degrees and ion temperatures above 117 million degrees in a reproducible way. The operational strategies and the control algorithms required to access and sustain these high-temperature plasmas have been successfully developed. This progress in the development of high-performance scenarios is essential for successful deuterium-tritium operation in HL-3 and for burning plasma research.

Future HL-3 research priorities include increasing heating power capacity to pursue scenarios with higher fusion triple product and operation with a higher temperature wall to decrease recycling levels and, eventually, in-vessel tritium retention. Machine-learning applications are also being integrated for real-time plasma shaping control, instability suppression, and disruption prediction—critical developments supporting the facility's transition to high-performance plasma operations to be followed by deuterium-tritium plasmas.