SUNIST Sino-UNIted Spherical Tokamak — a laboratory for controlled fusion
The SUNIST laboratory studies spherical tokamaks as a pathway towards affordable fusion energy. It has operated the SUNIST device since 2002 and now operates its high-field successor, SUNIST-2, which achieved first plasma in 2023.
Key parameters of SUNIST and SUNIST-2
Two generations of spherical tokamak: SUNIST, in operation since 2002, and its high-field successor SUNIST-2, in operation since 2023.
SUNIST · since 2002
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0.30 / 0.23 m
Major / minor radius (R0 / a)
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< 0.27 T
Toroidal magnetic field on axis
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< 120 kA
Plasma current
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~1019 m-3
Electron density
SUNIST-2 · since 2023
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0.53 / 0.33 m
Major / minor radius (R0 / a)
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1.0 T
Toroidal magnetic field on axis
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500 kA
Plasma current — design value reached in 2025
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≤ 2.0
Maximum elongation (κ)
A place to discover new physics
The SUNIST laboratory is a place to discover new physics and to invent new technologies that may make fusion an affordable and effectively inexhaustible energy source for humanity as soon as possible.
The pathway currently selected by the lab is the spherical tokamak. The lab operates SUNIST, which produced its first plasma on 4 November 2002 and was substantially upgraded in 2008, and has since built and commissioned its successor, SUNIST-2, which achieved first plasma in 2023.
Over its first two decades of operation SUNIST produced roughly 100,000 discharges. Research on the device spans equilibrium reconstruction, heating and current drive, MHD stability and disruptions, turbulence and transport, fuelling, wall conditioning and plasma diagnostics.
About the device
What the laboratory works on
Spherical tokamaks confine hot plasma in a compact, low-aspect-ratio geometry. Work on SUNIST covers both the plasma physics of the device and the engineering needed to create, control and observe it.
Flux saving & 3D eddy currents
A split vacuum vessel that trades symmetry for Ohmic flux — and the three-dimensional eddy currents that result.
Read more →Heating & current drive
Electron-cyclotron start-up, Alfvén wave current drive and electron-Bernstein wave heating and mode conversion.
Read more →MHD stability & disruptions
Internal reconnection events, minor disruptions, toroidal Alfvén eigenmodes and tearing modes during current ramp-up.
Read more →Turbulence & transport
Edge fluctuations, anomalous transport, nonlinear energy transfer and a quasi-coherent mode in the core plasma.
Read more →Diagnostics
Magnetic probes, a 105 GHz five-channel interferometer and coverage of the full electromagnetic spectrum.
Read more →Fuelling & wall conditioning
High-field-side supersonic molecular beam injection, gas-puff repeatability, baking and glow-discharge cleaning.
Read more →Twenty years of SUNIST research
A review series in eight chapters — the device, the plasma physics and the diagnostics, with figures and equations from the original manuscript.
SUNIST-2
SUNIST-2, the laboratory's high-field successor, has been operating since March 2023. Designed for a 1 T toroidal field and 500 kA plasma current, it is used to study high-field confinement, magnetic-reconnection heating and repetitive pulsed operation; the plasma current reached its design value of 500 kA in 2025.
Results reported at the 30th IAEA Fusion Energy Conference (2025) and in recent papers; see the SUNIST-2 page for details.
About SUNIST-2
ISTW 2022 · 21st International Spherical Torus Workshop
The laboratory hosted the 21st ISTW virtually on 31 October – 4 November 2022. The programme, book of abstracts and presentation files remain available as an archive.
Find us
Room 158, Building of Engineering Physics (Gongwuguan)
Tsinghua University, Haidian District
Beijing 100084, China
