Energy · 2021

High-temperature superconducting magnet

A 20 tesla REBCO magnet shrinks the size a power-producing tokamak needs.

In September 2021 Commonwealth Fusion Systems and MIT ran a large high-temperature superconducting magnet at 20 tesla. Because fusion power scales with field strength to the fourth power, it enables compact machines like the SPARC tokamak under construction in Massachusetts.

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What it built on 2

What it led to 2

Watch

Highlights from the Live-Streamed 20 Tesla HTS Magnet Demo EventCommonwealth Fusion Systems · YouTube

Related measurements

The dashed line marks when it first worked.

Record fusion triple product Latest: 1.73×10²² keV·s/m³ (2017) Source: Wurzel & Hsu 2022, Physics of Plasmas 29, 062103; Wurzel & Hsu 2025 update, Physics of Plasmas 32, 112106

Nuclear electricity generation Latest: 2.81k TWh (2025) Source: Our World in Data