The Soviet device that proved magnetic confinement could work — and launched the tokamak era.
Before T-3, the global fusion community was skeptical that any magnetic bottle could hold a plasma long enough to matter. Soviet physicists at the Kurchatov Institute in Moscow changed that perception permanently. The T-3 tokamak, operational from 1962, delivered electron temperatures above 10 million degrees and confinement times that eclipsed every competing concept of its day. When a British team from Culham Laboratory arrived in 1969 with independent Thomson-scattering diagnostics and confirmed the Soviet claims, the world pivoted to tokamaks almost overnight.
T-3 was a relatively compact device with a major radius of 1.0 m and a minor radius of 0.12 m. It operated with a toroidal magnetic field of approximately 2.5 T and achieved plasma currents up to 60 kA. The vacuum vessel was a stainless-steel torus with discrete copper windings providing the confining field. By the standards of later machines it was modest in scale, but its physics output was extraordinary.
At the 1968 IAEA Fusion Energy Conference in Novosibirsk, Lev Artsimovich presented T-3 results claiming electron temperatures near 1 keV with confinement times of several milliseconds. Western scientists, long frustrated by their own devices' poor performance, were cautiously excited but demanded independent verification. The following year, a team led by Nicol Peacock from Culham used laser Thomson scattering — a technique the Soviets did not possess — to measure the T-3 plasma directly. The results confirmed and even slightly exceeded the Soviet claims.2
The impact was immediate. Within two years, the United States converted its Model C stellarator at Princeton into the Symmetric Tokamak, and tokamak programs launched in Japan, Europe, and across the Soviet Union. The tokamak became the dominant approach to magnetic confinement fusion, a position it still holds more than five decades later.
T-3 established several foundational principles. It demonstrated that a strong toroidal magnetic field combined with a plasma current could produce stable, hot confinement. It validated the theoretical framework developed by Igor Tamm and Andrei Sakharov in the 1950s. And it showed that empirical confinement scaling — later formalized in devices like TFTR and JET — could be meaningfully extrapolated from small machines to larger ones.3
The device also revealed the importance of plasma purity. Early T-3 discharges suffered from impurity radiation that cooled the plasma edge, a problem that would drive decades of materials and wall-conditioning research in every subsequent tokamak.4
T-3 was eventually succeeded by T-4, T-10, and the larger T-15 at Kurchatov, each building on its foundational results. But none matched the historical significance of T-3 itself: the machine that proved the tokamak concept and reshaped the trajectory of fusion energy research worldwide.5