India's first superconducting tokamak — built at the Institute for Plasma Research in Gujarat to develop the long-pulse, steady-state plasma operations essential for a fusion power plant.
SST-1 — the Steady State Superconducting Tokamak — is India’s first tokamak to use superconducting magnets. Located at the Institute for Plasma Research (IPR) in Gandhinagar, Gujarat, SST-1 was designed and built entirely by Indian scientists and engineers as a national project to develop the technologies and expertise needed for steady-state fusion plasma operations. Its construction represented a major step in India’s fusion program, which had previously operated only the smaller, copper-magnet ADITYA tokamak.[1]
SST-1 is a medium-sized tokamak with a major radius of 1.1 m and a minor radius of 0.20 m. The toroidal field, produced by 16 superconducting NbTi coils operating at 4.5 K, reaches 3.0 T on axis. The device is designed to carry a plasma current of up to 220 kA. Its most distinctive design feature is the emphasis on steady-state operation: SST-1 was built with the explicit goal of sustaining plasma discharges for 1,000 seconds — roughly 17 minutes — using a combination of lower hybrid current drive (LHCD), electron cyclotron resonance heating (ECRH), neutral beam injection (NBI), and ion cyclotron resonance heating (ICRH).[2]
SST-1’s development was a long and sometimes difficult process. Design work began in the early 1990s, and construction started in 1995. The superconducting magnet system, cryostat, and vacuum vessel were all designed and fabricated domestically, making SST-1 one of the few superconducting tokamaks built entirely within a developing nation. First plasma was achieved in June 2013, a milestone that came later than originally planned due to the technical challenges of integrating superconducting magnets, high-vacuum systems, and plasma-facing components in a device of this complexity.[3]
The commissioning phase revealed issues typical of first-of-a-kind superconducting systems, including challenges with vacuum integrity, baking procedures for wall conditioning, and management of the cryogenic system during plasma operations. These experiences provided invaluable training for the IPR team and directly informed the design of India’s next-generation device.
SST-1’s experimental program has focused on achieving progressively longer plasma discharges while developing plasma heating and current-drive systems. The device has operated in both limited and diverted plasma configurations, with an open divertor geometry. Experiments have explored plasma start-up optimization, wall conditioning with glow discharge cleaning and boronization, and the use of ECRH and LHCD for plasma sustainment. While SST-1 has not reached its ultimate 1,000-second goal, the operational experience has been essential for developing India’s fusion engineering workforce.[4]
SST-1’s most important legacy may be institutional rather than purely scientific. The project trained a generation of Indian fusion scientists and engineers in superconducting magnet technology, cryogenics, and long-pulse plasma operations — skills that India has since deployed to its contributions to the ITER project. India is a full ITER partner and is responsible for manufacturing several critical ITER components, including cryostat segments, in-wall shielding blocks, and diagnostic systems. IPR has announced plans for SST-2, a significantly larger superconducting tokamak that would serve as India’s step toward a fusion DEMO, though detailed design parameters and a construction timeline have not been finalized.[5]