The purpose of this website is to share and archive information for the IEA Spherical Tori Technology Collaboration Program (ST TCP).


The spherical torus (ST) machine has emerged as an innovative example of fusion confinement that could allow progress to be made in fusion energy development. Though ST devices have the capacity to operate at high temperatures (more than 60 million degrees centigrade), the magnets are potentially simpler than conventional tokamaks and may have lower construction and operating costs. Although the ST plasmas are similar to the standard aspect ratio tokamak plasmas in many ways, the range of physics parameters can lead to important new plasma behaviours such as increased stability. In addition, creating plasma in a spherical torus reduces transport because of the flow shear and geometric configuration.


There are currently four (4) Contracting Parties (EU, Japan, South Korea, USA) to the Implementing Agreement for Co-operation on Spherical Tori (ST IA). Created in 2007, the aims of the ST IA are to enhance the effectiveness and productivity of fusion energy science and technology in preparation for ITER by:

    • Strengthening co-operation among spherical torus research programmes and facilities

    • Contributing to and extending the scientific and technology database of toroidal confinement concepts to the ST physics regime

    • Providing a scientific and technological basis for the successful development of fusion power using the spherical torus (see example from IAEA-FEC 2018 here)

Additional information from the IEA is available for the Technology Collaboration Program for Fusion Power and for the ST.

Please visit the pages listed on the left-hand side of this webpage for additional information.