The company grew out of the Culham Laboratory, home of JET, the world’s most powerful operating tokamak. The team at Culham also developed spherical tokomaks – pioneering a more compact, more efficient design. With the advent of high temperature superconductors (HTS), the founders of Tokamak Energy realized that it would be theoretically possible to produce spherical tokamaks that would perform similarly to existing machines with room size facilities, rather than the “aircraft hangar” size of designs like JET. This gave them the opportunity to start a company to exploit the new technology, and there has already been much success with small prototypes.
Of course, there were many technical challenges still to address. For one of these, Cobham’s Opera software was used to assess the electromagnetically induced forces and field profile in a new design. HTS coils need to be mechanically supported with minimum heat transfer. Ideally, this would be one that is a self-supporting structure which allows the use of minimal connections to the room-temperature world. To investigate possible designs, the new tokamak prototype, ST40, will use a single massive copper turn for each of the toroidal field (TF) coils (rather than HTS), as this is considerably less expensive. The consequence of this is, however, that it can no longer be assumed that current density is uniform across the cross-section. Hence, an accurate simulation of the fields, currents and resulting forces was required, since the Lorentz force acting on the coils is determined from the product of the current density and flux density (J x B),
Tokamak Energy simulated several variations on the design, each examining the fields and forces for multiple cases representing different times in the operating scenario. They also calculated the inductance of the TF coil system.
Paul Noonan, R&D Projects Director for ST40 at the company comments:
“At that point, Tokamak Energy will have assembled some profoundly exciting experimental and theoretical evidence of the viability of producing fusion power from compact, high field, spherical tokamaks”.