Speaker
Description
The Levitated Dipole Reactor (LDR) is a promising concept for confining fusion relevant plasmas. In an LDR, a high field dipole magnet (core) is levitated in a large vacuum chamber, mimicking the plasma confinement physics observed in planetary magnetospheres. The performance of an LDR is largely determined by the ability of the core magnet to resist the natural diamagnetic expansion of the fusion plasma, which places requirements on the magnet’s strength and stored energy. One key challenge in scaling LDRs is managing the Lorentz force generated by the superconductor. Naive magnet designs that satisfy the plasma performance requirements have been shown to have large tensile stresses in the REBCO HTS windings, leading to permanent degradation of the HTS tape no matter the supporting structure.
OpenStar, a fusion startup based in New Zealand, is aiming to build LDRs for the grid. An optimisation scheme has been developed that alters the core magnet cross section to maximises the plasma pressure for a target core magnet hoop stress. Alongside this, a new magnet structure has been developed that leverages high tensile modulus materials and large precompressions to reduce conductor strain to acceptable levels. Together, these technologies enable the design of feasible core magnets with HTS strains less than 0.4% while maintaining suitable performance for a D-T fusion power plant.
This work discusses in detail how these technologies have been used in the design of OpenStar’s Tahi experiment. The Tahi core magnet, which requires a 1m diameter core magnet with a peak field of at least 20T, aims to prove the viability of these technologies and pave the way for full scale LDRs.
