OpenStar Technologies: Towards the levitated dipole as a fusion device

OpenStar Technologies, a private company from Wellington, New Zealand, is developing the levitated dipole as a commercial fusion device. Predicted favorable properties of dipole-confined plasmas such as high-betas and good energy confinement combined with engineering advantages such as a relatively cheap, replaceable, and singular plasma-confining magnet merit their investigation as fusion power plants. A major consideration for levitated dipole reactors (LDRs) is the thickness of the neutron and gamma shielding on the dipole magnet which sets the location of the inner plasma limiter, defining a ‘first closed flux surface’, and thereby reducing the effective magnetic flux on the plasma. Reducing shielding allows for smaller magnets but makes it difficult to achieve a balance of plant with net energy gain due to the increased cryogenic load on the superconducting coils. Starting from a stress-limited magnet design, a reactor study for an LDR was conducted which accounts for this tradeoff between heat shielding and fusion performance, allowing for a plant design which optimizes the engineering fusion gain, Q_eng. Once a solution for an engineering breakeven device has been found, other important parameters are considered to ensure that the LDR is an economic power plant.