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Description
Openstar Technologies is advancing the Levitated Dipole fusion reactor concept. OpenStar’s first experiment, ‘Junior’ retired engineering risk and matched performance of similar experiments elsewhere. The next experiment, Tahi, will enable new fusion science and produce a triple product greater than 1e19 [keVm-3s]. Magnetic confinement for this experiment is provided by the Tahi Core Magnet - a 20 T HTS magnet which is levitated inside a large vacuum chamber. This work introduces the experiment, details the magnet's systems and presents the latest updates on the Tahi Core Magnet.
This magnet is a similar size to the Junior magnet; however, it is designed to produce 4x higher peak magnetic field. This is achieved by adding more conductor and operating at a lower temperature. Consequently, the magnet operates close to the critical strain of the HTS tape. This magnet is designed to explore the edge of the of the strain envelope, as hoop stresses will be a limiting factor in larger devices.
The magnet consists of approximately 50km of 4mm wide Rebco tape, bundled into a simply stacked cable within a structure. The conductor is arranged in the shape of a torus, with an outside diameter of approximately 1 meter. The operating current and temperature are approximately 8 kA and 30 K respectively. A zero-field region exists in the centre of the toroid, which is required for the onboard power supplies.
The magnet, housed within a cryostat, operates between a levitated and docked position within the main vacuum chamber. Cooling is provided via a heat exchanger loop while in the docked position. The float time is dictated by the thermal mass of the magnet balanced against heat loads. Charging and maintenance is provided by an onboard power supply.
Details of cable bundling, coil winding, manufacturing and testing facilities have also been included.
