FAQ on High Temperature Superconductors (HTS)
on wide HTS
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To produce stellarator magnets, competitors wind narrow tapes (4-12 mm in width) on 3D structures. The complexity lies in fabricating the 3D structures and installing the tapes in 3D, with millimetric precision.
We simplify manufacturing by means of wide cylindrical HTS films that can be easily laser-patterned and wrapped on a former. The complexity now lies in the patterning, which is not a problem: commercial lasers easily draw patterns with 10 µm precision. This greatly exceeds stellarator accuracy needs, by far.
In addition, these wide tapes will be commercially valuable for other applications.
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There is a wide range of applications for wide HTS, ranging from the simplification of HTS-based electric motors and generators especially for off-shore wind turbines, high-field gyrotron and MRI magnets, fault current limiters, undulators for synchrotrons and magnets for particle accelerators for physics research, material testing and cancer therapy.
on HTS magnets
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Superconductors are required to carry high electrical currents and thus generate the strong magnetic fields needed for magnetic fusion. Regular conductors like copper are not suitable for the job due to Ohmic losses caused by the Joule effect. Engineering challenges aside, those losses would make the energy balance unfavorable, hence would make it impossible or extremely difficult for a magnetic fusion device to provide net energy.
Magnetic fusion needs superconductors, at least traditional Low Temperature Superconductors (LTS) or, even better, recently available High Temperature Superconductors (HTS). HTS can superconduct higher currents, at higher magnetic fields, and at higher temperatures -albeit still quite cold compared to room temperature. The higher temperature of operation reduces the cooling costs, but the real game-changer here is the higher current and field, allowing for more compact fusion devices.
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For our 1 GWe stellarator fusion power plants, the power requirements for cryogenics are currently estimated to be less than 28 MW. Further work is underway to refine the calculations and cryogenic system design.
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To provide some sense of forces on our HTS magnets in the stellarator fusion power plan, peak radial pressure will be on the order of 250 MPa, more than twice the pressure at the greatest depths in the ocean.
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We have built a 20 cm bore non-insulated HTS magnet providing peak fields approaching 1 T. Currently we are assembling a 1 m non-insulated HTS magnet providing peak fields of 6 T generating the background field for some liquid metal flow experiments.
other questions
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Meter-wide tapes are not available today. We are building the film-deposition machines that will demonstrate this technology and manufacture meter-wide HTS tapes in-house. In parallel, we occasionally purchase standard HTS tapes of 4-12 mm width from various vendors to build HTS magnets and start addressing aspects related to future, larger tapes and coils -from energizing the coil to deliberately quenching it, to testing diagnostics, construction techniques, materials, etc.
Have a question and don’t see it here?
Send it to contact@renfusion.eu. FAQs will be answered here, less frequent questions will be answered by individual e-mails.