PPPL and OpenStar sign levitated dipole fusion MOU

The levitating core magnet in OpenStar’s Tama Nui design can be swapped out for servicing, a feature of levitated dipole fusion

(Image courtesy of OpenStar Technologies)

OpenStar Technologies has signed a memorandum of understanding with the Princeton Plasma Physics Laboratory (PPPL), linking the New Zealand company’s levitated dipole fusion programme to a US Department of Energy-funded national laboratory, managed by Princeton University, with decades of plasma physics and fusion research behind it. The agreement covers scientific, academic and educational cooperation, and it follows OpenStar’s move from its Junior prototype to a published design for a grid-scale machine.

How levitated dipole fusion confines plasma

In a levitated dipole fusion device, a superconducting ring magnet floats freely inside the vacuum chamber and produces the field that holds the superheated plasma in place. OpenStar aims to draw on the concept’s inherent plasma stability and a modular design that is predicted to allow straightforward maintenance at plant scale.

For OpenStar, Chief Product Officer Thomas Berry described the agreement as a chance to draw on PPPL’s knowledge and infrastructure for its levitated dipole fusion work, while giving the laboratory the chance to work with a fast-moving company focused on commercial fusion energy. Laura Berzak Hopkins, PPPL’s Deputy Director for Research and Chief Research Officer, focused on the physics, describing the plasma inside a levitated dipole as behaving in ways that other fusion systems cannot reproduce. She framed that as an opportunity for unique scientific discovery and for addressing challenges facing other confinement approaches.

Garnier traces LDX to a PPPL control room

Darren Garnier, OpenStar’s Chief Science Officer, traces the concept’s lineage to a PPPL control room. In his account, the first levitated dipole experiment, LDX, began as a conversation between two physicists sitting through recovery from a plasma disruption on the laboratory’s flagship tokamak, where they discussed a configuration that does not disrupt at all. He credits PPPL with 75 years at the centre of fusion plasma physics and describes OpenStar as carrying the concept forward today.

LDX was a joint MIT and Columbia University project, and OpenStar describes Garnier as LDX’s former Chief Experimentalist, who joined from a research post at MIT. OpenStar has also signed a twelve-month collaboration agreement with the MIT Plasma Science and Fusion Center, using physics simulations to investigate ion cyclotron resonance heating in the dipole.

Levitated dipole fusion beyond Junior

PPPL’s release describes Junior as fully commissioned. A paper from OpenStar’s team puts the design at a REBCO high-temperature superconducting magnet of about 5.6 tesla inside a 5.2 metre vacuum chamber, built in under two years for less than US$10 million, with first plasmas arriving in late 2024 during its first experimental campaign.

In February, at a public demonstration attended by Prime Minister Christopher Luxon, OpenStar floated a half-tonne magnet while it confined plasma. Inside the magnet, an all-superconducting flux pump power supply stored 170 kilojoules, which OpenStar reports as a record for a flux pump supply, and the supply needs only 10 watts to keep the magnet active for an indefinite float time, a figure OpenStar attributes to the design’s efficiency.

Tama Nui, OpenStar’s grid-scale levitated dipole fusion plant, now has a deuterium-tritium design published in Fusion Engineering and Design, announced in June. As OpenStar describes it, a cryogenic slush acts as an onboard thermal reservoir for the superconducting systems, a preliminary layered tungsten and boron carbide shield protects the core magnet from neutrons, and the core magnet can be swapped out and maintained outside the reaction chamber so that power can still be produced during maintenance.

Tahi and the 20 tesla step

PPPL’s Berzak Hopkins looks forward to growing the partnership with OpenStar’s team as the company works towards fusion. The next machine is Tahi, which OpenStar plans to run at a magnetic field of up to 20 tesla, and the New Zealand Government is lending up to NZ$35 million through its Regional Infrastructure Fund to support a specialised facility for it. OpenStar expects further experiments on Tahi to supply the data needed to scale towards a commercial levitated dipole fusion device, which it aims to have in production in the 2030s.

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