General Fusion

General Fusion is a Canadian company based in Burnaby, British Columbia, which is developing a fusion power device based on magnetized target fusion (MTF). The company is funded by a variety of investors.

The fusion device under development injects plasma in the form of a compact toroid into a hollow cylinder, which is then compressed to fusion-relevant densities and pressures. In contrast to most MTF systems, which use magnets to compress the plasma, the General Fusion design instead uses a large number of steam-driven pistons to mechanically compress a vortex of liquid metal.[1][2][3] As of 2017 General Fusion was developing subsystems for use in a prototype to be built in three to five years.[4]

In 2018, the company published several papers on a new design using a spherical tokamak as the plasma source, as opposed to the compact toroid. It is not clear in existing references whether this represents a major change of the original concept.[5]

Organization

As of 2016, General Fusion had 65 employees[6] and had raised over C$150 million in funding from a global syndicate of investors.[7][8] The company was founded in 2002 by former Creo Products senior physicist and principal engineer Michel Laberge.[9]

The company is led by a management team consisting of Christofer M. Mowry, the CEO, Bruce Colwill, the CFO, Michel Laberge, the Chief Science Officer, and Michael Delage, the CTO.[10]

Michel Laberge founded the company in 2002. Laberge holds a PhD in physics from the University of British Columbia in 1990, and completed a post doc at the L’ecole Polytechnique and the National Research Council in Ottawa. Before he founded General Fusion, Laberge was a senior physicist and principal engineer at Creo Products for nine years.[10]

Christofer Mowry came from a position as the CEO and Chairman of General Synfuels International. Prior to that, he founded and ran Generation mPower, a company that sold Small Modular Reactors (SMRs), a nuclear energy technology. He served as President of B&W Nuclear Energy and Chief Operating Officer of WSI.[10]

Michael Delage holds multiple responsibilities at General Fusion, including building partnerships with international research institution. He oversees partnerships with governments and other companies, as well as General Fusion's technology development strategy. Previously, Michael co-founded residential demand response technology company Energate Inc. He also worked as a design engineer on robotic systems for the International Space Station.[10]

The board of directors is chaired by Frederick W. Buckman Sr., former CEO of Consumers Power.[11] Advising the board is a Scientific Advisory Committee, which includes Carol M. Browner,[12] physicist T. Kenneth Fowler[6] and former astronaut Mark Kelly.[13]
Technology
Diagram of the General Fusion power plant
Power plant design

General Fusion's Magnetized Target Fusion system uses a ~3 meter sphere filled with a mixture of molten lead and lithium. The liquid metal is spun to open up a vertical cylindrical cavity in the centre of the sphere (vortex). This vortex flow is established and maintained by an external pumping system; liquid flows into the sphere through tangentially directed ports at the equator and exits radially through ports near the poles of the sphere.[14]

Attached to the top of the sphere is a plasma injector, from which a pulse of magnetically-confined deuterium-tritium plasma fuel is injected into the center of the vortex. A few milligrams of gas are used per pulse, and the gas is ionized by a bank of capacitors to form a spheromak plasma (self-confined magnetized plasma rings) composed of the deuterium-tritium fuel.[15][16] The company demonstrated plasma lifetimes up to 2 milliseconds and electron temperatures in excess of 400 eV.[17]

The outside of the sphere is covered with steam pistons, which push the liquid metal and collapse the vortex, thereby compressing the plasma. The compression increases the temperature of the plasma to the point where the deuterium and tritium nuclei fuse, releasing energy in the form of fast neutrons.[16]

This energy heats up the liquid metal, which is then pumped through a heat exchanger and used to generate electricity via a steam turbine. The plasma formation and compression process repeats and the liquid metal is continuously pumped through the system. Some of the steam is recycled to power the pistons.[18][14]

An earlier concept used steam pistons to simultaneously impact a set of stationary anvils on the surface of the sphere to create acoustic pressure waves in the liquid metal.[16] The pressure waves would converge to become a spherical shockwave at the center of the sphere. This approach created excessively strong magnetic fields, which caused instabilities in the liquid metal wall. As of October 2017, the approach was to use slower pistons and compression time of 40 ms for lower peak energy densities.[19]

In addition to its role in compressing the plasma, the use of a liquid metal liner shields the power plant structure from neutrons released by the deuterium-tritium fusion reaction, overcoming the problem of structural damage to plasma-facing materials.[20][14] The use of liquid lithium in the mixture enables the breeding of tritium fuel, while the liquid metal provides a means of extracting the energy from the system via a heat exchanger.[14][21]
LINUS
Main article: LINUS (fusion experiment)

General Fusion's approach is based on the LINUS concept developed by the United States Naval Research Laboratory (NRL) beginning in 1972.[22][23][24] Researchers at NRL suggested an approach that retains many of the advantages of liner compression to achieve small, high-energy-density fusion, while using a liquid metal as the liner to avoid neutron damage to the tokamak wall.[25]

In the LINUS concept, a rotating liquid lithium liner is imploded mechanically, using high pressure helium as the energy source. The liner acts as a cylindrical piston to compress a magnetically-confined plasma adiabatically to fusion temperature and relatively high density (~1017 ions.cm−3).[22] In the subsequent expansion the plasma energy and the fusion energy carried by trapped alpha particles is directly recovered, making the mechanical cycle self-sustaining. The LINUS reactor can thus be regarded as a fusion engine, except that there is no shaft output: all the energy appears as heat.[22]

The liquid metal acts as both a compression mechanism and heat transfer mechanism, allowing the energy from the fusion reaction to be captured as heat.[22] LINUS researchers anticipated that the liner could also be used to breed tritium fuel for the power plant, and would protect the machine from high-energy neutrons by acting as a regenerative first wall.[22]

Synchronizing the timing of the compression system was not possible with the technology of the time, and the proposed design was never constructed.[24] General Fusion's Chief Scientist, Michel Laberge, claimed that these timing limitations can now be overcome.[6]
Research and development

The company developed the sub-systems of the power plant, including plasma injectors and compression driver technology.[26] Patents were awarded for a fusion energy reactor design,[27] as well as enabling technologies such as plasma accelerators,[28] methods for creating liquid metal vortexes[29] and lithium evaporators.[30]
Plasma injectors
Plasma injector

Plasma injectors provide the fuel supply for the MTF power plant, injecting a deuterium-tritium plasma into the compression chamber.[31]

Compact toroid plasmas are formed by a coaxial Marshal gun (a type of plasma railgun), with magnetic fields supported by internal plasma currents and eddy currents in the flux conserver wall.[32] The company has constructed and operated more than a dozen plasma injectors.[33] These include large two-stage injectors with formation and magnetic acceleration sections (dubbed "PI" experiments), and three generations of smaller, single-stage formation-only injectors (MRT, PROSPECTOR and SPECTOR).[17] In 2016 the company published research demonstrating spheromak plasma lifespans of up to 2 milliseconds and temperatures in excess of 400 eV on its SPECTOR generation of injectors.[17] As of December 2017, the PI3 plasma injector was operational and held the title as the world's most powerful plasma injector, ten times more powerful than its predecessor.[34]
Compression driver technology
Pistons for plasma compression

Pneumatic pistons were initially used to create a converging spherical wave to compress the plasma. Each system consists of a 100 kg, 30 cm diameter hammer piston driven down a 1 m long bore by compressed air.[35][16] The hammer piston strikes an anvil at the end of the bore, generating a large amplitude acoustic pulse that is transmitted to the liquid metal in the compression chamber via the piston anvil.[35] To create a spherical wave, the timing of these strikes must be controlled to within 10 µs of each other. The company has recorded sequences of consecutive shots with impact velocities of 50 m/s and timing synchronization within 2 µs.[35]

A proof-of-concept prototype compression system was constructed in 2013 with 14 full size pistons around 1 meter diameter spherical compression chamber to demonstrate pneumatic compression and collapse of a liquid metal vortex.[36][35]
Liquid metal systems

The proof-of-concept prototype compression system incorporates technology for forming a vortex of liquid metal as would be required in an MTF power plant. This consists of a 15 tonne liquid lead reservoir, pumped at 100 kg/s to form a vortex inside a 1-meter diameter spherical compression chamber.[36][35]
Research collaborations

Microsoft: In May 2017 General Fusion and Microsoft announced a collaboration to develop a data science platform based on Microsoft's Azure cloud computing system. A second phase of the project was to apply machine learning to the data, with the goal of discovering insights into the behavior of high temperature plasmas. The new computational program would enable General Fusion to mine over 100 terabytes of data from the records of over 150,000 experiments. It will use this data to optimize the designs of their fusion system's plasma injector, piston array, and fuel chamber. During this collaboration, the Microsoft Develop Experience Team was to contribute their experience and resources in machine learning, data management, and cloud computing.[37]
Los Alamos National Laboratory: General Fusion entered a cooperative research and development agreement (CRADA) with the U.S. Department of Energy's Los Alamos National Laboratory for magnetized target fusion research.[38]
McGill University: McGill University and General Fusion acquired an Engage Grant from the Natural Sciences and Engineering Research of Canada to study General Fusion's Magnetized Target Fusion technology. Specifically, the project was to use McGill's diagnostic capabilities to develop techniques to understand the behavior of the metal wall during plasma compression and how it may affect the plasma.[39]
Princeton Plasma Physics Laboratory: MHD simulation of compression during MTF experiments[40]
Queen Mary University of London: General Fusion funded a research study on high fidelity simulations of non-linear sound propagation in multiphase media of nuclear fusion reactor pursued using QMUL CLithium and Y codes.[41]
Hatch Ltd: General Fusion and Hatch Ltd. joined in 2015 to create a fusion energy demonstration system. The project aimed to construct and demonstrate, at power plant scale, the primary subsystems and physics underpinning General Fusion's technology, including their proprietary Magnetized Target Fusion (MTF) technology. Simulation models will be used to verify that this fusion energy system is commercially and technically viable at scale.[26]

Funding

General Fusion receives funding through a variety of investors, including Chrysalix venture capital, the Business Development Bank of Canada—a Canadian federal Crown corporation, Bezos Expeditions, Cenovus Energy, GrowthWorks Capital, Khazanah Nasional—a Malaysian sovereign wealth fund, and Sustainable Development Technology Canada.[42]

As of late 2016, General Fusion had received over $100 million in funding from a global syndicate of investors and the Canadian Government's Sustainable Development Technology Canada (SDTC) fund.[7]

Chrysalix Energy Venture Capital, a Vancouver-based venture capital firm, led a C$1.2 million seed round of financing for General Fusion in 2007.[2][43][44] As of 2011 General Fusion remained in Chrysalix' portfolio.[45] Other Canadian venture capital firms that participated in the seed round were GrowthWorks Capital and BDC Venture Capital.

In 2009 a consortium led by General Fusion was awarded C$13.9 million by Sustainable Development Technology Canada (SDTC) to conduct a four-year research project on "Acoustically Driven Magnetized Target Fusion";[46] SDTC is a foundation established by the Canadian government.[47] The other member of the consortium is Los Alamos National Laboratory.[46]

A 2011 Series B round raised $19.5 million from a syndicate including Bezos Expeditions, Braemar Energy Ventures, Business Development Bank of Canada, Cenovus Energy, Chrysalix Venture Capital, Entrepreneurs Fund, and GrowthWorks Capital.[48][49]

In May 2015 the government of Malaysia's sovereign wealth fund, Khazanah Nasional Berhad, led a $27 million funding round.[50]

SDTC awarded General Fusion a further C$12.75 million in March 2016 to for the project "Demonstration of fusion energy technology" in a consortium with McGill University (Shock Wave Physics Group) and Hatch Ltd.[26]

In October 2018 Canadian Minister for Innovation, Science and Economic Development, Navdeep Bains, announced that the Canadian government's Strategic Innovation Fund would invest C$49.3 million in General Fusion.[8]

In December 2019, General Fusion successfully raised a further $65 million in Series E equity financing, which it said would permit it to finally begin the design, construction, and operation of its Fusion Demonstration Plant.[51][52]
Crowdsourcing

Beginning in 2015, the company conducted three crowdsourcing challenges through Waltham, Massachusetts-based firm Innocentive.[53]

The first challenge was Method for Sealing Anvil Under Repetitive Impacts Against Molten Metal.[53] General Fusion successfully sourced a solution for "robust seal technology" capable of withstanding extreme temperatures and repetitive hammering, so as to isolate the rams from the liquid metal that fills the sphere. The company awarded Kirby Meacham, an MIT-trained mechanical engineer from Cleveland, Ohio, the $20,000 prize.[54]

A second challenge, Data-Driven Prediction of Plasma Performance, began in December 2015 with the aim of identifying patterns in the company's experimental data that would allow it to further improve the performance of its plasma.[55]

The third challenge ran in March 2016, seeking a method to quickly and reliably induce a substantial current to jump a 5–10 cm gap within a few hundred microseconds, and was titled "Fast Current Switch in Plasma Device".[56] A prize of $5,000 was awarded to a post-doctoral researcher at Notre Dame, Indiana.[57]
See also

China Fusion Engineering Test Reactor
DEMO
Fusion Industry Association
ITER
Lockheed Martin Compact Fusion Reactor
Spherical Tokamak for Energy Production
TAE Technologies
TerraPower
Tokamak Energy

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vte

Fusion power, processes and devices
Core topics

Nuclear fusion
Timeline List of experiments Nuclear power Nuclear reactor Atomic nucleus Fusion energy gain factor Lawson criterion Magnetohydrodynamics Neutron Plasma

Processes,
methods
Confinement
type
Gravitational

Alpha process Triple-alpha process CNO cycle Fusor Helium flash Nova
remnants Proton-proton chain Carbon-burning Lithium burning Neon-burning Oxygen-burning Silicon-burning R-process S-process

Magnetic

Dense plasma focus Field-reversed configuration Levitated dipole Magnetic mirror
Bumpy torus Reversed field pinch Spheromak Stellarator Tokamak
Spherical Z-pinch

Inertial

Bubble (acoustic) Laser-driven Magnetized Liner Inertial Fusion

Electrostatic

Fusor Polywell

Other forms

Colliding beam Magnetized target Migma Muon-catalyzed Pyroelectric

Devices, experiments
Magnetic confinement
Tokamak

International

ITER DEMO PROTO

Americas

Canada STOR-M United States Alcator C-Mod ARC
SPARC DIII-D Electric Tokamak LTX NSTX
PLT TFTR Pegasus Brazil ETE Mexico Novillo [es]

Asia,
Oceania

China CFETR EAST
HT-7 SUNIST India ADITYA SST-1 Japan JT-60 QUEST [ja] Pakistan GLAST South Korea KSTAR

Europe

European Union JET Czech Republic COMPASS GOLEM [cs] France TFR WEST Germany ASDEX Upgrade TEXTOR Italy FTU IGNITOR Portugal ISTTOK Russia T-15 Switzerland TCV United Kingdom MAST-U START STEP