How it Works: The Crucial Role of Our Compression System

General Fusion’s Magnetized Target Fusion (MTF) technology features a plasma injector, a liquid metal cavity, and a compression system. The compression system consists of high-pressure, pneumatic pistons surrounding a rotating internal chamber. It is responsible for squeezing and heating the hydrogen plasma to fusion conditions.

General Fusion combines enabling technologies with proven industrial processes and advances in fundamental fusion science to create a faster and more practical path to deliver fusion energy. Our system design avoids barriers faced by other fusion technologies because it is straightforward to manufacture and scale. MTF uses simple electromagnets and avoids expensive lasers. The power conversion systems are also readily available in the market.

What is the compression system?

Our technology works similar to a diesel engine where fuel and air are injected into a vessel, and then a piston rapidly compresses the mixture. The compression heats the fuel and air mixture until it combusts and releases energy. In General Fusion’s machine, the plasma injector is the fuel injector, the compression system completes the function of the piston, and the liquid metal cavity acts as the cylinder.

General Fusion has tapped into diverse capabilities globally to develop numerous compression testbeds, including the Cylindrical Water Compressor (CWC). For example, aerospace companies provided insight and expertise due to their experience in applicable practical machines.

In addition, to complete the Fusion Demonstration Plant (FDP), we are bringing together leaders in engineering and industrial design. Sheffield Forgemasters will identify routes to manufacture the vessel – a central component of the compression system.

How does it work?

  • The process starts with a compressed gas driver system
  • 500 high-pressure, pneumatic pistons surround a rotating internal chamber
  • The rotating chamber is filled with liquid metal
  • The liquid metal is spun until it forms a cavity
  • The pistons are precisely synchronized to push the liquid metal inward
  • Using timing and pressure variations, this changes the shape of the collapsing vortex from a cylinder into a sphere


The liquid metal liner shields the structure from neutrons released by the fusion reaction, preventing structural damage to plasma-facing materials – this is often referred to as the First Wall problem.

Computational fluid dynamics (CFD)

CFD uses computer modelling to show us how liquids interact with the machine. For example, we can predict how the pistons will collapse the liquid metal cavity with this modelling. Our CFD experts work with our physicists and engineers to address specific challenges the team wants to solve. With CFD, we can run numerous tests virtually in a short period.

From there, we conduct physical tests using our testbeds. The information we gain from the physical tests is fed back to the CFD team to continue to increase the accuracy of the models. With this iterative approach, we can create an ecosystem of testing that optimizes the design for our FDP and commercial pilot plant.

A top view of the compression chamber and the shaping process of the liquid liner. The video shows experimental testbed results on a shaped collapse using water, with laser lines used to map the surface. The liner will be liquid metal in the FDP. The pressure from the pistons surrounding the rotating liquid liner is fine-tuned to shape its inner surface. It starts as cylindrical and gradually becomes spherical.

Preparing for the FDP

In the last decade, we ran thousands of experiments on our testbeds. The latest addition to our suite of testbeds is the CWC, completed in August 2020. The cylindrical design of the CWC is the latest evolution of our technology design. The CWC is built to 1:10 scale of the demonstration facility and has already run more than 600 tests to date using water instead of liquid metal.

Technology economics

The FDP will validate the performance and economics of our technology. From there, we will develop our commercial pilot plant.

The commercial pilot plant will generate power. To do this, the compression system will pulse up to once per second. The system’s ability to ramp up or down is a benefit of our technology. It makes it possible for customers, such as utilities, to adjust power output to manage electricity demand fluctuations throughout the day. In addition, since energy sources such as solar and wind are not available on-demand, fusion energy offers a clean energy source that will extend the benefits of renewables. The result? A cleaner future as the world moves closer to a zero-carbon economy.