Magnetized target fusion is a hybrid approach to fusion that lies between magnetic confined fusion (MCF) and inertial confinement (ICF).  This is a series contenter for a real fusion reactor and has been described as a low cost path to commercial fusion. It is strickly speaking an inertial method. The density is increased through a pulsed plasma operation that compresses the fuel, and since temperature is the average energy per unit density, as long as heat is not lost to the surroundings, the temperature of the fuel is raised by a similar amount. In traditional ICF, more energy is added through the lasers that compress the target, energy that leaks away through a variety of processes. No more energy is added in MTF. Instead, a magnetic field is created before compression that confines fuel, and insulates it so less energy is lost to the outside. General Fusion uses a novel mechanical-acoustic compression to achieve the compression. The result, compared to ICF, is a somewhat-dense, somewhat-hot fuel mass that undergoes fusion at a medium reaction rate, so it only must be confined for a medium length of time.

Jeff Bezos, CEO of Amazon Backs MCF

In order to pursue this MCF approach General Fusion was set up as a venture backed company and funded is a series A round of US $13.75M in 2009. The A round was to finance the first phase of General Fusion’s development and demonstration project. The funding was led by Chrysalix Energy Venture Capital, and included investments from GrowthWorks, Braemer Energy Ventures, and Entrepreneurs Fund.  This was followed in 2011 by a series B round of US$19.5M. The Series B investors included the personal investment company of Jeff Bezos, CEO of Amazon, as well as Cenovus Energy, through its Environmental Opportunity Fund, together with existing investors.

Recently (March 15, 2012), Rick Wills joined as Chairman of the company, bringing deep strategic and operational experience to General Fusion’s Board from his years as Chairman and CEO of Tektronix.  The fact that such a such a series player has come on board is very positive news for the future of Magnetized Target Fusion (MTF).

While MCF and ICF attack the Lawson criterion problem from different directions, MTF attempts to work between the two. Magnetic fusion confines a dilute plasma at about 10¹⁴ cm⁻³. Inertial fusion works around 10²⁵ cm⁻³. MTF aims for 10¹⁹ cm⁻³. At this density, the fusion rate is relatively slow, so some confinement time is needed to allow fuel to undergo fusion. Here too, MTF works between the one second times of magnetic methods, and the nanosecond times of inertial, aiming for times on the order of 1 µs. In MTF, magnetic fields are used to slow down plasma losses, and inertial compression is used to heat the plasma.

The Twenty Year Rule in Fusion

I was for a brief period on the Scientific Committee of the JET fusion project at Culham and I got a understanding of the complexities of fusion reactors. So while Fusion has many advantages over Fision, the technology has made very slow progress. A common joke in Fusion was the twenty year rule which was the equivalent of Moore’s Law. No matter how much research is done a commercial fusion reactor will always take another twenty years to build. I hope that the investors in General Fusion have really found a solution that can be achieved in less than 20 years, and that this really is a practical route. I wish them every success.