|Fig. 1: Illustration of the MIT MIT Affordable, Robust, Compact (ARC) fusion reactor. (Reproduced with permission from the MIT Plasma Science and Fusion Center)|
Fusion power has the potential to generate enormous amounts of power in a clean and sustainable way. It works by forcing deuterium and tritium together at extremely high pressures and temperatures to produce helium and a high energy neutron particle. This process produces nearly no pollutants and any radioactive waste products would have a significantly shorter half life than that produced by nuclear fission. However attempts at nuclear fusion have been plagued with problems, as current approaches consume significantly more energy achieving the high temperatures and pressures than the amount of energy produced through the fusion process. The goal of producing more energy than the amount consumed is known as net gain.
Right now the approach to net gain with the most support is the ITER, or the International Thermonuclear Experimental Reactor. This is built from a partnership between seven different countries, the European Union, India, China, Japan, Russia, South Korea, and the United States.  They plan to build an enormous toroidal reactor in France, which will produce ten times more power than it consumes.  The reactor was originally expected to cost over $8 billion, but the cost has now ballooned to over $15 billion. Furthermore the reactor was expected to be completed in 2016 but has now been pushed back to 2019. The project has received significant amounts of criticism for being overly expensive and complex.
An alternative to the ITER is the MIT ARC as shown in Fig. 1, which stands for Affordable, Robust, and Compact. They claim they can build a reactor half the size of the ITER while producing the same amount of power at a significantly lower production cost. This is enabled by a class of newly discovered superconductors known as barium copper oxides, which allows them to increase the power of the magnetic field.  Since fusion power increases with the fourth power of the magnetic field, this allows them to produce significantly more power from a smaller reactor. They claim that using barium copper oxide superconductors allow them increase the power tenfold.  Furthermore, since the reactor is based on the same tokamaks as the ITER, the dynamics of the fusion process is well understood.
These improvements to the magnetic fields also trickle down to other parts of the reactor. For example the core is designed to be removable, so that the fusion process can be studied easily without having to dismantle the entire reactor.  Furthermore, new concepts for fusion cores can be easily researched. Also, older reactors used solid containment walls which would degrade quickly over time due to the harshness of enduring fusion. These can now be replaced with liquid containment barriers, which can be easily recirculated and recycled, further lowering the cost of operation.  Overall, these design improvements should yield a reactor that can produce three times as much energy as it consumes. They claim that further design improvements could yield a reactor that produces up to six times more energy than it consumes.
Despite the improvements due to the increase in magnetic field strength, no plans to build the reactor exist currently, and the design remains a theoretical concept.
© Qingping He. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 K. Tomabechi et al., "ITER Conceptual Design," Nucl. Fusion 31, 1135 (1991).
 B. Sorbom et al., "ARC: A Compact, High-Field, Fusion Nuclear Science Facility and Demonstration Power Plant with Demountable Magnets", Fusion Eng. Des. 100, 378 (2015).