These issues have led other researchers to question whether a tokamak might ever be able to serve as the basis for a practical reactor. Dr. Thomas McGuire, head of a team working on a novel Compact Fusion Reactor program, or CFR, for Lockheed Martin’s Skunk Works advanced projects division, had this to say on the matter in an interview with Aviation Week in 2014:
“The problem with tokamaks is that ‘they can only hold so much plasma, and we call that the beta limit,’ McGuire says. Measured as the ratio of plasma pressure to the magnetic pressure, the beta limit of the average tokamak is low, or about ‘5% or so of the confining pressure,’ he says. Comparing the torus to a bicycle tire, McGuire adds, ‘if they put too much in, eventually their confining tire will fail and burst—so to operate safely, they don’t go too close to that.’”
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“The CFR will avoid these issues by tackling plasma confinement in a radically different way. Instead of constraining the plasma within tubular rings, a series of superconducting coils will generate a new magnetic-field geometry in which the plasma is held within the broader confines of the entire reaction chamber. Superconducting magnets within the coils will generate a magnetic field around the outer border of the chamber. ‘So for us, instead of a bike tire expanding into air, we have something more like a tube that expands into an ever-stronger wall,’ McGuire says. The system is therefore regulated by a self-tuning feedback mechanism, whereby the farther out the plasma goes, the stronger the magnetic field pushes back to contain it. The CFR is expected to have a beta limit ratio of one. ‘We should be able to go to 100% or beyond,’ he adds.”
I built a Compact Fusion Reactor for my bicycle as a teenager for my newspaper route. The toroid worked inside the tire tubes. Kids being kids.