Nuclear Fusion 105 - Researchers Are Working On Reverse Field Configuration Designs For Nuclear Fusion - Part 3 of 6 Parts

Part 3 of 6 Parts (Please read Part 1 and 2 first)
    The major problem with magnetic confinement is that hot, ionized plasmas needed to achieve fusion cannot be easily confined by a magnetic field. They twists and thrash  about almost like a living thing. This accounts for the great popularity of the tokamak design in nuclear fusion research. The tokamak was a major breakthrough for Soviet physicists when it was introduced in the 1960s. By using very strong magnetic fields that confine and guide the plasma in a donut-shaped chamber, tokamaks were about to control the plasma better than other approaches at the time. This is why funding sources keep pouring money into the ITER project. The ITER is a huge tokamak that weights three times what the Eiffel Tower weights. Its vacuum chamber is ninety-five feet in diameter and it is taller than a seven story building. The ITER has to be this big to achieve break-even fusion power generation.
      To Cohen and many other fusion researchers, ITER has revealed many problems with the tokamak design for fusion reactors. The size, cost and complexity of ITER are far beyond what any utility will be willing to pay for the generation of electricity. Dean says that he cannot find anyone at a major utility that even knows what a tokamak is.
      Another major problem with tokamaks is that their design only allows them to burn a fuel consisting of deuterium and tritium. This fuel is by far the easiest to ignite because it requires comparatively low plasma temperatures of about one hundred million degrees Kelvin. When a deuterium nucleus and a tritium nucleus fuse to form a helium-4 nucleus with two protons and two neutrons, an excess neutron is ejected with high energy. Because the neutron is electrically neutral and cannot be controlled by magnetic fields, it escapes from the confined plasma and hits the wall of the tokamak. This damages the materials making up the wall making them brittle and weaker. This means that the walls of the tokamak may have to be replaced every year which is a maintenance cost that no utility would want to pay for.
     By the late 1990s, these tokamak problems were encouraging Cohen and other researchers to take a fresh look at the Field Reverse Configuration (FRC) reactor design which has been discovered in the 1960s. The key advantage of an FRC reactor is that it does not control its plasma with brute force like a tokamak. Instead of using external magnets to confine the plasmas as in a tokamak, the magnetic fields that confine plasma in an FRC reactor are mostly generated by electrical currents flowing through the plasma itself. These self-organizing processes can be found in other plasma structures in other designs such as the “spheromaks” and “dense plasma focus” reactors. However, FRC plasmas are much hotter and denser that that produced by these other designs so FRCs are the focus of more money and effort that these other self-organizing plasma reactor designs.
   
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