High beta fusion reactor
The high beta fusion reactor (also known as the 4th generation prototype T4) is a project being developed by a team led by Charles Chase of Lockheed Martin’s Skunk Works. The "high beta" configuration allows a compact fusion reactor design and speedier development timeline. It was first presented at the Google Solve for X forum on February 7, 2013.
Lockheed Martin's plan is to "build and test a compact fusion reactor in less than a year with a prototype to follow within five years."
The project began in 2010.
In October 2014 Lockheed Martin announced that they will attempt to develop a compact fusion reactor that will fit "on the back of a truck" and produce 100 MW output - enough to power a town of 80,000 people.
The chief designer and technical team lead for the Compact Fusion Reactor (CFR) is Thomas McGuire, who did his PhD dissertation on fusors at MIT. McGuire studied fusion as a source of space propulsion in graduate school in response to a NASA desire to improve travel times to Mars.
Nuclear fusion works by stripping electrons from atoms of two isotopes of hydrogen, deuterium and tritium, mixing the resulting nuclei and confining the mixture, called a plasma, into a small space. The plasma then is heated to accelerate the nuclei (in a gas, particle speed is a function of temperature). This is necessary because both nuclei are positively charged and high velocity is necessary to overcome electrostatic repulsion to force them to collide. At high enough speed, fusion produces a helium atom and a highly energetic neutron, whose energy can be captured by slowing it down. Transferring this energy to a coolant allows it to be used to generate electricity. A small amount of deuterium and tritium can match the performance of a conventional nuclear reactor, but without the nuclear waste and with much lower radiation risk.
Lockheed is targeting a relatively small device that is approximately the size of a conventional jet engine. The prototype is approximately 1 meter by 2 meters in size. The company claims that this enables a much faster development cycle since each design iteration could be produced more quickly and at far lower cost than large-scale projects such as the Joint European Torus or ITER.
The CFR uses two mirror sets. A pair of ring mirrors is placed inside the cylindrical reactor vessel at either end. The other mirror set encircles the reactor cylinder. The ring magnets produce a type of magnetic field known as a diamagnetic cusp, in which the magnetic forces rapidly change direction and push the nuclei towards the midpoint between the two rings. The fields from the external magnets push the nuclei back towards the vessel ends. This process is known as ‘recirculation’.
One of the project's innovations is the use of superconducting magnets. They allow strong magnetic fields to be created with less energy than conventional magnets. The CFR has no net current, which Lockheed claims eliminates the prime source of plasma instabilities. The plasma also has a favorable surface-to-volume ratio, which improves confinement. The plasma's small volume reduces the energy needed to achieve fusion. The project plans to replace the microwave emitters that heat the plasma in their prototypes with neutral beam injection, in which electrically neutral deuterium atoms transfer their energy to the plasma. Once initiated, the energy from fusion maintains the necessary temperature for subsequent fusion events. The CFR's beta (ratio of plasma pressure to magnetic field pressure) is an order of magnitude greater than in tokamaks.
The ring magnets require protection from the plasma's damaging neutron radiation. Also plasma temperatures must reach many millions of Kelvin. The magnets have to be kept just above absolute zero to maintain superconductivity.
The 'blanket' component that lines the reactor vessel has two functions: it captures the neutrons and transfers their energy to a coolant and forces the neutrons to collide with lithium atoms, transforming them into tritium to fuel the reactor. The weight of the blanket is a key element for mobile applications. The project estimates that it could weigh 300–1000 tons.
Physics professor and director of the UK's national Fusion laboratory Steven Cowley called for more hard data, pointing out that the current thinking in fusion research is that "bigger is better". Other fusion reactors achieve 8 times improvement in heat confinement when machine size is doubled.
- Beta (plasma physics)
- Inertial electrostatic confinement
- Magnetic mirror
- Fusion power
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