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Transcript
Alternative approaches to fusion energy NI T HIN R A MU Overview • Lockheed Martin compact fusion reactor • Working • Magnetic mirror • Two mirror sets, diamagnetic cusps, superconducting magnets • Prospects • Tri Alpha compact toroid • Working • Field reversed configuration, aneutronic fusion • Prospects • Z Machine • Working • Prospects Lockheed Martin Compact Fusion Reactor Compact Fusion Reactor: Magnetic Mirror • Charged particles moving perpendicular to a uniform magnetic field move in a circular path perpendicular to the magnetic field due to the Lorentz Force • Radius of circular motion inversely proportional to magnetic field strength • If a component of the charged particle’s velocity is parallel to the magnetic field, the resultant trajectory will be helical • At some point, the magnetic field lines will change direction • A component of it will decelerate the charged particle • Two magnetic mirrors can be used to confine a charged particle Compact Fusion Reactor: Working • Two mirror sets • A pair of ring mirrors is placed inside the cylindrical reactor vessel at either end • Other mirror set encircles the reactor cylinder • The ring magnets produce a type of magnetic field known as a diamagnetic cusp, in which 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. Compact Fusion Reactor: Working • Magnetic field strength is an increasing function of distance from the center • As plasma pressure causes plasma to expand, the magnetic field becomes stronger at the plasma edge, increasing containment • Higher Beta • Economical • Employs superconducting magnets. • Allow strong magnetic fields to be created with less energy than conventional magnets • Has no net current • eliminates the prime source of plasma instabilities. • Has a favourable surface-to-volume ratio, which improves confinement. • The plasma's small volume reduces the energy needed to achieve fusion. Compact Fusion Reactor: Prospects • Compact • Should fit on the back of a truck • Small size shortens the development cycle • Each design iteration is shorter and lower cost than large-scale projects like ITER • Possible to make riskier design choices • Can incorporate new knowledge into the design cycle • Produce 100W of power • Enough to power a town of 100,000 people • Commercial fusion power possible by 2040 worldwide (2080 for projects such as ITER) • Many scientists sceptical as very few details released C2: Field reversed configuration • Little to no toroidal field component • Confined solely by a poloidal field • Lack of a toroidal field means high beta • makes the FRC attractive as a fusion reactor • uniquely suited to aneutronic fuels because of the low required magnetic field • More economical C2: Aneutronic fusion • Neutrons carry less than 1% of total released energy • Other fusion reactions release up to 80% of their energy in neutrons C2: Working (https://www.youtube.com/watch?v=ezluaNMzHjE ) C2: Prospects • Advantage of less neutron radiation • Less ionising damage • Neutron activation • No biological shielding, remote handling needed • Criticism • Overly fast relaxation time in highly nonthermal plasmas could lead to much less fusion gain than expected Z Machine C2: Inertial confinement fusion 1. Laser beams or laser-produced X-rays rapidly heat the surface of the fusion target, forming a surrounding plasma envelope 2. Fuel is compressed by the rocket-like blow off of the hot surface material 3. During the final part of the capsule implosion, the fuel core reaches 20 times the density of lead and ignites at 100,000,000 ˚C 4. Conditions necessary for fusion reached Z Machine: Working • In a Z-pinch machine the wires (right) are replaced by a plasma • can be thought of as many current-carrying wires • The contraction is counteracted by the increasing gas pressure of the plasma • Normally arranged by placing the plasma vessel inside the core of a transformer, arranged so the plasma itself would be the secondary • In Z-pinch machines the current is generally provided from a large bank of capacitors and triggered by a spark gap • Z-pinch devices are inherently pulsed in nature. Z Machine: Prospects • Ultra-high temperatures reached in 2006 (2.66 to 3.7 billion kelvins) are much higher than those required for the classical hydrogen, deuterium and tritium fusion previously considered Conclusion • Offer much more fast way to fusion energy for all • More compact reactors • Decentralised power sources could be used in developing countries • Energy for all • Faster development cycles, improvements • Maybe worldwide fusion availability by 2040 instead of 2080 • Much cleaner energy • Aneutronic fusion • No radiation problems • Many unknowns about the viability of these projects; they are still clouded in secrecy