1. MAGNETIC CONFINEMENT FUSION Zack Draper | Physics 485 November 23, 2015

2. Works cited www.iter.org(International Thermonuclear Experimental Reactor) lasers.llnl.gov(National Ignition Facility) www.ccfe.ac.uk(Culham Centre for Fusion Energy) Sustained Spheromaks with Ideal N = 1 Kink Stability and Pressure Confinement. Physics of Plasmas (2014) Imposed-dynamo current drive. Nuclear Fusion (2012) The dynomak: An advanced spheromak reactor concept with imposed-dynamo current drive and next-generation nuclear power technologies. Fusion Engineering and Design (2014) Waldrop, M. Mitchell. "Plasma Physics: The Fusion Upstarts." Nature.com. Nature Publishing Group, 23 July 2014. Web. 10 Nov. 2015. "Inertial Confinement Fusion: How to Make a Star.” National Ignition Facility & Photon Science, n.d. Web. 10 Nov. 2015.

3. Two nuclei combine to form a new nucleus The mass of the nuclei is converted to energy E = mc 2 Fusion releases energy increasing atomic number, while fission decreases it D + T → α + n + 17.6MeV How fusion works http://mrwhibley.weebly.com/nuclear-binding-energy.html http://chemistry.tutorvista.com/nuclear-chemistry/nuclear-fusion.html

4. Solar fusion There is one fusion reactor we are all familiar with—the sun Most energy released by the sun comes from fusion of hydrogen to form helium Fusion occurs at a solar-core temperature of 14 million kelvin

5. Early attempts In early 1920s it was realized fusion powers the sun Since 1940s, scientists have used fusion, first to make bombs, later to create controlled reactions No one has yet extracted more energy from a sustained reaction than was needed to start the process

6. Overcoming the coulomb barrier To release energy by fusing nuclei, the coulomb barrier must be overcome Energy must be added to the system Temperatures above 40 million Kelvin are required http://burro.cwru.edu/academics/Astr221/StarPhys/coulomb.jpg

7. Types of fusion reactions To control materials at fusion temperatures, they must be confined Nothing can come in sustained contact with plasma at 40 million Kelvin without melting Tungsten has the highest melting point of any element (only 3687 Kelvin) Two methods have been developed, inertial confinement and magnetic confinement

8. Inertial confinement A small fuel pellet of deuterium and tritium is heated and pressurized with laser light The outer shell explodes, creating a shock wave that travels inward through the target Fusion occurs, ideally releasing more energy than was input If all material fused, the energy released would be comparable to burning a barrel of oil lasers.llnl.gov

9. Usually considered a more developed technology, it will be the focus of the talk The presence of positively charged ions and negatively charged electrons makes plasma electrically conductive Magnetic confinement takes advantage of this, using magnetic fields to control a plasma fuel Magnetic confinement

10. Confining plasma with a solenoid The simplest way to control plasma is by placing it in a solenoid The magnetic field pressure balances with the plasma pressure to keep it in a steady state http://www.electronics-tutorials.ws/io/io_6.html https://figures.boundless.com/30709/large/figure-23-05-02a.jpe

11. Toroidal fusion reactors A solenoid does not confine the plasma at its ends The solution is to wrap the solenoid around, creating a torus Particles drift away from the center to the outer edge of the solenoid where the field is weaker http://www.wikiwand.com/de/Stellarator

12. Stellarator A stable plasma equilibrium requires helical magnetic field lines Stellarators use superconducting helical coils to create areas with different magnetic field strengths This prevents drifting particles http://www.physics.ucla.edu/icnsp/Html/spong/spong.htm

13. Tokamaks Tokamaks also use electromagnets to create the toroidal fields that contain the plasma Unlike stellarators, tokamaks create a poloidal field by inducing a current in the plasma https://en.wikipedia.org/wiki/Tokamak

14. ITER The ITER Tokamak will be the largest and most powerful fusion device in the world Designed to produce 500 MW of fusion power for 50 MW of input power Will be the first fusion device to create net energy, but will not capture the energy produced as electricity Confinement times will last from 400 to 600 seconds, and temperatures will reach 150 million Kelvin http://phys.org/news/2015-09-iter-superconductor-production-nears.html

15. Dynomak The reactor at the UW is a type of spheromak Engineering simplicity and reactor economics were a priority so a spheromak was chosen Spheromaks are similar to Tokamaks, relying on plasma current to create the poloidal field This reduces reliance on expensive superconducting coils The hope is that the reactor could be cost competitive with conventional power sources

16. Reaching the required temperatures Magnetic fields create a current, which energizes electrons and ions As collisions between these particles heat the plasma, the resistance decreases and a maximum temperature is reached Charged deuterium ions are accelerated in a magnetic field, passed through an ion beam neutralizer, then injected into the plasma High-frequency light waves can increase the temperature Once fusion has started, the energy released can maintain the high temperatures

17. Capturing the energy The majority of energy comes from high energy neutrons Neutrons are not confined by the magnetic fields and are absorbed by surrounding walls Their kinetic energy becomes thermal energy Heat will be captured by coolant circulating in the vessel walls The heat will be used to produce steam and, by way of turbines and alternators, electricity

18. Lawson's criterion Net Power = Efficiency × (Fusion − Radiation Loss − Conduction Loss) Fusion = Number Density of Fuel A × Number Density of Fuel B × Cross Section × Energy Per Reaction One measure of merit is the triple product of density, temperature, and confinement time, nTτ E

19. Benefits Deuterium is distilled from water and tritium is produced during the reaction as neutrons interact with lithium No harmful toxins or greenhouse gases like carbon dioxide No high activity, long-lived nuclear waste No enriched materials that could be exploited to make nuclear weapons A Fukushima-type nuclear accident is not possible

20. Drawbacks Unproven at commercial scale No full scale production expected till at least 2050 “Fusion is 50 years away and always will be” Commercial power plants could be extremely expensive to build Extremely high temperatures are needed and confinement is difficult to maintain

21. Conclusion Fusion is a renewable source of energy offering us virtually limitless power without threatening the environment Magnetic confinement offers the most promising advances in fusion technology Research into stellarators, tokamaks, and spheromaks continues all around the globe Commercially viable reactors are decades away, but projects like ITER bring us closer to the future that has been promised for over 60 years