USE OF TOROIDAL AND POLOIDAL MAGNETIC FIELDS IN PLASMA CONFINEMENT FUSIONPAUL RIZZOLOJOSEPH TRENTADUE

Fusion and Energy in the Modern World

Energy consumption in the world has continued to increase ever since the industrial revolution

Standard energy solutions today lack the properties of longevity, Eco friendliness, and safety

Nuclear fusion provides an energy solution which Is safe Has a fuel supply allow it to operate long term Operates without harming the environment

Tokamak reactors are currently the best way to attempt fusion energy

Nuclear Fusion

Nuclear fusion is a physical process turning two light atoms into one heavier atom Contrasted with fission, which splits a heavy atom into two lighter

atoms Releases energy according to Einstein's equation General reaction

411H → 4

2He + 2[0+1e + 0

0γ + 00ν (26.7 MeV)

Achieved by turning the sample of fuel into a superheated plasma Under the right combination of pressure and temperature, fusion

begins (ignition)

Temperature (Kelvin)

Pressure (atm)

Tokamak Reactors ~150,000,000 ~100 Our Sun ~15,000,000

Tokamak Reactors

Tokamaks are magnetic confinement reactors Use magnets to confine plasma within which fusion takes place

Components include: Heating system Cooling system Vacuum system Magnet system Diverter system

ITER

The International Thermonuclear Experimental Reactor (ITER) “The way” in Latin

Tokamak reactor under construction in Cadarache, France Expected completion ~2020 Full-scale experiments ~2027 Estimated cost - $16 billion

Largest tokamak ever built

Plasma Volume

Plasma Current

Power Output Magnetic Field

840 m3 15 MA 500 MW 5.2 T

Magnet Systems in Tokamak Reactors

Superconducting magnets are used to confine plasma (deuterium and tritium) and provide energy to develop fusion conditions The field produced by these magnets must:

Be a torus Contain magnetic islands Induce a current in the plasma Rotate helically about its toroidal axis

Magnet Systems in Tokamak Reactors

A torus is a doughnut shape as pictured A magnetic island is a structure within a magnetic field

Defining characteristic is a closed flux surface A charged particle inside a magnetic island will feel an inward force

in all directions This is necessary in a tokamak in order to confine the plasma

ie. there is no net force on the plasma stream

Magnet Systems in Tokamak Reactors

Induction of current in the plasma comes from poloidal, or secondary, magnetic field

Variance of flux from this field through the plasma causes an electric field, in turn producing current Current strength is approximately 15 Mega-Amperes (ITER) Standard household lightbulb will have a current around .833

Amperes This current aids in the initial heating of plasma

Heating is mostly done with neutral beam injection form the heating system

Magnet Systems in Tokamak Reactors

Rotation about the toroidal and poloidal axis is important to keep plasma in a steady state of rotation

Keeps loss of particles in the plasma stream to a minimum Scrape-off Layer

Layer of particles on outer boundary of plasma stream Loss of particles from SOL is minimized by simultaneous rotation

about the toroidal and poloidal axis Static plasma and plasma rotating in one direction is not optimal

Fusion Reactors: Inertial Confinement Fusion

This type of fusion uses lasers to compress and heat a fuel pellet National Ignition Facility (NIF) has run first energy positive* fusion

experiment Energy output of fuel was 14 kilo-Joules Laser energy output was 1.8 mega-Joules

Discrepancy in energy comes from loss of energy between laser emission and fuel capsule

Overall promising method, Laser Inertial Fusion Energy (LIFE) program working to convert NIF technology to useable energy output

Fusion Reactors: Stellarators

Stellerators are most closely related with tokamaks, as both are magnetic confinement type designs

These reactors differ from tokamaks in their geometry Plasma volume is confined into a much more complicated, but theoretically

more efficient, shape Based on shape, there is no need for induction of current through plasma

volume This provides:

Elimination of bootstrap friction Reduction of plasma disruption Efficient current drive

More theoretically desirable than tokamaks, but realistically extremely hard to design and manufacture

Ethics and Sustainability of Fusion Reactors

Replacing fission reactors as well as non-nuclear energy production with fusion is desirable: Fusion produces more energy per unit fuel than fission

Much more than any non-nuclear energy method like oil Fusion uses harmless fuel, compared to fission’s uranium and plutonium

Fuels used are deuterium and tritium, hydrogen isotopes Eliminates hazards including transportation and storage of radioactive

materials Fusion has a quasi-unlimited fuel source (the oceans)

The water in Earth’s oceans have enough hydrogen for 1 billion years of deuterium

Tritium breeding being researched, 1,000 years of lithium in reserve

Ethics and Sustainability of Fusion Reactors

Fusion does not harm the environment Use of fusion power plants satisfies the current needs for energy

without impeding the ability of future generations to satisfy that need

In Conclusion:

Tokamak reactors are magnetic confinement fusion devices which use magnets to confine plasma within which fusion occurs

Tokamaks are the ideal reactor class Feasible to design and manufacture

Other fusion reactor types include Stellerators Inertial confinement

NIF LIFE

In Conclusion:

Energy from fusion is ideal Low safety risk

No dangerous fuel transportation/ storage Risk of catastrophic failure is low

Sustainable Extremely abundant fuel Safe for environment Long lasting solution

Ethical Increases quality of society both now and in the future

USE OF TOROIDAL AND POLOIDAL MAGNETIC FIELDS IN PLASMA CONFINEMENT FUSION

Background: Energy and the Nuclear Energy Fields The quest for clean, renewable energy has captivated the minds of many great scientists and engineers of the 20th and 21st centuries. These great men and women have developed many spectacular technologies in an attempt to find the perfect energy source. One of the most heavily researched and funded fields of energy is the nuclear field. Nuclear energy can be divided into two further fields known as fission and fusion. The technologies in both fields operate in manners that use much less fuel, as compared to traditional fossil fuel technologies, produce much less waste, and produce little to no greenhouse gases.

Of the two types of nuclear energy, fusion is seen as the most desirable long term outcome. Fusion, as opposed to fission, produces almost no long lasting radioactive particles as waste, produces more energy, and are immune to catastrophic failures due to meltdowns. For these reasons, and many others including long term cost and efficiency, fusion reactors are considered a much more sustainable source of energy, should the technology be perfected.

Magnetic Confinement Reactors

Tokamaks StellaratorsTokamak reactors, use magnets to create toroidal and poloidal magnetic fields. Superheated plasma is suspended in a torus, a donut like ring, where it is now free to react without damaging the systems that induce the fusion.

In general, magnetic confinement reactors are fusion reactors that use magnetic systems to suspend superheated fuel in a magnetic field. The most common fuel is a mixture of hydrogen isotopes, deuterium and tritium. The key difference between different magnetic confinement reactors is plasma geometry. But, in general, these reactors are composed of many cooperative complex systems. Each reactor contains a diverter. This system extracts excess particles and produced energy from the reaction to protect the reactors. Each reactor also contains a vacuum and a cryostat which are both systems that also protect the magnets and reactor from the superheated plasma.

Stellarator reactors use magnets as well. However, the systems are required to be much more complicated. The geometry of the plasma in stellarators is designed in twisted and inverted shapes much more complex than a donut shaped torus. Consequently, magnet systems are required to be much more complex as well as corresponding systems like the diverter. For these reasons, the ideal stellarator designs are much more theoretical

The model above is of the currently under construction International Thermonuclear Experimental Reactor (ITER). ITER is currently being built in France through a joint effort of many nations including the United States, Japan, China, South Korea, India, Russia, and the European Union nations. Based on ITER’s design, it is expected, if successful, to produce a net energy, something unheard of in the current nuclear fusion field. The reactor is expected to be completed by 2020 and full scale fusion reactions are expected to be achievable in the reactor by 2027.

Inertial ConfinementInertial confinement reactors seek to pressurize fuel to a greater degree rather than heat it. One of the most successful reactors is known as the National Ignition Facility located in California. This reactor uses a super laser to attempt to induce fusion in a pellet of fuel. The laser fires and the diffused beams penetrate a shell containing the fuel source. This site has seen some limited success. They have managed to induce fusion but it produced much less energy than was used to power the laser, and the reaction was only a few fractions of a second long. This initial success may sound promising, but unless the research team at NIF and other inertial confinement facilities design a way to ignite the fuel find a way to keep the capsule from melting and mixing with the fuel while also minimizing the inputted laser energy, they are not likely to make any technological breakthrough in the fusion field.

The more desired fusion reaction can be summarized as follows:• Combination of two lighter atoms into a

heavier one• Energy is released by Einstein’s equation: • General Reaction:

411H → 42He + 2[0+1e + 00γ + 00ν (26.7 MeV

• Atomic combination is the result of the repulsive forces between two atoms being overcome by heat and pressure

Magnet Systems in a Tokamak ReactorThe most important of the systems in the tokamak reactor is the magnet system. The superconducting magnets must produce a field that confines the plasma fuel. This shape then aids in the establishing of a current through the plasma, necessary for the reaction in a tokamak. For a tokamak, this shape is a torus. The torus structure, see image below, helps to induce a current through the plasma and isolate any forces that would affect the plasma in order to suspend it in the field.

Induction of the current comes from a secondary field aided by the toroidal design. This second field, a poloidal field, creates a variance of flux through the plasma which in turn induces an electrical current in the plasma which aids in initial heating of the fuel. After the current heats the fuel to a sufficient temperature, further heating of the fuel is achieved through the use of neutral beam injection.The torus design further helps protect the reactor due to

its rotation around its poloidal and toroidal fields. The magnets create this steady rotation which helps to contain any particles in the fuel stream from escaping the field. However, this is not a perfect system, which is why there are many other complex systems, such as the diverter, that protect the rest of the tokamak.

Conclusion• Fusion is more sustainable than other current energy

sources.• Safety, future cost, efficiency, environmentally

safe• Of current fusion types, magnetic confinement is most

promising.• Of the magnetic types, tokamak reactors are best

understood and better researched.• Magnetic systems in tokamaks are the key components in

achieving fusion.• Create the conditions necessary for fusion.

Paul Rizzolo and Joseph Trentadue

CO2 Emissions of different sources of electricity production

Energy Hydraulic Nuclear Wind Solar Gas Oil Coal

CO2 Emissions (g/kWh) 4 6 3-22 60-150 430 818 800-1050