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Magnetic Compression Fusion Reactor

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Humanity collectively used almost 160,000TWh of Energy in 2019.

This figure is stubbornly difficult to imagine in any useful sense but let’s try anyway. Suppose you have sole access to the entirety of the 2019 energy quota and you’re a bit peckish, so you decide you’re going to use it on toast.

All of it. All day. All night. No sleep. No breaks. Only toast.

With a 1200w toaster it would take you just over 15.2 billion years until you run out of toasting juice. A few billion years longer than the current age of the universe.

If your toaster is of the two-slice peasant variety and you like your toast pasty (let’s say 2 minutes a pop), you could build a stack of toast around 9,143,000km tall. That’s enough toast to reach the Moon 24 times over. It would take about half a minute for light to travel from the top of the stack to you and your toaster. Your towering toasty monolith would weigh the equivalent of over half the current human population. A magnificent monument to the wonders of sliced bread.

Or at least it would have been had you survived long enough to see it. Death is a cruel Mistress. Thankfully the toaster, a cherished family heirloom, is passed down from generation to generation. A tradition of dedicated toaster-wielders faithfully continuing onward with the mission in your honor until Freidrick the Crisp (your great-great-great-great-great-great grandson) invents the toast robot. An invention of necessity after an unfortunate toasting accident destroys his ability to carry on the line. Time passes and the toast flows. At some point Robotoast 9000 becomes sentient leading to the robot revolution and humanities inevitable demise. Time carries on without us and so does the toast. The robots eventually decide to leave Earth in search of a new home. Robotoast stays to continue toasting as a sort of homage to the humans. A way of saying sorry about the whole Extinction thing. The Sun expands completely engulfing the Earth. The final toasting. At this point there would STILL be over halfway to go before the quota has been met.

This is getting a little off topic, the point is, it’s an insane amount of energy and the demand grows steadily year on year. We utilize several different methods to meet the need, but the overwhelmingly largest portion comes from fossil fuels. In total, non-renewables equated to 86% of global power generation in 2019.

Renewables will eventually overtake fossil fuels, but how much energy will humans need in the future? In the last 100 years energy usage has grown 884%. Will we see the same growth in the next 100 too? what about the next 1000 years? We can only speculate.

In any case it’s prudent to look beyond the renewable technologies of today in search of more efficient methods for the future.

Idea

In this concept a specially arranged set of copper coils are used to produce an exoergic fusion reaction by focusing an electromagnetic field on a single point in the center of the vacuum chamber. Like Inertial Confinement Fusion reactors the fuel is static (at least once the fuel has reached the center of the chamber), but in this design it is heated by exciting the atoms with a magnetic field. The electromagnetic arrangement forces the fusion fuel to compress toward a single point and with a high enough current the coulomb barrier is overcome and nuclei begin to fuse together. The fusor shares similarities with the Farnsworth and Hirsch-Meeks Fusors.

Design Description

The Fusion Reactor design utilizes an inner coil arranged to create an electromagnetic field that focuses its strength at a singularity in the center of the Reactor when current is passed through it. The inner containment sphere is made of a magnetically permeable material and a vacuum is generated within. The inner containment sphere is then seeded with an amount of fusion gas fuel and allowed to normalize. The fuel would most likely be a mix of Deuterium and Tritium (D-T) however a Hydrogen and Helium 3 (He3-H) mix would offer better energy efficiency. Using this fuel instead will depend highly on the effectiveness of the system. Helium 3 requires much higher temperatures to ‘ignite’. The fuel inside is in a near perfect vacuum so although the center of the sphere is many millions of degrees K, the outer edges will not be excessively hot.

Outside of the inner coil is a second outer coil. This coil is wrapped around the first in a perpendicular fashion in the same spherical arrangement. When fusion occurs, the inner coil experiences a spike in current that, through inductance, is transferred to the outer coil. The inner coil and outer coil are coupled with capacitors at either ends. The capacitor on the negative end of the outer coil is made up of two regular capacitor plates and an insulator material. The capacitor on the positive end of the outer coil has the same arrangement with the exception of an overhang on one of the plates, such that it creates an open-air gap between the two capacitor plates.

When fusion occurs and the excess energy is transferred to the outer coil the capacitors create a ‘traffic jam’ of charge between the inner coil and the outer coil. The voltage between the two plates of the positive end capacitor increases until it exceeds the breakdown voltage of air. When this happens, electricity arcs over the air gap of the capacitor plates causing another peak in fusion, perpetuating the cycle.

The fusion reactor thus continuously cycles between high and low periods and the current of the inner coil undulates accordingly. Because of this continuous ebbing and flowing of current, the outer coil continually captures the energy through inductance. Cables located on either end of the outer coil extract the excess energy from the reactor. The amount extracted will determine the time between each cycle. In this manner it is possible to control the rate at which energy is generated by the reactor.

Its anticipated that if more energy is extracted, the time to the next reaction will increase and the total output over a given time is reduced. If less is extracted, the time between each cycle is reduced and the total output is increased. If too much is taken in one cycle, the breakdown voltage required to cause an arc between the air-gap of the capacitor plates will not be reached and fusion will eventually come to a complete stop. If not enough is extracted, the reactor may become unstable and damage could occur such as destruction of the insulators and heat damage of the interior.

Inductance only occurs when there is a change to the current in the inner coil so it is unlikely the fusion reactor will ever experience a runaway reaction. When the amount extracted is optimal the cycle between high and low fusion will happen many times a second. From a human perspective it will appear continuous.

An insulator sphere is located between the two coils fully enclosing the inner coil. The purpose of this sphere is to create an enclosed space for coolant to be pumped around the inner coil and to homogenize inductance across the surface of the coils. It also creates a barrier between the two coils to prevent arcing. It is unclear whether this coolant is necessary and will be the subject of further study and/or experimentation.

A second insulator layer covers the outer coil and is further covered by a copper sphere. These two layers combined are intended to act as a barrier to prevent excessive magnetic discharge outside of the reactor. Charge is collected from the copper sphere through some means of electrostatics and then grounded. The final outer containment sphere is to protect from accidental electrostatic discharge off of the copper sphere.

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Benefits

There are a few key benefits to this design over current fusion reactor designs:

Better plasma containment: The design contains all fusion to a single point in the centre of the reactor, largely preventing issues with heat transferal from the plasma. Other fusion reactors such as Tokomaks use a toroidal design that require the plasma to flow constantly around a doughnut circuit requiring precise engineering and placement of the magnets to effectively contain it.
Simple design: The two primary coils are of extremely simple design and, owing to the nature of magnetism within a coil, do not require overly precise manufacture to effectively contain the plasma.
Compact design: because of the simplistic design, the fusion reactor can be made smaller and more compact than current fusion reactors. It is unclear exactly what the limit is to how small a reactor of this design can be, but it may be possible to produce versions small enough for transport and the needs of individual buildings.
Cost of production: The simplistic design also makes production and prototyping cheaper in comparison to other methods. A working prototype would not necessarily need a multinational financial effort to achieve.
Energy capture: Current fusion reactor designs do not have an efficient way of collecting the energy created by the fusion reaction. They typically capture the energy indirectly from the heat created by the plasma and so are yet to achieve over-unity. This method captures the energy directly through inductance and so is much more likely to capture enough energy from the fusion process to be worthwhile as a power source.

Drawbacks

A few potential design issues have been identified so far that would need addressing:

Plasma escape at the termination points of the coils: When fusion begins to occur there is the potential that instead of the reaction being contained in a perfect sphere like a tiny star, it takes an ellipsoid shape with heat escaping toward the coil surface at either ends of its termination points. As an attempt to remedy this issue the concept has the two coils arranged perpendicular to one another. The theory is that when current is passed to the outer coil it will counterbalance the weak spot in the magnetic field of the inner coil.
Inefficient inductance: Inductance does not occur when coils are perpendicular to one another as the magnetic field lines of the two coils need to converge for current to transfer across. The coils of this reactor are spherically arranged so are not entirely perpendicular at all points and are most aligned with each other at the termination points. This potentially means that Inductance will be inefficient between the two coils. To solve the problem the outer coil can simply be rotated to be in line with the inner coil, however as stated above this could adversely affect the shape of the magnetic field within the fusion chamber.
Coolant distribution: The current design has a series of pipes channeling through the outside of the reactor into the two coil chambers. The issue with this is that it may affect the positioning of the outer coil to feed coolant to the inner coil which could impact the integrity of the magnetic field lines. One potential solution to this is to channel the coolant directly through the coils themselves. If the coils are made of copper tubing instead of wire, liquid nitrogen can be pumped inside of them avoiding the need to penetrate through the outer coil. Although the charge on the outside of the copper tubing would be high when in operation, the inside should be neutral.
Insufficient potential difference between capacitor plates to increase fusion: The current design relies on high and low phases of fusion for inductance to occur. This is achieved with the arc capacitor but the amount of energy transferred from the outer coil back to the inner coil when an arc occurs may be too small to have a meaningful impact on the amount of fusion occurring inside the reactor. One way to remedy this is to remove the capacitors and control the amount of energy being directed into and out of the reactor in an external control system.

Supporting Info

Supporting Files

Sources

https://ourworldindata.org/energy

http://www.fusor.eu/theory.html

https://www.britannica.com/science/nuclear-fusion/History-of-fusion-energy-research#ref496508

Poster

Jon Knutton

Just doing my thing

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Magnetic Compression Fusion Reactor

Magnetic Compression Fusion Reactor

Publish Date

Type

Category

Challenge

Idea

Benefits

Drawbacks

Supporting Info

Supporting Files

Sources

Poster

Jon Knutton