Fusion With Our Past

Fusion energy has been known as the gateway to our civilization's future. Fusion reactions yield the largest amount of energy per unit of mass than any other reaction that we know of, and it is in our near technological reach. The amount of energy produced from fusion fuel would be so large that, once commercially stabilized, the fuel would be so inexpensive and require such modest amounts to operate, that electricity would eventually be virtually free. This, however, is the bliss of idealism. We have yet to actually achieve remotely close to any of these claims, and it seems as though that almost-in-reach phase is lasting much longer than we anticipated.

Going in Circles

Nuclear fusion is no walk in the park; our universe has made that very clear. The amount of money required to build a Magnetic Confinement Fusion Reactor (MCF), also known as a Tokamak, is enormous. Not only that, but our efficiency at collecting the energy from the MCF device once the fusion has taken place has proven to be one of the biggest hurdles thus far. Additionally, the size of the vessel made to contain the plasma for a commercial-sized unit is typically large enough for a human to crawl into. This makes magnetically confining the plasma incredibly difficult and energy intensive to produce the required magnetic fields to contain the plasma for long enough to induce fusion before it all dissipates.

For a more mathematical explanation of this, the time required in MCF is because of the Lawson Criterion. This criterion essentially says 𝐧τ ≥ 10¹⁴ for fusion to occur (using deuterium tritium fuel), where τ is confinement time of the plasma, and 𝐧 is the plasma density. This simply means that there must be a certain amount of plasma within a given area for a certain amount of time for fusion to statistically be able to occur on a utilizable scale. These parameters can be altered to achieve 10¹⁴ either by a very large density of plasma and small confinement time (which is how Inertial Confinement (ICF) works), or by having a large τ and and small plasma density (n), such as how MCF operates.

Most of the reactions performed in a MCF device (aside from Helium-3, which is a very rare fuel) produce neutrons as byproducts, thus causing neutron irradiation inside the reaction chamber. This causes serious damage to the device, and the reactor vessel must have absorption barriers. The issue with this is that, neutrons, being neutral, are incredibly difficult to stop since they are not affected by electric forces and only are absorbed if they come into contact with the nuclei of an atom. For this to be put into perspective, an atom is about 10⁻¹⁰ m in diameter, whereas the nuclei of the atom is about 10⁻¹⁵ m in diameter. This creates interactions with these particles to be much less likely and thus, much more difficult to stop. This makes utilizing these devices on a small-scale incredibly difficult, and limits its applicational use.

One would think, from its excessive funding, that magnetic confinement (and inertial confinement) have been deemed the most potential fusion reactors. Its size and method may be suitable for a power plant type reactor, however, there are many other applications for fusion energy reactors we must consider besides simply producing commercial electricity.

First before I talk about the DPF device, this video is very helpful in giving you an understanding on how this complex system works.

Dense Plasma Focus Device

The Dense Plasma Focus (DPF) device is not a new design, it has been around for quite some time and has been frequently overlooked. This device, however, has one ability over fusion reactors that deems it very favourable. It can create temperatures up to 1.4 billion ℃. Why is this helpful? Because now we can use fuels that MCF and ICF are unable to. Essentially, it allows us to choose whatever fusion fuel we'd like to use, and the one most often chosen is boron-11 and hydrogen. When this fuel fuses it produces no neutrons, which is known as an aneutronic reaction. This is incredibly helpful since neutrons are one of the largest concerns when it comes to reactor safety. In addition to this, all of the products are charged particles with extremely high energies. This allows us to easily contain the reaction products, and instead of sapping that energy into boiling water to produce electricity, we can extract electricity directly with no intermediate energy losses(!). This is done by induction, where essentially wires are wrapped around the ion discharge-tube, and electricity is produced in the coil as the ions are expelled from the main chamber.

Lets say we don't want to make electricity, and instead we want to make thrust. The particles leaving this chamber have so much energy that they can create massive amounts of thrust (up to 1000kN). Additionally, all byproducts are charged particles, so even ions shot in the opposite direction that we want to travel can be redirected with magnetic fields. Now, lets think about this for a minute:

1. Produces no neutrons
2. Creates electricity with no need of working fluid (such as water)
3. Produces significant thrust

Is this not the perfect device to have on any kind of aircraft or space-vehicle? Not only that, but the fuel is so light and effective we would need significantly less fuel storage, as well as the capability to refuel virtually anywhere in the cosmos (since hydrogen is so abundant everywhere in the universe, and boron-11 constitutes 80 percent of natural boron in our solar system).

Looks to me like our species invested in the wrong fusion program.