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Explained! The science of V4F

The V4F consortium knows that nuclear fusion is an interesting, but complex topic. The theory sounds so simple: You have two molecules and want to make one out of them. But reality is much more complicated, and actually making that happen is a difficult challenge. You might have already watched our explainer video on the front page to give you an overview of our project. Below is an article in three sections explaining our idea and concept in a way that is hopefully digestible for all those interested in science.

1. Orbital Angular Momentum and why we want to use it in V4F

Core to the concept of V4F is the exploitation of the orbital angular momentum of light. But what exactly is this? Orbital angular momentum describes the motion of particles in 3D space in basic mechanics. Now we need to translate this concept into photonics. 
Trying to keep it simple, we can imagine the orbital angular momentum of light as a photon propagating along a helix. Just like a child is winding down a helter skelter slide. Because light is both a wave and a particle at the same time, this movement of the photons creates a twisted light beam, in a shape similar to twisted pasta. 

This twisted light beam has a very interesting property for the V4F project: It generates a magnetic field. In this article series, we will explore why this is so important on our quest to make fusion energy a reality.

2. Nuclear fusion, aneutronic fusion and why it can solve the energy crisis

The concept of nuclear fusion is far from new, and the idea is simple: The nuclei of two (or more) atoms merge into one larger nucleus, thereby releasing energy. We won’t go into the details of this energy release, since that would mean diving into the theory of quarks. 
In the historically performed fusion experiments, deuterium and tritium (two heavy isotopes of hydrogen) were used to produce helium atoms, neutrons and energy. However, tritium is radioactive, and the release of neutrons comes with a host of complications, such as damaging ionizing radiation, neutron activation, subsequent radioactive waste, frequent reactor maintenance, and others. Thus, fusion reactions that don’t produce neutrons would make the reactor design and waste management much simpler.
Enter proton boron fusion. A reaction between a proton and a boron molecule would produce 3 helium atoms and energy, but no neutrons. While this reaction is more demanding than the “traditional” reaction between deuterium and tritium, the use of OAM beams in V4F can relax the conditions and make aneutronic proton-boron fusion possible. Our next article on inertial confinement fusion will explain how that 

Aneutronic fusion has huge potential to solve the energy crisis. The alternatives are well known: Fossil fuels are producing greenhouse gases, nuclear fusion produces radioactive waste and renewable energies (e.g. solar energy) falls short when the environmental conditions fall short (e.g. at night, during cloudy periods, …). Fusion energy could produce virtually limitless energy on demand and without producing toxic wastes. If we can get the conditions right, that is. So far, this has been the problem, but V4F aims to help overcome it. 

3. Inertial confinement and why helical light beams help

We have already explored what nuclear fusion is. Let’s add to that an explanation of the conditions that need to be met, before fusion happens: Nuclear fusion is what powers the sun. It is no secret that the conditions on the sun are vastly different from earth: on the surface, the temperature is around 5700°C and the gravity 28x that of the earth. At the centre of a star, it’s even hotter and denser.
These extreme conditions strip the atoms of their electrons, leaving the “naked” nuclei and a cloud of free electrons around. This state is called plasma. Only then can nuclear fusion happen, otherwise the electrons surrounding a nucleus would prevent that collision of nuclei. To realise nuclear fusion, we basically need to build a star on earth. This is not a simple task. So how do we do it?
There are two main approaches called inertial confinement fusion and magnetic confinement fusion. Both approaches try to press fusion fuel together so hard and with so much heat, that fusion happens. 
The work we do in V4F is aimed at inertial confinement fusion, so we will explore how this works. The idea itself sounds very simple: You shoot intense lasers at a small pellet containing fusion fuel coated by some lighter material. The extreme intensity of the lasers rapidly heats the fuel pellet and causes the outer material layer to evaporate. This reaction creates a shock wave travelling into the opposite direction, so towards the centre of the pellet. This presses the core of fusion fuel together and drives an implosion, allowing nuclei to collide with each other and fuse. 

Source: Science Direct

Of course, this process is very difficult to control. The lasers need to produce enough heat and compression in a symmetrical way to not allow any material to escape outwards. The tiniest leak could prevent any nuclear fusion to happen. So how could the V4F concept make this process easier to achieve?
As explained in the first section, twisted light carries orbital angular momentum, which in turn can generate magnetic fields. When using one of our novel OAM lasers for fusion, the pellet will be encompassed in this magnetic field in addition to the transferred heat, helping to press the fuel together even more and further increase the temperature and density achieved in this reaction. This prevents material to escape and improves the conditions to be similar to a star, so nuclear fusion can happen, and we can produce energy.

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