The Sun provides an excellent example of the power of fusion and its potential as an energy source. Much of the Sun’s mass consists of hydrogen, a simple element composed of just one proton and one electron. The combination of extreme temperature and pressure from gravity in the Sun’s core causes the protons from the hydrogen atoms to combine or “fuse,” thus creating new atoms of helium. This process releases a vast amount of energy which we experience every day in the form of the light and heat produced by the Sun’s fusion core.
While it is conceptually the same, producing fusion on Earth faces several significant challenges.
First, fusion requires getting the hydrogen fuel to extremely hot temperatures in order for the reactions to occur. When hydrogen gas is compressed, it heats up. When it heats up enough, the electrons are ripped away from their proton nuclei forming a state of matter called plasma. In this way, the Sun produces the needed hot temperature by using its massive gravity to compress the hydrogen plasma in its core. On Earth it is impossible to create this amount of pressure from gravity. Instead, scientists have figured out ways to heat up the plasma fuel to the needed temperature using many kinds of technological solutions.
The second challenge is time. The Sun’s fusion of hydrogen to helium is a multi-step process; however the first step can take a billion years to complete. The Sun can afford to wait but here on Earth, we need something faster. The solution to this problem comes down to selecting a different fuel. It must be both abundant and can be fused much quicker.
Deuterium, which is one of hydrogen’s isotopes, meets both of those needs. Deuterium is plentiful, as it is available in the form of “heavy water,” which is abundant in Earth’s oceans. Most importantly, when two hot deuterium ions meet, they have a much higher chance of fusing than the protons of the hydrogen plasma in the Sun. This means that fusion reactions start to occur as soon as the fuel is hot enough.
The third challenge remains unsolved. While scientists fully understand the process of fusion, they still have not been able to achieve “ignition,” that is, continued, self-sustained burn of the fusion fuel. While scientists have been able to create the conditions necessary for fusion and show evidence that some atoms have fused, no one has been able to create a self-sustaining fusion reaction.
To achieve ignition, three things are needed: high temperature, high density of fusion plasma fuel, and keeping the plasma hot for a long enough time.
The last criterion is known as “confinement,” and scientists are pursuing two ways to solve it.
The first is called “magnetic confinement.” Recall the extreme temperature of the fusion plasma fuel. If the hot fusion plasma touches the walls of the reaction chamber, it cools instantly below the temperature for fusion and a microscopic portion of the wall is instantly vaporized. The atoms of the wall go into the plasma further cooling it down and making additional fusions more difficult. Magnetic confinement attempts to use magnetic fields to prevent the plasma from coming into contact with any wall material. This scheme tries to keep the plasma hot for a long time but the trade-off is that it has a low density of fusion plasma fuel. This means the size of reaction chamber must be very large to achieve ignition. Magnetic confinement devices large enough to achieve ignition are estimated to cost tens of billions of dollars.
The second approach is called “inertial confinement,” and it is the way being pursued by Proton Scientific. Inertial confinement attempts to create as many fusion reactions as possible in a compressed solid fuel pellet before the hot reaction products disintegrate the pellet. The density is very high so the needed confinement time is very short. Because only a small number of fusion reactions are needed to initiate self-sustaining fusion, inertial confinement should be able to solve the confinement problem. Additionally, because the fuel pellet size does not need to scale up to achieve ignition, the overall device will be smaller meaning the eventual cost to build a commercial power plant based on this approach should be much less.
Proton Scientific’s Thunderbird pulsed-power generator allows us to speed up the process of solving confinement, as it can already produce a concentrated burst of power strong enough to achieve fusion. The team from Proton Scientific is continuing the tests needed to achieve ignition. This is a necessary step in order to get more energy from the fusion plasma than was put in to begin the process. From there, this excess energy can be harness to make electricity. Great efforts have already been made by the scientific community to solve many of the formidable challenges of fusion energy production. We are working to make the final push.