In a new research paper, scientists from Rice University, the University of Illinois at Urbana-Champaign and the University of Chile provide a glimpse into a potential new path toward the production of energy through nuclear fusion. Controlled nuclear fusion has been a ‘holy grail’ for scientists seeking who seek an unlimited supply of clean energy.
To avoid confusion with all-things nuclear, nuclear reactors use a type of nuclear reaction called nuclear fission (‘fission’ being a word for ‘splitting’ as with ‘splitting the atom’). Another type of nuclear reaction – nuclear fusion – happens in the Sun and other stars. Fusion powers the Sun and stars as hydrogen atoms fuse together to form helium, and matter is converted into energy.
Nuclear fusion refer to a reaction where two or more atomic nuclei come close enough together form one or more different atomic nuclei, together with subatomic particles (such as neutrons and protons). Energy is released as the result of the difference in mass between the products and reactants. This difference in mass is due to variations of atomic “binding energy”, which forms between the atomic nuclei before and after the reaction. The resulting fused atom ends up slightly lighter than the original two atoms. Here the difference in mass is converted to energy, as according to Einstein’s famous formula E=mc².
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The amount of energy is far greater than can be produced from nuclear fission; in fact, nuclear fusion releases about four times the energy produced when an atom is split in conventional nuclear fission.
The goal of nuclear fusion
The reason this process is of interest to scientists is the amount of power that could be produced. Nuclear fusion is the process that powers stars. While scientists have sometimes got tantalizingly close cold nuclear fusion has yet to be achieved. This is despite decades of attempts (not to mention billions of dollars spent), with research with controlled thermonuclear fusion beginning during the 1950s.
The appeal of nuclear fusion is to generate clean, safe, limitless energy for the world. The bulk of the research has centered on trapping a plasma (a term of an ionized gas) in a huge magnetic ring. Following this heavy hydrogen isotopes would be forced through with the aim of fusing them together in order to release large quantities of energy.
In terms of current research there are two main experimental approaches being considered. The first method is magnetic confinement, which uses strong magnetic fields to contain the hot plasma. The second method is inertial confinement. This involves compressing a small pellet containing fusion fuel to extremely high densities using strong lasers or particle beams.
One of the biggest nuclear fusion projects is the $20 billion Iter project located in Provence, France. The aim of this project is simple: to get more energy out of the intense fusion reactions than is put in. Speaking with The Guardian, Johannes Schwemmer, the director of Fusion for Energy, which is part of the Iter group, said: “It is a bet that is very important for humanity. We need to get this energy once and for all.”
The biggest obstacle to date has been one of plasma physics. The issue is, with a fusion reactor, the plasma needs to be heated to at least 100 million degrees Celsius and then forced to collide using electromagnets. Because plasma is unstable and unpredictable the collisions are difficult to create.
With the new study, researchers argue that instead of heating atoms to the ultra-high temperatures and smashing them in a collider, atoms could be ‘nudged’ to fuse through the use of shaped laser pulses. These are so-called ultrashort, tuned bursts of coherent light. This is what is termed a “femtochemical technique.” The science behind it is that nuclei can be pushed close enough towards a barrier that forces atoms of like charge to repel each other. When this happens atoms will theoretically fuse and then release sufficient heat through neutron scattering. In sufficient numbers this creates energy at sufficient magnitude to sustain a reaction. The tricky part will be achieving this in a controlled way.
To date the research is a proof-of-principle simulation looking at how effectively shaped-laser pulses can push a molecule of deuterium and tritium, to see if it would be possible to cause fusion. The research is based on a series of two dimensional simulations. Further research will look at how the light pulses can be sculpted to work out the optimal pulse shape. If this is achieved then an interesting new path towards the goal of nuclear fusion could be created.
The nuclear fusion research has been published in the journal Chemical Physics Letters, in a paper succinctly titled “Quantum controlled fusion.”
Essential Science
This article is part of Digital Journal’s regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week we looked at the deadly nerve agent VX and its role in political assassinations. The week before we looked at the novel use of virtual reality to help psychiatrists to assess people with schizophrenia.
