Scientists in California have made a major breakthrough in fusion power research, but the path to unlimited clean energy remains long and difficult.
The scientists described the significant result – which was recorded last year at the National Ignition Facility in Lawrence Livermore National Laboratory – in a paper published in Nature on Wednesday.
"The two notable parts that we report on are getting more fusion energy out of the fusion fuel than was deposited into the fusion fuel, and the other component of that is seeing this non-linear feedback process that we call bootstrapping where the alpha particles that come out of the helium reaction start leaving a significant amount of their energy behind causing the reaction to accelerate and amplify the output – it's nearly a doubling of the output due to the alpha particles," researcher Omar Hurricane tells El Reg. "They are important scientific steps on the way to pushing the fusion further."
In the 'Fuel gain exceeding unity in an inertially confined fusion implosion' paper the scientists describe how they were able to generate more energy from the ensuing reaction than that which was put into it via a laser.
"These experiments show an order-of-magnitude improvement in yield performance over past deuterium–tritium implosion experiments," they write.
For the experiment, the scientists fired the National Ignition Facility's laser at the target with an energy of two megajoules, though only at best 17 kilojoules reached the pellet of deuterium and tritium fuel.
Why did so little energy reach the actual pellet? "We need to make it dense and hot at the same time, the way these experiments work is we give up energy as the experiment proceeds and trade it away to get very high pressures," Hurricane explains.
"Right now what we're focused on is getting the central pressure at the final state of our implosion even higher, right now the experiments are creating pressures of around 150 billion atmospheres, our goal is more or less to double that. If we can double that - maybe a little bit more than doubling - we can start to get close to the conditions to ignite the fuel."
The researchers, though, are a long way away from attaining a break-even reaction; an ongoing fusion reaction where the energy being output is greater than the power needed for the igniting laser.
"In the sense where we are with this is we've assembled the stick of dynamite with the fuse and can light the fuse – all we need to do now is get that fuse to light all the way down to the stick of dynamite," Hurricane explained.
There are currently two main approaches to attaining a stable, ongoing reaction: the approach taken by the National Ignition Facility which sees an immensely high powered laser used to create vast pressures for a short time period and kickstart a reaction, and that taken by the 'Tokamak' approach.
A 'Tokamak' is, in simplified terms, a doughnut-shaped chamber that uses a magnetic field to confine and compress a plasma until it reaches fusion.
Countries around the world are in the process of building the mammoth 'ITER' facility in the South of France that will house a huge Tokamak along with other advanced gadgetry to create a long-term sustainable fusion reaction, and pave the way for the building of practical plants.
"Both approaches are credible," Hurricane says. "The magnetic fusion approach is almost the opposite [of the NIF] – trying to go for lower pressures but for longer times. This is such a hard problem it makes sense for multiple approaches."
Both approaches face the same problem: turbulence. The trickiest part of maintaining an ongoing fusion reaction is controlling the immense energies and forcing them into a stable configuration.
The key work for researchers at the National Ignition Facility, and ITER, will be in learning to "tamp down" this turbulence, Hurricane explains.
We imagine that champagne corks will be popping at the National Ignition Facility tonight – though hopefully not within the rather expensive fusion chamber.
"Rather than having another frustrating result where things aren't going the way we want things are starting to go the way we want," Hurricane said. "This is a really nice scientific step." ®