At the end of last year, Germany switched on a new type of massive nuclear fusion reactor for the first time, and it was successfully able to contain a scorching hot blob of helium plasma.
But since then, there's been a big question - is the device working the way it's supposed to? That's pretty crucial when you're talking about a machine that could potentially maintain controlled nuclear fusion reactions one day, and thankfully, the answer is yes.
A team of researchers from the US and Germany have now confirmed that the Wendelstein 7-X (W 7-X) stellerator is producing the super-strong, twisty, 3D magnetic fields that its design predicted, with "unprecedented accuracy". The researchers found an error rate less than one in 100,000.
"To our knowledge, this is an unprecedented accuracy, both in terms of the as-built engineering of a fusion device, as well as in the measurement of magnetic topology," the researchers write in Nature Communications.
That might not sound exciting, but it's crucial, because that magnetic field is the only thing that will trap hot balls of plasma long enough for nuclear fusion to occur.
Nuclear fusion is one of the most promising sources of clean energy out there - with little more than salt water, it offers limitless energy using the same reaction that powers our Sun.
Unlike nuclear fission, which is achieved by our current nuclear plants, and involves splitting the nucleus of an atom into smaller neutrons and nuclei, nuclear fusion generates huge amounts of energy when atoms are fused together at incredibly high temperatures. And it produces no radioactive waste or other byproducts.
Based on the longevity of our Sun, nuclear fusion also has the potential to supply humanity with energy for as long as we need it - if we can figure out how to harness the reaction, that is.
And that's a pretty big 'if', because scientists have been working on the problem for more than 60 years, and we're still a fair way off our goal.
The main challenge is that, in order to achieve controlled nuclear fusion, we have to actually recreate conditions inside the Sun. That means building a machine that's capable of producing and controlling a 100-million-degree-Celsius (180 million degree Fahrenheit) ball of plasma gas.
As you can imagine, that's easier said than done. But there are several nuclear fusion reactor designs in operation around the world right now that are trying their best, and the W 7-X is one of the most promising attemps.
Instead of trying to control plasma with just a 2D magnetic field, which is the approach used by the more common tokamak reactors, the stellerator works by generating twisted, 3D magnetic fields.
This allows stellerators to control plasma without the need for any electrical current - which tokamaks rely on - and as a result, it makes stellerators more stable, because they can keep going even if the internal current is interrupted.
Well, that was the idea of its design, at least.
Despite the fact that the machine successfully controlled helium plasma inDecember last year, and then the more challenging hydrogen plasma in February, no one had shown that the magnetic field was actually working as it should be.
To measure it, a team of researchers from the US Department of Energy and the Max Planck Institute of Plasma Physics in Germany sent an electron beam along the magnetic field lines in the reactor.
Using a fluorescent rod, they swept through those lines and created light in the shape of the fields. The result, which you can see in the image above, shows the exact type of twisted magnetic fields that it was supposed to make.
"We’ve confirmed that the magnetic cage that we’ve built works as designed,"said one of the lead researchers, Sam Lazerson from the US Department of Energy's Princeton Plasma Physics Laboratory.
Despite this success, W 7-X isn't actually intended to generate electricity from nuclear fusion - it's simply a proof of concept to show that it could work.
In 2019, the reactor will begin to use deuterium instead of hydrogen to produce actual fusion reactions inside the machine, but it won't be capable of generating more energy than it current requires to run.
That's something that the next-generation of stellerators will hopefully overcome. "The task has just started," explain the researchers in a press release.
It's not something that will happen tomorrow, but it's an incredibly exciting time for nuclear fusion, with W 7-X officially competing with France's ITER tokamak reactor - both of which have been able to trap plasma for long enough for fusion to occur.
The real question now is, which of these machines will be the first to bring us efficient power from nuclear fusion? We can't wait to find out.
The research has been published in Nature Communications.
MIT’s Alcator C-Mod Tokamak Nuclear Fusion Reactor Sets World Record
The interior of the fusion experiment Alcator C-Mod at MIT recently broke the plasma pressure record for a magnetic fusion device. The interior of the donut-shaped device confines plasma hotter than the interior of the sun, using high magnetic fields. Postdoc Ted Golfinopoulos, shown here, is performing maintenance between plasma campaigns.
On Friday, September 30, at 9:25 p.m. EDT, scientists and engineers at MIT’s Plasma Science and Fusion Center made a leap forward in the pursuit of clean energy. The team set a new world record for plasma pressure in the Institute’s Alcator C-Mod tokamak nuclear fusion reactor. Plasma pressure is the key ingredient to producing energy from nuclear fusion, and MIT’s new result achieves over 2 atmospheres of pressure for the first time.
Alcator leader and senior research scientist Earl Marmar will present the results at the International Atomic Energy Agency Fusion Energy Conference, in Kyoto, Japan, on October 17.
Nuclear fusion has the potential to produce nearly unlimited supplies of clean, safe, carbon-free energy. Fusion is the same process that powers the sun, and it can be realized in reactors that simulate the conditions of ultrahot miniature “stars” of plasma — superheated gas — that are contained within a magnetic field.
For over 50 years it has been known that to make fusion viable on the Earth’s surface, the plasma must be very hot (more than 50 million degrees), it must be stable under intense pressure, and it must be contained in a fixed volume. Successful fusion also requires that the product of three factors — a plasma’s particle density, its confinement time, and its temperature — reaches a certain value. Above this value (the so-called “triple product”), the energy released in a reactor exceeds the energy required to keep the reaction going.
Nuclear fusion has the potential to produce nearly unlimited supplies of clean, safe, carbon-free energy. This 360-degree tour provides look at MIT’s recently deactivated Alcator C-Mod tokamak nuclear fusion reactor, which set a world pressure record on its final day of operation.
Pressure, which is the product of density and temperature, accounts for about two-thirds of the challenge. The amount of power produced increases with the square of the pressure — so doubling the pressure leads to a fourfold increase in energy production.
During the 23 years Alcator C-Mod has been in operation at MIT, it has repeatedly advanced the record for plasma pressure in a magnetic confinement device. The previous record of 1.77 atmospheres was set in 2005 (also at Alcator C-Mod). While setting the new record of 2.05 atmospheres, a 15 percent improvement, the temperature inside Alcator C-Mod reached over 35 million degrees Celsius, or approximately twice as hot as the center of the sun. The plasma produced 300 trillion fusion reactions per second and had a central magnetic field strength of 5.7 tesla. It carried 1.4 million amps of electrical current and was heated with over 4 million watts of power. The reaction occurred in a volume of approximately 1 cubic meter (not much larger than a coat closet) and the plasma lasted for two full seconds.
Other fusion experiments conducted in reactors similar to Alcator have reached these temperatures, but at pressures closer to 1 atmosphere; MIT’s results exceeded the next highest pressure achieved in non-Alcator devices by approximately 70 percent.
While Alcator C-Mod’s contributions to the advancement of fusion energy have been significant, it is a science research facility. In 2012 the DOE decided to cease funding to Alcator due to budget pressures from the construction of ITER. Following that decision, the U.S. Congress restored funding to Alcator C-Mod for a three-year period, which ended on Sept. 30.
“This is a remarkable achievement that highlights the highly successful Alcator C-Mod program at MIT,” says Dale Meade, former deputy director at the Princeton Plasma Physics Laboratory, who was not directly involved in the experiments. “The record plasma pressure validates the high-magnetic-field approach as an attractive path to practical fusion energy.”
“This result confirms that the high pressures required for a burning plasma can be best achieved with high-magnetic-field tokamaks such as Alcator C-Mod,” says Riccardo Betti, the Robert L. McCrory Professor of Mechanical Engineering and Physics and Astronomy at the University of Rochester.
Alcator C-Mod is the world’s only compact, high-magnetic-field fusion reactor with advanced shaping in a design called a tokamak (a transliteration of a Russian word for “toroidal chamber”), which confines the superheated plasma in a donut-shaped chamber. C-Mod’s high-intensity magnetic field — up to 8 tesla, or 160,000 times the Earth’s magnetic field — allows the device to create the dense, hot plasmas and keep them stable at more than 80 million degrees. Its magnetic field is more than double what is typically used in other designs, which quadruples its ability to contain the plasma pressure.
C-Mod is third in the line of high-magnetic-field tokamaks, first advocated by MIT physics professor Bruno Coppi, to be built and operated at MIT. Ron Parker, a professor of electrical engineering and computer science, led its design phase. Professor Ian Hutchinson of the Department of Nuclear Science and Engineering led its construction and the first 10 years of operation through 2003.
Unless a new device is announced and constructed, the pressure record just set in C-Mod will likely stand for the next 15 years. ITER, a tokamak currently under construction in France, will be approximately 800 times larger in volume than Alcator C-Mod, but it will operate at a lower magnetic field. ITER is expected to reach 2.6 atmospheres when in full operation by 2032, according to a recent Department of Energy report.
Alcator C-Mod is also similar in size and cost to nontokamak magnetic fusion options being pursued by private fusion companies, though it can achieve pressures 50 times higher. “Compact, high-field tokamaks provide another exciting opportunity for accelerating fusion energy development, so that it’s available soon enough to make a difference to problems like climate change and the future of clean energy — goals I think we all share,” says Dennis Whyte, the Hitachi America Professor of Engineering, director of the Plasma Science and Fusion Center, and head of the Department of Nuclear Science and Engineering at MIT.
These experiments were planned by the MIT team and collaborators from other laboratories in the U.S. — including the Princeton Plasma Physics Laboratory, the Oak Ridge National Laboratory, and General Atomics — and conducted on the Alcator C-Mod’s last day of operation. The Alcator C-Mod facility, which officially closed after 23 years of operation on Sept. 23, leaves a profound legacy of collaboration. The facility has contributed to more than 150 PhD theses and dozens of interinstitutional research projects.
To understand how Alcator C-Mod’s design principles could be applied to power generation, MIT’s fusion group is working on adapting newly available high-field, high-temperature superconductors that will be capable of producing magnetic fields of even greater strength without consuming electricity or generating heat. These superconductors are a central ingredient of a conceptual pilot plant called the Affordable Robust Compact (ARC) reactor, which could generate up to 250 million watts of electricity.
Physicists achieve record-high efficiency in key nuclear fusion process
For the first time, an international team of scientists has figured out how to visualise energy dispersal in a process known as fast ignition - one of the most promising approaches we have to achieving controlled nuclear fusion.
If we can one day harness the power of nuclear fusion - the process of unleashing vast amounts of energy via high-speed atomic nuclei collisions that fuels our Sun and other stars - we would have access to a safe, clean, and virtually inexhaustible energy source. But scientists have been working on this for more than 60 years, and it’s still far from the realm of possibility, thanks to some pretty significant hurdles.
The good news? Significant hurdles haven't stopped the march of scientific advancement in the past, and the handful of research teams around the world that are leading some serious attempts at bringing nuclear fusion reactors to reality are making progress.
Last month, researchers from the Max Planck Institute for Plasma Physics in Germany switched on their mammoth, US$1.1 billion nuclear fusion machine (called a stellarator) after around 1.1 million construction hours, and so far,things are looking pretty promising.
Meanwhile, in the States, a separate team has been working on a different way to achieve controlled nuclear fusion - fast ignition (FI), which initiates nuclear fusion reactions using a high-intensity laser.
The process works in two stages to get the nuclear fusion process going. First off, you need to fire off hundreds of very powerful lasers to compress the fusion fuel, which is usually a mix of deuterium and tritium, to a high density. Next, a single high-intensity laser is used deliver heat energy to the compressed fuel to very rapidly ignite it, which initiates the self-sustaining process of nuclear fusion.
While fast ignition is still very much in the experimental phase, researchers argue that it’s a promising avenue towards nuclear fusion because it requires a lot less energy than other potential methods. But one of the big problems with it has been in directing that second-stage laser to hit the densest region of the fuel.
"Before we developed this technique, it was as if we were looking in the dark,"said one of the team, Christopher McGuffey from the University of California, San Diego. "Now, we can better understand where energy is being deposited so we can investigate new experimental designs to improve delivery of energy to the fuel."
"This has been a major research challenge since the idea of fast ignition was proposed," added his colleague, Farhat Beg.
All the team had to do was apply simple copper tracers to the spherical plastic fuel capsule. The when they fired the high-intensity laser, they could trace its movement around the capsule because the high-energy electrons it emits hit the tracers and produce visible X-rays.
Publishing in Nature, McGuffey and his colleagues describe how finally being able to visualise where their high-intensity laser is has allowed them to test different ways to improve energy delivery to the fuel target for the first time.According to K. G. Orphanides at Wired UK, the researchers credit this techinque with allowing them to achieve a record high of 7 percent efficiency - "a fourfold improvement on previous fast ignition experiments".
When the experimental design was scaled up, computer models predicted an energy delivery efficiency of up to 15 percent. “Our findings lay the groundwork for further improving efficiency, with 15 percent energy coupling predicted in FI experiments using an existing megajoule-scale laser driver," the team concludes.
When it comes to controlled nuclear fusion, we'll be dealing in baby steps for many years to come, but even tiny developments in the pursuit of something legitimately revolutionary are worth getting excited about. Watch this space.