Tag Archives: nuclear fusion

Scientists achieve milestone on path towards nuclear fusion energy

The possibility of developing practical nuclear fusion, the energy process that powers the stars, is now a step closer to reality. UK scientists at the Joint European Torus (JET) have reached a new record on the amount of energy released in a sustained fusion reaction, generating 59 megajoules of heat – equivalent to about 14 kilograms of TNT. This more than doubles the previous record of 21.7 megajoules achieved in 1997 at the same research facility.

While it’s still not a lot of energy, enough to boil 60 kettles of water, the achievement is widely being described as a “major milestone” on the path to eventually make fusion a viable and sustainable low-carbon energy source. 

“These landmark results have taken us a huge step closer to conquering one of the biggest scientific and engineering challenges of them all,” Ian Chapman, head of the UK Atomic Energy Authority, said in a statement. “It’s clear we must make significant changes to address the effects of climate change, and fusion offers so much potential.”

A major source of energy

Fusion occurs in the heart of starts and grants the energy that powers the universe. It’s the process through which two light atom nuclei combine to form a single heavier one, releasing bursts of energy as a consequence. It’s the opposite of nuclear fission, used in nuclear power stations, in which a large nucleus splits apart to form smaller ones. 

The benefits of fusion power make it a very attractive option, especially in the context of climate change and diminishing limited fossil fuel supplies. It produces no carbon emissions, with its only by-products being small amounts of helium, an inert gas that could also be useful. It’s also very efficient, less radioactive than fission, and saf — as the amount of fuel used in fusion devices is very small. 

The JET laboratory in central England uses a machine called tokamak for its studies. It’s the largest of its type in the world. Inside the machine, a small amount of fuel containing tritium and deuterium (isotopes of hydrogen) is heated to create plasma. This is kept in place using magnets as it spins around, fuses, and releases energy. 

Experiments at the lab have focused on whether fusion is feasible with a fuel based on deuterium and tritium, which seems to be the case based on the latest results. This is good news for Iter, a massive fusion project being built in France by a coalition of several governments. It will still take some time, though: if all goes well, Iter should start burning fuel by 2035. 

Countries have been working closely on fusion energy for years as, unlike nuclear fission used in the existing atomic power plants, the technology doesn’t produce radioactive material that can be then used for weapons. China, the EU, the US, India, Japan, and Russia have so far been involved in the mega project of Iter in France.  

If researchers manage to carry out nuclear fusion, it promises to supply a near-limitless source of clean energy. But so far no experiment has created more energy out than it puts in. The new results at JET don’t change that, but they indicate that a fusion reacts project that uses the same tech and fuel mix, Iter, could eventually achieve that goal. 

When will the Sun run out of fuel?

All life on Earth owes its existence to the Sun, whose rays have showered the planet with energy for billions of years. But, like all things, the Sun has its days numbered. Every star has a life cycle consisting of formation, main sequence, and ultimately death when it runs out of fuel — the Sun is no exception.

The good news is that before this will happen, our species should have evolved into something entirely different or long become extinct. According to scientists, the sun has enough fuel to keep it running for another 5 billion years. When that happens, the solar system will be transformed forever.

The life cycle of the Sun

Credit: Socratic.

The star is classed as a G-type main-sequence star, also known as a yellow dwarf. Like other G-type main-sequence stars, the Sun converts hydrogen to helium in its core through nuclear fusion. Each second, it fuses about 600 million tons of hydrogen to helium. The term yellow dwarf is a misnomer since G stars actually range in color from white to slightly yellow. The Sun is, in fact, white but appears yellow because of Rayleigh scattering caused by the Earth’s atmosphere.

The Sun and its planets have been around for about 4.57 billion years. They were all formed out of the same giant cloud of molecular gas and dust which, at some critical point, collapsed under gravity at the center of the nebula.

Due to a nonuniform distribution of mass, some pockets were denser, consequently attracting more and more matter. At the same time, these clumps of matter that were increasing in mass began to rotate due to the conservation of momentum. The increasing pressure also caused the dense regions of gas and dust to heat up.

Scientists’ models suggest that the initial cloud of dust and gas eventually settled into a huge ball of matter at the center, surrounded by a flat disk of matter. The ‘ball’ would eventually turn into the Sun once the temperature and pressure were high enough to trigger nuclear fusion, while the disk would go on to form the planets.

Scientists estimate that it took the Sun only 100,000 years to gather enough mass in order to begin fusing hydrogen into helium. For roughly a few million years, the Sun shone very brightly as a T Tauri star, before it eventually settled into its current G-type main-sequence configuration.

Like most other stars in the universe, the Sun is currently living through its ‘main sequence’ phase. Every second, 600 million tons of matter are converted into neutrinos and roughly 4 x 1027 Watts of energy. 

What happens to Earth after the sun dies

There is only a finite amount of hydrogen in the Sun which means it must eventually run out. Since its formation, scientists estimate the Sun consumed as much hydrogen as about 100 times the mass of the Earth.

As the Sun loses hydrogen, its fuel-holding core shrinks, allowing the outer layers to contract towards the center. This puts more pressure on the core, which responds by increasing the rate at which it fuses hydrogen into helium. Naturally, this means the Sun will get brighter with time.

Scientists estimate that the Sun’s luminosity increases by 1% every 100 million years. Compared to when it turned into a G-type main-sequence star 4.5 billion years ago, the Sun is now 30% more luminous.

All of this means that the Sun will slowly turn the heat up on Earth. About 1.1 billion years from now, the Sun will be 10% brighter, triggering a greenhouse effect on Earth similar to the warming that made Venus into a hellish planet.

As the Sun approaches the end of its life cycle, Earth’s ocean will boil and the planet will become uninhabitable as early as 1 billion years from now. Credit: Wikimedia Commons.

The heat transfer with Earth’s atmosphere would be huge by this point in time, causing the oceans to boil and the ice caps to melt. As the atmosphere becomes saturated with water, high energy radiation from the Sun will split apart the molecules, allowing water to escape into space as hydrogen and oxygen until the whole planet becomes a barren wasteland.

Life would stand no chance, permanently sealing Earth’s fate as the next Venus or Mars. Speaking of which, at this point into the future, Mars’ orbit would move into the habitable zone, which might become a second Earth for a short while before it too would become unsalvageable.

Some 3.5 billion years from now, the Sun will be 40% brighter than today.

And, in about 5.4 billion years, the Sun will run out of hydrogen fuel, marking the end of its main sequence phase. What will inevitably happen next is that the built-up helium in the core will become unstable and collapse under its own weight. Since the Sun first started fusing hydrogen, all of the helium it has produced has accumulated in the core with no way to get rid of it.

At this point, the Sun will be ready to enter its “Red Giant” phase, characterized by an enormous swelling in size due to gravitational forces that compress the core and allow the rest of the sun to expand. The Sun will grow so large that it will encompass the orbits of Venus and Mercury, and quite possibly even Earth. Some astronomers estimate it might grow to 100 times its current size.

What this means is that even if life on Earth somehow miraculously survives the tail-end of the Sun’s main sequence, it will most certainly be destroyed by a Red Sun so large it will touch our planet.

Don’t be blue, even stars have to die

The Sun will remain in a Red Giant phase for about 120 million years. At this point, the core of the Sun, when it reaches the right temperature and pressure, will start fusing helium into carbon, then carbon and helium into oxygen, neon and helium into magnesium, and so on all the way up to iron. This reaction is triggered when the last remaining shell of hydrogen that envelops the core is burned.

The Sun will then eventually expel its outer layers and then contract into a white dwarf. Meanwhile, all the Sun’s outer material will dissipate, leaving behind a planetary nebula.

“When a star dies it ejects a mass of gas and dust – known as its envelope – into space. The envelope can be as much as half the star’s mass. This reveals the star’s core, which by this point in the star’s life is running out of fuel, eventually turning off and before finally dying,” explained astrophysicist Albert Zijlstra from the University of Manchester in the UK.

“It is only then the hot core makes the ejected envelope shine brightly for around 10,000 years – a brief period in astronomy. This is what makes the planetary nebula visible. Some are so bright that they can be seen from extremely large distances measuring tens of millions of light years, where the star itself would have been much too faint to see.”

Cat’s Eye Nebula. Credit: NASA/ESA.

If it were much more massive, the Sun’s final fate would have been much more spectacular exploding into a supernova and perhaps forming a black hole. Due to its relatively small size, however, the Sun will likely live as a white dwarf for trillions of years before finally fading away entirely leaving the solar system in pitch-black darkness. The Sun has now become a black dwarf.

In summary: the sun has about 5-7 billion years left of its main sequence phase — the most stable part of its life. However, life on Earth might become extinct as early as 1 billion years from now due to the Sun becoming hot enough to boil the oceans.

Credit: Flickr, Mike Mozart.

Mayo experiment helps physicists solve nuclear fusion instability

Credit: Flickr, Mike Mozart.

Credit: Flickr, Mike Mozart.

Physicists at Lehigh University have used a common household item to study the fundamental hydrodynamics inside one of the most promising types of fusion reactors. The experiments involving mayonnaise gave the scientists new insights into what may be happening when gas and molten metal mix under the influence of high acceleration and centrifugal force.

Who knew that mayo has such an important role to play in a technology that might recreate the power of the sun here on Earth?

Fusing mayo

Nuclear fusion occurs when two smaller atoms collide at very high energies to merge, creating a larger, heavier atom. This is the nuclear process that powers the sun’s core, which in turn drives life on Earth. One promising method for achieving fusion that scientists in the United States are currently exploring is called inertial confinement. At research facilities such as the Lawrence Livermore National Laboratory and Los Alamos National Laboratory, scientists confine a gas — usually hydrogen isotopes — by freezing it inside pea-sized metal pellets. The pellets are placed inside a chamber where they are hit by a high-powered laser that can generate up to a few million Kelvin (400 million degrees Fahrenheit) — conditions ripe for fusion.

The extreme heat causes the gas inside to expand, bursting the metal casing before fusion can be reached. The process is similar to a balloon being squeezed — at some point, the rubber balloon bursts under pressure from the air inside.

In order to produce fusion in inertial confinement, scientists first need to solve the problem of the molten metal and heated gas mix — and this is where mayo comes in. The material properties of the mix at high temperatures are similar to that of mayo at low-temperature, according to Arindam Banerjee, an associate professor of mechanical engineering and mechanics at Lehigh University.

Banerjee’s area of expertise is in Rayleigh-Taylor instability, a phenomenon which occurs between materials of different densities when the density and pressure gradients are in opposite directions creating an unstable stratification.

“In the presence of gravity—or any accelerating field—the two materials penetrate one another like ‘fingers,'” Banerjee said in a statement.

Investigating this kind of instability is extremely challenging because it happens almost in an instant and the large measurement uncertainties of accelerated solids.

For their study, Banerjee and colleagues poured Hellman’s Real Mayonnaise into a Plexiglass container and then accelerated the sample inside a rotating wheel. The progress of the material was tracked with a 500fps high-speed camera, whose images were fed into an image processing algorithm that could detect parameters associated with Rayleigh-Taylor instability. The wavelength and amplitude growth rates were finally compared to existing analytical models.

Credit: Arindam Banerjee.

Credit: Arindam Banerjee.

These experiments allowed the research team to visualize both the elastic-plastic and instability evolution of the material. The authors concluded that the onset of the instability (“instability threshold”) was related to the size of the amplitude (perturbation) and wavelength (distance between crests of a wave) applied.

“There has been an ongoing debate in the scientific community about whether instability growth is a function of the initial conditions or a more local catastrophic process,” says Banerjee. “Our experiments confirm the former conclusion: that interface growth is strongly dependent on the choice of initial conditions, such as amplitude and wavelength.”

In the future, these findings will help researchers design better conditions for inertial confinement. Step by step, little by little, the world is moving closer to achieving nuclear fusion. On that note, researchers have triggered fusion before — it’s just that the energy required to trigger the reaction was larger than the energy produced by it. Some of the most promising fusion reactors include the International Thermonuclear Experimental Reactor (ITER) in France and the Wendelstein 7-X reactor in Germany. 

The findings appeared in the journal Physical Review E. 

Credit: ThePressProject.

Scientists discover new type of fusion reaction — merging quarks is eight times more powerful than single reactions in H-bomb

Israeli and American physicists have come across a new type of fusion reaction that is startlingly powerful. Initially, the scientists were a bit scared and thought it’s better not to publish the research least it fell into the wrong hands, leading to a planetary-bomb. The fusion, however, can’t sustain a chain reaction so scientists say the process is, for all practical reasons, harmless.

Credit: ThePressProject.

Credit: ThePressProject.

Matter, the stuff we see and interact with, is made of atoms,. In turn, these are made of protons and neutrons, which, in their own turn, are made of elementary particles called quarks and leptons. There are six ‘flavors’ or types of quarks physicists know of: up, down, strange, charm, top, and bottom. Yes, physicists have a knack for giving silly names to particles and phenomena. Up and down quarks have the lowest masses of all quarks.

Researchers at Tel Aviv University and the University of Chicago found a way to fuse two bottom quarks together. When they fuse, the two bottom quarks form a larger particle called a nucleon and release up to eight times more energy as the individual reactions in a Hydrogen-bomb, specifically 138 megaelectronvolts (MeV).


Credit: Wikimedia Commons.

In the case of a hydrogen bomb, there are millions of fusion events going on, so imagine what a quark-bomb would look like. You don’t need to run the math to realize it could even obliterate a planet.

Marek Karliner of Tel Aviv University and colleagues almost wanted to pull the plug on the research until they realized it is all a ‘one-trick pony’. What Karliner means by that is bottom quarks exist for just one picosecond or a mere one-trillionth of a second before turning into up quarks. That’s a way too brief period for a chain reaction to sustain itself so a quark-bomb would just fizzle instantly.

“We suggest some experimental setups in which the highly exothermic nature of the fusion of two heavy-quark baryons might manifest itself. At present, however, the very short lifetimes of the heavy bottom and charm quarks preclude any practical applications of such reactions,” the authors wrote in the study published in the journal Nature.

In and of itself, the research is highly valuable because it proves that subatomic particles can release massive amounts of energy when fusing together.

“It is important to emphasize that although our findings have aroused considerable interest in theory, they have no practical application,” said Karliner. “A nuclear fusion that occurs in a reactor or a hydrogen bomb is a chain reaction in a mass of particles, creating a huge amount of energy. This is not possible by melting heavy quarks, simply because the raw material cannot be accumulated in the melting process. If we thought for a moment that our discovery had some dangerous application, we would not publish it.”


The sun’s core rotates four times faster than its surface

We don’t know much about the early history of the sun but a surprising discovery might change that. According to an international team of astronomers, the sun’s core actually spins four times faster than its surface.


Credit: NASA.

Previously, astronomers presumed the core was simply rotating at the same pace with its surface like a unitary body. What happened instead though was that solar wind steadily slowed down the rotation of the outer part of the sun.

“The most likely explanation is that this core rotation is left over from the period when the sun formed, some 4.6 billion years ago,” said Roger Ulrich, a UCLA professor emeritus of astronomy, who has studied the sun’s interior for more than 40 years and co-author of the study that was published today in the journal Astronomy and Astrophysics.

“It’s a surprise, and exciting to think we might have uncovered a relic of what the sun was like when it first formed.”

The sun is actually comprised of four distinct layers. Energy is generated in the core, the innermost one, then blasts outward by radiation (mostly gamma-rays and x-rays) through the radiative zone and by convective fluid flows (boiling motion) through the convection zone, the outermost layer. The thin interface layer (the “tachocline”) between the radiative zone and the convection zone is where the sun’s magnetic field is thought to be generated.

Ulrich and colleagues learned this after they studied surface acoustic waves that hit the sun’s surface, some of which also penetrated the core. Once at the core, the acoustic waves interact with gravity waves whose motion resembles water bouncing back and forth in a half-filled tanker truck taking a curve. This interaction ultimately revealed the sloshing motions of the solar and by accurately measuring the acoustic waves, the team found out the time required for the waves to travel from the surface to the core and back.

This effort required 16 years of coordinated action by many research institutes to bring to fruition. Since two decades ago, some scientists have been proposing that the sun’s core rotates slower than its surface but it was only recently that the tech enabled an investigation. Instruments like GOLF (Global Oscillations at Low Frequency) on a spacecraft called SoHO proved to be essential, for instance.

It makes sense that the core and the surface of the sun can have such dissimilar properties. For one, the core — where nuclear fusion occurs — has a temperature of 15.7 million Kelvin while the surface is far, far colder measuring only 5,800 Kelvin in temperature. And as an interesting trivia — just to get an idea of the complexities involved in the many layers between the core and surface of the sun — by the most recent estimates, it takes about a million years for photons forged in the core to escape through the surface. From there, it only takes them eight minutes to reach Earth.

The findings appeared in the journal Astronomy & Astrophysics.

German nuclear fusion machine starts running

German scientists have turned on a device called a stellerator, the largest of its kind. The machine could pave the way for nuclear fusion, a clean and safe type of nuclear power.

This machine, called W7-X, cost approximately $1.1 billion, has a diameter of 52 feet (16 meters) and took 19 years to construct; the GIF above shows the layers of the machine.

Nuclear fusion

As we were telling you before, a stellarator is a device used to confine a hot plasma with magnetic fields in order to sustain a controlled nuclear fusion reaction. The basic idea is that the differing magnetic fields will cancel out the net forces on a particle as it travels around the confinement area. They were quite popular in the 50s and 60s, but their popularity greatly decreased in following decades, as other types of fusion research were carried.

The key is to create ungodly high temperatures up to 180 million degrees Fahrenheit (100 million Celsius) and generate, confine, and control a blob of gas, called a plasma. At these incredibly high temperatures, the very structure of the atom changes, and the electrons are ripped from the outer shells, leaving positive ions. Normally, these ions would just bounce off each other, but under these conditions, they can merge together, creating new atoms, and – BAM – you have nuclear fusion. Nuclear fusion shouldn’t be mistaken for the nuclear energy we are using at the moment, which generate energy from decaying atoms, not atoms that fuse together.

Fusion is the process that powers our Sun, and if we could somehow harvest that power, then it could (in time) be a green energy revolution.

“It’s a very clean source of power, the cleanest you could possibly wish for. We’re not doing this for us, but for our children and grandchildren,” one of the team, physicist John Jelonnek from the Karlsruhe Institute of Technology, said in a statement.

Flipping the switch

The 425-tonne machine took 19 years to construct, requiring 1.1 million construction hours in total. However, it seems to have been worth it as the first tests were carried smoothly.

“Everything went well today,” said Robert Wolf, a senior scientist involved with the project. “With a system as complex as this you have to make sure everything works perfectly and there’s always a risk.”

So far, the team was able to heat hydrogen gas to 80 million degrees for a quarter of a second. This might not sound like much, but it’s a clear proof of concept as well as an indication of things to come. Experiments will continue and a divertor for the elimination of impurities will be mounted inside the reactor, allowing plasmas to last as long as 30 minutes.

It has to be said, the device itself won’t generate useful amounts of energy, but it will (hopefully) demonstrate that this can be done realistically.

“In a later phase of W-X, starting in 2019, we will use deuterium and we will get fusion reactions, but not enough to get more energy out than we are putting in,” one of the team, Hans-Stephan Bosch, said, adding that there are no plans to add tritium to the hydrogen plasma to break even.


Germany is about to plug in a machine that could revolutionize the energy industry

For decades, scientists have been discussing about the possibility of a clean, virtually inexhaustible source of energy – and they still are. But with the work of researchers from the Max Planck Institute for Plasma Physics, that may soon change, and the way we think of energy might change. After over 1.1 million construction hours, they have completed the world’s largest fusion machine of its kind, appropriately called a ‘Stellaratron’.

This machine, called W7-X, cost approximately $1.1 billion, has a diameter of 52 feet (16 meters) and took 19 years to construct; the GIF above shows the layers of the machine.

A stellarator is a device used to confine a hot plasma with magnetic fields in order to sustain a controlled nuclear fusion reaction. The basic idea is that the differing magnetic fields will cancel out the net forces on a particle as it travels around the confinement area. They were quite popular in the 50s and 60s, but their popularity greatly decreased in following decades, as other types of fusion research were carried.

Stellarators are as awesome as they sound

The key to fusion is to create ungodly high temperatures up to 180 million degrees Fahrenheit (100 million Celsius) and generate, confine, and control a blob of gas, called a plasma. At these incredibly high temperatures, the very structure of the atom changes, and the electrons are ripped from the outer shells, leaving positive ions. Normally, these ions would just bounce off each other, but under these conditions, they can merge together, creating new atoms, and  – BAM – you have nuclear fusion. Nuclear fusion shouldn’t be mistaken for the nuclear energy we are using at the moment, which generate energy from decaying atoms, not atoms that fuse together.

Nuclear fusion is not an unfamiliar process though; it’s the process that fuels the Sun, so we know it can be done; however, doing it in a way that can be used economically has not yet been done, and even research-focused machines are sparse. This is where W7-X enters the stage.

The construction of this machine was, as you can guess, a gargantuan task; for almost 75 years, only a handful of stellarators were ever attempted, and even fewer were completed. The entire process is “devilishly hard”, and to make things even worse, one of the main contracted manufacturers went out of business at one point.

Well, for starters, the machine has 425 tonnes of superconducting magnets and support structure that must be chilled close to absolute zero. Cooling the magnets with liquid helium is “hell on Earth,” said Thomas Klinger, leader of the German effort.

“All cold components must work, leaks are not possible, and access is poor” because of the twisted magnets. Among the weirdly shaped magnets, engineers must squeeze more than 250 ports to supply and remove fuel, heat the plasma, and give access for diagnostic instruments. Everything needs extremely complex 3D modeling. “It can only be done on computer,” Klinger says. “You can’t adapt anything on site.”

A third of the required magnets didn’t function properly from the get-go. So construction of some major components had to be halted for redesigning; some years were a full fledged crisis period, but somehow they managed to get over it, and the first plasma is scheduled to take place by the end of the year.

A magnetic cage

The main problem with Stellarators, as with any fusion device, is containing the temperature, and for this, they use a magnetic cage. A current-carrying wire wound around a tube creates a straight magnetic field down the center of the tube that draws the plasma away from the walls, preventing them from melting. There are 50 six-ton magnetic coils around the main area, as shown below:

Other designs (tokamaks) have a different shape, which is safer, but only allows them to support the plasma in short bursts, while Stellarators can sustain the plasma for 30 minutes, research claims – this could generate massive amounts of clean, renewable energy; this machine could be a genuine game changer – if it works.

“The world is waiting to see if we get the confinement time and then hold it for a long pulse,” David Gates, the head of stellarator physics at the Princeton Plasma Physics Laboratory, told Science.


German regulators are expected to give the green light for the project by the end of the month, and we’ll find out then if it works, and how well.

The preamplifiers of the National Ignition Facility. The unified lasers deliver 1.8 megajoules of energy and 500 terawatts of power — 1,000 times more than the United States uses at any one moment. (Credit: Damien Jemison/LLNL)

Closer then ever to nuclear fusion, according to physicists

Physicists have been dreaming of achieving controlled nuclear fusion for decades, and year by year we’ve been getting closer to turning it into reality. A recent paper published in the journal Physics of Plasmas reports improvements in the design of an experimental set-up capable of igniting a self-sustained fusion reaction with high yields of energy. Researchers at the National Ignition Facility (NIF) claim they’re currently tackling one big obstacle that comes is in the way of fusion ignition.

The preamplifiers of the National Ignition Facility. The unified lasers deliver 1.8 megajoules of energy and 500 terawatts of power — 1,000 times more than the United States uses at any one moment. (Credit: Damien Jemison/LLNL)

The preamplifiers of the National Ignition Facility. The unified lasers deliver 1.8 megajoules of energy and 500 terawatts of power — 1,000 times more than the United States uses at any one moment. (Credit: Damien Jemison/LLNL)

Nuclear fusion is a nuclear reaction in which two or more atomic nuclei collide at very high speeds and energies and fuse together leading to the creation of a new atom. At the dawn of the Universe, there was only Hydrogen, and it is through fusion that all the other elements surfaced. If lighter elements are fused (lighter than Iron), the nuclear reaction releases energies – lots of it. If the fused elements are heavier than iron, then the reaction absorbs energy. This is why in fission, which is the exact opposite of nuclear fusion, very heavy elements are employed to release energy.

Nuclear fusion, however, requires tremendous amounts of energy to kick-start. The challenge lies in designing reactors that capable of producing more energy than it goes into igniting the reaction. Even so there are technical challenges in order to achieve the highly stable precisely directed implosion required for ignition. One such obstacle has been outlined the NIF researchers in their report.

Closer to a fusion dream

Schematic of NIF ignition target and capsule (credit: M. J. Edwards et al., Physics of Plasmas)

Schematic of NIF ignition target and capsule (credit: M. J. Edwards et al., Physics of Plasmas)

To achieve ignition, NIF reserachers used 192 laser beam that fire simultaneously inside a specially designed cryogenic hollow chamber called a hohlraum (German for “hollow room”), just the size of a pencil. Together the combined power of the lasers deliver 1.8 megajoules of energy and 500 terrawatts of power – 1,000 times more than the United States uses any single moment – inside the hohlraum in billionth-of-a-second pulses.  All this power is directed towards  a ball-bearing-size capsule containing two hydrogen isotopes, deuterium and tritium (D-T) inside the hallow chamber, which creates a sort of “X-ray oven” that implodes the isotope capsules  to temperatures and pressures similar to those found at the center of the sun.

“What we want to do is use the X-rays to blast away the outer layer of the capsule in a very controlled manner, so that the D-T pellet is compressed to just the right conditions to initiate the fusion reaction,” explained John Edwards, NIF associate director for inertial confinement fusion and high-energy-density science. “In our new review article, we report that the NIF has met many of the requirements believed necessary to achieve ignition—sufficient X-ray intensity in the hohlraum, accurate energy delivery to the target and desired levels of compression—but that at least one major hurdle remains to be overcome, the premature breaking apart of the capsule.”

The NIF researchers used monitoring tools to diagnose the capsule breaking step by step.

 “In some ignition tests, we measured the scattering of neutrons released and found different strength signals at different spots around the D-T capsule,” Edwards said.

“This indicates that the shell’s surface is not uniformly smooth and that in some places, it’s thinner and weaker than in others. In other tests, the spectrum of X-rays emitted indicated that the D-T fuel and capsule were mixing too much — the results of hydrodynamic instability — and that can quench the ignition process.”

The NIF scientists are now concentrating all their efforts on determining the exact nature of this instability and mitigate it. This is only one big obstacle the scientists face. There are still many major milestones that need to be reached, but advances and reports so far are promising – we’re getting there: tremendously large, clean and safe energy.