APPLICATION TECHNOLOGY

“There are also approaches where there is not a hohlraum, and the lasers shine directly on the capsule, which get dropped in at 10 times a second. This is called Direct Drive. However, even if there is no hohlraum, the fuel pellet likely needs some kind of protecting shell as it is dropped into the chamber. An advantage of IFE (compared to magnetic fusion) is that it is a pulsed system, and you would not have a continuous supply of deuterium/ tritium. This reduces the tritium inventory needed within the reactor system significantly.”

Whether a practical system uses hohlraums or some other containment, a huge number will be needed, if they are consumed at 10 per second. It would represent a big opportunity for manufacturers of such fixings – to keep the DT pellet in place momentarily while the lasers impinge on them.

The hohlraums being used by the NIF today are peanut-sized, gold-plated, open-ended cylinders with a peppercorn-sized pellet containing deuterium and tritium. Then, they fire a laser – which splits into 192 finely tuned beams that, in turn, enter the hohlraum from both ends and strike its inside wall. “We don’t just smack the target with all of the laser energy all at once,” points out Annie Kritcher, a scientist at NIF. “We divide very specific powers at very specific times to achieve the desired conditions.”

As the chamber heats up to millions of degrees under the laser barrage, it starts producing a cascade of x-rays that violently crush the fuel pellet. They shear off the pellet’s carbon outer shell and begin to compress the hydrogen isotopes inside – heating them to hundreds of millions of degrees – squeezing and crushing the atoms into pressures and densities higher than the centre of the sun.

When NIF launched in 2009, the fusion world record belonged to the Joint European Torus (JET) in the United Kingdom. In 1997, using a magnet-based method called a tokamak, scientists at JET produced 67 percent of the energy they put in. That record stood for over two decades until late 2021, when the NIF reaching 70 percent. In its wake, many laser-watchers whispered the obvious question – could NIF reach 100 percent?

But fusion is a notoriously delicate science, and the results of a given fusion experiment are difficult to predict. Tiny, accidental differences in the set-up – from the angles of the laser beams to slight flaws in the pellet shape – can make immense differences in a reactions outcome. It’s for that reason that each NIF test, which takes about a billionth of a second, involves months of meticulous planning.

“All that work led up to a moment just after 01:00am on Monday 5th December, when we took a shot… and as the data started to come in, we saw the first indications that we’d produced more fusion energy than the laser input,” said NIF Scientist Alex Zylstra.

“To be honest…we’re not surprised,” said Mike Donladson, a systems engineer at General Fusion, a Canadian-based private firm that aims to build a commercially viable fusion plant by the 2030s. “I’d say this is right on track. It’s really a culmination of lots of years of incremental progress, and I think it’s fantastic.”

These numbers only account for the energy delivered by the laser – omitting the fact that this laser, one of the largest and most intricate on the planet, needed about 300 megajoules from California’s electric grid to power on in the first place.

“The laser wasn’t designed to be efficient,” said LLNL Scientist Mark Hermann. “The laser was designed to give as much juice as possible.” Balancing that energy-hungry laser may seem daunting, but researchers are optimistic. The laser was built on late 20 th century technology, and NIF leaders say they do see a pathway to making it more efficient and even more powerful. Even if they do that, experts need to work out how to fire repeated shots that gain energy. That’s another massive challenge, but it’s a key step toward making this a viable base for a power plant.

“Scientific results like today’s are fantastic,” states Donaldson. “We also need to focus on all the other challenges that are required to make fusion commercialisable.”

Whilst inertial fusion seems to have taken a lead over MCF, whichever form of inertial fusion becomes viable, it will need hohlraums or holders in their millions – particularly if they are consumed at 10 per second. This could represent a huge opportunity for the fixings business, as this will be the limit rather than the availability of fuel. The shovel becomes the focus rather than the coal and one hopes it would be ‘goodbye’ to coal – and the other fossil fuels – forever.