NIF: US lab takes further step towards nuclear fusion goal

Image source, Philip Saltonstall

US physicists have confirmed that they achieved a stage in nuclear fusion last year.

fusion power promises an unlimited source of clean energy, which is why there is a longstanding effort to crack it.

When fusion reactions become the main source of heating in the process, it's called burning plasma.

Experiments were carried out at the National Ignition Facility in California.

A heavy chemical element is split into lighter ones in the process of nuclear energy. A heavier one can be made by combining two light elements.

Nuclear fusion has been a problem for researchers since the 1950s. The effort to build a star on Earth has been likened to the process that powers the Sun. Nuclear fusion is not a commercially viable energy source.

The problem is not getting the reactions going, it's getting more energy out of the fusion process than you put in.

NIF uses a powerful laser to heat and compress hydrogen fuel inside a capsule. The 192 beams from this laser are directed towards a peppercorn-sized capsule containing different forms of the element hydrogen.

The fuel is compressed to 100 times the density of lead and then heated to 100 million degrees Celsius, which is hotter than the center of the Sun. The gas generated by heating the target is called plasma. The parts of the atom known as atomic nuclei are stripped from them in the plasma. The energy can be generated in the process.

Image source, LLNL

When fusion reactions become the dominant source of heating in the plasma, the heat provides the energy for even more fusion.

For the first time in any fusion research facility, more fusion energy is emitted from the fuel than is required to initiate the fusion reactions.

Challenges in controlling the plasma shape have limited previous attempts to reach this stage. Researchers at NIF came up with an improved experimental design involving the use of capsule that can hold more fuel and absorb more energy.

The energy is lost from the process when it is achieved. This is the last milestone before the bigger goal ofignition and self-sustaining energy production.

The fusion reactions release more energy than the laser can deliver.

In August of 2021, NIF reported that 70% of the way to ignition had been reached.