Nov 26, 2020 16:42:00

'Fusion power generation' is a big step toward realization, laser fusion approaches an intermediate milestone

Fusion power generation has been said to be a

future technology that produces clean energy, but in recent years, great progress has been made in its research and development. The intermediate milestone in laser fusion power generation is said to be in 'plasma combustion,' but the National Ignition Facility (NIF) in the United States has announced that it is reaching this intermediate milestone. ..

Laser fusion reactor approaches'burning plasma' milestone | Science | AAAS
https://www.sciencemag.org/news/2020/11/laser-fusion-reactor-approaches-burning-plasma-milestone

As of 2020, most of the energy on earth is covered by fossil fuels, but fossil fuels are finite and emit a lot of greenhouse gases, so the development of alternative sustainable energy is urgently needed. I am. Fusion energy is considered as one of the possibilities.

Fusion energy refers to the energy obtained by fusing atoms with light and small nuclei such as hydrogen and helium, and nuclei of isotopes. Nuclear fusion power generation can be broadly divided into the ' magnetic confinement method ' that generates strong magnetic field lines and confine plasma, and the ' inertial confinement method ' that causes nuclear fusion by irradiating fuel with a powerful laser. Several research institutes are developing these methods, and the international thermonuclear experimental reactor 'ITER' to be constructed in France uses a magnetic confinement method, but construction has started but it is still a goal. It is far from realizing energy efficiency.

On the other hand, NIF is conducting fusion power generation using the inertial confinement method.

In the inertial confinement method, plasma is generated by irradiating the surface of the fuel with a laser, and at the same time, the expanding plasma is suppressed by the power of the laser to generate an

implosion . The high temperature and pressure generated by this is a mechanism for nuclear fusion of light elements inside the fuel. In order to realize this method, it is necessary to irradiate the fuel with a very powerful laser from all directions with high accuracy.

In fusion power generation using a laser, there is a method of irradiating the fuel directly with a laser, but NIF heats a small metal called hohlraum, and the fuel capsule is heated by the X-ray pulse generated at that time, and fusion occurs. We have adopted an indirect mechanism of what happens.

NIF has been conducting fusion power generation experiments since 2010, but in the first three years, only about 1 kJ of energy could be obtained with a single laser irradiation, which was far from the purpose. Researchers say they were 'overly dependent on simulations' about the situation at the time.

Researchers then upgraded the testing equipment and added neutron detectors to enable a 3D view of where the fusion reaction is taking place. The research team also tracks energy leaks to identify and resolve problems. In addition, the researchers said that the temperature rose slowly and was difficult to compress in the initial laser irradiation, so the researchers raised the temperature so that the fuel capsule could absorb more X-ray energy. And the material of the capsule has changed from plastic to dense diamond so that the fuel can be burned more efficiently.

After years of making these changes, NIF is now able to generate nearly 60kJ of energy with a single laser irradiation. According to NIF director Mark Harman, NIF will soon irradiate the laser continuously to measure 'how close the NIF is to plasma combustion'. In this measurement, the amount of energy per time is expected to be close to 100 kJ. Once the NIF reaches the threshold, fusion will be easier, Harman said.

It is still unknown whether fusion power generation will become a reality, but there are still many things to try for that purpose. 'I'm an optimist and I'll push NIF as much as I can,' said Harman, who changed the shape and type of Hohlraum and double-walled to more efficiently confine X-ray energy. He says he will challenge various ideas such as fuel capsules.