A research team at Osaka University has investigated a new method for generating nuclear fusion power. They are showing that the relativistic effect of ultra-intense laser light improves upon current “fast ignition” methods in laser-fusion research to heat the fuel long enough to generate electrical power. These findings could provide another spark for laser fusion, ushering in a new era of carbonless energy production.

Schematic image of fast ignition laser fusion utilizing relativistic effects of ultra-intense laser light. Image Credit: Osaka University. Click image for the largest view.

The team’s research paper has been published in the journal Nature Communications. At this writing the paper is not behind a paywall and it is well worth the read.

Current nuclear power uses the fission of heavy isotopes, such as uranium, into lighter elements to produce power. But fission power has major concerns, such as spent fuel disposal and the risk of meltdowns. A promising alternative to fission is nuclear fusion. Like all stars, our sun is powered by the fusion of light isotopes, notably hydrogen, into heavier elements. Fusion has many advantages over fission, including the lack of hazardous waste or risk of uncontrolled nuclear reactions.

However, getting more energy out of a fusion reaction than was put into it has remained an elusive goal. This is because hydrogen nuclei strongly repel each other, and fusion requires extreme heat and pressure conditions – like those found in the interior of the sun, for instance – to squeeze them together. One method, called “inertial confinement” uses extremely high-energy laser pulses to heat and compress a fuel pellet before it gets the chance to be blown apart. Unfortunately, this technique requires extremely precise control of the laser’s energy so that the compression shock waves all arrive at the center simultaneously.

Now a team led by Osaka University has developed a modified method for inertial confinement that can be performed more consistently using a second laser shot. In “super-penetration” fast ignition, the directly irradiated second laser produces fast-moving electrons in dense plasma that heat the core during compression to trigger fusion.

First author Tao Gong said, “By utilizing the relativistic behavior of the high-intensity laser, the energy can be reliably delivered to fuel in the imploded plasma aiming the ignition.”

The fuel for this method, which is usually a mix of the hydrogen isotopes deuterium and tritium, is easier to obtain than uranium, and becomes harmless helium after fusion.

Senior author Kazuo Tanaka explained further, “This result is an important step towards the realization of laser fusion energy, as well as for other applications of high-energy density physics, including medical treatment.”

This is surprising news. Your humble writer was only aware of the U.S. laser ignition facility. It great news indeed that there is a second effort underway with an innovative outlook that is making some progress.

It does look like a double strike of the lasers, first to heat and then another to further heat and compress might be a path well worth more research. Perhaps the one day the heat released will be more energetic than the power used to set the reaction off. It does look like this team has hit an innovation worthy of much more attention and funding.


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