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Why is laser efficiency important for inertial confinement fusion power plants?

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3D illustration of the interior reaction chamber of a tokamak fusion reactor, showing a large, cylindrical, metallic structure with curved walls and bright light panels. — fusion reactor A tokamak is a device used in nuclear-fusion research for magnetic confinement of plasma.

In an inertial confinement fusion (ICF) power plant, laser efficiency is critical because the overall economic and operational viability of the reactor depends on the net energy balance.

For a reactor to be practical, it must produce significantly more energy than is consumed by its systems. The process requires a driver—typically a high-power laser—to compress a fuel pellet to extreme densities and temperatures. The ratio of the fusion energy released by the pellet to the energy delivered by the driver is known as the pellet gain.12

High pellet gains (often 100 or more) are required to compensate for the inefficiencies inherent in the system, including the energy lost during the conversion of electricity into laser light and the subsequent conversion of that light into the energy that implodes the target. If the laser system is inefficient, the energy required to drive the reaction may approach or exceed the energy generated by the fusion process, rendering the power plant incapable of producing a net surplus of electricity in a cost-effective manner.23