Fast Ignition Fusion

Conventional inertial confinement fusion (as described in the confinement section) uses shock waves launched by the lasers/radiation to travel into the dense fuel to heat it to fusion temperatures. This is broadly analogous to a diesel engine in which the fuel is compressed until it ignites spontaneously.

Conventional Inertial Confinement Fusion

Conventional inertial confinement fusion

This puts a very high requirement on symmetry of the spherical capsule and of the distribution of energy contained within the driving lasers/radiation. If these are not symmetrical then different parts of the capsule will reach maximum density at different times and the capsule will break apart without the fusion process taking place.

A new scheme separates the compression and heating phases much like a petrol combustion engine. In the petrol engine the fuel is compressed by the piston and then ignited via the spark plug. In the case of fast ignition, the driving lasers are the pistons, compressing the fuel to high density around the tip of a gold cone.

Fast Ignition Fusion

Fast ignition fusion

The spark plug in this case is a multi kj, short pulse laser which is injected into the tip of the gold cone. When the laser interacts with the gold, plasma is formed and energetic electrons produced travel into the dense fuel to deposit their energy and raise the fuel to fusion temperatures.

Stages of Fast Ignition