He nucleus, more commonly called an alpha particle, interacts strongly with surrounding material and stops rapidly, depositing 3.5 MeV of heat close to the site of the fusion reaction. The neutron, which has no charge, can only slow down by colliding with other nuclei, transferring small amounts of kinetic energy to each just as a cue ball when it hits a pool ball, until finally the neutron is absorbed by some atom's nucleus, potentially several meters from the original fusion reaction. In an IFE power plant, the neutrons stop in a thick blanket of material that contains 6 Li lithium , the material that breeds the tritium that provides the fusion fuel. Nuclear processes in the blanket generate another 3.2 MeV of energy for each fusion reaction. Even at six-trillion fusion reactions per second, the RTNS makes less than 2 watts of fusion power, while consuming thousands of times as much electricity.
High temperatures provide the key to driving fusion.
In gases, temperature provides a measure of the kinetic energy stored in the random motion of atoms, and the higher the temperature, the higher the velocities that the atoms reach. Heating gases above a few thousand degrees generates collisions strong enough to strip electrons from nuclei, transforming the gas into an ionized plasma. At extremely high temperatures, tens of millions of degrees, some of the nuclei can reach speeds as high as the deuterium nuclei in the RTNS, and collisions of deuterium and tritium nuclei can begin to cause fusion reactions. Further increases in plasma temperature can increase the fraction of the collisions with energies greater than 110,000 eV, and the fraction of collisions resulting in D-T fusion. Fusion reactions in turn create high-velocity alpha particles, which stop and deposit their kinetic energy, heating the surrounding plasma.