The reaction is fueled with deuterium, a widely available non-radioactive hydrogen isotope composed of one proton, one neutron, and one electron. The deuterium is confined in the space between the atoms of a metal solid such as erbium or titanium. Erbium can indefinitely maintain 10 cm deuterium atoms (deuterons) at room temperature. The deuteron-saturated metal forms an overall neutral plasma.  The electron density of the metal reduces the likelihood that two deuterium nuclei will repel each other as they get closer together.
A dynamitron electron-beam accelerator generates an electron beam that hits a tantalum target and produces gamma rays, irradiating titanium deuteride or erbium deuteride. A gamma ray of about 2.2 megaelectron volts (MeV) strikes a deuteron and splits it into proton and neutron. The neutron collides with another deuteron. This second, energetic deuteron can experience screened fusion or a stripping reaction.
Although the lattice is notionally at room temperature, LCF creates an energetic environment inside the lattice where individual atoms achieve fusion-level energies. Heated regions are created at the micrometer scale.