When this beam struck a target of erbium deuteride, the team detected neutrons coming from the target with precisely the energy expected if they were generated by the nuclear fusion of two deuterium nuclei.
An alternative is Inertial confinement fusion (ICF), in which fusion of nuclei is initiated by heating and compressing a fuel target, typically in the form of a pellet containing deuterium and tritium contained in a device called a hohlraum (hollow space or cavity) using an extremely powerful laser.