Fusor — example of electrostatic confinement. (Source: Wikipedia.org)

A concept that uses a strong electrostatic potential to accelerate ions to the centre of the device where they fuse. The simplest type of electrostatic confinement is a fusor, composed of two concentric spherical electric grids. Ions are accelerated by the potential difference between the grids to the centre of the fusor where they can collide and fuse. Fusors are compact and simple devices that are used as neutron sources. Other concepts such as the Polywell or Penning trap use a magnetic field to hold electrons to create a potential well for ion acceleration.