Fusor. (Source: Wikipedia.org)

A device that uses a strong electric field to accelerate ions to its centre where they fuse. A fusor consists of spherical electrodes immersed in each other. Ions accelerated at the outer anode are directed towards the inner cathode but because the inner cathode is shaped like a wire mesh, the ions fly through it to the centre of the device where they can meet their counterparts and fuse. The fusor is a relatively compact, simple and low-cost device. It is used for fusion research or as a neutron source.