Abstract: A method of producing fusion reactions comprises the steps of bringing deuterium ions from an ion source to run in a substantially closed path for accumulation of the ions to a predetermined density, whereupon the ions are deflected towards a reaction center inside this closed path. An apparatus for a fusion reactor includes two annular, coaxially disposed magnets (12,20) which are disposed to produce magnetic fields in a vacuum tank. The inner magnet (20) produces a homogenous field transversely to the plane in which deuterium ions are intended to circulate prior to reaction, and the outer magnet (12,14) produces an inhomogenous field which decreases outwardly in radial direction and is also directed transversely to said plane. Electrodes (16,18) are provided to produce a radial electric field in the area having said inhomogenous magnetic field, which electric field is directed transversely to this inhomogenous field.