High Quality Content by WIKIPEDIA articles! A polywell device is a type of fusion reactor that traps electrons in a magnetic confinement inside its hollow center. The negatively charged electrons then attract positively charged ions, creating nuclei of sufficient speed to undergo fusion in inertial electrostatic confinement. The polywell consists of positively charged electromagnet coils that are arranged in a polyhedron called a MaGrid. Electrons are introduced from outside and are accelerated into the MaGrid due to the electric field. Within the MaGrid, magnetic fields confine most of the electrons. Those that escape are retained by the electric field. This configuration traps the electrons in the middle of the device. The electrons act as a virtual cathode (negative electric potential).