 By comparison, researchers at University of Wisconsin–Madison reported a neutron rate of up to 5×109 per second at voltages of 120 kV from an electrostatic fusor without magnetic fields.Bussard asserted, by using superconductor coils, that the only significant energy loss channel is through electron losses proportional to the surface area.He also stated that the density would scale with the square of the field (constant beta conditions), and the maximum attainable magnetic field would scale with the radius.