Confinement Limitations in Gridded Inertial Electrostatic Confinement Fusion Devices

Abstract

Multiple improvements to the Inertial Electrostatic Confinement (IEC) fusion concept are presented. Prior efforts have consisted of considerable theoretical effort and numerous ground experiments resulting in the fusion of D-D, D-T, and DHe 3 at rates on the order of 10 10 reactions per second. Theory developed in the paper shows that prior experiments which observed a linear relationship between reaction rate and background pressure were ‘confinement’ limited. With improved ion confinement, the reaction rate and the pressure should decouple at high pressure where the beam-beam reactions are not yet dominant. Highly efficient beam-beam reaction rates are found to dominate the total reaction rate as ion lifetime is increased. The ion lifetime is limited mainly by collisions with background particles and by defocusing. The naturally low background pressure available in space environment effectively eliminates background pressure as a constraint on ion lifetime, leaving defocusing as the main ion lifetime limiter. In order to improve ion confinement, multiple grids are introduced to produce focusing channels for ions. The other main loss mechanism is electrons streaming from the core region to the anode. An additional grid is placed within the cathode, providing a central trap for core electrons. Theory predicts that improvements in confinement should be verifiable using existing relatively high pressure ground systems and the proposed experiment design is presented. The build-up of space charge in the focusing lenses is used to estimate improvements in confinement from <10 passes to the order of 1000 passes, boosting the performance of IEC reactors by 2 orders of magnitude, yielding in the near-term, fast neutron source suitable for medical, security, research and industrial applications.