Effects of Grid Cathode Structure on a Low-Input-Power Inertial Electrostatic Confinement Fusion Device

The effects of grid cathode structure on a low-input-power inertial electrostatic confinement fusion (IECF) device were studied to achieve a high neutron production rate (NPR). An increase in geometric transparency of the grid cathode by decreasing the number of wire rings is known to mean that the recirculation ion current is increased. We expected that this increase would contribute to an increase in the NPR. However, our experimental results showed that the NPR in the low-input-power IECF device (V = 10.0-30.0 kV, I = 40.0 mA) increased by decreasing the transparency. We clarified this tendency by analyzing the equipotential lines near the grid. As a result, we found that the distortion of these lines near the grid was lessened by decreasing the transparency. Lessening the distortion of these lines, rather than increasing the in recirculation ion current, was effective in increasing the NPR in the low-input-power IECF device. In addition, we find that the effect of mitigating these lines depended on the applied voltage.