Consolidated electron emission effects in an IEC device

Gridded inertial electrostatic confinement (IEC) devices are of interest to the research community for their multiple near-term applications. The number of applications of an IEC device increases with increasing fusion reaction rate. However, all attempts to improve the fusion reactivity of the IEC device have resulted in a linear or less than linear response with the power supply current. This work is geared toward determining the reasons for the observed response of the IEC device. Such an understanding would help formulate new ways to improve the efficiency of the device. Experiments were conducted with single loop grids built from different materials (Re and W25%Re) to study the electron emission from the cathode in an IEC device. A single loop grid produces a (~line) cylindrical fusion source and was used to study the electron emission from cathode. Electron emission from the cathode increases non-linearly due to the presence of multiple sources (secondary electron emission, field emission and photoemission), as a result of which the ion current increases in a less than linear fashion with the power supply current. The ion recirculation current equation has been updated to accommodate various electron contributions. Several techniques to mitigate the electron emission from the cathode are suggested in this paper.