Kinetic characteristics of ions in an inertial electrostatic confinement device

The kinetic analyses are quite important when it comes to understanding the particle behavior in any device as they start to deviate from a continuum nature. In the present study, kinetic simulations are performed using the particle-in-cell method to analyze the behavior of ions inside a cylindrical inertial electrostatic confinement fusion (IECF) device which is being developed as a tabletop neutron source. Here, the lighter ions, like deuterium, are accelerated by applying an electrostatic field between the chamber wall (anode) and the cathode (cylindrical gridded wire), placed at the center of the device. The plasma potential profiles obtained from the simulated results indicate the formation of multiple potential well structures inside the cathode grid depending upon the applied cathode potential (from $-1$ to $-5$ kV). The ion density at the core region of the device is found to be of the order of ${10}^{16}{\text{m}}^{-3}$, which closely resembles the experimental observations. Spatial variation of ion energy distribution function has been measured in order to observe the characteristics of ions at different cathode voltages. Finally, the simulated results are compared and found to be in good agreement with the experimental profiles. The present analysis can serve as a reference guide to optimize the technological parameters of the discharge process in IECF devices.

Figure 1

Schematic diagram of the cylindrical IECF device with different accessories.

Figure 2

Cross section of simulation region with the cathode grid.

Figure 3

Observation of recirculation of ions in both (a) simulated profile and (b) in experiment.

Figure 4

Surface plot of potential profile at $-1$ kV cathode voltage.

Figure 5

Simulated potential profiles (blue lines) compared with the experimental ones (dashed red lines) during (a) $-1$ kV, (b) $-2$ kV, (c) $-3$ kV, (d) $-4$ kV, and (e) $-5$ kV cathode voltage.

Figure 6

Contour plot of ion density at $-1$ kV cathode voltage.

Figure 7

Simulated ion density profiles (blue lines) compared with the experimental ones (dashed red lines) during (a) $-1$ kV, (b) $-2$ kV, (c)$-3$ kV, and (d) $-4$ kV cathode voltage.

Figure 8

Comparison of potential profile of 8 (dashed blue lines) and 16 gridded (red lines) cathodes in both (a) simulated and (b) experimental plots during $-2$ kV cathode voltage operation.

Figure 9

Comparison of ion density profile of 8 (dashed blue lines) and 16 gridded (red lines) cathodes in both (a) simulated and (b) experimental plots during $-2$ kV cathode voltage operation.

Figure 10

Different positions (zones) at which IEDF is measured is shown in panel (a). Simulated profiles of IEDF at cathode voltages $-1, -2$, and $-3$ kV along $x$ component of velocity in three different zones are shown in panels (b)–(d), respectively.