Kinetic characteristics of ions in an inertial electrostatic confinement device

Abstract

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 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.

Optical emission from a ‘beam mode’ transparent cathode glow discharge

“…The grid-focussing effect we observed at discharge conditions will also operate at lower pressures, where ion flow can recirculate through an IEC cathode, and where ion sources are often placed peripherally e.g. references [18,24,25,30]. Our observations illustrate the importance of good grid alignment where multiple electrodes are used, as has been demonstrated for more complicated arrangements in spherical geometry [16,17,21].…”

“…Glow discharges in which ions and neutrals are significantly energetic are relatively uncommon, and have mostly been studied in IEC for non-power fusion applications. Early IEC work was conducted at lower pressures [3][4][5][6], but since a simple discharge source was developed at the University of Illinois in the 1990s [7][8][9][10][11] research has been directed towards better understanding and improving the efficiency of benchtop fusion devices [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31], since near-term applications increase with performance. These generally use a spherical or cylindrical hollow wire-grid cathode, operated either as self-sustained 'transparent cathode' discharge (TCD) or with an ionisation source.…”

Effect of Positive Polarity in an Inertial Electrostatic Confinement Fusion Device: Electron Confinement, X-ray Production, and Radiography

“…Electrostatic particle-in-cell (PIC) simulation have been carried out using XOOPIC code 27,28 to characterise the particle behaviour inside the cylindrical IECF device. The code has the ability to operate in two-dimensional space in both Cartesian and cylindrical coordinate systems, including threedimensional velocity space.…”

“…In that case, the ions re-circulate along certain channels across the cathode grids and the electrons move in the opposite direction towards the wall of the chamber. Confinement of secondary electrons also takes place inside the potential well along-with the ions which results in the formation of multiple virtual electrodes inside the cathode 28 . However, if the polarity of the central grid is altered, i.e., the grid is biased with positive voltage then, this time the electrons oscillate across the grid openings and the ions move towards the wall region.…”