An experiment on the formation of virtual electrode and ion sheath characteristics has been carried out in a hot cathode discharge plasma produced inside a cylindrical inertial electrostatic confinement fusion device. The plasma parameters such as electron temperature and plasma density are evaluated by using a Langmuir probe. Transition from a single potential well to multiple potential wells, i.e., virtual electrodes inside the cathode grid, is observed when the bias voltage applied to the cathode is increased from –1000 to –5000 V. An emissive probe has been used for the measurement of plasma potential due to its greater accuracy than the conventional Langmuir probe. Ion sheath potential structures and presheath characteristics for different cathode potentials have been investigated using the emissive probe and are found to be consistent with the Debye sheath model. A detailed discussion on the obtained results has been presented in this paper.
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.
The basic interest of studying the ion flow dynamics in a disk-shaped inertial electrostatic confinement fusion (IECF) device is to achieve an explicit condition where large fusion products are possible from such a portable device, and then, it can be used for a wide range of applications. We modified the existing IECF device by introducing two external grids along with the central grid and investigated the plasma properties using the Langmuir probe technique at different operating voltages in this new configuration of the device. By taking measurements of the plasma properties throughout the chamber, the device is optimized for better ion confinement and ion flow behavior. A well-established comparison of plasma properties, such as ion density and potential in this new arrangement, has been carried out with the single-gridded IECF system. The triple grid arrangement switches to a lower working pressure region, and hence high energetic ion beams are procured. Because of the different discharge mechanisms, variations in plasma potential profile and ion confinement processes are observed when compared to the single-gridded IECF device.
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