Formation of multiple anodic fire spots inside an electrostatic cavity

Abstract

Charged particles exhibit self‐organized behaviour during the discharge state transitions inside an electrostatic cavity, along with the energy redistribution in different coherent modes with progressive anode potential. Multiple sheath formations around the spherical metallic ball anode placed inside the cavity transit to intensely glowing multiple anode spot formations (fireballs) on the anode surface with progressive anode potential. The intensely glowing anode spots reorganize over the anode surface and multiply quickly on increasing the anode potential. The nonlinear analysis of the fluctuating discharge current reveals the presence of self‐organized criticality (SOC) during different states of discharge along with a strong memory effect within (10–104) time lags in every state of discharge. The multiple anode spots exhibit long‐range correlation in the absence of a magnetic field, indicating SOC behaviour. The present study investigates energy distribution among the coherent modes of discharge through the application of the Empirical Mode Decomposition technique. The analysis indicates that the introduction of a magnetic field results in the interchange of coherent modes carrying most of the energy during multiple spot formations. The present experimental configuration produces stable multiple coherent modes along with the evolution of anodic sheath layers in the absence and then in the presence of the magnetic field. Relating SOC with such discharge transitions may help to understand the relation between complex structure formations in plasma with nonlinear aspects of glow discharge, which is of vital importance in the investigation of complexities in space plasma.

Study of nonlinear characteristics in hollow cathode discharge in unmagnetized plasmas

“…In Figure 9a and Figure 9b, 1 0 1 0 1 2 follows in P2 and 1 0 1 1 1 2 patterns observed in the P3 and the pattern continues for the whole signal which signifies the regular MMO patterns in the discharge state at V dc ∼ 370 V. Such patterns indicate the occurrence of ionization instability. [25] On increasing the discharge voltage, the pattern turns significantly irregular at V dc ∼ 400 V, as shown in Figure 10a with 1 0 1 4 1 4 , 1 0 1 5 1 4 , and so on. Such irregular patterns are also observed in the P2 and P3 as shown in Figure 10a, b.…”

“…Hollow cathode discharges (HCD) are generating high-density plasma in comparison to the planner cathode glow discharge by electrostatically confining the oscillating charges for a longer time. [1][2][3][4][5] The HCD plasma discharges have been studied theoretically and as well as experimentally through different parametric changes like discharge voltage variation, working gas pressure, varying the inter-electrode distance, and introducing an external magnetic field. [6,7] The electrostatic confinement in the hollow cathode source leads to efficient ionization.…”