Role of thermionic emission in the formation of negative electric potential and oscillations in low pressure discharges

Because of the larger surface-area-to-volume ratio, micro-discharges can be sustained by surface emission processes. If the cathode is heated, micro-discharge can be sustained mainly by thermionic emission. However, we still knew little about how this kind of plasma is ignited and sustained. In order to explore the breakdown process of dc-driven micro-discharge sustained by thermionic emission, a one-dimensional implicit particle-in-cell/Monte Carlo collision method is adopted, coupled with the external circuit and thermionic emission model. The breakdown process of micro-discharge lasts about 8μs, and this process can be roughly divided into two phases, i.e., pre-breakdown and breakdown phase. The dynamic plasma parameters during the evolution process are analyzed, such as particle density, electron energy distribution function, electric potential, average particle temperature, and particle current density. The plasma electrical characteristics as well as the article and power balance, are also presented to show the evolutionary features of the whole gas breakdown process.

Section: Introductionmentioning

confidence: 99%

Numerical characterization of the breakdown process of dc-driven micro-discharges sustained by thermionic emission

Zhong¹,

Wu²,

Li³

et al. 2022

“…Eliseev et al [32] simulated the DC discharge of argon at atmospheric pressure and found that when the surface temperature is high enough, the glow discharge will transform into an arc discharge. Volkov et al [33] investigated the effect of cathode TE on the negative potential formed at the cathode (LaB 6 sheet) in both high-and low-pressure modes. The unstable behavior, cathodic prepotential reversal and self-excited plasma parameters oscillate at higher rather than low voltage.…”

Section: Introductionmentioning

confidence: 99%

Breakdown mode and parameter space of micro-discharge sustained by thermionic emission

Zhong

et al. 2023

Gas breakdown driven by thermionic emission(TE) in a microgap to produce lowtemperature plasma was studied by one-dimensional implicit Particle-in-cell/MonteCarlo collision(PIC/MCC) model. The influence of background gas pressure, externaldriving voltage, cathode temperature and discharge gap on argon glow micro-dischargein the parallel plate was simulated. Different parameters and conditions have differenteffects on the gas breakdown at small size. The discharge gap of 100’s μm has littleinfluence on gas breakdown and only changes the plasma distribution. As the appliedvoltage increases, the gas changes from non-breakdown mode to breakdown mode, andgas breakdown is more sensitive to the applied voltage than the gas pressure at lowvoltages. In all breakdown modes, the gas pressure hardly changes the plasma evolutioncharacteristics. At appropriate cathode temperatures, the density of electrons and ionsincreases rapidly, forming a stable sheath and the equivalent resistance of the dischargegap becomes smaller as the temperature rises, the plasma is in abnormal glow discharge.

“…Here, the cathode is made of material with a low work function (LaB 6 [35,36]), and the working substance is supplied from the crucible. In [37], the role of thermionic emission in the formation of negative electric potential and oscillations in such a discharge was investigated.…”

Section: Introductionmentioning

confidence: 99%

Plasma mass separation in configuration with potential well

Liziakin¹,

Антонов²,

Smirnov³

et al. 2021

Self Cite

The details of the charged particle separation by mass in the configuration with axial magnetic and radial electric fields are studied. The radial electric field, oriented to the discharge axis, is induced in a background reflex discharge with a hot cathode (−550 V, 8–14 A). The plasma source is based on a hot cathode arc discharge with independent metal vapor injection (18–21 V, 30 A) was situated at 18 cm from the axis. It was shown that the separated Ag + Pb mixture is transported across the magnetic field under the background discharge electric field. Effective separation is possible in such a system, while the separation coefficient increases from 4.9 to 6.2–8.4 when the mixture injection point is moved away from the background discharge axis from 18 to 23 cm. The effect of mixture injection on the plasma potential distribution is examined. It was shown that the presence of a plasma source of separated substances can cause a local (1–2 cm) distortion of the background plasma potential profile. Such distortion, as well as fluctuations of the background plasma potential, can significantly affect the width of the deposited spots of separated substances.