Kinetic simulation of direct-current driven microdischarges in argon at atmospheric pressure

Abstract

A one-dimensional, implicit particle-in-cell Monte Carlo collision model is used to simulate the plasma kinetic properties at steady state in a parallel-plate direct current argon glow microdischarge under various operating conditions, such as driving voltage (30 − 1000 V) and gap size (10 − 1000 µm) at atmospheric pressure. First, a comparison between rf and dc modes is shown for the same pressure, driving voltage and gap spacing. Furthermore, the effect of gap size scaling (in the range of 10 − 1000 µm) on the breakdown voltage, peak electron density and peak electron current density at breakdown voltage is examined. The breakdown voltage is lower than 150 V in all gaps considered. The microdischarge is found to have a neutral bulk plasma region and a cathode sheath region with size varying with the applied voltage and the discharge gap. In our calculations, the electron and ion densities are of the order of 10 18 − 10 23 m −3 , which is in the glow discharge limit, as the ionization degree is lower than1%. The electron energy distribution function (EEDF) shows a two-energy group distribution at a gap of 10 µm, and a three-energy group distribution at larger gaps such as 200 and 1000 µm, emphasizing the importance of the gap spacing in dc microdischarges.

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

“…The SEE is related to the electric field strength of the discharge gap and the energy of the particles. Its emission coefficient is related to many factors, such as electrode material, primary electron energy, and electrode surface state (clean or dirty) [1,30]. The emission coefficient is β = 0.1 [31,32].…”

“…Micro-discharge is the plasma generated in a small length of the order of hundreds of microns [1][2][3]. Because it can generate stable and self-sustaining plasma under atmospheric pressure, the micro-discharge has received intense research efforts in recent decades [4].…”

“…Because it can generate stable and self-sustaining plasma under atmospheric pressure, the micro-discharge has received intense research efforts in recent decades [4]. In fact, the micro-discharge has significant features such as small reaction size, highvoltage stability, and high particle density [1,4], it has a wide range of applications in light sources, optical switches, plasma medicine, material synthesis, environmental applications, and chemical sensing [1,[5][6][7]. It has been known that the cathode surface-emission processes play an essential role in the microdischarge [4,8], which includes thermionic emission, field electron emission, and secondary electron emission (SEE).…”

Numerical investigation of plasma behavior in a micro DC ion thruster using the particle-in-cell/Monte Carlo collision (PIC/MCC) method

“…The PIC-MCC is based on first principles and minimizes the number of assumptions made on the calculation [38]. This method has been widely employed in the analysis of various kinds of plasma discharge such as direct-current driven microdischarges [39,40], dielectric barrier discharge [41], micro-hollow cathode discharges [35,[42][43][44] etc. The PIC-MCC method proceeds as follows: first, the distributions of some 'macro particles' that represent a large number of real charged particles determines the charge-current density in the computational domain; second, we can accumulate the particle charge or current to grids, thus electromagnetic field in the plasma can be obtained by solving Maxwell equations; then the velocities and positions of all particles are updated based on the electric field and magnet field using the leap-frog algorithm [45], during which the collisions between particles and boundary conditions are dealt with; finally, plasma parameters such as particle number densities and plasma potential can be obtained, and the overall motion of the plasma is obtained by the sum of all particle orbits.…”

Simulation study of the influences of beryllium on the tokamak start-up process

“…In this work a PIC–MCC method (Lapenta, Brackbill & Ricci 2006) is used. This method which was developed previously has been applied to different plasma areas, such as microdischarges in the low-temperature plasma (Jiang, Zhang & Bogaerts 2014; Zhang, Jiang & Bogaerts 2014), magnetized capacitively coupled plasma (Yang et al. 2017 a , b ; Wu et al.…”