Contribution of surface-wave (SW) sustained plasma columns to the modeling of RF and microwave discharges with new insight into some of their features. A survey of other types of SW discharges

Abstract

maintenance E-field sustaining the discharge comes out as an internal parameter, i.e. it is operator independent, in contrast to what is generally believed whatever the kind of E-field sustained discharges; (ii) the smaller the volume in which power is absorbed with respect to the volume in which it is spent, the higher the intensity of the maintenance E-field: this leads to higher atomic (molecular) excitation rates inside than outside the absorption region (such is the case in microdischarges); (iii) the value of θ L varies significantly with the SW field frequency, decreasing with increasing frequency from the RF domain to that of microwaves; (iv) the power lost θ L , which is the power cost to sustain an electron-ion pair in an SWD, can serve to evaluate the efficiency of the various discharge regimes (diffusion and volume recombination with either single or step-wise ionisation); (v) the EM E-field intensity under the electron cyclotron resonance (ECR) condition passes through a minimum, not a maximum, contrary to what is generally claimed; (vi) similarity laws, originally derived with DC discharges, are generalized to include RF and microwave discharges. For example, θ A /p as a function of pR (p is the gas pressure and R the discharge tube inner radius) replaces advantageously the widely used E/p versus pR similarity law since θ A is more easily measured than E 2 and further it prevents considering the latter as an external parameter, etc. The important EM power loss due to space-wave radiation in the immediate vicinity of the SW launching interstice has escaped the attention of those working with SWDs. This effect is documented experimentally, showing in addition that it can be significantly reduced by using a cylindrical conducting enclosure, coaxial with the discharge tube, having a small enough radius such that it acts as a circular waveguide at cut-off. A survey limited to underlining specific properties and innovative features of SWDs other than plasma columns is conducted, which include planar SWDs and microwave discharges of the torch type sustained at atmospheric pressure, for instance, with the TIA and TIAGO E-field applicators: it is shown that their flame actually results from an SWD.

Effect of Plasma-Activated Medium and Water on Replication and Extracellular Virions of Herpes Simplex Virus-1

“…Variation of gas-flow speed and/or applied microwave power led to different discharge properties including plasma column length, temperature of neutral particles in the plasma (called plasma gas temperature), and concentration of charged and excited particles. We used applied wave powers of 13, 15, or 20 W in the experiments, with reflected power kept under 1 W. Discharge conditions were chosen so that plasma torch length was sufficient to treat samples (12,13, and 17 mm at wave powers of 13, 15, or 20 W, respectively) and plasma gas temperature did not exceed 40°C.…”

“…It is known that the properties of SWD at the same axial position measured from the plasma column end are similar. 13 That is why for the plasma treatment we have used the last 2-3 mm of the plasma torch to be in contact with the sample or the liquid surface like in the previous work. 14…”

Electromagnetic energy rotation along plasma-metal interface in cylindrical waveguides initiated by azimuthal surface waves

“…The presented analysis of electromagnetic energy transfer in cylindrical plasma-filled waveguides can be of interest, first of all, for plasma electronics, 17 plasma production in gas discharges, 24,27,28…”

Higher Radial Modes of Azimuthal Surface Waves Above the Upper-Hybrid Frequency in Cylindrical Waveguides Partially Filled by Plasma

“…Surface type electromagnetic waves in plasmas are known to have some advantages as compared to volume waves in technological applications [1][2][3]. Their excitation does not need to spend energy for creating the wave structure in the plasma core as it takes place in the case of volume waves.…”

“…In (1), m is azimuthal wavenumber,  is azimuthal angle and r is radial coordinate in cylindrical coordinates,  is wave angular frequency, and t is a time. The results of [3,4] were generalized in [5] to the case of higher radial modes in low-frequency (LF) range is the lower hybrid frequency,  e and  e are electron cyclotron and plasma frequencies, respectively.…”