Oscillation modes of dc microdischarges with parallel-plate geometry

Two different oscillation modes in microdischarge with parallel-plate geometry has been observed: relaxation oscillations with frequency range between 1.23 and 2.1 kHz and free-running oscillations with 7 kHz frequency. The oscillation modes are induced by increasing power supply voltage or discharge current. For a given power supply voltage, there is a spontaneous transition from one to other oscillation mode and vice versa. Before the transition from relaxation to free-running oscillations, the spontaneous increase of oscillation frequency of relaxation oscillations form 1.3 kHz to 2.1 kHz is measured. Fourier Transform Spectra of relaxation oscillations reveal chaotic behaviour of microdischarge. Volt-Ampere characteristics associated with relaxation oscillations describes periodical transition between low current, diffuse discharge and normal glow. However, free-running oscillations appear in subnormal glow only.Comment: Submitted to: New Journal of Physic

New and versatile minature microwave plasma source

Miniature Microwave Inductively Coupled Plasma (MMWICP) source is characterized by means of Optical Emission Spectroscopy (OES) in nitrogen gas flow, which gives the information on basic plasma properties. Depending on the incident power the discharge runs in E-mode or in more efficient H-mode. The high resolution radial images of the source reveal different morphologies of different discharge modes. The measurements show an unexpected limitation in dissipated power, accompanied by spontaneous transition from H- to E-mode. The efficiency of the source is high: about 67% of incident power (P0) is deposited in the discharge, which is estimated from OES

Modelling of a miniature microwave driven nitrogen plasma jet and comparison to measurements

The MMWICP (miniature microwave ICP) is a new plasma source using the induction principle. Recently Klute et al presented a mathematical model for the electromagnetic fields and power balance of the new device. In this work the electromagnetic model is coupled with a global chemistry model for nitrogen, based on the chemical reaction set of Thorsteinsson and Gudmundsson and customized for the geometry of the MMWICP. The combined model delivers a quantitative description for a non-thermal plasma at a pressure of p = 1000 Pa and a gas temperature of Tg = 650–1600 K. Comparison with published experimental data shows a good agreement for the volume averaged plasma parameters at high power, for the spatial distribution of the discharge and for the microwave measurements. Furthermore, the balance of capacitive and inductive coupling in the absorbed power is analyzed. This leads to the interpretation of the discharge regime at an electron density of ne ≈ 6.4 × 1018 m−3 as E/H-hybridmode with an capacitive and inductive component

Modelling of a miniature microwave driven nitrogen plasma jet and comparison to measurements

The MMWICP (miniature microwave ICP) is a new plasma source using the induction principle. Recently Klute et al presented a mathematical model for the electromagnetic fields and power balance of the new device. In this work the electromagnetic model is coupled with a global chemistry model for nitrogen, based on the chemical reaction set of Thorsteinsson and Gudmundsson and customized for the geometry of the MMWICP. The combined model delivers a quantitative description for a non-thermal plasma at a pressure of p = 1000 Pa and a gas temperature of Tg = 650–1600 K. Comparison with published experimental data shows a good agreement for the volume averaged plasma parameters at high power, for the spatial distribution of the discharge and for the microwave measurements. Furthermore, the balance of capacitive and inductive coupling in the absorbed power is analyzed. This leads to the interpretation of the discharge regime at an electron density of ne ≈ 6.4 × 1018 m−3 as E/H-hybridmode with an capacitive and inductive component

Theoretical investigation of a novel microwave driven ICP plasma jet

Theoretical investigation of a novel microwave driven ICP plasma jet 26 Jun 2019, 16:15 15m Gold Coast III/IV (Double Tree at the Entrance to Universal Orlando) Oral 2.7 Microwave Plasma Interaction 2.7 Microwave Plasma Interaction III Speaker Mr Michael Klute (Ruhr University) Description Microwave and radio frequency driven plasmas-jets play an important role in many technical applications. They are usually operated in a capacitive mode known as E-mode. This mode, however, couples considerable power to ions which limits the plasma density and the efficiency and gives rise to negative side effects such as erosion. The inductive coupling, known as H-mode, eliminates these disadvantages and is attractive for large scale plasmas. A novel small scale, microwave driven plasma-jet has been proposed by \textit{Porteanu et al.}[1]. It is operated as an inductive discharge and that has been recently characterized using optical emission spectroscopy (OES) by \textit{Stefanovic et al.}[2]. In this work the proposed plasma-jet is examined theoretically. A global model of the new device is presented based on the volume-integrated balances of particle number and electron density, and a series representation of the electromagnetic field in the resonator. An infinite number of modes can be found ordered by the azimuthal wave number m. The mode m=0 can be identified with the inductive mode and will be called H-mode, the mode m=1 is the capacitive mode and will be called E-mode. By equating the electromagnetic power that is absorbed by the plasma with the loss power, stable operating points and hysteresis effects can be investigated. In a second step the spatially resolved electromagnetic field strength will be considered. All results will be compared to the results of the OES measurements and imagines obtained from CCD-imaging. [1]Porteanu et al.\textit{Plasma Sources Sci.Technol.}\textbf{22}, 035016 (2013) [2] Stefanovic et al.\textit{Plasma Sources Sci.Technol.}\textbf{27}, 12LT01 (2018) [3] Porteanu et al.\textit{Plasma Sources Sci.Technol.} accepted (2019

Power Consumption in a Miniature Microwave Inductively Coupled Plasma Source

Miniature Microwave Inductively Coupled Plasma (MMWICP) source is a novel and versatile non-thermal plasma source, which profit of high electron density and high power efficiency. In its compact version a single MMWICP source comprises a quartz tube of 5 mm inner diameter enclosed by a copper resonator of 8 mm thickness. This basic unit can be combined in an array of two (double), four (Quadriga) or more sources. Here, the single source is characterized by Optical Emission Spectroscopy (OES). A continuous stream of nitrogen gas is running through the glass cylinder at a pressure of 2000 Pa. This specific pressure is chosen to satisfy the Local Field Approximation (LFA), which is used in the latter data analysis. For the OES measurements nitrogen as a test gas is selected for its well-known population kinetics. In particularly, the second positive system of neutral nitrogen (380 nm line) and first positive system of nitrogen molecular ion (391 nm) are monitored, for which the population kinetics can be described by a simple collision radiative model. The OES measuring unit consists of a macro objective, CCD camera and two narrow band-pass filters, which isolate the corresponding emission lines. With previously absolutely calibrated OES unit, the radially resolved absolute line intensities are collected with a 28 micrometer resolution. Simultaneously, an absolutely calibrated high resolution Echelle spectrometer monitors the rotational lines distribution form respective emissions. Using the rate equations of collision-radiative model and BOLSIG+ for solving a Boltzmann equation under the assumption of LFA, it is possible to measure the spatially resolved electron density and electric field. Moreover, the spatially resolved deposited power density is calculated. In the presentation we will discussed the power dissipation in CCP, ICP and hybrid mode of operation. In respect to power efficiency MMWICP will be compared to other microwave plasma sources

Inductively Coupled Plasma at Atmospheric Pressure, a Challenge for Miniature Devices

Inductively coupled plasma (ICP) sources are preferred to the capacitive (CCP) sources because of their higher electron density and plasma purity. The use of microwaves for the plasma excitation allows not only to obtain a dense plasma with a low gas temperature but also to generate such a plasma at higher pressures. We present a miniaturized device capable of working up to atmospheric pressure. The plasma is generated in a quartz tube with an outer diameter of 7 – 12 mm. The microwave plasma interaction has been studied using an original method, the “Hot-S-Parameter” spectroscopy, presented in detail in [1]. The variation of the resonance frequency and generally of the reflected power as a function of frequency provides information about the type of coupling and about the plasma conductivity, i.e., electron density and scattering frequency. The microwave data are correlated with photographs of the plasma shape and with results of the optical emission spectroscopy (OES) of nitrogen [2]. At 1000 Pa, and 80 W at 2.45 GHz, a nitrogen plasma reaches an electron density of 3 1019 m−3 and a gas temperature of 1600 K [2]. The miniaturized source includes an impedance matching circuit. Based on microwave and optical measurements we estimate the power absorbed by the plasma at 1000 Pa to be about 60 % of the incident power. This efficiency is much higher than in standard reactors driven at 13.56 MHz. The source has been successfully tested with argon at atmospheric pressure. This fact opens new perspectives for the use as an array of remote plasma sources for thin-film depositions

New Records of Bruchidius Spermaphagous Species in Albizia julibrissin and Laburnum anagyroides and Their Parasitoid Complex in Serbia

Background and Purpose: Bruchidius villosus feeding in seed of Laburnum anagyroides, and Bruchidius terrenus seed pest of Albizia julibrissin are first recorded and completely new seed-beetle to Serbian Bruchinae fauna. This Chrysomelids which were found in Republic of Serbia during intensive studies from 2012 to 2014 are likely related to a mostly Paleotropical group, including also members of genera Bruchidius, Megabruchidius and Acanthoscellides. These seed-beetles develop in pods of these two woody legumes, widely grown ornamental trees and shrubs. Several recent reports reveal that this species are well established in France, Hungary, and Bulgaria. Materials and Methods: Bruchine and their legume hosts were observed by extensive field sampling throughout Serbia over three years and by rearing the beetles from the samples in the laboratory. Bruchines and the parasitoids were mass-reared in climate controled rooms under conditions close to those of their area of origin: 12:12 L:D, 3-23 °C and ≤80 % RH (depends of host plant ongoing phenology or experimental needs-proof of weevil monophagous feeding preferences). For the purpose of analyzing the observed phenomena (its intensity and relevance), some of the standard methods of statistical analysis and conclusion have been used. Results: Levels of seeds infestation still in the pods were high and comparable to other studies. Bruchine beetle infestation in the dehiscent fruits of host plants may be greater after the seeds and pods drop to the ground, as bivoltine generation occurs, but this has yet to be tested. Hypotheses on the geographic origin of this new species are also discussed. The effect of native parasitoids occurrence could potentially be interesting, given that their appearance suggest their specialization on the Bruchidius beetle species which is a common seed-predator on the leguminous seeds. Conclusions: The establishment of this new species is investigated using both morphological data and idioecological analyses. For this purpose, a methodology was developed to assess weevil field densities in a natural environment. However, this needs to be more carefully tested with a larger sample size and experiments. Significant levels of infested seed, leads to the conclusion that these seed parasites could be an important reducing factor of generative reproducing host plant potential

3-dimensional semi-analytic model of a microwave driven miniature plasma jet

Microwave or Radio frequency driven plasma jets play an important role in various technical applications and are usually operated in a capacitive mode. The MiniatureMicroWaveICP (MMWICP) is a new promising plasma source and successfully transfers the induction principle to a miniature plasma jet. This work presents a 3-dimensional semi-analytic model of the electron density of the MMWICP. The model is based on a drift-diffusion equation which is coupled to the electromagnetic model of the MMWICP presented by Klute et al in Plasma Sources Sci. Technol. 29 065018 (2020). An analytic solution is found by expanding the expression of the electron density into a series of eigenfunctions. The 3-dimensional profile of the electron density is simulated for characteristic values of the power absorbed by the plasma. The results show that the spatial distribution of the electron density is highly depended on the absorbed power. The results are found to be in good agreement with experimental measurements.74th Annual Gaseous Electronics Conferenc