Discharge Emission Research Articles

Phase-resolved optical emission of dusty rf discharges: Experiment and simulation

The spectral emission of atoms in a dusty radio frequence (rf) discharge plasma in argon and helium has been measured with a gated ICCD camera. The spatially and temporally resolved emission/excitation of the argon and helium atoms during the rf cycle in the dusty discharge was compared to the dust-free case. In the bulk plasma above the dust cloud, the emission is clearly enhanced in the dusty discharge with respect to the pure discharge, whereas in the sheath the emission is reduced. In addition, the emission of a dusty argon plasma is studied via particle-particle particle-mesh (P³M) simulations. The rf dynamics with a single dust particle trapped in the sheath was calculated. Like in the experiment the dust modifies the atomic emission. The spatiotemporal excitation pattern of the experiment is reproduced and a detailed understanding of the difference in excitation of the discharge with and without dust is presented.

Zinc coatings for hot sheet metal forming: Comparison of phase evolution and microstructure during heat treatment

The production of high strength steel parts via hot forming of manganese boron steels is an appropriate solution satisfying the strictest lightweight demands in modern body in white engineering. Since cathodic corrosion protection is essential for automotive parts, manufacturer demands zinc based coatings suitable for hot sheet metal forming. For that reason, microstructure and phase evolution during and after typical heat treatment, prior to hot sheet metal forming, of zinc and zinc based coatings have been investigated by glow discharge emission spectroscopy, scanning electron microscopy with EDX analysis, X-ray diffraction and nanoindentation. Therefore, characteristics of the heating behavior dependent on the different surfaces have been studied. It was hereby possible to compare the alloying behavior of hot dip zinc coating to that of electro-plated intermetallic zinc–nickel coating at different temperatures. Surface analysis revealed a ZnO layer formation on the heat treated Zn–Ni coating. Moreover, the present study proves a significant stabilization of the alloying process and the resulting phases due to the presence of nickel. Hence, electro-plated uniphase, intermetallic Zn–Ni coatings are highly suitable for hot sheet metal forming applications owing to their good thermal stability when compared to hot dip zinc coatings.

Emission properties of a pulsed-periodic barrier discharge initiated in helium-iodine and argon-iodine mixtures

The subject of investigation is the emission properties of a pulsed-periodic barrier discharge initiated by submicrosecond pulses (f = 40–1000 Hz) in He-I2 and Ar-I2 mixtures. The investigation is carried out in the spectral range 200–400 nm at a pressure of the working medium of 1–100 kPa and an iodine partial pressure of 130–200 Pa. The dependence of UV emission from the plasma of the barrier discharge at the 342 nm I2(D′ → A′) band and the iodine atom spectral line at 206.2 nm on the argon and helium partial pressures, excitation pulses repetition rate, and charging voltage of the capacitor of a short high-voltage pulse modulator is optimized. The contribution of the 206.2 nm I* spectral line to the UV emission of the barrier discharge is estimated.

G070041 プラズマジェットイグニッションにおける流体力学的効果が希薄予混合気の燃焼促進に与える影響([G07004]エンジンシステム部門一般セッション(4):エンジンシステム)

This study clarified the influence of high temperature gas jet on combustion enhancement effect for lean mixture in the plasma jet ignition by the use of combustion bomb. The hot gas jet was generated by the plasma and was ejected after the plasma jet finished injecting. The combustion chamber had a cylindrical shape with 80 mm of diameter and 40 mm of thickness and its volume was about 201 cm3, and the igniter was attached to the bottom of combustion chamber. The igniter was composed by central electrode, orifice and cavity. Tests were carried out with propane-air mixture at equivalence ratio of 0.6 and cavity depth, orifice diameter and discharge energy were varied. The hot gas jet was visualized by schlieren method in the absence of combustion, and combustion development processes were also visualized and the combustion pressure was measured. The voltage throughout electrical discharge and the plasma luminescence was also measured. The electrical discharge began early and the intense luminescence was emitted from plasma jet as the supplied energy increased. The electrical discharge and light emission durations were not so influenced by igniter configuration. The initial flame kernel and hot gas jet were similarly developed. For small diameter orifice and large volume cavity, flame propagation was enhanced and combustion duration was shortened, because the hot gas jet velocity increased. Because the discharging duration was very short as compared with combustion period, the hot gas jet was more effective against the combustion enhancement than the plasma generated by electrical discharge.

An Overview of Unipolar Charger Developments for Nanoparticle Charging

Charging of nanoparticles is an important process in aerosol sizing. A unipolar charger is one of the most important upstream components in aerosol particle sizing and measurement systems by electrical mobility analysis. The aim of particle charging for an electrical mobility analyzer is to impose a known net charge distribution on the aerosol particles for each size. Charger performance depends on the extrinsic charging efficiency and stable operation. A well-designed unipolar charger should provide high extrinsic charging efficiency and stability that can be accurately determined for any given operating conditions. Depending on the mechanisms used to generate the ionized gas, the chargers can be classified into: (i) a corona discharge chargers, (ii) a radioactive chargers, and (iii) a photoelectric chargers. In this article, a brief overview on the development of existing unipolar aerosol chargers for nanoparticles is presented. Descriptions of the operating principles as well as detailed physical characteristics of these chargers, including the corona discharge, ionizing radiation, and photoelectron emission, are given.

Elaboration of equipment and methods of continuous recording of electric activity of clariid catfish (Clariidae, Siluriformes) in social and reproductive behavior

Equipment and methods of simultaneous continuous long-term recording of electric activity of clariid catfish (Clariidae) is elaborated. All electric organ discharges (EOD) in any position and orientation of free swimming fish are fixed by simultaneous recording of electric voltage with two mutually perpendicular pairs of electrodes. Light-emitting diodes controlled by a microprocessor allow for the possibility to observe the moments of discharge emission both in real time and during scanning of videorecords. According to its parameters, the created equipment corresponds to characteristics of EOD of clariid catfish, performs primary treatment of signals, and stores in its inner flash memory all discharges recorded in a prolonged experiment (duration up to several days, number of EOD up to several tens of thousands). Various examples of EOD are presented recorded by means of the elaborated methods in clariid catfish (C. macrocephalus, C. batrachus, C. fuscus, and hybrids C. gariepinus × C. macrocephalus) when they manifested aggressive-defensive and spawning behavior. The procedure of treatment of EOD is suggested, including that of special bursts of EODs generated by females in pairing.

No shot in the dark: Myxozoans chemically detect fresh fish

This work reports the discovery of an hitherto unknown chemical recognition trait enabling a parasitic life cycle in aquatic habitats. We believe this is the first record of a natural, host-derived chemical molecule identified as a recognition cue for the phylum Myxozoa. The actinospores of these parasites attach to fish hosts via polar filaments that are extruded upon mechanical stimulation after preceding recognition of a chemical trigger contained in surface mucus. Our goal was to identify this signal. We separated compounds from a purified active fraction derived from trout mucus by a novel HPLC method. By subsequent nuclear magnetic resonance analysis of distinct components and testing in bioassays we elicited stimulation of polar filament discharge and sporoplasm emission in actinospores of three myxozoan spp., Myxobolus cerebralis, Myxobolus pseudodispar and Henneguya nuesslini, by the free nucleosides inosine, 2′-deoxyinosine and guanosine. These nucleosides also activated sporoplasm emission. Nucleosides appear to be appropriate cues for rapid host recognition by the waterborne parasite stages since they are continuously released into surface mucus. The recognition mechanism is not specific for susceptible host species, at least in the myxozoan spp. examined. In addition, a novel function of nucleobase derivatives as semiochemicals was uncovered and a wider impact of this molecule class in parasite recognition systems and aquatic chemical ecology is predicted. The relevance for disease prevention and cell culturing remains to be explored.

Mechanistic study of ultralow k-compatible carbon dioxide in situ photoresist ashing processes. I. Process performance and influence on ULK material modification

In situ photoresist (PR) ashing processes are attractive because of the ease of process integration with plasma etching processes. The authors have examined the performance of carbon dioxide (CO2) as a source gas for in situ PR ashing processes compatible with ultralow k (ULK) materials and compared it with the results obtained using O2. They performed measurements of 193 nm PR ashing rates in a dual frequency capacitively coupled plasma reactor. The damage to porous ULK feature sidewalls was simulated by exposing blanket ULK films in a non-line-of-sight fashion in a small gap structure to the plasma-generated reactants. The pressure for the in situ ashing processes was varied from 10 to 100 mTorr, and the self-bias voltages ranged from floating potential to ∼−400 V. To increase line-of-sight etching of PR by inert ion bombardment, Ar/CO2 mixtures with up to 75% Ar were investigated. The ULK material modifications were analyzed by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Plasma-damage of the ULK material primarily is detected as the removal of carbon from the SiCOH ULK films. To compare the performance of different ashing processes for PR stripping from ULK material, the authors introduced an ashing efficiency (AE) parameter which is defined as the thickness of PR removed over the thickness of ULK simultaneously damaged, and can be considered a process figure of merit. AE with CO2 was about three times greater than AE with O2 for the same process conditions. When a 75% Ar/CO2 gas mixture was used and a −100 V substrate bias was applied during PR ashing, a PR ashing rate of 200 nm/min could be achieved for a 10 mTorr Ar/CO2 plasma. For this process, the measured AE was 230, more than 10× greater than AE achieved with O2 discharges using the same conditions. The authors found that ULK damage showed a direct dependence on the atomic oxygen densities of both CO2 and O2 discharges which was characterized by optical emission of discharges. The question whether in-diffusion of carbon species from CO2 discharges into ULK material was significant was also examined. For this the authors substituted C13O2 for C12O2 and performed ToF-SIMS analysis of the exposed ULK films. No significant amount of C13 from C13O2 plasmas was detected either on the surface or in the bulk of the C13O2 plasma-exposed ULK.

Spatial and temporal investigation of high power pulsed magnetron discharges by optical 2D-imaging

Optical 2D-imaging in combination with Abel inversion was used to study the spatial and temporal evolution of the plasma-induced emission of HIPIMS discharges. A titanium target, as well as an aluminium-doped zinc target was sputtered in an argon atmosphere of pressures 0.53 Pa and 1.33 Pa and an average power of 650 W and 400 W, respectively. The discharge was observed optically employing various wavelength filters to investigate the development of selected species, namely argon and titanium neutrals, as well as argon and zinc neutrals and ions. The argon neutral emission did not only differ substantially from the DC case but also underwent a significant development during the pulse ‘on’-time, showing a structure similar to an ion acoustic wave travelling away from the target, as well as rarefaction of the working gas while sputtering with high discharge peak currents. In addition, the intensity profile of argon and zinc ions revealed an increased width in front of the target which is then reflected by a wider sputter distribution of the target material. Indeed, it was found that the width of the metal neutral emission increased with increasing discharge current. Their emission revealed two distinct maxima and the loss of intensity in between these maxima could be explained by an increased ionisation of the sputtered metal flux.

Emission in argon and krypton at 147 nm excited by runaway-electron-induced diffusion discharge

Plasma emission of a pulsed diffuse discharge produced at increased pressures due to the preionisation of the gap by runaway electrons is studied in argon, krypton, and xenon. Nanosecond voltage pulses with the amplitude ∼220 kV were applied to the discharge gap. It is shown that the presence of xenon (∼0.01%) in argon and krypton leads to the emergence of high-power narrowband radiation at awavelength of 147 nm. It is assumed that this radiation belongs to the bands of heteronuclear molecules Xe*Ar and Xe*Kr.

Investigation on the effect of impurities in xenon based dielectric barrier discharge lamps

In any discharges, the existence of impurities could cause a severe change or bring a negative or positive effect to the discharge and plasma characteristics. The authors purposely added a few kinds of impurities and investigated their effect on the discharge. The common and typical impurities of H2, N2, CO2 and CH4 were applied in varying concentration percentages into a xenon dielectric barrier discharge lamp. Their discharge condition, emission spectra and electrical characteristics were studied. The plasma generation differs from one type of impurity to another. With two different concentrations of hydrogen applied, at 5% concentration it would stabilize the discharge and at 0.5% concentration it would cause an additional collision process where a strong peak of atomic lines was observed. Nitrogen with two types of concentration, i.e. 1% and 0.1%, exhibits two kinds of characteristics in emission spectroscopy. From the electrical parameters, the voltage across the gap shows the lamps with impurities have a higher value compared with the pure xenon lamp.

Influence of the pre-ionization background and simulation of the optical emission of a streamer discharge in preheated air at atmospheric pressure between two point electrodes

This paper presents simulations of positive and negative streamers propagating between two point electrodes in preheated air at atmospheric pressure. As many discharges have occurred before the simulated one, seed charges are taken into account in the interelectrode gap. First, for a pre-ionization background of 109 cm−3, we have studied the influence of the data set used for transport parameters and reaction rates for air on the simulation results. We have compared results obtained in 1997 using input parameters from Morrow and Lowke and from Kulikovsky. Deviations as large as 20% of streamer characteristics (i.e. electric field in the streamer head and body, streamer velocity, streamer radius, streamer electron density) have been observed for this point-to-point configuration. Second, we have studied the influence of the pulsed voltage frequency on the discharge structure. For the studied discharge regime, a change in the applied voltage frequency corresponds to a change in the pre-ionization background. In this work, we have considered a wide range of pre-ionization values from 104 and up to 109 cm−3. We have noted that the value of the pre-ionization background has a small influence on the electron density, electric field and location of the negative streamer head. Conversely, it has a significant influence on the positive streamer characteristics. Finally, we have compared instantaneous and time-averaged optical emissions of the three band systems of N2 and (1PN2, 2PN2 and ) during the discharge propagation. We have shown that the emission of the 2PN2 is the strongest of the three bands, in agreement with experimental observations. It is interesting to note that even with a short time averaging of a few nanoseconds, which corresponds to currently used instruments, the structure of the time-averaged emission of the 2PN2 is different from the instantaneous one and shows negative and positive streamers with smaller radial expansions and more diffuse streamer heads.

Results from a 64-pixel PIN-diode detector system for low-energy beta-electrons

The KATRIN neutrino mass experiment is based on a precise energy measurement (Δ E/ E=5×10 −5) of electrons emerging from tritium beta decay ( E max=18.6 keV). This is done by a large electrostatic retarding spectrometer (MAC-E Filter), which is followed by an electron detector. Key requirements for this detector are a large sensitive area (∼80 cm 2), a certain energy resolution (Δ E=600 eV @ 18.6 keV) but also a certain spatial resolution (∼3 mm), which leads to a multi-pixel design. As a tentative design on the way to the final detector, but also for operational service on the so-called pre-spectrometer experiment, a detector system with a reduced size (16 cm 2) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode, was designed and built. While the design and very first measurements have been presented in Wuestling et al. [6], this publication shows the operational performance of the detector system. The robust concept of the electronics allowed adaptation to mechanically different experimental setups. The spacial resolution of the detector system proved to be essential in examining Penning trap induced background and other effects in the pre-spectrometer experiment. The detector performance test runs include energy resolution and calibration, background rates, correlation between pixels (crosstalk), spatially resolved rate analysis, and a dead-layer measurement [7]. The detector allows for background searches with a sensitivity as low as 1.3×10 −3 cps/cm 2 in the energy range of 20 keV. This allows the pre-spectrometer to be characterized with e-gun illumination with a signal to background ratio of better than 10 5 and the search for ultra low Penning discharge emissions.

Development of a nonequilibrium microwave discharge at the end of a cylindrical electrode in nitrogen at reduced pressures

Excitation of a microwave discharge at the end of a cylindrical electrode in nitrogen at a pressure of 1 Torr and incident powers of 60–140 W was investigated experimentally by using K-008 and K-011 video cameras and analyzing oscillograms of discharge emission. The times during which the discharge is established in the radial and axial directions are found to be on the order of 10−4 and 10−2 s, respectively. The results obtained are analyzed using one-dimensional simulations of a discharge in nitrogen in a quasistatic approximation. The kinetic scheme includes 50 processes involving electrons, ions, and excited molecules and atoms. The time evolution of the concentrations of molecular nitrogen in the N2(C3IIu) and N2(B3IIg) states, responsible for the recorded discharge emission, is compared with the experimental data.

Characterization of ion emission of an extreme ultraviolet generating discharge produced Sn plasma

The ion emission of a Sn-based discharge produced extreme ultraviolet producing plasma is characterized with the combined use of different time-of-flight techniques. An electrostatic ion spectrometer is employed to measure the average charge distribution of the emitted Sn ions. A dedicated Faraday cup configuration is used to measure the total ion flux from the source for different discharge energies. High-energy Sn ions emitted by the plasma with energies up to 100 keV have been identified. The number of high-energy ions increases for higher electrical input energy into the plasma while the signal associated with the expanding plasma ions does not show such dependence. The ion energy distribution for a bulk of detected ions is calculated based on the Faraday cup measurements and compared with theoretical plasma expansion dynamics.

Comparison of pilot and industrial scale atmospheric pressure glow discharge systems including a novel electro-acoustic technique for process monitoring

A comparison of a pilot and industrial scale atmospheric pressure polymer processing plasma system has been carried out using process-monitoring diagnostic tools during treatment of amorphous polyethylene terephthalate. These systems have been compared using optical emission spectroscopy (OES), photodiode (PD) analysis and multi-variate analysis of the applied electrical and emitted electro-acoustic signals to facilitate scale up operations from the pilot to the industrial scale system. The voltage, current, electro-acoustic intensity and frequency of the plasma systems were found to change systematically with an increase in applied plasma power and addition of oxygen (O2) into a helium (He) plasma. The plasma drive frequency was pulled by the plasma reactance from approximately 26 to 16 kHz on the pilot system and from approximately 36 to 32 kHz on the industrial system, for an increase in applied plasma power and addition of O2. The OES analysis revealed a number of peaks associated with nitrogen (N2) species between 250 and 450 nm due to the presence of air within the He plasma. Temporally resolved analysis of the discharge emission carried out using a PD showed an increase in the number of discharge events per power cycle with an increase in power and a decrease in emission intensity for addition of O2 into the He plasma for both the pilot and industrial scale systems. Using these diagnostic tools both plasma stability and run to run variations were assessed. A visual analysis of the 1.2 m wide plasma was also carried out where a more homogeneous plasma was observed at higher powers.

Production of High‐Density Capacitively Coupled Plasma with RF Multi‐Hollow Cathode and/or High Secondary Electron Emission for DLC Film Preparation

AbstractThe effects of a hollow cathode discharge and secondary electron emission from a radio‐frequency‐biased electrode on the growing rate of diamond‐like carbon films were studied. The rate of deposition for amorphous hydrogenous carbon thin films of about 200 nm·min−1 was attained at a voltage of −700 V with radio‐frequency plasma using CH4 gas. Because of its non‐uniformity, the profile was improved by changing the hole arrangement. A radial roughness of the deposited films of about 35 nm, for a film thickness of about 1 µm, was obtained with the best arrangement.

306 ハニカム型放電リアクタを用いたVOCの分解(大気環境保全・改善技術(2))

There is problem for health and the environment by chronic exposure of volatile organic compounds (VOCs). Non-thermal plasma technology offers a reformative approach to the problem of removing various VOCs. In this study, VOC decomposition using honeycomb type discharge reactor has been experimentally investigated. Discharge plasma was occurred at end face of zeolite honeycomb. Humidity of the feed gas was considered discharge parameter on zeolite honeycomb. Discharge emission was observed, adsorption and desorption of VOC on zeolite honeycomb were investigated. A toluene, which is one of the most commonly used VOCs, was used and the decomposition characteristics by discharge plasma were investigated.

Two-temperature modelling of pulsed high pressure caesium radiative discharge with recombination mechanism of light emission

A two-temperature model of pulsed high pressure caesium (HPC) discharge is developed on the basis of the radiative many component gas dynamic equations. The time-dependent radial distributions of the temperatures, concentrations and radial velocities of motion are determined for all plasma components. Peculiarities of plasma heating in the discharge are considered. It is shown that the main mechanism of the heat exchange in HPC discharge is intensive nonlocal radiative heat transfer. The spectrum of radiation, emitted from discharge plasma, is investigated. It is shown that, in the dense discharge plasma, a lowering of the ionization potential of an atom and the merging of the highest terms of spectral series (because of their broadening) result in a significant shift of the thresholds of recombination 6P and 5D continua. It explains the formation of an almost continuous spectrum of the discharge emission in the visible range. Luminous characteristics of the discharge are calculated. The luminous efficacy η = 90 lm W−1 and a colour rendering index Ra = 98 are obtained. The study shows that the pulsed HPC discharge is an effective mercury-free light source with recombination mechanism of emission.

Emision of Cl2* molecules in a barrier discharge

The energy and spectral parameters of emission of a barrier discharge in chlorine and its mixtures with inert gases are studied experimentally. The barrier discharge in chlorine was homogeneous at pressures up to ≈9 Torr and its spectrum contained the 3Π2g→3Π2u, 3Π2g→3Σ2u+ and 1Σu+→1Σg+ bands of Cl2* molecules. After the addition of an inert gas, the 257.8-nm 3Π2g→3Π2u band made the main contribution to the spectrum. The maximum efficiency and power of the Cl2 excilamp were obtained for the chlorine—argon mixture and amounted to 0.7% and 1.3 W, respectively.