Ar Emission Research Articles

Comparing the three-dimensional morphological asymmetries in the ejecta of Kepler and Tycho in X-rays

Aims. Recent simulations have shown that asymmetries in the ejecta distribution of supernova remnants (SNRs) may be a reflection of asymmetries left over from the initial supernova explosion. Thus, SNR studies provide a vital means for testing and constraining model predictions in relation to the distribution of heavy elements, which are key to improving our understanding of the explosion mechanisms in Type Ia supernovae. Methods. The use of a novel blind source separation method applied to the megasecond X-ray observations of the historic Kepler and Tycho supernova remnants has revealed maps of the ejecta distribution. These maps are endowed with an unprecedented level of detail and clear separations from the continuum emission. Our method also provides a three-dimensional (3D) view of the ejecta by individually disentangling red- and blueshifted spectral components associated with images of the Si, S, Ar, Ca, and Fe emission. This approach provides insights into the morphology of the ejecta distribution in those two remnants. Results. Those mappings have allowed us to thoroughly investigate the asymmetries in the intermediate-mass elements and Fe distribution in two Type Ia supernova remnants. We also compared the results with the core-collapse Cassiopeia A remnant, which we had studied previously. The images obtained confirm, as expected for Type Ia SNRs, that the Fe distribution is mostly closer to the core than that of intermediate-mass elements. They also highlight peculiar features in the ejecta distribution, such as the Fe-rich southeastern knot in Tycho.

Optical emission spectroscopy of an industrial thermal atmospheric pressure plasma jet: Parametric study of electron temperature

The plasma parameters of an industrial atmospheric pressure plasma jet (APPJ) are measured as a function of the electric power of the plasma generator, the gas flow, and the distance from the jet nozzle exit. The APPJ device operates an electric discharge under Argon gas flow resulting into a continuous Argon plasma jet in the kW power range expanding into ambient air. The plasma temperature Te and electron number density Ne are determined by optical emission spectroscopy (OES) analyzing up to 17 emission lines of neutral Ar (I) and singly-ionized Ar (II) species using the Saha-Boltzmann plot (SBP) method. For the accurate determination of plasma parameters a methodology is developed to overcome fundamental limitations in OES of Argon plasma that is due to the strongly different intensities of Ar (I) and Ar (II) emission lines. The most significant step is the use of spectral bandpass filters in the optical collection system. The experimental parameters of the jet device are playing a crucial role for APPJ applications (e.g. thermal load to the workpiece, plasma chemistry interaction etc.). We measure Te and Ne in dependence of the experimental parameters and obtain consistent and accurate values of Te = 9000 ± 150 K and Ne = 5 × 1015 cm−3 (typ.). For comparison, plasma characterization using only the neutral Ar lines gives inaccurate and inconsistent Te values. This highlights the importance of using also the ionic Ar lines. The developed methodology may be diversified and applied also for OES of other rare gas plasma.

Spectral study of the Galactic ridge X-ray emission with Suzaku: Comparison of the spectral shape with point sources

Abstract The Galactic ridge X-ray emission (GRXE) is unresolved X-ray emission located on the Galactic plane, and whether the GRXE comes from truly diffuse plasma or unresolved point sources is still debatable. We present results of spectral analysis of the GRXE with Suzaku. In order to examine the point source origin, we fitted the GRXE spectra in the 1.2–10 keV energy band with a point source model, which is a mixture of active binary stars (ABs) and non-magnetic cataclysmic variables (non-mCVs), and found that the model cannot represent the GRXE spectral shape as long as the standard metal abundances of these species are assumed. In particular, the standard abundance model cannot account for the observed intensities of Si, S, and Ar lines as well as the previously reported Fe line. Assuming spatial densities in the solar neighborhood, integration of the ABs and non-mCVs accounts for only 30% of the observed GRXE flux. Other species of the point sources or diffuse emission with stronger Si, S, Ar, and Fe emission lines shall explain the rest.

Emirates Mars Ultraviolet Spectrometer's (EMUS) Observation of Argon in the Martian Thermosphere

AbstractThe Emirates Mars Ultraviolet Spectrometer (EMUS) is a far ultraviolet spectrometer on‐board the Emirates Mars Mission's (EMM) which arrived at Mars on 9 February 2021. EMUS is designed to observe key neutral species in the Martian thermosphere (100–200 km) and exosphere (≥200 km). EMUS has observed two neutral argon (Ar) emission lines, Ar I 104.8 nm and Ar I 106.6 nm, in the thermosphere. Our interest in these emissions stem from argon's non‐reactiveness, making it a tracer for transport between the upper and lower atmosphere. We report average argon disk brightness measured by EMUS and compare them to measurements from Earth orbiting observatories. For the first time, this work investigates the variability of Ar I 106.6 nm brightness due to emission angles, solar zenith angles, solar longitudes, local times and latitudes. To contrast the behavior of inert argon we compare these results with the photochemically reactive oxygen 135.6 nm.

Feasibility of two-dimensional die-level plasma process monitoring using spatially resolvable optical emission spectrometers

We demonstrated the feasibility of die-level process monitoring using spatially resolvable optical emission spectrometers (SROESs) in a low-pressure plasma reactor. The spatially resolved Ar emission line intensities and their intensity ratios were obtained from uniformly generated and intentionally perturbed plasma by inserting conductors of known sizes at known locations. The sheath and perturbed plasma distributions were identified from the Ar emission line intensity and their intensity ratio in the lateral direction to the SROES installment orientation. However, the resolution in the axial direction was insufficient to identify the sheath and perturbed the plasma distribution. We propose the superimposition of measured plasma emission intensities from two perpendicularly aligned SROESs for die-level process monitoring. The insufficient axial resolution can be compensated for by the lateral resolution of another SROES, and die-level process monitoring using SROES can thus be realized.

Effects of O2 addition on the plasma uniformity and reactivity of Ar DBD excited by ns pulsed and AC power supplies

Dielectric barrier discharges (DBDs) have been widely used in ozone synthesis, materials surface treatment, and plasma medicine for their advantages of uniform discharge and high plasma-chemical reactivity. To improve the reactivity of DBDs, in this work, the O2 is added into Ar nanosecond (ns) pulsed and AC DBDs. The uniformity and discharge characteristics of Ar ns pulsed and AC DBDs with different O2 contents are investigated with optical and electrical diagnosis methods. The DBD uniformity is quantitatively analyzed by gray value standard deviation method. The electrical parameters are extracted from voltage and current waveforms separation to characterize the discharge processes and calculate electron density n e. The optical emission spectroscopy is measured to show the plasma reactivity and calculate the trend of electron temperature T e with the ratio of two emission lines. It is found that the ns pulsed DBD has a much better uniformity than AC DBD for the fast rising and falling time. With the addition of O2, the uniformity of ns pulsed DBD gets worse for the space electric field distortion by O2 −, which promotes the filamentary formation. While, in AC DBD, the added O2 can reduce the intensity of filaments, which enhances the discharge uniformity. The ns pulsed DBD has a much higher instantaneous power and energy efficiency than AC DBD. The ratio of Ar emission intensities indicates that the T e drops quickly with the addition of O2 both ns pulsed and AC DBDs and the ns pulsed DBD has an obvious higher T e and n e than AC DBD. The results are helpful for the realization of the reactive and uniform low temperature plasma sources.

Laser-induced breakdown spectroscopy signal enhancement effect for argon caused by the presence of gold nanoparticles

The effect of the presence of nanoparticles (NPs) on the laser induced breakdown spectroscopy (LIBS) signal of argon gas was studied experimentally. 10–20 nm diameter gold NPs, produced by a spark discharge nanoparticle generator, were suspended in argon gas. The effect of particle size, number concentration and mass concentration, as well as laser pulse energy on the LIBS argon signal was systematically investigated. It was found that the breakdown threshold of the gas decreases considerably, facilitating the detection of Ar emission at such laser fluences, which do not allow plasma formation without the presence of the NPs. Our observations persist even at aerosol mass concentrations that are too low to allow the direct detection of nanoparticles. The effect, which is attributed to electron thermo- and field emission induced by the high intensity laser pulse, shows an asymptotically increasing magnitude with the aerosol mass concentration. The signal enhancement was found to be 102–104 and the effect is suggested to be useful in trace gas analysis or for the indirect detection of NPs. The achievable indirect aerosol mass concentration detection limit was estimated to be in the parts per trillion regime (as low as 50 ng·m−3), which is comparable to the best literature values reported for direct analysis.

Observations of visible argon line emissions and its spatial profile from Aditya-U tokamak plasma.

The spectroscopic studies of medium and high Z impurities have been the subject of interest in fusion research due to their role in mitigating plasma disruption and reducing heat load on the plasma facing components. Line emissions from these impurities provide the rotation velocity and ion temperature measurements along with the understanding of the overall impurity behavior in plasma. In the Aditya-U tokamak, the spatially resolved Ar II line emissions have been observed using a high resolution multi-track spectroscopic diagnostic consisting of a 1m Czerny-Turner spectrometer coupled with a charge coupled device (CCD) detector using seven lines of sight viewing plasma tangentially along the toroidal direction. The spatially resolved Ar II lines at 458.96nm have been observed. The singly ionized Ar emission peaks at the radial location of ρ = 0.8 of the plasma having a minor radius of 25cm. Moreover, a 0.5m UV-visible spectrometer coupled with a CCD detector and having a line of sight passing through the plasma midplane from the radial port was used to record visible Ar survey spectra within the 670-810nm wavelength range, and all these lines have been identified for further analysis.

On the rotational–translational equilibrium in non-thermal argon plasmas at atmospheric pressure

This work examines the rotational–translational equilibrium in non-thermal, argon-based plasmas at atmospheric pressure. In particular, rotational temperatures (T rot) and neutral gas temperatures (T g) are compared along the axis of plasma columns sustained by either radiofrequency (RF) or microwave (MW) electromagnetic fields. Water vapours or N2 admixtures are added to the high-purity argon plasmas to record the rotational temperatures from the emission spectra of either the OH(A2Σ + − X2Π i ) or the N2 +(B2Σ u + − X2Σ g + ) rovibrational systems. T g values are also deduced from the line broadening of selected Ar emission lines using an hyperfine spectrometer. In the MW Ar/H2O plasma, T g decreases from ∼2100 K close to the wave launcher to ∼1600 K near the end of the plasma column, while T rot is mostly constant in the 1500 K range. In presence of N2 admixtures instead of water vapours, T g is higher by about 300 K (from ∼2400 K to ∼1900 K), while T rot decreases from ∼3200 K to ∼2750 K along the plasma column. A discrepancy between T g and T rot is also observed in the much colder RF plasmas with T g ∼ 400 K and T rot ∼ 515 K. Such departure from the rotational–translational equilibrium in both plasmas is ascribed to the influence of electrons competing with neutrals to impose their own temperature on the distribution of rotational levels of both ground and excited states.

Effect of hydrogen isotope on plasma impedance and thermal pinching induced by single aerosol droplets injected into an inductively coupled plasma

The mass of the hydrogen isotope in micrometer-sized aqueous droplets introduced into an ICP has been found to affect the degree of resulting plasma perturbation. Studied plasma perturbations include local plasma cooling, plasma shrinkage due to thermal pinching, and changes in plasma impedance. The local cooling effect caused by a vaporizing aerosol droplet was found to be similar between H2O and D2O. This finding is likely a result of the similar heat capacities and vaporization rates of H2O and D2O droplets and of the comparable thermal conductivities and dissociation kinetics of H2O and D2O vapor. In contrast, a clear isotope effect was observed for plasma shrinkage and impedance change, with H2O causing a considerably stronger effect. Plasma shrinkage, gauged by the reduction in Ar emission at the edge of the plasma, was detected at all observation heights within the load-coil region, with D2O droplets causing as much as 30% less of an effect than H2O. Likewise, D2O droplets induce significantly less change in plasma impedance than H2O droplets. Depending on experimental conditions and the probing method, changes in plasma impedance caused by monodisperse D2O droplets were only 52%–80% that of H2O. The lower influence on plasma shrinkage and impedance change for D2O droplets is believed to be related to the much lower thermal conductivity of atomic deuterium, around 70% that of atomic hydrogen (protium). The time required for the plasma impedance to return to its original steady-state value was comparatively long (~10 ms) and similar for H2O and D2O droplets.

Calibration of Raman wavenumber in large Raman images using a mercury‐argon lamp

AbstractRaman imaging is an emerging tool for the analysis of meteorites, as it is capable of describing mineralogy, carbon composition/speciation, and crystal orientation all within a petrographic context. Adequately examining the heterogeneous composition of a meteorite often requires long image collection times on the timescale of days. However, the wavenumber calibration of the Raman spectrometer drifts over long timescales resulting in low wavenumber precision for the Raman spectra comprising a large Raman image. This decrease in wavenumber precision can compromise the analysis of geological markers that can provide important information on a meteorite sample. We examine, in detail, the change in bandwidth and wavenumber of the Raman bands and Hg–Ar emission lines in our Raman images as a function of time and laboratory temperature. To overcome the drift in calibration, we utilize a commercial WITec Raman instrument with a built‐in Hg–Ar calibration lamp to individually calibrate each spectrum in the Raman image. We show that using the Hg–Ar calibration, we can improve the wavenumber precision for the spectra in our Raman images from ~±0.15 to ~±0.05 cm−1 for Raman spectra collected over multiple days. This is important as it improves measurements of mineral chemistry, latent strain, and other features that are dependent upon accurate peak position determination. We also examine the spectral signal‐to‐noise ratio needed to minimize the wavenumber error when fitting bands to Gaussian/Lorentzian profiles. We then use our results to suggest a general method for calibrating the wavenumber of Raman spectra in large Raman images.

Experimental and PIC MCC study of electron cooling—re-heating and plasma density decay in low pressure rf ccp argon afterglow

In this work, experimental and theoretical study of pulsed discharge in argon has been carried out. The experimental data on the dynamics of electron density, electron temperature, and plasma potential have been obtained by probe measurements (using hairpin and Langmuir probes) in the afterglow between two RF pulses. This dynamics is thoroughly analyzed by comparison with the results of the kinetic PIC MC simulations. The main processes that cause electron cooling have been revealed for two different time stages. The first afterglow stage is characterized by the rapid decrease of the electron temperature. During this stage, inelastic electron collisions with Ar atoms in the ground state play an important role in the electron cooling. During the second long-scale stage, only diffusion along the electron energy scale via Coulomb or elastic collisions can provide the observed effect of the gradual electron cooling. The effects of elastic and Coulomb collisions on the electron cooling have been separated and analyzed by means of PIC MC simulations. The temporal evolution of the electron concentration spatial distribution and the plasma boundary sheaths size has been also analyzed on the base of 1D PIC MC simulations. A good agreement between the probe measurements and the PIC simulations data on plasma density, ambipolar potential and electron temperature is observed. To perform a more detailed study of EEDF and electron temperature dynamics, the relative intensity of Ar(2p1) → Ar(1s2) emission at 750 nm has been measured. A very good agreement between the measured emission intensity and the calculated excitation rate of Ar(2p1) at different time scales validates the electron temperature temporal dynamics obtained by the used PIC model.

Comparative studies of compact kHz and MHz driven low pressure plasmas by emission and laser spectroscopy

The temporal evolution of a low pressure argon plasma driven by a combination of radio frequency and kilohertz frequency power sources was characterized by phase resolved optical emission and laser absorption spectroscopy. The compact, low pressure plasma was formed in a hybrid surface/jet geometry and powered by a high voltage power supply operating at 31 kHz and by a lower voltage RF supply operating at 13.56 MHz. An accurate evaluation of the 1s state density dynamics was performed by means of laser absorption measurements of the 1s5 and 1s4 sublevels. The emission spectra were recorded with a submicrosecond temporal resolution and evaluated using an extended Corona model. In comparison with the modeling results, the phase dependent ratio of different Ar(2p) → Ar(1s) emission lines was used to determine temporal profiles of electron temperature and relative electron density. The results were compared with the results from time averaged emission measurements by performing an identical analysis. Strong spatial and temporal variations of plasma parameters were observed when the plasma was driven solely by the 31 kHz source, resulting in nonequilibrium conditions for long living states. Inconsistent observations in the reconstructed temporal development of plasma energy and density were further investigated by illustrating full spatiotemporal reconstruction of plasma parameters. These results permit clear identification of strong spatial gradients through the tube.

Simulation, design, and first test of a multi-energy soft x-ray (SXR) pinhole camera in the Madison Symmetric Torus (MST).

A multi-energy soft x-ray pinhole camera has been designed and built for the Madison Symmetric Torus reversed field pinch to aid the study of particle and thermal-transport, as well as MHD stability physics. This novel imaging diagnostic technique combines the best features from both pulse-height-analysis and multi-foil methods employing a PILATUS3 x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. Further improvements implemented on the new cooled systems allow a maximum count rate of 10 MHz per pixel and sensitivity to the strong Al and Ar emission between 1.5 and 4 keV. The local x-ray emissivity will be measured in multiple energy ranges simultaneously, from which it is possible to infer 1D and 2D simultaneous profile measurements of core electron temperature and impurity density profiles with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. The expected time and space resolutions will be 2 ms and <1 cm, respectively.

Determination of Arsenic by Hydride Generation—Laser-Induced Breakdown Spectroscopy: Characterization of Interelement Interferences

ABSTRACTIn this study, interelement interferences were evaluated for the determination of arsenic in aqueous samples through laser-induced breakdown spectroscopy (LIBS) hyphenated with a hydride generation sample introduction system. Optimum instrumental and chemical parameters were selected and variation in LIBS signal intensity was recorded for As solution in the presence of comparable concentrations of interfering elements. No significant change in the signal intensity of As(I) 228.8 nm line was observed in the presence of alkali/alkali earth metals; however, the presence of hydride-forming elements has shown a noticeable decrease in the line emission strength of arsenic. The least variation in arsenic signal was observed in the presence of Ge, the most volatile of all. However, the signal has decreased to a greater extent in the presence of Sn, Sb, and Pb. The presence of interfering elements on electron temperature and electron number density of arsenic plasma has also been studied. Plasma temperatures calculated using both As and Ar emission lines in the Boltzmann equation were similar, being around 5000 K. The McWhirter criterion for stationary and homogenous plasmas was utilized for the establishment of the local thermodynamic equilibrium under the plasma conditions studied. Applicability of the technique for multielemental analysis of water samples was tested through spiking experiments. Arsenic signal showed 26% decrease in the multielemental mixture solution. LIBS is among a few atomic spectroscopic techniques that facilitate rapid and simultaneous multielemental analysis without extensive sample preparation steps. However, the analytical performance of the technique still requires more serious efforts to compete with other conventional techniques for routine analysis of environmental samples.

Cleaning level of the target before deposition by reactive direct current magnetron sputtering

We present a thorough study of the target-cleaning phase to estimate the healthiness of the target in a direct current (DC) magnetron sputtering deposition. The study is based on real-time plasma monitoring by means of optical emission spectroscopy during a traditional cleaning phase in an Ar atmosphere. In this work we demonstrate that intensities of Ar emission lines are sufficient indicators of the target cleanliness degree. To derive these results SiOxNy thin films were grown by reactive DC magnetron sputtering on silicon wafers for different deposition configurations of Ar, O2 and N2 fluxes. Refractive index of the resulting films is measured by in-situ spectroscopic-ellipsometry. A simple but robust estimator is used to determine the time when the target is ready to start deposition. Hence, this approach can be suited for an industrial environment since the time invested in the cleaning phase can be minimized avoiding the waste of material and time.

Optical and mass spectroscopic properties of microwave CH4/H2/Ar plasma for diamond deposition in a resonance cavity

The properties of microwave CH4/H2/Ar plasma for diamond deposition in a resonant cavity have been investigated by optical emission spectroscopy (OES) and quadrupole mass spectroscopy (QMS). Ar emission intensity decreases monotonically with gas pressure, where electron impact excitation plays an important role. Hα. CH and C2 intensities exhibit the different pressure dependences, which decrease at first and then rise with the further increasing of gas pressure, suggesting the change of electron activation mechanism to thermally driven chemistry for the formation of excited reactive hydrocarbon species at high gas pressures. The addition of small amounts of CH4 to the H2/Ar plasma causes increases in emissions of Hα and CH generated from the CH4 dissociation. With further increase of CH4 flow rate, both emissions and abundances of 2-carbon species enhance, while a reduced intensity of CH emission is observed, reflecting the complex dissociation and dimerization reactions of hydrocarbon species. The dissociation of CH4 is enhanced in plasma under higher power condition. A slight change can be observed in both emission and abundance of hydrocarbon species with increasing Ar flow rate.

Uniformity optimization and dynamic studies of plasma jet array interaction in argon

In this paper, the uniformity of a microsecond pulse driven argon plasma jet array is studied by optimizing experimental parameters, such as the ground electrode position d, gas flow rate, and pulse frequency. The results show that when d is less than 10 mm, there are always two plasma jets that cannot be ignited; while all jets are ignited with equal length at d = 12.5 mm. The plasma jet transition from laminar to turbulent at 6 l/min, presenting a “bead-like” structure. The jet length increases with the pulse repetition frequency and reaches a plateau at around 1.5 kHz. The ICCD images show that the plasma jets emerged preferably from the two quartz tubings located at the two ends of the linear array. The spatial-temporal resolved spectra show that the Ar emission (763.5 nm) and N2 emission (337.1 nm) at the end of the array (e.g., Jet #1) appeared earlier than that of the jet in the middle (e.g., Jet #2). On the contrary, the emission intensities of Ar in Jet #2 are higher than in Jet #1. This is due to the higher electric field and air diffusion at the plasma array boundary.

A diffuse plasma jet generated from the preexisting discharge filament at atmospheric pressure

A diffuse plasma jet was realized by expanding the preexisting argon filamentary discharge into a diffuse one at atmospheric pressure. Examination of emission spectra from the plasma jet shows that the emission intensities of OH and Ar increase with the argon flow near the quartz tube nozzle, while the N2 emission intensity first increases, then decreases, and finally approximately remains unchanged with the increase in the argon flow of interest. It is also found that with the argon flow set at 0.4 l/min, most of the reactive species are gathered close to the nozzle, the OH and Ar emission intensities decrease quickly after the plasma propagates out of the nozzle, but the N2 emission is able to propagate over a larger distance. These distinct spectral emission features of OH, N2, and Ar are attributed to the different generation and quenching mechanisms of their corresponding excited states, i.e., OH(A Σ2 +), N2(C Π3 μ), and Ar(4p)/Ar(4s) in the argon plasma jet. Additionally, the formation of the diffuse plasma jet has been clarified by observing the discharge burning phase and solving the Poisson equation for the electric field distribution in an argon cylindrical dielectric-barrier discharge. The filamentary discharge deposits charged particles onto the dielectric. The positive surface charges in the positive half cycle induce a relatively high field in the local region close to the dielectric. The relatively high field and the high pre-ionization in this local region play a key role in initiating the diffuse positive corona.

Ground state atomic oxygen in high-power impulse magnetron sputtering: a quantitative study

The ground state density of oxygen atoms in reactive high-power impulse magnetron sputtering discharges has been studied quantitatively. Both time-resolved and space-resolved measurements were conducted. The measurements were performed using two-photon absorption laser-induced fluorescence (TALIF), and calibrated by optical emission actinometry with multiple Ar emission lines. The results clarify the dynamics of the O ground state atoms in the discharge afterglow significantly, including their propagation and fast decay after the plasma pulse, as well as the influence of gas pressure, O2 admixture, etc.