FRVT - Artículos en Revistas Internacionales
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Item Ambient Species Density and Gas Temperature Radial Profiles Derived from a Schlieren Technique in a Low Frequency Non-thermal Oxygen Plasma Jet.(2017) Chamorro, Juan Camilo; Prevosto, Leandro; Cejas, Ezequiel; Kelly, Héctor; Mancinelli, Beatriz; Fischfeld, GerardoA quantitative interpretation of the schlieren technique applied to a non-thermal atmospheric-pressure oxygen plasma jet driven at low-frequency (50 Hz) is reported. The jet was operated in the turbulent regime with a hole-diameter based Reynolds number of 13,800. The technique coupled to a simplified kinetic model of the jet effluent region allowed deriving the temporally-averaged values of the gas temperature of the jet by processing the gray-level contrast values of digital schlieren images. The penetration of the ambient air into the jet due to turbulent diffusion was taken into account. The calibration of the optical system was obtained by fitting the sensitivity parameter so that the oxygen fraction at the nozzle exit was unity. The radial profiles of the contrast in the discharge off case were quite symmetric on the whole outflow, but with the discharge on, relatively strong departures from the symmetry were evident in the near field. The time-averaged gas temperature of the jet was relatively high, with a maximum departure of about 55 K from the room temperature; as can be expected owing to the operating molecular gas. The uncertainty in the temperature measurements was within 6 K, primarily derived from errors associated to the Abel inversion procedure. The results showed an increase in the gas temperature of about 8 K close to the nozzle exit; thus suggesting that some fast-gas heating (with a heating rate *0.3 K/ls) still occurs in the near field of the outflow.Item Cathode-sheath model for field emission sustained atmospheric pressure discharges(2021) Cejas, Ezequiel; Prevosto, Leandro; Minotti, Fernando; Ferreyra, Matías; Chamorro, Juan Camilo; Fina, BrendaThe cathode-sheath region of a discharge in atmospheric pressure air with a flat copper cathode is numerically investigated by using a simple fluid model that takes into account non-local ionization. The effects of the cathode temperature are considered. Results are obtained in a wide current density range of 1–102 A/cm2 , which spans from normal glow discharge, through abnormal glow discharge, up to the early stages of the arcing transition. It is shown that the glow-to-arc transition arises from a field-emission instability at the cathode when the cur rent density is larger than 10 A/cm2 , i.e., when the cathode field exceeds a critical value of about 45 V/lm for the conditions considered. It is also shown that the cathode temperature significantly influences the cathode-sheath region. The proposed model is validated by comparing the numerical results with available experimental data.Item Cathode-sheath model for field emission sustained atmospheric pressure discharges.(2021-03-16) Cejas, Ezequiel; Prevosto, Leandro; Minotti, Fernando Oscar; Ferreyra, Matías; Chamorro, Juan CamiloThe cathode-sheath region of a discharge in atmospheric pressure air with a flat copper cathode is numerically investigated by using a simple fluid model that takes into account non-local ionization. The effects of the cathode temperature are considered. Results are obtained in a wide current density range of 1–102 A/cm2 , which spans from normal glow discharge, through abnormal glow discharge, up to the early stages of the arcing transition. It is shown that the glow-to-arc transition arises from a field-emission instability at the cathode when the cur rent density is larger than 10 A/cm2 , i.e., when the cathode field exceeds a critical value of about 45 V/lm for the conditions considered. It is also shown that the cathode temperature significantly influences the cathode-sheath region. The proposed model is validated by comparing the numerical results with available experimental data.Item Effect of in–package cold plasma treatments on the quality of minimally processed apples.(2023) Denoya, Gabriela Inés; Polenta, Gustavo Alberto; Apóstolo, Nancy Mariel; Cejas, Ezequiel; Fina, Brenda; Chamorro, Juan Camilo; Ferreyra, Matías; Prevosto, Leandro; Vaudagna, SergioCold plasma technology is being increasingly used for food preservation and, incipiently, for minimal processing of fruit. Therefore, the objective of this work was to study the effect of in-package cold plasma (generated in atmospheric–pressure air by a low–frequency -50 Hz- dielectric barrier discharge operated at 30 kV) on the quality of minimally processed apples during refrigerated storage. Apple slices were subjected to the different treatments following a completely randomized design with 3 x 3 factorial arrangement. The independent variables were the exposure time (0, 1, 3 min) and the storage times (1, 4, 7 days). Cold plasma treatments preserved the quality of the fruit, maintaining the tissue structure. Plasma treatment applied for 1 min rendered apple slices with the highest antioxidant content but only at day 1. Even though polyphenoloxidase activity was reduced by the treatment, it was not sufficient to stabilize the antioxidant content during storage.Item Effects of non-thermal plasma technology on Diaporthe longicolla cultures and mechanisms involved.(2021-01-05) Pérez Pizá, María Cecilia; Grijalba, Pablo Enrique; Cejas, Ezequiel; Chamorro, Juan Camilo; Ferreyra, Matías; Zilli, Carla; Vallecorsa, Pablo; Yannarelli, Gustavo; Prevosto, Leandro; Balestrasse, Karina; Santa Cruz, DiegoBACKGROUND: The Diaporthe/Phomopsis complex (D/P) is a group of soybean seed-borne fungi. The use of chemical fungicides, either for seed treatment or during the crop cycle, is the most adopted practice for treating fungal diseases caused by this complex. Worldwide, there is a search for alternative seed treatments that are less harmful to the environment than chemicals. Non-thermal plasma (NTP) is a novel seed treatment technology for pathogen removal. This research aimed to evaluate the effects of NTP on the in vitro performance of pure cultures of Diaporthe longicolla and elucidate the mechanisms underlying these effects. RESULTS: Active D. longicolla mycelium, growing in vitro, was exposed to different NTP treatments, employing a dielectric bar rier discharge arrangement with different carrier gases (N2 or O2). Fungal growth, fresh biomass and colony appearance were negatively affected by plasma treatments (TN3 and TO3). Lipid peroxidation and antioxidant activities were higher in plasma treated colonies comparison with non-exposed colonies (control). Fungal asexual spores (conidia) were also exposed to NTP, showing high susceptibility. CONCLUSION: Exposure of D. longicolla colonies to NTP severely compromised fungal biology. Ozone production during treat ment and lipid peroxidation of fungal cell membranes appeared to be involved in the observed effects. © 2020 Society of Chemical IndustryItem Effects of the Plasma-Activated Water on the Quality and Preservation of Fresh-Cut Lettuce.(2023) Chamorro, Juan Camilo; Denoya, Gabriela Inés; Santamaría, Brenda; Fina, Brenda; Ferreyra, Matías; Cejas, Ezequiel; Rodriguez, Anabel; Vaudagna, Sergio; Prevosto, Leandro— The effect of the application of plasma-activated water (PAW) on the quality and preservation of fresh-cut lettuce is reported in this article. PAW was produced by using a liquid cathode air discharge. The average (bulk) water temperature was kept at ∼22 ◦ C during the activation procedure and stored at 4 ◦ C for up to five days. The pH value, electrical conductivity, and concentrations of H2O2 and NO− in liquid at day 1 were 2.81, 1492µS/cm, and 77.8 and 223.4 mg/L, respectively, with slight variations over the whole storage time. No measurable amounts of NO− 10 2 were found. Twenty pieces of lettuce leaves were washed for 1 and 5 min in 1 L of PAW and stored for one and five days. PAW treatments were compared to tap water treatments. The lettuce samples were stored at 4 ◦ C and analyzed on days 1, 3, and 7. The chromatic parameter results suggest that PAW treatments significantly reduce the degradation of lettuce chlorophyll from day 3 of refrigerated storage. The lettuce firmness was not significantly modified. The microbiological results of aerobic mesophilic, enterobacteriaceae, and psychrotrophs populations have shown that lettuce treated with PAW after three days of storage exhibited the strongest inactivation efficiency. Psychrotrophs counts were maintained for up to seven days. Similar inactivation efficiencies were found regardless of the PAW storage time. PAW treatments also favored both the antioxidant capacity FRAP, ABTS, and DPPH, and the total phenolic.Item Indigo Carmine Degradation in Water Induced by a Pulsed Positive Corona Discharge in Air: Discharge and Postdischarge Effects.(2022) Ferreyra, Matías; Fina, Brenda; Milardovich, Natalio; Chamorro, Juan Camilo; Santamaría, Brenda; Balestrasse, Karina; Prevosto, LeandroIn recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating in ambient air is reported. Degradation levels in different volumes of IC in solution with distilled water treated with different plasma exposure times immediately after discharge (0 h), and in the postdischarge up to 24 h were examined. To explain the IC discoloration in the postdischarge phase, a chemical model was developed. The stability of the reactive species in solution nitrate (NO3 −), nitrite (NO2 −) and hydrogen peroxide (H2O2 ), as well as the properties of the solution (electrical conductivity, pH) were also measured. The results suggest that the hydroxyl radical (OH˙) as well as ozone (O3 ) are the main oxidizing species during the discharge phase, being primarily formed in the gas phase through plasma-mediated reactions and then transferred to the liquid by diffusion, while the OH˙ production in the bulk liquid through the decomposition of peroxinitrous acid (O=NOOH) plays a major role in the IC degradation during the postdischarge. These results are associated with a noticeably increase in the energy-yield values observed at 24 h post-treatment.Item Investigation of the relevant kinetic processes in the initial stage of a double-arcing instability in oxygen plasmas.(2018) Mancinelli, Beatriz; Prevosto, Leandro; Chamorro, Juan Camilo; Minotti, Fernando; Kelly, HéctorA numerical investigation of the kinetic processes in the initial (nanosecond range) stage of the double-arcing instability was developed. The plasma-sheath boundary region of an oxygen operated cutting torch was considered. The energy balance and chemistry processes in the dis charge were described. It is shown that the double-arcing instability is a sudden transition from a diffuse (glow-like) discharge to a constricted (arc-like) discharge in the plasma-sheath boundary region arising from a field-emission instability. A critical electric field value of 107 V/m was found at the cathodic part of the nozzle wall under the conditions considered. The field-emission instability drives in turn a fast electronic-to-translational energy relaxation mechanism, giving rise to a very fast gas heating rate of at least 109 K/s, mainly due to reactions of preliminary dissocia tion of oxygen molecules via the highly excited electronic state populated by electron impact. It is expected that this fast oxygen heating rate further stimulates the discharge contraction through the thermal instability mechanism.Item Modelling of the Plasma–Sheath Boundary Region in Wall-Stabilized Arc Plasmas: Unipolar Discharge Properties.(2017) Mancinelli, Beatriz; Prevosto, Leandro; Chamorro, Juan Camilo; Minotti, Fernando; Kelly, HéctorA two-dimensional model of the non-equilibrium unipolar discharge occurring in the plasma–sheath boundary region of a transferred-arc was developed. This model was used to study the current transfer to the nozzle (1 mm diameter) of a 30 A arc cutting torch operated with oxygen. The energy balance and chemistry processes in the discharge were described by using a kinetic block of 45 elementary reactions and processes with the participation of 13 species including electronically excited particles. The nonlocal transport of electrons was accounted for into the fluid model. The dependence of the ion mobility with the electric field was also considered. Basic discharge properties were described. It has been found that a large part (* 80%) of the total electric power (1700 mW) delivered in the bulk of the sheath region is spent in heating the positive ions and further dissipated through collisions with the neutral particles. The results also showed that the electron energy loss in inelastic collisions represents only * 25% of the electron power and that about 63% of the power spent on gas heating is produced by the ion– molecule reaction, the electron–ion and ion–ion recombination reactions, and by the electron attachment. The rest of the power converted into heat is contributed by dissociation by electron-impact, dissociative ionization and quenching of O(1 D). Some fast gas heating channels which are expected to play a key role in the double-arcing phenomena in oxygen gas were also identified.Item Non-thermal plasma application improves germination, establishment and productivity of Gatton panic grass (Megathyrsus maximus) without compromising forage quality.(2022) Pérez Pizá, María Cecilia; Clausen, Liliana; Cejas, Ezequiel; Ferreyra, Matías; Chamorro, Juan Camilo; Fina, Brenda; Zilli, Carla; Vallecorsa, Pablo; Prevosto, Leandro; Balestrasse, KarinaMegathyrsus maximus (Gatton panic) is a tropical grass highly valued both for its use as forage and for its biofuel potential. A major constraint in establishing pastures of this cultivar is the low viability and germination ofseeds and the poorinitialseedling establishment. We used non-thermal plasma (NTP, partially ionised gas) as a novel technology to treat seeds of this grass, aiming to improve their quality (i.e. germination traits). We also followed the performance of seedlings grown from NTP-treated seeds under field conditions by assessing seedling establishment, biomass production and forage quality during the first regrowth period, which is the critical period for pasture establishment. Two NTP treatments were performed through dielectric barrier discharges employing N2 as carrier gas. Non-treated seeds served as the control. Results showed that the viability of NTP treated seeds was, on average, 1.5-fold higher than the control, and that germination energy and germination percentage of treated seeds was superior to the control by 2.1-fold and 2.2-fold, respectively. A field experiment showed that seedling establishment parameters (dynamics of cumulative emergence, emergence coefficient, and weighted average emergence rate) and pasture early productivity (represented by shoot dry matter) were enhanced by NTP treatment (phenolic sheet–polyester film barrier and 3 min exposure), showing 1.4–2.6-fold higher values than the control, confirming the results of the laboratory assays. Although NTP markedly increased the shoot dry matter production of the pasture, which was related to higher tiller population density and greater tiller weight, it did not affect the forage quality of the plants grown in the field. We conclude that NTP technology is suitable to improve seed germination of Gatton panic, in turn leading to improvements in seedling establishment and biomass production under field conditions without compromising forage quality.Item Non-thermal plasma as emerging technology for Tribolium castaneum pest-management in stored grains and flours.(2022) Zilli, Carla; Pedrini, Nicolás; Prieto, Eduardo; Girotti, Juan Roberto; Vallecorsa, Pablo; Ferreyra, Matías; Chamorro, Juan Camilo; Cejas, Ezequiel; Fina, Brenda; Prevosto, Leandro; Balestrasse, KarinaThe red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is a major secondary pest on wheat stored in metal bins, silo-bags and is also frequently found in wheat products such as flour. Non-thermal plasmas (NTPs) are (quasi-neutral) partially ionized gases that may be produced by a variety of electrical dis charges. We propose the use of an atmospheric pressure dielectric barrier discharge (DBD) as an emerging technology in post-harvest integrated pest management. To this aim, a series of experiments were performed in order to test the lethality of such plasmas on three life stages of T. castaneum by measuring insect mortality and their impacts on physiological and biochemical parameters affecting insect fitness. The different NTP treatments were performed by increasing the time of exposure to either O2 or N2 used as carrier gases. After 24 hours, high levels of mortality (30–100%) were reached for each applied treatment, in both larval and adult populations. Mortality seems to be related to a significant water content loss and redox imbalance. Atomic force microscopy (AFM) scanning of the prothoracic surface showed that nitrogen causes more severe damage than oxygen. As a consequence of the cuticle damage, the quinone-containing secretions of the prothoracic and abdominal glands were affected. We also carried out experiments on egg-containing flours to test the ovicidal activity of NTP. The flours were evaluated at three and twelve weeks after treatments. A 3-min nitrogen treatment showed ovicidal properties, while the remaining NTPs partially killed the eggs and delayed the emergence of larvae and adults. In conclusion, we propose an inexpensive physical treatment, which controls the entire life cycle of a major grain pest, avoiding chemical residues.Item Non‑Thermal Plasmas Afect Plant Growth and DNA Methylation Patterns in Glycine max.(2021) Pérez Pizá, María Cecilia; Ibañez, Verónica; Varela, Anabella; Ferreyra, Matías; Chamorro, Juan Camilo; Zilli, Carla; Vallecorsa, Pablo; Fina, Brenda; Prevosto, Leandro; Marfil, Carlos; Cejas, Ezequiel; Balestrasse, KarinaNon-thermal plasmas (NTP) are partially ionized gases that represent a promising technology for seed treatment to enhance seed health while promoting germination and vigor in a fast, cost-efective, and eco-friendly way. The seed treatment with NTP generates phenotypic variations in plants that could be related to changes in DNA methylation. This work analyses the efects of two diferent NTP: nitrogen for 3 min (PMN3) and oxygen for 2 min (PMO2) applied to soybean (Glycine max) seeds. Growth parameters of plants grown from treated and untreated seeds were evaluated at two growth stages: 6 and 20 days after sowing (DAS). MSAP (Methylation Sensitive Amplifed Polymorphism) markers were assayed to evaluate epigenetic changes induced by NTP treatments. Plants obtained from PMN3 and PMO2-treated seeds were phenotypically similar to each other: exhibited a superior growth at both stages. At 6 DAS root and shoot length and fresh weight surpassed the Control, while at 20 DAS root length and fresh and dry weight were higher than Control. PMN3 and PMO2 induced DNA methylation changes with respect to the Control plants, with higher diferentiation at 20 DAS than at 6 DAS. The epigenetic variability and the phenotypic variability correlated only at 20 DAS (R2=0.5). The observed phenotypic diferences among Control and NTP-treated plants could not be explained by overall changes in the methylation levels, but both demethylation and methylation changes at specifc loci appear to be operating in response to NTP treatments.Item On the Gas Heating Mechanism for the Fast Anode Arc Reattachment in a Non-transferred Arc Plasma Torch Operating with Nitrogen Gas in the Restrike Mode.(2015) Prevosto, Leandro; Kelly, Héctor; Mancinelli, Beatriz; Chamorro, Juan CamiloThe present work provides a detailed kinetic analysis of the time-resolved dynamics of the gas heating during the arc reattachment in nitrogen gas in order to understand the main processes leading to such a fast reattachment. The model includes gas heating due to the relaxation of the energy stored in the vibrational as well as the electronic modes of the molecules. The results show that the anode arc reattachment is essentiality a threshold process, corresponding to a reduced electric field value of E/N * 40 Td for the plasma discharge conditions considered in this work. The arc reattachment is triggered by a vibrational instability whose development requires a time of the order of 100 ls. For E/N\80–100 Td, most of the electron energy is transferred to gas heating through the mechanism of vibrational–translational relaxation. For larger values of E/N the electronic– translational energy relaxation mechanism produces a further intensification of the gas heating. The sharp increase of the gas heating rate during the last few ls of the vibrational instability give rises to a sudden transition from a diffuse (glow-like) discharge to a constricted arc with a high current density (*107 A/m2 ). This sudden increase in the current density gives rise to a new anode attachment closer to the cathode (where the voltage drop between the original arc and the anode is the largest) thus causing the decay of the old arc spot.Item On the physical processes ruling an atmospheric pressure air glow discharge operating in an intermediate current regime(2015-02-06) Prevosto, Leandro; Kelly, Héctor; Mancinelli, Beatriz; Chamorro, Juan Camilo; Cejas, EzequielLow-frequency (100 Hz), intermediate-current (50 to 200 mA) glow discharges were experimentally investigated in atmospheric pressure air between blunt copper electrodes. Voltage–current characteristics and images of the discharge for different inter-electrode distances are reported. A cathode-fall voltage close to 360V and a current density at the cathode surface of about 11 A/cm2, both independent of the discharge current, were found. The visible emissive structure of the discharge resembles to that of a typical low-pressure glow, thus suggesting a glow-like electric field distribution in the discharge. A kinetic model for the discharge ionization processes is also presented with the aim of identifying the main physical processes ruling the discharge behavior. The numerical results indicate the presence of a non-equilibrium plasma with rather high gas temperature (above 4000 K) leading to the production of components such as NO, O, and N which are usually absent in low-current glows. Hence, the ionization by electron-impact is replaced by associative ionization, which is independent of the reduced electric field. This leads to a negative current-voltage characteristic curve, in spite of the glow-like features of the discharge. On the other hand, several estimations show that the discharge seems to be stabilized by heat conduction; being thermally stable due to its reduced size. All the quoted results indicate that although this discharge regime might be considered to be close to an arc, it is still a glow discharge as demonstrated by its overall properties, supported also by the presence of thermal non-equilibrium. VC 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4907661]Item Physicochemical Properties and Time Stability of Plasma Activated Water by a Liquid-Cathode Glow-Type Discharge in Air: The Effect of Air Confinement.(2023) Santamaría, Brenda; Ferreyra, Matías; Chamorro, Juan Camilo; Cejas, Ezequiel; Fina, Brenda; Prevosto, LeandroNonthermal discharges in atmospheric pressure air in contact with water produce large amounts of reactive species in the gas phase that can enter into the water by diffusion, thus inducing the formation of secondary reactive species in the liquid phase, including those long-lived species such as NO2 NO3, and H2O2. Depending on the controllable parameters of the discharge, the plasma activated water (PAW) may acquire differ 8 ent physicochemical properties, resulting in various applications. Physicochemical measurements of PAW obtained by means of a water-cathode glow-type discharge in atmospheric pressure air operating in open and closed reactor conditions are reported. The discharge was operated in a millisecond pulsed-dc regime at an rms current value of 100 mA and a power of 100 W. A large volume of 1 L of distilled water was treated for 30 min. In both cases, low pH values of ∼2.5 and very high levels of NO3(up to 250 mg/L) in PAW were obtained; however, in the closed system, no H2O2 was found and high concentrations of nitrite (120 mg/L) were measured, while in the open system, large levels of H2O2 were observed (45 mg/L) and no NO 2 was found. Likewise, the electrical conductivity value for the closed reactor (≈2000 µS/cm) was significantly higher than for the open reactor (≈1000 µS/cm). The reasons for these different behaviors in terms of PAW chemistry are discussed. Also, the time stability of PAW was measured.Item Plasma Cutting of Concrete: Heat Propagation and Molten Material Removal From the Kerf.(2019) Chamorro, Juan Camilo; Prevosto, Leandro; Cejas, Ezequiel; Milardovich, Natalio; Mancinelli, Beatriz; Fischfeld, GerardoAn experimental investigation of heat propagation in the case of plasma cutting of concrete is reported. The experiments were carried out by using a high-enthalpy nitrogen plasma jet generated in a dc vortex-stabilized nontransferred arc torch. Concrete plates of different thicknesses up to 52 mm and with and without steel reinforcement were used. The plates were placed horizontally while cutting. The heat conduction losses inside the material were estimated by comparing thermocouple measurements and theoretical temperatures obtained with an analytical model of the heat propagation in the material. The influence of the molten concrete layer that separates the plasma to the solid material due to the high viscosity of the liquid concrete was accounted for. The power losses below the material in the extinguishing plasma have also been determined from calorimet ric measurements. For different plate thicknesses and cutting velocities, a complete power balance of the process is performed with the calculation of the cutting efficiency on the basis of various relevant power terms. In addition, the hydrodynamics of the molten concrete layer in the kerf is analyzed. For a mean power level of 11.2 kW and a nitrogen gas flow rate of 25 Nl/min, the torch is able to cut a concrete plate of 52 mm in thickness with a speed of 20 mm/min and a whole efficiency of about 30%. The viscosity force is the main limiting factor on the cutting velocity in thick plates.Item Quantitative Schlieren Diagnostic Applied to a Nitrogen Thermal Plasma Jet.(2018) Chamorro, Juan Camilo; Prevosto, Leandro; Cejas, Ezequiel; Kelly, Héctor— A quantitative interpretation of the schlieren technique applied to an atmospheric pressure, vortex-stabilized nitrogen thermal plasma jet generated in a direct-current nontransferred arc plasma torch (nitrogen gas flow rate of 25 NL/min, power level of 15 kW), discharging into ambient air is reported. A Z-type, two-mirror schlieren system was used in the research. The technique allowed inferring the temporally averaged values of the temperatures and densities of different species present in the plasma jet in a wide range of radial and axial distances. Deviations from kinetic equilibrium in the calculation of the plasma refractive index were accounted for, but maintaining the assumption of the local chemistry equilibrium. The influence of several assumptions on the accuracy of the measurements was considered. The results have shown that for a distance of 3.5-mm downstream from the nozzle exit, the kinetic equilibrium is realized (being both electron and gas temperatures values around 11 000 K), but noticeable deviation from kinetic equilibrium appears toward the jet border. On the other hand, a marked deviation from the kinetic equilibrium was found in the whole far field of the plasma jet, where the electron temperature remains still quite high (about 10 000 K at 30-mm downstream of the nozzle exit), well decoupled from the gas temperature (about 7000 K at the same distance). The obtained results are in reasonable good agreement with those previously reported by some of the authors by using a double floating probe method in the same plasma torch.Item Quantitative Schlieren Diagnostics Applied to a Millisecond Pulsed‑DC Hybrid Discharge in Atmospheric Pressure Air.(2022) Cejas, Ezequiel; Chamorro, Juan Camilo; Prevosto, LeandroThe gas temperature of a hybrid discharge in atmospheric pressure air is investigated by using quantitative schlieren imaging. The discharge is stabilized in a pin-to-plate electrode geometry and operated in a millisecond pulsed-DC regime with current amplitudes up to 75 mA and a duration of 10 ms, applied at a frequency of 100 Hz. An equilibrium com position model is considered to account for the production of N, O, and NO, which infu ence the Gladstone–Dale coefcient of air at high-gas temperatures. Also, a procedure is described which allows the determination of the errors introduced in the time-average gas refraction index due to gas temperature fuctuations. The results show that the axial values of the gas temperature profles span a large range from~1000 to 5000 K, nearly following the evolution of the discharge current. The temperature values found agree well with those reported in the literature for atmospheric pressure air plasmas, ranging from micro-glow to hybrid discharges.