Jet Discharge Research Articles

Turbulent transport mechanisms and their impact on the pedestal top of JET plasmas with small-ELMs

Abstract Understanding the transport mechanisms that regulate the H-mode pedestal structure is crucial for developing regimes with edge dynamics that are compatible with the thermal and particle load constraints of plasma facing components. In this regard, at the JET tokamak, H-mode plasma regimes featuring small-ELM (BSE) dynamics have been developed, expelling less plasma energy per ELM compared to the standard type-I ELM. The pedestal of these new regimes remains stable against peeling-ballooning modes, leaving its structure unexplained.
In this study, three baseline H-mode JET discharges, a reference with type-I ELM and two BSE regimes, are selected to investigate the turbulent transport mechanisms occurring in pedestals with different structures. The turbulence analysis is conducted using local gyrokinetic simulations around the pedestal top position. The results show that at ion-scales, while hybrid ITG-KBM and KBM are destabilized in the type-I ELM discharge, the BSE regimes are dominated by hybrid ITG-TEM, suggesting a different role of turbulent transport in the two cases. At electron-scales, both regimes are dominated by toroidal and slab ETG, the latter extending up to very small scales. Simulations of turbulence driven by hybrid ITG-TEM focuses on the impact and competition of electromagnetic (EM) effects and equilibrium $\vb*{E}\times\vb*{B}$ shearing. A strong EM stabilization mechanism is found, resulting in a saturated turbulence regime with spectra different from those in the electrostatic limit (ES$_l$). Additionally, while increasing $\vb*{E}\times\vb*{B}$ shearing reduces transport in ES$_l$ simulations, it is observed to have the opposite effect in the EM regime. Finally, stiff ETG transport is also shown to produce transport levels compatible with experimental observations.
The findings of this study suggest the EM stabilization and its competition with $\vb*{E}\times\vb*{B}$ shearing as new key elements determining the nature of the turbulent transport mechanisms around the pedestal top, which need to be considered in reduced models for pedestal limits.

Surface modification of carbon fibres via plasma-activated water for mitigating burnout risk from direct plasma treatment

This study presents a novel plasma jet discharge device designed to indirectly treat carbon fibre materials with plasma-activated water. This innovative method effectively mitigates issues related to carbon fibre conduction and combustion, which are common challenges encountered when directly modifying fibres using a plasma jet. Specifically, the atmospheric composition is adjusted to modulate the active particles in the liquid phase. The experimental results demonstrate that this technique significantly increases the surface wettability of carbon fibres without damaging their structure. Under the conditions of argon/oxygen cascade discharge, oxygen-containing substances generate ionomers that activate the water, which in turn introduces oxygen-containing groups (e.g., C−O, C=O, O−C=O) onto the carbon fibre surface. These groups catalyse monomer polymerisation on the material surface, which increases the wettability of the carbon fibres, as evidenced by a significant reduction in the water contact angle from 80.12° to 55.31°. This in turn improves the bonding strength with epoxy resin and slightly increases the monofilament strength. Furthermore, composites produced by this method exhibit 21% higher interlaminar shear strength than the untreated sample and an increased O/C ratio of up to 24.55%. In summary, these findings provide a valuable theoretical basis for enhancing the surface properties of carbon fibre composites through plasma–liquid interactions and open new possibilities for high-performance carbon fibre–resin matrix composites.

Hydrogen isotopic ratio by residual gas analysis during the JET DT campaigns

Abstract The analysis of hydrogen isotope content is crucial for understanding the operation of fusion devices. Hydrogen isotopic analysis in the core and plasma edge is conducted through neutron and spectroscopic diagnostics. In the case of exhaust gas, mass spectrometry is employed using residual gas analyzers (RGAs), along with optical gas analysis (OGA) utilizing an optical Penning gauge. The use of traditional quadrupole mass spectrometers for RGA encounters challenges during discharges with tritium gas due to signal overlap of different hydrogen molecules at the same mass number. This paper introduces a novel technique to address this issue through a cross-related analysis of RGA data with OGA results. Another consideration in mass spectrometry analysis is the instrument’s varying sensitivity concerning the gas mass number. The paper includes gas calibration data results for all the quadrupoles used in the JET gas analysis. Hydrogen isotopic ratios are calculated from RGA detected currents using simple formulas. The results of this procedure are presented for selected DT JET discharges in relation to the JET pulse time, and they are compared with corresponding optical data. Time-averaged hydrogen isotopic ratio values are computed for numerous discharges during the DT and T campaigns.

Thermal-induced buoyant water jet discharge under shallow coastal water conditions

A novel discharge dispersion model is developed to simulate the complex three-dimensional flow behaviour of thermal-induced buoyant water jets under current-wave coexisting conditions. The model solved the governing fluid flow and energy equations for two immiscible and incompressible phases (water and air) which were weakly coupled by applying the Boberbeck-Boussinesq approximation. Different turbulence models, such as k−ε multiphase, k-ω SST, k-ω SST-multiphase, k-ω SST-stable, and realizable k−ε were applied. Extensive verification of the model's performance is conducted by comparing the developed model results against a diverse range of analytical and experimental data. First, a series of simulations are carried out to evaluate the performance of the model in reproducing the results of the wave hydrodynamic and interactions with the submerged trapezoid bar. This is followed by numerically replicating the experimental results of a vertical non-buoyant submerged jet under current-only and current-wave environments. Finally, the potency of the coupled hydro-thermal algorithm is assessed by validating against different thermal-induced buoyant submerged jet experimental tests. For this purpose, numerical prediction of the developed model is tested against physical experiments for a series of tests for thermal-induced buoyant submerged horizontal jets in stationary water and inclined thermal-induced buoyant water jet under the influence of current-wave environments. Results showed that the k-ω SST-multiphase provides the best agreement with the laboratory measured data in terms of flow, temperature distribution field, plume trajectory and dilution. The findings confirmed that the developed model can be used as a reliable tool in precisely modelling characteristic of thermal-induced buoyant water jet in shallow coastal waters.

Elucidating the bacterial inactivation mechanism by argon cold atmospheric pressure plasma jet through spectroscopic and imaging techniques.

This study aims to assess the potential bacterial inactivation pathway triggered by argon (Ar) cold atmospheric pressure plasma jet (CAPJ) discharge using spectroscopic and imaging techniques. Electrical and reactive species of the Ar CAPJ discharge was characterized. The chemical composition and morphology of bacteria pre- and post-CAPJ exposure were assessed using Fourier transform infrared (FTIR), Raman micro-spectroscopy, and transmission electron microscopy (TEM). A greater than 6 log reduction of E. coli and S. aureus was achieved within 60 and 120 s of CAPJ exposure, respectively. Extremely low D- values (< 20 s) were recorded for both the isolates. The alterations in the FTIR spectra and Raman micro-spectra signals of post-CAPJ exposed bacteria revealed the degree of destruction at the molecular level, such as lipid peroxidation, protein oxidation, bond breakages, etc. Further, TEM images of exposed bacteria indicated the incurred damages on cell morphology by CAPJ reactive species. Also, the inactivation process varied for both isolates, as evidenced by the correlation between the inactivation curve and FTIR spectra. It was observed that the identified gas-phase reactive species, such as Ar I, O I, OH•, NO+, OH+, NO2-, NO3-, etc. played a significant role in bacterial inactivation. This study clearly demonstrated the effect of CAPJ exposure on bacterial cell morphology and molecular composition, illuminating potential bacterial inactivation mechanisms.

Optimizing plasma-activated water for enhanced microbial control in agricultural produce processing

The study utilized a pinhole plasma jet discharge system to generate plasma-activated water (PAW) for the removal of microbes on bird's eye chili. Optimal conditions for PAW generation were determined using response surface methodology, achieving maximum microbial inactivation. The novelty of this study lies in designing a PAW system model for agricultural cooperatives using the Quality Function Deployment (QFD) methodology, which integrates customer and engineer/designer perspectives. The results demonstrate a maximum 82.54% microbial removal rate on bird's eye chili under optimal conditions (e.g., exposure time = 20 min, Ar gas flow rate = 5 L/min, and O2 mixture = 2% Ar gas), indicating effective antimicrobial activity of plasma-activated water. Furthermore, a model of the PAW system for agricultural cooperatives, including cost and electrical power usage estimates, is proposed based on the correlation matrix of QFD. This conceptual PAW model for agricultural cooperatives warrants further investigation to assess its consistency in sterilization efficiency and long-term effects on treated agricultural products.

Effects of using nanosecond repetitively pulsed discharge and turbulent jet ignition on internal combustion engine performance

Robust ignition of hard-to-ignite fuels is essential for future spark ignited internal combustion engines, particularly for introducing efficiency-enhancing diesel-like process parameters like air excess or high amounts of exhaust gas recirculation (EGR). On the one hand, novel plasma-based ignition systems like Nanosecond Repetitively Pulsed Discharge (NRPD) are promising in extending the ignition limits and the early flame development speed. On the other hand, Turbulent Jet Ignition is effective for shortening the combustion duration and decreasing the unburned hydrocarbon emissions.This article investigates experimentally the combination of NRPD ignition and TJI. The aim is to use a technology for robust inflammation (NRPD) in combination with a technology for fast combustion of the bulk charge (TJI). For this purpose, a turbocharged light-duty four-cylinder engine operated with natural gas is used. The engine can be fitted with a classical Open Chamber (OC) spark plug or with Pre-Chambers (PC). The PCs can be filled uniquely with fuel and air coming from the Main Chamber (MC) (“passive PC”), or additional fuel can be added to the PCs (“active PC”). The air-to-fuel ratio and EGR rate can be freely controlled. Five different combustion strategies are investigated with NRPD ignition and compared against an inductive discharge ignition system. The combustion strategies are passive PC with air and EGR dilution, active PC with air dilution, and Open Chamber (OC) with air and EGR dilution. HRR evaluations and a loss analyses are performed to interpret the results.Despite the faster inflammation present with NRPD ignition, similar peak efficiencies and emissions are reached in OC configuration using the inductive discharge and NRPD ignition systems, which are achieved by varying air-to-fuel ratios (AFR) and EGR rates. Above dilution levels for peak efficiency, the efficiency using NRPD ignition decreases at a slower pace and tolerates higher AFR and EGR rates, thanks to a more complete and shorter combustion.For the PC experiments using NRPD ignition, an efficiency increases and a reduction of emissions compared to inductive discharge ignition are present for the investigated AFR and EGR rates for both active and passive PC operations. The efficiency increase is present due to a stronger pre-chamber discharge and thanks to a faster end phase of combustion. Actively fueling the PC results in faster and more complete combustion that is overcompensated by the increased wall heat losses, reducing the overall efficiency. The results show that passive PC with NRPD ignition may be an ideal ignition concept that maximizes engine efficiency and minimizes emissions.

The impact of atmospheric air plasma treatment on the polyfunctional end-use polyester fabric using new synthetic pyrazole dye

Before gluing, bonding, and painting, a variety of materials' surfaces can be modified using the widely used plasma treatment technique. These materials include plastics, glass, metals, and wood. Materials' physical and chemical properties are changed in an environmentally responsible way to enhance or confer particular qualities. The recently used technology known as low-temperature atmospheric pressure plasma (LTAPP) allows heat-sensitive materials to be surface modified in a simple, one-step process. Polymer-based materials are frequently surface modified using LTAPP treatment to improve adhesion, printability, and surface sterility. Polyester's superior mechanical and physical qualities have led to its widespread use as a technical textile and garment material in the form of fibers, films, and plastics. Its limited versatility in terms of end use has been caused by its poor surface properties as the hydrophobic nature of polyester surface, roughness, the crystallinity, and lack of dyeability which are the main drawback restricting its use in different textile applications especially during wet treatments unlike natural fibers. In order to increase the fabric's hydrophilicity and dyeability, the surface of a polyester fabric was altered in this study using atmospheric pressure plasma treatment with atmospheric plasma jet and dielectric barrier discharge (APJ-DBD) technology in air. The primary obstacles in making dielectric barrier discharge (DBD) plasma treatment suitable for industrial purposes are the extended duration of treatment and the utilization of elevated voltage levels. The combination between the atmospheric plasma jet and the dielectric barrier discharge reduces the optimal treatment time to 1 min and the applied voltage to 3.3 kV. After being exposed to oxygen plasma species for a brief period of time (between 30 and 300 s), and were analyzed using an X-ray diffraction machine, an X-ray photoelectron spectroscopy (XPS), static contact angle, and a scanning electron microscope (SEM) to investigate changes in the morphology and chemical nature of the surface, respectively. Fabric wettability increased as a result of plasma treatment, which also increased the fabric's surface roughness, as demonstrated by SEM and X-ray diffraction. The contact angle decreases by increasing the treatment time. The dyeability of untreated and plasma-treated samples was examined with respect to washing, rubbing, perspiration, sublimation, and light fastness. Additionally, color strength was examined. Adequately, compared to the untreated fabric, polyester treated with plasma showed improved dyeing performances. The technical reactivity of poly (ethylene-terephthalate) (PET) fabrics was found to be effectively increased by atmospheric air plasma treatment, creating new avenues for surface modification in light of the expanding environmental and energy-saving concerns.

Carbon nanostructures synthesis by catalyst-free atmospheric pressure plasma jet

In this study, carbon nanostructures were synthesized utilizing a warm plasma jet at atmospheric pressure in a continuous and catalyst-free process. The procedure and apparatus were designed and constructed in our laboratory. Plasma was generated with 600 W of electrical energy, using a high-voltage, high-frequency alternating current power source. The working gas utilized was a propane/butane mixture, with a concentration ratio of 60:40, respectively. A production rate of 300 mg min−1 of powdered material was achieved, with a particle size between 20 and 100 nm. The product was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Results show the formation of multilayer carbon nanostructures with a low content of functional groups; the obtained material presented structural defects and amorphous carbon. This work demonstrates that, with adequate control, warm plasma jet discharges can be employed for the synthesis of carbon nanostructures. The process is scalable and can be utilized for hydrocarbon reforming and hydrogen production. However, further studies are needed to improve the quality of the nanostructures and process efficiency. The synthesized material can potentially be used in gas adsorption or in the manufacture of polymeric nanocomposites with enhanced thermal, electrical, and mechanical properties.

Investigation of dredging pattern due to changes in jet cross-section

Sediment management is a significant part of the decision-making process that hydraulic engineers need to undertake as it has a direct bearing on the environment. Sediment dredging from around intake structures and reservoirs impose a high operating cost. Jets can efficiently remove large quantities of sediment at low operational costs. This study assesses the scouring pattern development by changing nozzle parameters to achieve maximum scouring conditions. Toward this end, scour holes induced by jets generated using the nozzles with four inner angles (30°, 45°, 60°, and 90°) are tested on a cohesionless sediment bed. The experimental results show that the inner nozzle angle, α, and the densimetric Froude number, F0, affect the scour pattern. This work illustrates that the scour hole dimensions grow with increasing α and F0. Based on the velocity measurements, for the range of jet discharges considered herein, the relative velocity Um/ U0 is increased by 20%–25% for the nozzle with α = 90° compared to the nozzle with α = 30°.

Abstract B030: Synergistic antitumor effects of cold atmospheric plasma and temozolomide in glioblastoma: multimodal approaches integrating in-vitro, in vivo, and in silico investigations for novel and enhanced therapeutic advancements

Abstract Glioblastoma multiforme (GBM) is a common and aggressive brain cancer with a median survival rate of 12 to 18 months after diagnosis. Despite standard treatments, including surgery, radiotherapy, and Temozolomide (TMZ), GBM remains highly resistant to therapy due to its infiltrative pattern of invasion, rapid growth, and propensity to relapse [1]. While overall mortality rates remain high, there is a crucial need for a better understanding of the molecular mechanisms and gene mutations involved in GBM and the development of more effective and adaptive therapeutic approaches. Modulating reactive oxygen species (ROS) levels has been suggested as a therapeutic strategy to selectively target the destruction of cancer cells. To address this, we propose a combination therapy utilizing multi-operational plasma devices, including using cold atmospheric plasma (CAP) jet and plasma discharge tube (PDT) in conjunction with TMZ for GBM treatment. CAP functions by elevating reactive oxygen and nitrogen species (RONS) levels and specifically targeting tumor spread. We investigated various plasma devices and their characteristics using optical emission spectroscopy (OES) and measured the electromagnetic potential and emissions of the PDT. The OES of PDT displayed a similar spectrum as the CAP jet, indicating the presence of ROS. In this study, we performed transcriptomic analysis of glioblastoma cells using high throughput deep RNA-Seq with next-generation sequencing (NGS) to quantify genome-wide gene expression changes. Additionally, we examined signaling pathways and predicted structural changes in consequential proteins caused by gene spectrum up or down-regulation. Our results demonstrate that the combination treatment of CAP and TMZ downregulated vital genes involved in MAPK, P53, DNA repair, and cell cycle pathways. The combination of CAP &amp; TMZ showed a significant antitumor effect, inducing apoptosis and damaging essential proteins in GBM cells. In vitro and microscopic studies verified these results, showing nuclear and cell membrane disruption in cancer cells post-plasma treatment. Our findings demonstrate that the combination of CAP/PDT and TMZ effectively sensitizes GBM cells to TMZ, leading to apoptosis. We have previously shown a non-invasive application of CAP jet on the skull of tumor-bearing mice causing ~78% tumor inhibition [2]. Our current study highlights the potential of PDT for non-invasive treatment in vitro, offering a modality for intracranial delivery in in-vivo models. In conclusion, we propose CAP/PDT and TMZ combination therapy as novel non-invasive treatments for GBM in murine models. This approach offers a promising avenue for addressing the dire need for more effective treatments with minimal impact on normal cells. Further investigations and validation in clinical settings are warranted to significantly improve GBM management and patient outcomes.

End-to-end Mathematical Model of a Radio-Frequency Inductive Jet Discharge of Lowered Pressure

End-to-end Mathematical Model of a Radio-Frequency Inductive Jet Discharge of Lowered Pressure

A hybrid physics/data-driven logic to detect, classify, and predict anomalies and disruptions in tokamak plasmas

Disruptions are abrupt collapses of the configuration that have afflicted all tokamaks ever operated. Reliable observers are a prerequisite to the definition and the deployment of any realistic strategy of countermeasures to avoid or mitigate disruptions. Lacking first principle models of the dynamics leading to disruptions, in the past decades empirical predictors have been extensively studied and some were even installed in JET real time network. Having been conceived as engineering tools, they were often very abstract. In this work, physics and data-driven methodologies are combined to identify the main macroscopic precursors of disruptions: magnetic instabilities, abnormal kinetic profiles and radiation patterns. Machine learning predictors utilising these observers can not only detect and classify these anomalies but also determine their probability of occurrence and estimate the time remaining before their onset. These tools have been applied to a database of about two thousand JET discharges with various isotopic compositions including DT, in conditions simulating in all respects real time deployment. Their performance would meet ITER requirements, and they are expected to be easily transferrable to larger devices, because they rely only on normalised quantities, form factors, and physical/empirical scaling laws.

Real-time disruption prediction in multi-dimensional spaces leveraging diagnostic information not available at execution time

This article describes the use of privileged information to train supervised classifiers, applied for the first time to the prediction of disruptions in tokamaks. The objective consists of making predictions with real-time signals during the discharges (as usual) but after training the predictor also with any kind of data at training time that is not available during discharge execution. The latter kind of data is known as privileged information. Taking into account the limited number of foreseen real time signals for disruption prediction at the beginning of operation in JT-60SA, a predictor with a line integrated density signal and the mode lock signal as privileged information has been developed and tested with 1437 JET discharges. The success rate with positive warning time has been improved from 45.24% to 90.48% and the tardy detection rate has diminished from 50% to 8.33%. The use of privileged information in an adaptive way also provides a remarkable reduction of false alarms from 11.53% to 1.15%. The potential of the methodology, exemplified with data relevant to the beginning of JT-60SA operation, is absolutely general and can be applied to any combination of diagnostic signals.

3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool

Precise values for radiated energy in tokamak disruption experiments are needed to validate disruption mitigation techniques for burning plasma tokamaks like ITER and SPARC. Control room analysis of radiated power (P rad) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, radiation is toroidally asymmetric and 3D, due to fast-growing 3D MHD modes and localized impurity sources. To address this problem, Emis3D adopts a physics motivated forward modeling (‘guess and check’) approach, comparing experimental bolometry data to synthetic data from user-defined radiation structures. Synthetic structures are observed with the Cherab modeling framework and a best fit chosen using a reduced χ 2 statistic. 2D tomographic inversion models are tested, as well as helical flux tubes and 3D MHD simulated structures from JOREK. Two nominally identical pure neon shattered pellet injection (SPI) mitigated discharges in JET are analyzed. 2D tomographic inversions with added toroidal freedom are the best fits in the thermal quench (TQ) and current quench (CQ). In the pre-TQ, 2D reconstructions are statistically the best fits, but are likely over-optimized and do not capture the 3D radiation structure seen in fast camera images. The next-best pre-TQ fits are helical structures that extend towards the high-field side, consistent with an impurity flow under the magnetic nozzle effect also observed in JOREK simulations. Whole-disruption radiated fractions of 0.98+0.03/ −0.29 and 1.01+0.02/−0.17 are found, suggesting that the stored energy may have been fully mitigated by each SPI, although mitigation efficiencies well below ITER and SPARC requirements for high energy pulses are still within the large uncertainties. Emis3D is also used to validate JOREK SPI simulations, and confirms improvements in matching experiment from changes to impurity modeling. Time-dependent toroidal peaking factors are calculated and discussed.

Effect of pineapple leaf and ramie fiber length and weight percentage on the hybrid polymer composites dry sliding wear and air jet erosion studies

AbstractIn this work, pineapple leaf fiber (PALF) and ramie hybrid fiber‐reinforced epoxy composite samples were evaluated for their hardness strength and resistance to dry slide wear and air jet erosion. Primary reinforcement using the hybrid material was chosen from different lengths (10, 15, 20, and 25 mm) and weight percentages (10%, 20%, 30%, 40%, and 50%). The hardness strength of the hybrid composite varied from 74 to 97 Shore D hardness strength. A dry sliding wear test was conducted with the key parameters of load (20, 30, and 40 N), time (20, 10, 7 min), and speed (160, 320, and 479 rpm). By using the data analyzing software, Taguchi optimization method, the key contribution parameters were identified. In the air jet erosion experiment, impact angle (45°, 60°, and 90°), erodent velocity (28, 41, and 72 m/s), and discharge rate (1, 2.5, and 3.3 g/min) parameters were used. Fiber and matrix materials agglomeration effect and bonding behavior were identified by using the scanning electron microscope (SEM) images. The 20 mm length with 30% of the PALF and ramie hybrid fiber‐reinforced composite sample achieved high hardness strength (97 shore D) and created a high resistance toward wear and erosion studies.Highlights Natural plant pineapple leaf and ramie fibers are mixed with an epoxy matrix. Used Taguchi analysis to determine the means and signal‐to‐noise ratios Different weight percentages of the PALF and ramie hybrid composites Dry sliding wear and air jet erosion studies are conducted. Individual parameter contributions were identified.

Removal of Cochineal Dye Color through Atmospheric Pressure Plasma Discharge Jet

The extensive utilization of dyes across diverse industries has resulted in environmental pollution, leading to the degradation of water bodies. To prevent environmental contamination, the use of eco-friendly dyes and innovative processes for dye degradation is crucial. This study aimed to investigate the color removal process of cochineal dye (Dactylopius coccus Costa) using the atmospheric pressure plasma jet (APPJ: Atmospheric Pressure Plasma Jet) technique. The dye extracted from the cochineal insect was treated with APPJ and the resulting color removal process was analyzed. Optical emission spectroscopy (OES) was used to investigate the plasma emission lines, and UV-Vis spectroscopy was used to monitor the color removal process. The results revealed that the decolorization of cochineal dye was a result of an oxidative degradation process caused by the interaction of the reactive species (NO3− and NO2−) generated by the APPJ plasma discharge with the dye molecules. This color removal process occurs in an acidic medium, leading to a pH change from 5.4 to 2.7. These pH changes can be attributed to fluctuations in the concentrations of reactive species such as nitrates and nitrites in the liquid phase. UV-Vis spectroscopy measurements showed that 90% of the cochineal color was removed within the first 10 min of treatment. This study enhances our understanding of natural color removal and provides insights into its mechanism, opening up possibilities for controlled modification and applications in various fields.

Spectroscopic detection of the gallium methylene (GaCH2 and GaCD2) free radical in the gas phase by laser-induced fluorescence and emission spectroscopy.

GaCH2, a free radical thought to play a role in the chemical vapor deposition of gallium-containing thin films and semiconductors, has been spectroscopically detected for the first time. The radical was produced in a pulsed discharge jet using a precursor mixture of trimethylgallium vapor in high pressure argon and studied by laser-induced fluorescence and wavelength resolved emission techniques. Partially rotationally resolved spectra of the hydrogenated and deuterated species were obtained, and they exhibit the nuclear statistical weight variations and subband structure expected for a 2A2-2B1 electronic transition. The measured spectroscopic quantities have been compared to our own abinitio calculations of the ground and excited state properties. The electronic spectrum of gallium methylene is similar to the corresponding spectrum of the aluminum methylene radical, which we reported in 2022.

Efficacy of argon cold atmospheric pressure plasma jet on hospital surface decontamination and its impact on the surface property

The emergence of antimicrobial resistance has become a major contributor to healthcare-associated infections. Recently, the cold atmospheric pressure plasma jet (CAPJ) discharges have garnered attention of the researchers globally for their novel antimicrobial property. This research evaluated the effectiveness of an in-house developed CAPJ on the inactivation of multidrug-resistant (MDR) E. coli and S. aureus artificially inoculated over stainless steel and aluminium test surfaces. A greater than ∼5 log10 reduction of E. coli, whereas reduction of ∼3.4–4.6 log10 for S. aureus on the test surfaces was achieved on 180 s CAPJ exposure. Extremely low D- values (in the range of ∼27–63 s) were recorded for both isolates. In addition, this study assessed the impact of repeated CAPJ exposure on surface property, by replicating the process of hospital surface decontamination. Surface properties such as wettability, roughness, and elemental composition varied non-linearly on repetitive Ar CAPJ exposure on test surfaces. It was observed that the identified gas-phase species such as excited atoms (Ar I, and O I), positive ions (NO+, O2 +, OH+, O+, N2 +, Ar+, etc), negative ions (N2O2 −, N2O3 −, NO3 −, NO2 −, etc), radical RONS (OH•), and non-radical RONS (O I, NO+, OH+, N2O3 −, NO3 −, NO2 −, etc) would contribute to bacterial load reduction on the test surface along with any alteration in surface characteristic. There may be chemical and physical processes involved in the above activity. This investigation into understanding the effects of CAPJ surface decontamination on surface properties would aid in determining its potential applications in healthcare settings.

Effects of cavitation and hydraulic flip on liquid film formed by jet impinging on the wall

The technology of the liquid film formed by jet impinging on the wall is widely applied in the aerospace, steel quenching, and cleaning. In this paper, the spreading and evolution of the liquid film are experimentally studied. The effects of the cavitation and hydraulic flip on the film are examined, and it is identified that they are a serious problem of the nozzle design. Results demonstrate that the jets formed by using a nozzle with 120° contraction angle and 3.5 mm outlet length sequentially produce the cavitation and hydraulic flip as the Reynolds number increases. Small contraction angle or long outlet length promotes the stability of the discharge coefficient and jet states and inhibits the occurrence of the cavitation and hydraulic flip. For the flip jet, the jet cross section is axially switched. Several patterns of the liquid film, such as the gravity flow, gravity flow with dry patch formation, rivulet flow with outward streams, and outward flow with triple rivulets, etc., are observed as the jet regime and inclination angle change. Particularly, for the film formed by the cavitation jet, the rivulets and dry patches emerge in the tail of the film; meanwhile, a lot of splashing droplets are generated. For the film generated by the flip jet, the bifurcation of the film shapes occurs. An impressive flow feature is that the two sprays are formed when the flip jet impinges on the wall, which is caused by the collision of the fluids in the secondary impingement zones.