Pub Date : 2020-10-30DOI: 10.1088/2516-1067/abc097
G. S. Rakib, M. A. Malek, K. Kabir, M. K. Islam
Numerical studies have been conducted using the Lee model code to compute the neutron yield Yn of the PF1000 plasma focus device as a function of operating gas pressure ( P ). The result is compared with the available experimental data. The operating gas Deuterium (D) is substituted with Deuterium-Tritium (D-T) (1:1) gas mixture in the numerical studies and then the Yn is investigated with the function of P. Associated plasma dynamic properties such as axial velocity va, radial shock front speed vs, piston speed vp, and maximum pinch temperature Tpinch(max) are studied and correlations of the parameters with the pressure variation are established. Relevant plasma focus properties such as peak discharge current Ipeak, pinch current Ipinch, ion density ni, and energy input into the pinch EINP are discussed as functions of pressure thus provide correlation of Yn with other relevant plasma focus properties over the operating gas pressure range. The neutron yield performance of the D-T gas mixture is compared to that of the D gas and the optimum gas pressure for the highest neutron yield is identified.
{"title":"Numerical experiments on D-T gas filled PF1000 device with pressure variation","authors":"G. S. Rakib, M. A. Malek, K. Kabir, M. K. Islam","doi":"10.1088/2516-1067/abc097","DOIUrl":"https://doi.org/10.1088/2516-1067/abc097","url":null,"abstract":"Numerical studies have been conducted using the Lee model code to compute the neutron yield Yn of the PF1000 plasma focus device as a function of operating gas pressure ( P ). The result is compared with the available experimental data. The operating gas Deuterium (D) is substituted with Deuterium-Tritium (D-T) (1:1) gas mixture in the numerical studies and then the Yn is investigated with the function of P. Associated plasma dynamic properties such as axial velocity va, radial shock front speed vs, piston speed vp, and maximum pinch temperature Tpinch(max) are studied and correlations of the parameters with the pressure variation are established. Relevant plasma focus properties such as peak discharge current Ipeak, pinch current Ipinch, ion density ni, and energy input into the pinch EINP are discussed as functions of pressure thus provide correlation of Yn with other relevant plasma focus properties over the operating gas pressure range. The neutron yield performance of the D-T gas mixture is compared to that of the D gas and the optimum gas pressure for the highest neutron yield is identified.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44396603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-28DOI: 10.1088/2516-1067/abc1fc
M. Sharma, A. Patel, N. Ramasubramanian, Y. Saxena, P. K. Chattopadhyaya, R. Ganesh
Two magnetic configurations of Multi-cusp Plasma Device (MPD) have been explored to obtain high quiescence level, large uniform plasma region with nearly flat mean density and temperature profiles. In particular, properties of plasma in a Six Pole Six Magnet (SPSM) and Twelve Pole Six Magnet (TPSM) cusp configurations are rigorously compared and reported here. It is found that more uniform plasma with nearly flat profiles is found in TPSM along with increased quiescence level. Findings are experimentally verified across various magnetic field strengths for both configurations.
{"title":"Role of multi-cusp magnetic field on plasma containment","authors":"M. Sharma, A. Patel, N. Ramasubramanian, Y. Saxena, P. K. Chattopadhyaya, R. Ganesh","doi":"10.1088/2516-1067/abc1fc","DOIUrl":"https://doi.org/10.1088/2516-1067/abc1fc","url":null,"abstract":"Two magnetic configurations of Multi-cusp Plasma Device (MPD) have been explored to obtain high quiescence level, large uniform plasma region with nearly flat mean density and temperature profiles. In particular, properties of plasma in a Six Pole Six Magnet (SPSM) and Twelve Pole Six Magnet (TPSM) cusp configurations are rigorously compared and reported here. It is found that more uniform plasma with nearly flat profiles is found in TPSM along with increased quiescence level. Findings are experimentally verified across various magnetic field strengths for both configurations.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44048382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-28DOI: 10.1088/2516-1067/abbe9b
Rakesh Ruchel Khanikar, P. J. Boruah, H. Bailung
Atmospheric pressure non-thermal plasma jets are becoming subject of great attention in various fields such as plasma processing and biomedical applications due to their ability to produce highly reactive species and good reaction chemistry at low gas temperatures. In the present study, a non-thermal plasma jet operating on argon gas at atmospheric pressure aimed mainly towards surface modification and thin film deposition applications has been developed. Optical emission spectroscopy is used to evaluate the plasma parameters. The gas temperature (800 ± 50 K) is estimated from OH(A-X) rotational band. The excitation temperature is measured using intensity ratio of two argon lines and is found to be 0.241–0.273 eV and the corresponding electron temperatures have been measured. Electron density of the order of 1014 cm−3 has been obtained from the Stark broadening of Balmer H β line. The plasma jet has been successfully employed to deposit a superhydrophobic thin film of SiwCxHyOz using hexamethyldisiloxane (HMDSO) precursor monomer. The deposited film has been analyzed using XRD, FTIR, SEM, AFM, and contact angle analyzer. All the treated surfaces have shown superhydrophobic property with a contact angle greater than 150° showing numerous potential in various applications. This method is a relatively easy and environmental friendly way of fabricating superhydrophobic surfaces.
{"title":"Development and optical characterization of an atmospheric pressure non-thermal plasma jet for superhydrophobic surface fabrication","authors":"Rakesh Ruchel Khanikar, P. J. Boruah, H. Bailung","doi":"10.1088/2516-1067/abbe9b","DOIUrl":"https://doi.org/10.1088/2516-1067/abbe9b","url":null,"abstract":"Atmospheric pressure non-thermal plasma jets are becoming subject of great attention in various fields such as plasma processing and biomedical applications due to their ability to produce highly reactive species and good reaction chemistry at low gas temperatures. In the present study, a non-thermal plasma jet operating on argon gas at atmospheric pressure aimed mainly towards surface modification and thin film deposition applications has been developed. Optical emission spectroscopy is used to evaluate the plasma parameters. The gas temperature (800 ± 50 K) is estimated from OH(A-X) rotational band. The excitation temperature is measured using intensity ratio of two argon lines and is found to be 0.241–0.273 eV and the corresponding electron temperatures have been measured. Electron density of the order of 1014 cm−3 has been obtained from the Stark broadening of Balmer H β line. The plasma jet has been successfully employed to deposit a superhydrophobic thin film of SiwCxHyOz using hexamethyldisiloxane (HMDSO) precursor monomer. The deposited film has been analyzed using XRD, FTIR, SEM, AFM, and contact angle analyzer. All the treated surfaces have shown superhydrophobic property with a contact angle greater than 150° showing numerous potential in various applications. This method is a relatively easy and environmental friendly way of fabricating superhydrophobic surfaces.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46366617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-23DOI: 10.1088/2516-1067/abc1b9
Y. Cressault, P. Teulet, X. Baumann, A. Gleizes
This tutorial is intended to provide a basic overview of non-equilibrium phenomena for thermal plasmas. Thermal plasmas (TPs) mainly issued from electrical discharges are often assumed to be in ≪ equilibrium ≫ as opposed to ≪ non-equilibrium plasmas ≫ where non-equilibrium phenomena are more pronounced. As a first approximation it can be shown that TPs are close to a local thermodynamic equilibrium (LTE) which is often taken as their reference state. However, in many situations, deviations from LTE can clearly exist. The main goal of this brief tutorial is to explain to interested scientists the main phenomena, mechanisms and characteristics associated to TPs or quasi-TPs. Then we introduce the different laws of the thermodynamic equilibrium applied to these plasmas and show that not all of them are valid in TPs, which lead us to define the LTE. However, even if the transport phenomena are non-equilibrium mechanisms, we show with illustrations that they are studied and estimated within the framework of the LTE. The next sections focus on phenomena named ‘departures from equilibrium’ for thermal plasmas. For convenience and educational reasons, we split them into the departures from the chemical and the thermal equilibria respectively. In each case we present and clearly define the mechanisms that promote equilibrium and those that tend to create departures. We present not only experimental setups that highlight these deviations but also the basis for the mathematical models that allow them to be simulated, before concluding the tutorial with the outlooks and challenges currently under research.
{"title":"Non-equilibrium phenomena in thermal plasmas","authors":"Y. Cressault, P. Teulet, X. Baumann, A. Gleizes","doi":"10.1088/2516-1067/abc1b9","DOIUrl":"https://doi.org/10.1088/2516-1067/abc1b9","url":null,"abstract":"This tutorial is intended to provide a basic overview of non-equilibrium phenomena for thermal plasmas. Thermal plasmas (TPs) mainly issued from electrical discharges are often assumed to be in ≪ equilibrium ≫ as opposed to ≪ non-equilibrium plasmas ≫ where non-equilibrium phenomena are more pronounced. As a first approximation it can be shown that TPs are close to a local thermodynamic equilibrium (LTE) which is often taken as their reference state. However, in many situations, deviations from LTE can clearly exist. The main goal of this brief tutorial is to explain to interested scientists the main phenomena, mechanisms and characteristics associated to TPs or quasi-TPs. Then we introduce the different laws of the thermodynamic equilibrium applied to these plasmas and show that not all of them are valid in TPs, which lead us to define the LTE. However, even if the transport phenomena are non-equilibrium mechanisms, we show with illustrations that they are studied and estimated within the framework of the LTE. The next sections focus on phenomena named ‘departures from equilibrium’ for thermal plasmas. For convenience and educational reasons, we split them into the departures from the chemical and the thermal equilibria respectively. In each case we present and clearly define the mechanisms that promote equilibrium and those that tend to create departures. We present not only experimental setups that highlight these deviations but also the basis for the mathematical models that allow them to be simulated, before concluding the tutorial with the outlooks and challenges currently under research.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48009122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-24DOI: 10.1088/2516-1067/abb56f
A. Rawat, A. Ganguli, R. Narayanan, R. D. Tarey
This work attempts to correlate the plasma density and RF harmonic profiles with respect to the pressure (at 13.56, 27.12 and 40.68 MHz) with the stochastic and ohmic power absorption mechanisms in a Capacitively Coupled Discharge (CCD), over a wide pressure range (0.6–1000 mTorr). Diagnostics include calibrated capacitive probe, compensated Langmuir Probe (LP) and uncompensated floating LP for measuring plasma parameters and RF signals. Pressure profiles of stochastic and ohmic powers, P Stoch and P Ohm (at 13.56 MHz) are obtained from their ratio (ξ) and the power absorbed by the electrons. Normalized profiles of an effective power (∼ PStochρ×POhm1−ρ; ρ : pressure dependent parameter) are tuned to reproduce closely the normalized plasma density profiles from which relative contributions of stochastic/ohmic mechanisms are determined. It is shown that up to ≈30 mTorr, plasma production is stochastic while beyond that both methods contribute jointly. The RF harmonic profiles can be analysed similarly. Higher harmonics produced by the intrinsic nonlinearity of the stochastic process should appear most clearly in the plasma at low pressures where the latter operates alone. On the other hand, the fundamental RF voltage that is always present in the plasma, can also produce higher harmonics at the probe tip by driving the nonlinear probe sheath. Thus, the harmonics produced directly by the stochastic nonlinearity are inextricably mixed up with those arising due to the probe sheath. Significantly, one may conclude therefore that it is not possible to investigate the stochastic mechanism of power absorption by a study of its harmonics when the latter are measured using invasive probes.
{"title":"Correlation of stochastic and ohmic power absorption with observed RF harmonics and plasma parameters in capacitively coupled discharges","authors":"A. Rawat, A. Ganguli, R. Narayanan, R. D. Tarey","doi":"10.1088/2516-1067/abb56f","DOIUrl":"https://doi.org/10.1088/2516-1067/abb56f","url":null,"abstract":"This work attempts to correlate the plasma density and RF harmonic profiles with respect to the pressure (at 13.56, 27.12 and 40.68 MHz) with the stochastic and ohmic power absorption mechanisms in a Capacitively Coupled Discharge (CCD), over a wide pressure range (0.6–1000 mTorr). Diagnostics include calibrated capacitive probe, compensated Langmuir Probe (LP) and uncompensated floating LP for measuring plasma parameters and RF signals. Pressure profiles of stochastic and ohmic powers, P Stoch and P Ohm (at 13.56 MHz) are obtained from their ratio (ξ) and the power absorbed by the electrons. Normalized profiles of an effective power (∼ PStochρ×POhm1−ρ; ρ : pressure dependent parameter) are tuned to reproduce closely the normalized plasma density profiles from which relative contributions of stochastic/ohmic mechanisms are determined. It is shown that up to ≈30 mTorr, plasma production is stochastic while beyond that both methods contribute jointly. The RF harmonic profiles can be analysed similarly. Higher harmonics produced by the intrinsic nonlinearity of the stochastic process should appear most clearly in the plasma at low pressures where the latter operates alone. On the other hand, the fundamental RF voltage that is always present in the plasma, can also produce higher harmonics at the probe tip by driving the nonlinear probe sheath. Thus, the harmonics produced directly by the stochastic nonlinearity are inextricably mixed up with those arising due to the probe sheath. Significantly, one may conclude therefore that it is not possible to investigate the stochastic mechanism of power absorption by a study of its harmonics when the latter are measured using invasive probes.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49389189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-23DOI: 10.1088/2516-1067/abb8e6
L. Bardos, H. Barankova
Experimental examination of possibility to affect the shapes of flames under combustion of the liquified petroleum gas (LPG) were performed by several non-conventional cold atmospheric plasma arrangements. The lateral fused hollow cathode, the microwave surface wave plasma jet and the combination of these systems confirmed possibility of an efficient control of the flame shapes, increasing stability of flames and broadening of their front parts.
{"title":"Shaping of the flame geometry by non-conventional cold plasma arrangements","authors":"L. Bardos, H. Barankova","doi":"10.1088/2516-1067/abb8e6","DOIUrl":"https://doi.org/10.1088/2516-1067/abb8e6","url":null,"abstract":"Experimental examination of possibility to affect the shapes of flames under combustion of the liquified petroleum gas (LPG) were performed by several non-conventional cold atmospheric plasma arrangements. The lateral fused hollow cathode, the microwave surface wave plasma jet and the combination of these systems confirmed possibility of an efficient control of the flame shapes, increasing stability of flames and broadening of their front parts.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41497368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-18DOI: 10.1088/2516-1067/abb649
K. P. Singh, Anil Kumar Malik
We model electron acceleration using paraxial approximation (PA) and seventh order correction description (O7) of a laser field in vacuum in the presence of an axial magnetic field. The effect of initial momentum, laser intensity, spot size, and initial position of electron on optimum value of magnetic field and electron energy for linearly and circularly polarized laser pulse has been investigated. We show that PA fails to obtain correct values of optimum magnetic field and electron energy. The amplitude of oscillations of the electron increases with time in the presence of axial magnetic field and PA fails to correctly take into account focusing and defocusing of laser and obtain correct results.
{"title":"Limitations of paraxial approximation to model elec-tron acceleration by a laser pulse in vacuum in the presence of an axial magnetic field","authors":"K. P. Singh, Anil Kumar Malik","doi":"10.1088/2516-1067/abb649","DOIUrl":"https://doi.org/10.1088/2516-1067/abb649","url":null,"abstract":"We model electron acceleration using paraxial approximation (PA) and seventh order correction description (O7) of a laser field in vacuum in the presence of an axial magnetic field. The effect of initial momentum, laser intensity, spot size, and initial position of electron on optimum value of magnetic field and electron energy for linearly and circularly polarized laser pulse has been investigated. We show that PA fails to obtain correct values of optimum magnetic field and electron energy. The amplitude of oscillations of the electron increases with time in the presence of axial magnetic field and PA fails to correctly take into account focusing and defocusing of laser and obtain correct results.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48293911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-04DOI: 10.1088/2516-1067/abb2fd
H. Jakob, Min Kwan Kim
Atmospheric non-thermal plasma is gaining increasing attention for various applications including food, medical and healthcare technologies because of its unique capability in producing reactive species. In spite of its promising potential, generating non-thermal plasma over large and complex geometries such as the human body or a narrow channel is still challenging and is limiting the use of atmospheric non-thermal plasma. In this study, we propose two new electrode systems, printed and knitted electrodes, to enhance scalability and flexibility of a conventional atmospheric non-thermal plasma source. The flexibilities of both electrode systems are quantified for varying curvatures to generate non-thermal plasma over complex geometries. Moreover, both electrode systems are assessed for varying system size to assess the ability of large scale plasma geometries. Electrical and optical diagnostics including Optical Emission Spectroscopy (OES), are used to monitor the property of plasma generated by these systems. The present study shows that both printed and knitted electrodes can produce non-thermal plasma, however both have certain limitations. Concluding from these findings, a schematic of new hybrid electrode system for the treatment of large surfaces or narrow long channels is proposed to eradicate these limitations.
{"title":"Generation of non-thermal plasmas over large and complex surfaces","authors":"H. Jakob, Min Kwan Kim","doi":"10.1088/2516-1067/abb2fd","DOIUrl":"https://doi.org/10.1088/2516-1067/abb2fd","url":null,"abstract":"Atmospheric non-thermal plasma is gaining increasing attention for various applications including food, medical and healthcare technologies because of its unique capability in producing reactive species. In spite of its promising potential, generating non-thermal plasma over large and complex geometries such as the human body or a narrow channel is still challenging and is limiting the use of atmospheric non-thermal plasma. In this study, we propose two new electrode systems, printed and knitted electrodes, to enhance scalability and flexibility of a conventional atmospheric non-thermal plasma source. The flexibilities of both electrode systems are quantified for varying curvatures to generate non-thermal plasma over complex geometries. Moreover, both electrode systems are assessed for varying system size to assess the ability of large scale plasma geometries. Electrical and optical diagnostics including Optical Emission Spectroscopy (OES), are used to monitor the property of plasma generated by these systems. The present study shows that both printed and knitted electrodes can produce non-thermal plasma, however both have certain limitations. Concluding from these findings, a schematic of new hybrid electrode system for the treatment of large surfaces or narrow long channels is proposed to eradicate these limitations.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46363153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-02DOI: 10.1088/2516-1067/abb4c3
R. Bansemer, L. Scholten, J. Winter, K. Weltmann
A sinusoidally-excited Venturi-DBD operating in neon has been investigated. The Ne(1s5) metastable density has been quantified spatially resolved using laser atomic absorption spectroscopy for different pressure levels. Density values of up to 7 · 1016 m−3 could be determined at atmospheric pressure and up to 3 · 1016 m−3 at 100 mbar. For all investigated parameters, the Ne(1s5) density was found to be distinctly higher in the proximity of the cathode than in the anode region. Complementary investigations of the discharge development using phase-resolved optical emission spectroscopy complete the characterization of the device. The discharge was found to show typical properties of a glow-like discharge regarding current waveform and luminosity distribution. In addition, the influence of nitrogen and oxygen impurities and admixtures in the process gas has been determined. A substantial impact was found on both the Ne(1s5) concentration and the current waveform.
{"title":"Spectroscopic investigation of a neon-operated DBD at atmospheric and intermediate pressure","authors":"R. Bansemer, L. Scholten, J. Winter, K. Weltmann","doi":"10.1088/2516-1067/abb4c3","DOIUrl":"https://doi.org/10.1088/2516-1067/abb4c3","url":null,"abstract":"A sinusoidally-excited Venturi-DBD operating in neon has been investigated. The Ne(1s5) metastable density has been quantified spatially resolved using laser atomic absorption spectroscopy for different pressure levels. Density values of up to 7 · 1016 m−3 could be determined at atmospheric pressure and up to 3 · 1016 m−3 at 100 mbar. For all investigated parameters, the Ne(1s5) density was found to be distinctly higher in the proximity of the cathode than in the anode region. Complementary investigations of the discharge development using phase-resolved optical emission spectroscopy complete the characterization of the device. The discharge was found to show typical properties of a glow-like discharge regarding current waveform and luminosity distribution. In addition, the influence of nitrogen and oxygen impurities and admixtures in the process gas has been determined. A substantial impact was found on both the Ne(1s5) concentration and the current waveform.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41797692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-21DOI: 10.1088/2516-1067/abae81
S. Cristofaro, R. Friedl, U. Fantz
Negative hydrogen ion sources for NBI systems at fusion devices rely on the surface conversion of hydrogen atoms and positive ions to negative hydrogen ions. In these sources the surface work function is decreased by adsorption of caesium (work function of 2.1 eV), enhancing consequently the negative ion yield. However, the performance of the ion source decreases during plasma pulses up to one hour, suggesting a deterioration of the work function. Fundamental investigations are performed in a laboratory experiment in order to study the impact of the plasma on the work function of a freshly caesiated stainless steel surface. A work function of 2.1 eV is achieved in the first 10 s of plasma, while further plasma exposure leads to the removal of Cs from the surface and to the change of the work function: a value of around 1.8–1.9 eV is measured after 10–15 min of plasma exposure and then the work function increases, approaching the work function of the substrate (≥4.2 eV) after 5 h. The Cs removal must be counteracted by continuous Cs evaporation, and investigations performed varying the Cs flux towards the surface have shown that a Cs flux of at least 1.5 × 1016 m−2s−1 is required to maintain a work function of 2.1 eV during long plasma exposure at the laboratory experiment.
{"title":"Correlation of Cs flux and work function of a converter surface during long plasma exposure for negative ion sources in view of ITER","authors":"S. Cristofaro, R. Friedl, U. Fantz","doi":"10.1088/2516-1067/abae81","DOIUrl":"https://doi.org/10.1088/2516-1067/abae81","url":null,"abstract":"Negative hydrogen ion sources for NBI systems at fusion devices rely on the surface conversion of hydrogen atoms and positive ions to negative hydrogen ions. In these sources the surface work function is decreased by adsorption of caesium (work function of 2.1 eV), enhancing consequently the negative ion yield. However, the performance of the ion source decreases during plasma pulses up to one hour, suggesting a deterioration of the work function. Fundamental investigations are performed in a laboratory experiment in order to study the impact of the plasma on the work function of a freshly caesiated stainless steel surface. A work function of 2.1 eV is achieved in the first 10 s of plasma, while further plasma exposure leads to the removal of Cs from the surface and to the change of the work function: a value of around 1.8–1.9 eV is measured after 10–15 min of plasma exposure and then the work function increases, approaching the work function of the substrate (≥4.2 eV) after 5 h. The Cs removal must be counteracted by continuous Cs evaporation, and investigations performed varying the Cs flux towards the surface have shown that a Cs flux of at least 1.5 × 1016 m−2s−1 is required to maintain a work function of 2.1 eV during long plasma exposure at the laboratory experiment.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48320066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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