Pub Date : 2024-07-25DOI: 10.1088/1361-6595/ad678f
Ho-Jun Moon, Jiwon Jung, Junyoung Park, Chin-Wook Chung
The effect of transparent capacitively coupled plasmas (TCCP) is investigated by using a transparent ITO electrode instead of the metal electrode of capacitively coupled plasmas (CCP). To compare CCP and TCCP, the CCP is made by coating the powered electrode with metal and the TCCP is made by coating the powered electrode with Indium Tin Oxide (ITO) on the quartz window. To compare the properties of electrodes based on ITO electrodes and metal electrodes in the same size reactor, electrode voltage, electron temperature and electron density were measured at various applied RF powers and pressures at 13.56 MHz. The electron temperature decreases overall with increasing pressure, regardless of the electrode type. We observed that the total voltage between the powered electrode and ground is about two times higher for the TCCP than for the CCP. In addition, the electron density of the TCCP increases significantly by about two times that of the CCP. In this TCCP, the voltage applied to the sheath is calculated based on the expectation that the increase in electron density is related to the voltage applied to the sheath. The results of calculating the voltage applied to each sheath of the CCP and the TCCP agree well with our expectations. In addition, we calculated the total power absorption per unit area and confirmed that the total power absorption per unit area is significantly higher in the TCCP than in the CCP.
{"title":"Generation of high-density plasma via transparent electrode in capacitively coupled plasma","authors":"Ho-Jun Moon, Jiwon Jung, Junyoung Park, Chin-Wook Chung","doi":"10.1088/1361-6595/ad678f","DOIUrl":"https://doi.org/10.1088/1361-6595/ad678f","url":null,"abstract":"\u0000 The effect of transparent capacitively coupled plasmas (TCCP) is investigated by using a transparent ITO electrode instead of the metal electrode of capacitively coupled plasmas (CCP). To compare CCP and TCCP, the CCP is made by coating the powered electrode with metal and the TCCP is made by coating the powered electrode with Indium Tin Oxide (ITO) on the quartz window. To compare the properties of electrodes based on ITO electrodes and metal electrodes in the same size reactor, electrode voltage, electron temperature and electron density were measured at various applied RF powers and pressures at 13.56 MHz. The electron temperature decreases overall with increasing pressure, regardless of the electrode type. We observed that the total voltage between the powered electrode and ground is about two times higher for the TCCP than for the CCP. In addition, the electron density of the TCCP increases significantly by about two times that of the CCP. In this TCCP, the voltage applied to the sheath is calculated based on the expectation that the increase in electron density is related to the voltage applied to the sheath. The results of calculating the voltage applied to each sheath of the CCP and the TCCP agree well with our expectations. In addition, we calculated the total power absorption per unit area and confirmed that the total power absorption per unit area is significantly higher in the TCCP than in the CCP.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"52 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141802636","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 : 2024-07-23DOI: 10.1088/1361-6595/ad6690
M. Sobolewski
Plasma simulations require accurate yield data to predict the electron flux that is emitted when plasma-exposed surfaces are bombarded by energetic particles. One can measure yields directly using particle beams, but it is impractical to create a separate beam of each particle produced by typical plasmas. In contrast, measurements made in situ, during plasma exposure, provide useful values for the total emitted flux and effective yield produced by all incident particles. Here, in situ measurements were made at thermally oxidized and bare silicon wafers placed on the radio-frequency (rf) biased electrode of an inductively coupled plasma (icp) system. The rf current and voltage across the sheath at the wafer were measured, along with Langmuir probe measurements of ion current density and electron temperature. The measurements are input into a numerical sheath model, which allows the emitted electron current to be distinguished from other currents. The effective yield, i.e., the ratio of the total emitted electron flux to the incident ion flux, was determined at incident ion energies from 40 eV to 1.4 keV, for Si and SiO2 surfaces in Ar, CF4, and Ar/CF4 mixtures at 1.33 Pa (10 mTorr). Yields for Ar plasmas are compared with previous work. For SiO2 surfaces in Ar/CF4 mixtures and pure CF4, the yield is dominated by ion kinetic emission, which is the same for all mixtures, and, presumably, for all ions. For SiO2 surfaces in Ar/CF4 and CF4, the yield at high energies can be explained in part by fragmentation of molecular ions, and the yield from Ar+ can be distinguished from the other ionic species. Analytic fits of the yields are provided for use in plasma simulations.
{"title":"In situ measurement of electron emission yield at Si and SiO2 surfaces exposed to Ar/CF4 plasmas","authors":"M. Sobolewski","doi":"10.1088/1361-6595/ad6690","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6690","url":null,"abstract":"\u0000 Plasma simulations require accurate yield data to predict the electron flux that is emitted when plasma-exposed surfaces are bombarded by energetic particles. One can measure yields directly using particle beams, but it is impractical to create a separate beam of each particle produced by typical plasmas. In contrast, measurements made in situ, during plasma exposure, provide useful values for the total emitted flux and effective yield produced by all incident particles. Here, in situ measurements were made at thermally oxidized and bare silicon wafers placed on the radio-frequency (rf) biased electrode of an inductively coupled plasma (icp) system. The rf current and voltage across the sheath at the wafer were measured, along with Langmuir probe measurements of ion current density and electron temperature. The measurements are input into a numerical sheath model, which allows the emitted electron current to be distinguished from other currents. The effective yield, i.e., the ratio of the total emitted electron flux to the incident ion flux, was determined at incident ion energies from 40 eV to 1.4 keV, for Si and SiO2 surfaces in Ar, CF4, and Ar/CF4 mixtures at 1.33 Pa (10 mTorr). Yields for Ar plasmas are compared with previous work. For SiO2 surfaces in Ar/CF4 mixtures and pure CF4, the yield is dominated by ion kinetic emission, which is the same for all mixtures, and, presumably, for all ions. For SiO2 surfaces in Ar/CF4 and CF4, the yield at high energies can be explained in part by fragmentation of molecular ions, and the yield from Ar+ can be distinguished from the other ionic species. Analytic fits of the yields are provided for use in plasma simulations.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"50 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141813350","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 : 2024-07-23DOI: 10.1088/1361-6595/ad6691
P. Hiret, Patrik Tognina, E. Faudot, Roland Steiner, Artem M Dmitriev, L. Marot, Ernst Meyer
The self-bias voltage Vbias and the plasma potential Vp are the key parameters to control plasma-wall interactions in radio-frequency (RF) asymmetric plasma discharges. Knowing these two parameters allows to monitor the ion energy distribution on the electrode surface. However, in a direct current (DC) coupled plasma, the plasma potential increased to hundreds of volts while no more Vbias developed on the driven electrode. In addition, the plasma potential is strongly impacted by the electrode-wall area ratio. Several analytical or semi-analytical models exist to explain this phenomenon and to approximate the plasma potential, knowing the electrode-wall area ratio considering capacitive sheaths or a combination of resistive and capacitive sheaths. The Vp and several other plasma parameters were investigated experimentally with a Langmuir probe and a Retarding field energy analyser (RFEA) for different electrode/wall area ratios in low-temperature RF plasma. The validity of the models was studied for an extensive range of area ratios with different pressures and RF driving amplitude. Moreover, the presence of strong stochastic heating of the plasma for area ratios below 6 was evidenced by an increased ion flux and an increased electron temperature.
{"title":"Variations of plasma potential in RF discharges with DC-grounded electrode","authors":"P. Hiret, Patrik Tognina, E. Faudot, Roland Steiner, Artem M Dmitriev, L. Marot, Ernst Meyer","doi":"10.1088/1361-6595/ad6691","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6691","url":null,"abstract":"\u0000 The self-bias voltage Vbias and the plasma potential Vp are the key parameters to control plasma-wall interactions in radio-frequency (RF) asymmetric plasma discharges. Knowing these two parameters allows to monitor the ion energy distribution on the electrode surface. However, in a direct current (DC) coupled plasma, the plasma potential increased to hundreds of volts while no more Vbias developed on the driven electrode. In addition, the plasma potential is strongly impacted by the electrode-wall area ratio. Several analytical or semi-analytical models exist to explain this phenomenon and to approximate the plasma potential, knowing the electrode-wall area ratio considering capacitive sheaths or a combination of resistive and capacitive sheaths. The Vp and several other plasma parameters were investigated experimentally with a Langmuir probe and a Retarding field energy analyser (RFEA) for different electrode/wall area ratios in low-temperature RF plasma. The validity of the models was studied for an extensive range of area ratios with different pressures and RF driving amplitude. Moreover, the presence of strong stochastic heating of the plasma for area ratios below 6 was evidenced by an increased ion flux and an increased electron temperature.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"116 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141811913","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 : 2024-07-19DOI: 10.1088/1361-6595/ad6586
Yu Li, Dingqing Wu, Xinyue Wang, Xiaohan Hu, Ke Xu, Huace Wu, R. Hai, Cong Li, Chunlei Feng, Hongbin Ding
The species including atoms and multiply charged ions in the laser produced molybdenum (Mo) plasma are investigated in this work using optical emission spectroscopy and time-of-flight electrostatic energy analyzer. Nanosecond laser (5 ns, 1064 nm,) pulses were focused on the Mo target surface with a spot size of 0.4 mm2, energy of ~150mJ/pulse (corresponding to a power density of ~7.5 GW/cm2) to generate the Mo plasma in vacuum environment. Time-resolved spectral analysis was carried out to investigate the temporal evolution of continuous background, atomic, and monovalent ionic spectral signals. The Saha-Boltzmann method is applied for spectral fitting, providing insight into the temporal evolution of electron temperature (Te) and electron density (ne). Over the time from 40 ns to 500 ns, the Te decreases from 3.6 eV to 0.52 eV, and the ne decreases from 2.5 × 1020 cm⁻³ to 1.05 × 1015 cm-3. Linear fitting extrapolation predicts the Te and ne could be even up to 6.3 eV and 2.5 × 1022 cm-3, respectively, at the early stage of 10 ns. This indicates the generation of multiply charged ions during the laser ablation process. The multiply charged ions up to 6 charge states were observed by the time-of-flight electrostatic energy analyzer and the energy distributions for the different charged ions were also obtained. It was found the ion kinetic energy is positively related to the number of charge state indicates the existence of acceleration electric field. The equivalent accelerating potential is determined as approximately 570 V at the current laser power density. This research provides a significant reference for the establishment of models for laser ablation plasmas and a profound understanding of the underlying physical processes.
{"title":"Study of atoms and multiply charged ions features in the nanosecond laser produced Mo plasma in vacuum using optical emission spectroscopy and time-of-flight electrostatic energy analyzer","authors":"Yu Li, Dingqing Wu, Xinyue Wang, Xiaohan Hu, Ke Xu, Huace Wu, R. Hai, Cong Li, Chunlei Feng, Hongbin Ding","doi":"10.1088/1361-6595/ad6586","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6586","url":null,"abstract":"\u0000 The species including atoms and multiply charged ions in the laser produced molybdenum (Mo) plasma are investigated in this work using optical emission spectroscopy and time-of-flight electrostatic energy analyzer. Nanosecond laser (5 ns, 1064 nm,) pulses were focused on the Mo target surface with a spot size of 0.4 mm2, energy of ~150mJ/pulse (corresponding to a power density of ~7.5 GW/cm2) to generate the Mo plasma in vacuum environment. Time-resolved spectral analysis was carried out to investigate the temporal evolution of continuous background, atomic, and monovalent ionic spectral signals. The Saha-Boltzmann method is applied for spectral fitting, providing insight into the temporal evolution of electron temperature (Te) and electron density (ne). Over the time from 40 ns to 500 ns, the Te decreases from 3.6 eV to 0.52 eV, and the ne decreases from 2.5 × 1020 cm⁻³ to 1.05 × 1015 cm-3. Linear fitting extrapolation predicts the Te and ne could be even up to 6.3 eV and 2.5 × 1022 cm-3, respectively, at the early stage of 10 ns. This indicates the generation of multiply charged ions during the laser ablation process. The multiply charged ions up to 6 charge states were observed by the time-of-flight electrostatic energy analyzer and the energy distributions for the different charged ions were also obtained. It was found the ion kinetic energy is positively related to the number of charge state indicates the existence of acceleration electric field. The equivalent accelerating potential is determined as approximately 570 V at the current laser power density. This research provides a significant reference for the establishment of models for laser ablation plasmas and a profound understanding of the underlying physical processes.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"104 51","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141821669","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 : 2024-07-19DOI: 10.1088/1361-6595/ad6587
B. Harris, J. Dedrick, Kari Niemi, E. Wagenaars
Atmospheric pressure plasma jets are efficient sources of reactive oxygen and nitrogen species with potential applications in medicine, materials processing, green industry and agriculture. However, selective control over the production of reactive species presents an ongoing challenge and a barrier to the widespread uptake of these devices in applications. This study therefore investigates the production of ozone by a radio-frequency plasma jet driven with tailored voltage waveforms composed of up to five consecutive harmonics, with a fundamental frequency of 13.56 MHz. The plasma is supplied with helium with small admixtures (0.1 % - 1.0 %) of oxygen gas. The ozone density in the far effluent is measured with Fourier transform infrared spectroscopy and the gas temperature in the plasma channel is determined with optical emission spectroscopy. Voltage waveform tailoring is found to enhance the ozone density in the far effluent of the plasma jet in comparison to operation with single-frequency voltage waveforms. Increasing the number of applied harmonics in the driving voltage waveform for a fixed peak-to-peak voltage enhances the ozone density but significantly increases the gas temperature within the plasma channel. Meanwhile, increasing the number of applied harmonics while maintaining a constant RF power deposition allows the density of ozone in the effluent to be increased by up to a factor of 4 relative to single-frequency operation, up to a maximum density of 5.7×10^14 cm^-3, without any significant change to the gas temperature. This work highlights that tailored voltage waveforms can be used to control the density of ozone delivered through the plasma effluent, marking an important step towards realising the potential of these plasmas for applications.
{"title":"Ozone production by an He+O2 radio-frequency atmospheric pressure plasma jet driven by tailored voltage waveforms","authors":"B. Harris, J. Dedrick, Kari Niemi, E. Wagenaars","doi":"10.1088/1361-6595/ad6587","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6587","url":null,"abstract":"\u0000 Atmospheric pressure plasma jets are efficient sources of reactive oxygen and nitrogen species with potential applications in medicine, materials processing, green industry and agriculture. However, selective control over the production of reactive species presents an ongoing challenge and a barrier to the widespread uptake of these devices in applications. This study therefore investigates the production of ozone by a radio-frequency plasma jet driven with tailored voltage waveforms composed of up to five consecutive harmonics, with a fundamental frequency of 13.56 MHz. The plasma is supplied with helium with small admixtures (0.1 % - 1.0 %) of oxygen gas. The ozone density in the far effluent is measured with Fourier transform infrared spectroscopy and the gas temperature in the plasma channel is determined with optical emission spectroscopy. Voltage waveform tailoring is found to enhance the ozone density in the far effluent of the plasma jet in comparison to operation with single-frequency voltage waveforms. Increasing the number of applied harmonics in the driving voltage waveform for a fixed peak-to-peak voltage enhances the ozone density but significantly increases the gas temperature within the plasma channel. Meanwhile, increasing the number of applied harmonics while maintaining a constant RF power deposition allows the density of ozone in the effluent to be increased by up to a factor of 4 relative to single-frequency operation, up to a maximum density of 5.7×10^14 cm^-3, without any significant change to the gas temperature. This work highlights that tailored voltage waveforms can be used to control the density of ozone delivered through the plasma effluent, marking an important step towards realising the potential of these plasmas for applications.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"101 35","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141821710","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}
Positive glow corona is a stable and quasi-homogenous form of corona discharge with periodic current pulses, which appears in atmospheric plasma applications, high voltage apparatus and grounded structures under thunderstorm. The debate on seed electron source responsible for pulsing nature of positive glow corona has persisted for decades. This paper presents the numerical simulation study of 1-D coaxial positive glow corona in pure N2 with trace oxygen contents ranging from 1% to 1 ppm. It is found that the reduction of oxygen content causes weaker glow current magnitude, longer time-to-crest, shorter oscillation period and more positive ion sheaths. As trace oxygen decreases from 1% to 10 ppm, the dominant source of secondary electrons transits from both detachment and photoionization to photoionization only. As trace O2 content drops from 0.1%, the dominant photoionization within ionization layer transits from the photoionization of O2 molecules to direct photoionization of N2 molecules. In high purity nitrogen, the detachment of O− dominates and the detachment of O2− can be neglected. As the trace oxygen decreases from 1% to 10 ppm, the dominant molecules involving O− detachment transits from N2 and O to N2(A). The dominant ionization responsible for electron multiplication during electric field recovery shifts from direct ionization of O2 and N2 in 1% trace oxygen to associative ionization between N2(A) and N2(a’) and direct ionization of N2 in 1ppm trace oxygen.
{"title":"Effect of trace oxygen on self-oscillation of positive glow corona in nitrogen near atmospheric pressure","authors":"Hengxin He, Wanxia Zhang, Lipeng Liu, Bin Luo, Ying Chen, Shiming Zhang, Mian Xiao, Yubin Huang, Shen Chen","doi":"10.1088/1361-6595/ad6501","DOIUrl":"https://doi.org/10.1088/1361-6595/ad6501","url":null,"abstract":"\u0000 Positive glow corona is a stable and quasi-homogenous form of corona discharge with periodic current pulses, which appears in atmospheric plasma applications, high voltage apparatus and grounded structures under thunderstorm. The debate on seed electron source responsible for pulsing nature of positive glow corona has persisted for decades. This paper presents the numerical simulation study of 1-D coaxial positive glow corona in pure N2 with trace oxygen contents ranging from 1% to 1 ppm. It is found that the reduction of oxygen content causes weaker glow current magnitude, longer time-to-crest, shorter oscillation period and more positive ion sheaths. As trace oxygen decreases from 1% to 10 ppm, the dominant source of secondary electrons transits from both detachment and photoionization to photoionization only. As trace O2 content drops from 0.1%, the dominant photoionization within ionization layer transits from the photoionization of O2 molecules to direct photoionization of N2 molecules. In high purity nitrogen, the detachment of O− dominates and the detachment of O2− can be neglected. As the trace oxygen decreases from 1% to 10 ppm, the dominant molecules involving O− detachment transits from N2 and O to N2(A). The dominant ionization responsible for electron multiplication during electric field recovery shifts from direct ionization of O2 and N2 in 1% trace oxygen to associative ionization between N2(A) and N2(a’) and direct ionization of N2 in 1ppm trace oxygen.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":" 20","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141827383","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 : 2024-07-17DOI: 10.1088/1361-6595/ad647a
Jintao Wu, C. Sang, Changjiang Sun, Bin Sun, Shuaishuai Gao, Y. Bian, Yao Peng, Qi Wang, Dezhen Wang
To obtain high-parameter plasma in target region of the linear plasma device MPS-LD and to realize the experimental simulation environment of tokamak divertor plasma, experimental and numerical simulations of argon helicon discharge are carried out. Langmuir probes are used to diagnose the electron density (ne) in source and target regions with different experimental parameters (magnetic field, RF power, puffing flow rate). A three-dimensional discharge model is developed by using drift-diffusion equations of electron density and electron energy with the aid of COMSOL. The helicon discharge with long straight plasma beam and bright blue core is experimentally achieved. The simulation and experiment results are compared, showing the validation of the model. The corresponding spatial ne distribution is obtained, and the dependences of ne on the main experimental parameters are confirmed. The energy conversion relationship between the helicon and plasma is found. Helicon wave prefers to transfer energy to the plasma in source region, where ne is significantly raised. It results in a strong ne gradient, which acts a barrier to prevent the propagation of helicon wave. Therefore, localized standing helicon wave is formed and it limits the increase of plasma density in target region. Increasing magnetic field strength (B < 1500G) and RF power (P < 1500W), ne in source region can be increased, but they have little effect on ne in target region.
{"title":"Experimental and simulation study of argon helicon discharge in the linear plasma device MPS-LD","authors":"Jintao Wu, C. Sang, Changjiang Sun, Bin Sun, Shuaishuai Gao, Y. Bian, Yao Peng, Qi Wang, Dezhen Wang","doi":"10.1088/1361-6595/ad647a","DOIUrl":"https://doi.org/10.1088/1361-6595/ad647a","url":null,"abstract":"\u0000 To obtain high-parameter plasma in target region of the linear plasma device MPS-LD and to realize the experimental simulation environment of tokamak divertor plasma, experimental and numerical simulations of argon helicon discharge are carried out. Langmuir probes are used to diagnose the electron density (ne) in source and target regions with different experimental parameters (magnetic field, RF power, puffing flow rate). A three-dimensional discharge model is developed by using drift-diffusion equations of electron density and electron energy with the aid of COMSOL. The helicon discharge with long straight plasma beam and bright blue core is experimentally achieved. The simulation and experiment results are compared, showing the validation of the model. The corresponding spatial ne distribution is obtained, and the dependences of ne on the main experimental parameters are confirmed. The energy conversion relationship between the helicon and plasma is found. Helicon wave prefers to transfer energy to the plasma in source region, where ne is significantly raised. It results in a strong ne gradient, which acts a barrier to prevent the propagation of helicon wave. Therefore, localized standing helicon wave is formed and it limits the increase of plasma density in target region. Increasing magnetic field strength (B < 1500G) and RF power (P < 1500W), ne in source region can be increased, but they have little effect on ne in target region.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":" 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141830030","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 : 2024-07-17DOI: 10.1088/1361-6595/ad647b
T. Srivastava, Arthur Dogariu, Anatoli Morozov, P. Bruggeman
Plasma-liquid interactions have been extensively studied with a focus on the transport of reactive species from the plasma to the liquid phase and their induced liquid phase chemistry and resulting applications. While solute transfer from the liquid to the gas phase in plasmas has been widely used in analytical chemistry, the underlying processes remain relatively unexplored. We report spatially and temporally resolved absolute density measurements of sodium in a plasma with a NaCl solution cathode using two-photon absorption laser induced fluorescence (TaLIF). The observed non-linear increase in sodium density with solution conductivity is shown to correlate with droplet generation as visualized by Mie scattering. The findings are explained by droplet generation by electrospray induced by Taylor cone formation as underpinning mechanism for the introduction of sodium in the plasma.An analytical sheath model combined with a scaling law shows an increase in electric field force with solution conductivity that is consistent with the observed non-linear increase in sodium density in the plasma with solution conductivity.
{"title":"Liquid-to-Gas transfer of sodium in a liquid cathode glow discharge","authors":"T. Srivastava, Arthur Dogariu, Anatoli Morozov, P. Bruggeman","doi":"10.1088/1361-6595/ad647b","DOIUrl":"https://doi.org/10.1088/1361-6595/ad647b","url":null,"abstract":"\u0000 Plasma-liquid interactions have been extensively studied with a focus on the transport of reactive species from the plasma to the liquid phase and their induced liquid phase chemistry and resulting applications. While solute transfer from the liquid to the gas phase in plasmas has been widely used in analytical chemistry, the underlying processes remain relatively unexplored. We report spatially and temporally resolved absolute density measurements of sodium in a plasma with a NaCl solution cathode using two-photon absorption laser induced fluorescence (TaLIF). The observed non-linear increase in sodium density with solution conductivity is shown to correlate with droplet generation as visualized by Mie scattering. The findings are explained by droplet generation by electrospray induced by Taylor cone formation as underpinning mechanism for the introduction of sodium in the plasma.An analytical sheath model combined with a scaling law shows an increase in electric field force with solution conductivity that is consistent with the observed non-linear increase in sodium density in the plasma with solution conductivity.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":" 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141830817","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 : 2024-07-03DOI: 10.1088/1361-6595/ad5eba
B. Beglaryan, A. Zakuskin, S. Zaytsev, Timur A. Labutin
The spatial distribution profiles of particles in plasma sources push forward our understanding of plasma evolution and physicochemical processes occuring inside. Optical probe methods, such as laser-induced fluorescence, are advanced tools for spatially resolved plasma studies. In our work, we focused on investigation of distribution of neutral Ca and Fe atoms and CaO and FeO molecules in laser-induced plasma by means of laser-induced fluorescence. The development of excitation-emission schemes for Fe and FeO and the practical implementation of schemes for Ca and CaO allowed us to construct distribution maps of these species in laser plasma at 10 and 100 Torr pressures. Both atomic and molecular fluorescence was observed much further from the plasma formation point than the region of bright spontaneous atomic emission. Additionally, by comparing fluorescence intensity distributions with plasma imaging data, we explain the origin of some pecularities in observable plasma inhomogeneity.Distributions of Ca and CaO fluorescence intensity, as well the distribution of CaO/Ca intensity ratio, demostrate that the monoxide is distributed within the plume by the shock wave, but its concentration in the outer layers of plasma is influenced by recombination with atmospheric oxygen.
等离子体源中粒子的空间分布剖面推动了我们对等离子体演变和内部发生的物理化学过程的理解。激光诱导荧光等光学探测方法是研究等离子体空间分辨率的先进工具。在我们的工作中，我们主要通过激光诱导荧光来研究激光诱导等离子体中的中性钙和铁原子以及 CaO 和 FeO 分子的分布。铁和氧化铁的激发-发射方案的开发以及钙和氧化钙方案的实际实施，使我们能够在 10 托和 100 托压力下构建这些物种在激光等离子体中的分布图。与明亮的自发原子发射区域相比，在距离等离子体形成点更远的地方观测到了原子和分子荧光。此外，通过比较荧光强度分布和等离子体成像数据，我们解释了可观测到的等离子体不均匀性中一些奇特现象的起源。钙和氧化钙荧光强度的分布以及氧化钙/钙强度比的分布表明，一氧化碳在冲击波的作用下分布在等离子体羽流中，但其在等离子体外层的浓度受到与大气中氧气重组的影响。
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Pub Date : 2024-07-03DOI: 10.1088/1361-6595/ad5eb9
Xiao-Kun Wang, I. Korolov, S. Wilczek, R. Masheyeva, Yong-Xin Liu, Yuan-Hong Song, Peter Hartmann, Zoltán Donkó, J. Schulze
Based on experiments and simulations, various plasma parameters are found to undergo a hysteresis as a function of the driving voltage amplitude in capacitively coupled CF4 discharges. Phase Resolved Optical Emission Spectroscopy reveals that the discharge operates in a hybrid combination of the drift-ambipolar and α-mode at low voltage. In this mode, the electric field and mean electron energy are high in the electronegative plasma bulk region. As the cross section for electron attachment is appreciable only at high electron energies, this mode results in strong negative ion production and keeps the electron density low as well as the mode of plasma operation stable, when the voltage is increased moderately. Increasing the driving voltage amplitude further ultimately induces a mode transition into a pure α-mode, once the electron density increases strongly. Decreasing the voltage again results in a reverse mode transition at a lower voltage compared to the previous mode transition, because the electron density is now initially high in the bulk and, thus, the bulk electric field and mean electron energy are low resulting in inefficient generation of negative ions via electron attachment. This keeps the electron density high even at lower driving voltages. This effect leads to the emergence of two steady states of plasma operation within a certain voltage range. The different electron energy distribution functions in these two states result in markedly different generation and density profiles of F atoms, with higher values occurring in the increasing voltage branch of the hysteresis. The ion flux and mean energy at the electrodes also differ. The voltage range, where the hysteresis occurs, is affected by the ion induced secondary electron coefficient (γ). A larger value of γ results in a shift of the hysteresis voltage range towards lower values.
根据实验和模拟，发现在电容耦合 CF4 放电中，各种等离子体参数随驱动电压振幅的变化而发生滞后。相位分辨光学发射光谱显示，在低电压下，放电以漂移双极模式和 α 模式的混合组合方式运行。在这种模式下，电负等离子体主体区域的电场和平均电子能量都很高。由于只有在电子能量较高时电子附着的截面才显著，因此这种模式会产生大量负离子，并在适度增加电压时保持较低的电子密度和稳定的等离子体运行模式。一旦电子密度剧增，进一步提高驱动电压幅度最终会诱导模式转换为纯粹的 α 模式。再次降低电压会导致在较低电压下发生反向模式转换，因为此时电子密度在块体中较高，因此块体电场和平均电子能量较低，导致通过电子附着产生负离子的效率较低。这样，即使在较低的驱动电压下，电子密度也会保持在较高水平。这种效应导致在一定电压范围内出现两种稳定的等离子运行状态。这两种状态下的电子能量分布函数不同，导致 F 原子的生成量和密度曲线明显不同，在滞后的电压上升分支出现的数值更高。电极上的离子通量和平均能量也有所不同。出现滞后的电压范围受离子诱导二次电子系数（γ）的影响。γ值越大，滞后电压范围越小。
{"title":"Hysteresis in radio frequency capacitively coupled CF4 plasmas","authors":"Xiao-Kun Wang, I. Korolov, S. Wilczek, R. Masheyeva, Yong-Xin Liu, Yuan-Hong Song, Peter Hartmann, Zoltán Donkó, J. Schulze","doi":"10.1088/1361-6595/ad5eb9","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5eb9","url":null,"abstract":"\u0000 Based on experiments and simulations, various plasma parameters are found to undergo a hysteresis as a function of the driving voltage amplitude in capacitively coupled CF4 discharges. Phase Resolved Optical Emission Spectroscopy reveals that the discharge operates in a hybrid combination of the drift-ambipolar and α-mode at low voltage. In this mode, the electric field and mean electron energy are high in the electronegative plasma bulk region. As the cross section for electron attachment is appreciable only at high electron energies, this mode results in strong negative ion production and keeps the electron density low as well as the mode of plasma operation stable, when the voltage is increased moderately. Increasing the driving voltage amplitude further ultimately induces a mode transition into a pure α-mode, once the electron density increases strongly. Decreasing the voltage again results in a reverse mode transition at a lower voltage compared to the previous mode transition, because the electron density is now initially high in the bulk and, thus, the bulk electric field and mean electron energy are low resulting in inefficient generation of negative ions via electron attachment. This keeps the electron density high even at lower driving voltages. This effect leads to the emergence of two steady states of plasma operation within a certain voltage range. The different electron energy distribution functions in these two states result in markedly different generation and density profiles of F atoms, with higher values occurring in the increasing voltage branch of the hysteresis. The ion flux and mean energy at the electrodes also differ. The voltage range, where the hysteresis occurs, is affected by the ion induced secondary electron coefficient (γ). A larger value of γ results in a shift of the hysteresis voltage range towards lower values.","PeriodicalId":508056,"journal":{"name":"Plasma Sources Science and Technology","volume":"138 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141682542","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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