Pub Date : 2020-06-22DOI: 10.1088/2516-1067/ab9b69
S. Iséni
In this study, the dynamic of guided ionization wave (IW) generated by an atmospheric pressure plasma jet (APPJ) device operating in helium is experimentally investigated. The present work focuses on the properties of the intense electric field (EF) driving the IW. Taking advantages of APPJs to produce guided and reproducible IWs, the induced EF vector is characterized spatially and temporally along the direction of propagation. With this approach, EF vector mapping of guided IWs have been measured and documented for the first time. In the first part, the propagation within a glass tube of the first IW is investigated. Under the present conditions, a second guided IW is observed and propagates, leading to the formation of a guided streamer. The EF due to transient charge deposited on the wall surface is observed, particularly at the end of the tube. In the second part, one reports on the EF vector mapping under a dielectric substrate in contact with guided IWs. EF strength up to 55kVcm−1 has been measured and corroborates prior results from predictive numerical simulations. Intriguing configurations of the EF lines will be of significant interest to validate theoretical models in order to refine the non-equilibrium plasma chemistry kinetics. Furthermore, this preliminary work provides important insights into various applications involving IW driven discharges such as liquid activation, environmental treatments, plasma medicine, active flow control and plasma agriculture.
{"title":"Mapping the electric field vector of guided ionization waves at atmospheric pressure","authors":"S. Iséni","doi":"10.1088/2516-1067/ab9b69","DOIUrl":"https://doi.org/10.1088/2516-1067/ab9b69","url":null,"abstract":"In this study, the dynamic of guided ionization wave (IW) generated by an atmospheric pressure plasma jet (APPJ) device operating in helium is experimentally investigated. The present work focuses on the properties of the intense electric field (EF) driving the IW. Taking advantages of APPJs to produce guided and reproducible IWs, the induced EF vector is characterized spatially and temporally along the direction of propagation. With this approach, EF vector mapping of guided IWs have been measured and documented for the first time. In the first part, the propagation within a glass tube of the first IW is investigated. Under the present conditions, a second guided IW is observed and propagates, leading to the formation of a guided streamer. The EF due to transient charge deposited on the wall surface is observed, particularly at the end of the tube. In the second part, one reports on the EF vector mapping under a dielectric substrate in contact with guided IWs. EF strength up to 55kVcm−1 has been measured and corroborates prior results from predictive numerical simulations. Intriguing configurations of the EF lines will be of significant interest to validate theoretical models in order to refine the non-equilibrium plasma chemistry kinetics. Furthermore, this preliminary work provides important insights into various applications involving IW driven discharges such as liquid activation, environmental treatments, plasma medicine, active flow control and plasma agriculture.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44031669","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}
The application of cold atmospheric plasma (CAP) in cancer treatment has received extensive attention. However, little research was observed on the anticancer effects of CAP to tumor stem cells. Here, we analyzed the discharge characteristics of a CAP jet and plasma-induced effects on acute myeloid leukemia (AML) stem cells. Our results showed that the most active particles can be produced when helium is doped with 0.5% oxygen and the jet device is driven by a pulsed power supply. And when using this plasma jet device to treat acute myeloid leukemia (AML) stem cells, it is found that CAP jet can effectively inhibit the cell activity of AML stem cells, which provides new ideas for the treatment of AML.
{"title":"Evaluation of the anticancer effects induced by cold atmospheric plasma on leukemia stem cells","authors":"Rui Feng, Ning Ning, Miao Tian, Sansan Peng, Shuai Wang, Bing Li, Hao Zhang, Dehui Xu","doi":"10.1088/2516-1067/ab9154","DOIUrl":"https://doi.org/10.1088/2516-1067/ab9154","url":null,"abstract":"The application of cold atmospheric plasma (CAP) in cancer treatment has received extensive attention. However, little research was observed on the anticancer effects of CAP to tumor stem cells. Here, we analyzed the discharge characteristics of a CAP jet and plasma-induced effects on acute myeloid leukemia (AML) stem cells. Our results showed that the most active particles can be produced when helium is doped with 0.5% oxygen and the jet device is driven by a pulsed power supply. And when using this plasma jet device to treat acute myeloid leukemia (AML) stem cells, it is found that CAP jet can effectively inhibit the cell activity of AML stem cells, which provides new ideas for the treatment of AML.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab9154","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43574987","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 : 2020-05-29DOI: 10.1088/2516-1067/ab97f4
S. Knott, A. Ruth, P. J. Mc Carthy
Using a magnetic mirror plasma device, helium ion temperatures were investigated using high resolution Doppler spectroscopy of the He II line at 468.6 nm. The objective was to improve the quality of fits to Langmuir probe data. Measured temperatures, which represent an average value over a line of sight, ranged from 0.07 eV to 0.32 eV with higher values reached in stronger magnetic fields. An analytic expression for the line of sight integral of a variable width Gaussian signal is presented, and it is demonstrated that the integrated signal can, in practice, be accurately fitted by a single Gaussian line shape. A large number of spectra was acquired using a randomized experimental design with four independently controllable engineering variables and three discrete magnetic fields. Separate parameterizations of the results for each magnetic field in terms of the engineering variables showed that the data could already be well fitted using only the plasma current as a predictor. The fit to the ion temperature data was significantly improved when both the plasma current and filament bias voltage were used as predictors. The helium gas fill pressure had negligible predictive value for the ion temperature. (figures in this article are in colour only in the electronic version).
{"title":"Measurement and parameterization of sub-1 eV ion temperatures in a helium plasma confined by a magnetic mirror","authors":"S. Knott, A. Ruth, P. J. Mc Carthy","doi":"10.1088/2516-1067/ab97f4","DOIUrl":"https://doi.org/10.1088/2516-1067/ab97f4","url":null,"abstract":"Using a magnetic mirror plasma device, helium ion temperatures were investigated using high resolution Doppler spectroscopy of the He II line at 468.6 nm. The objective was to improve the quality of fits to Langmuir probe data. Measured temperatures, which represent an average value over a line of sight, ranged from 0.07 eV to 0.32 eV with higher values reached in stronger magnetic fields. An analytic expression for the line of sight integral of a variable width Gaussian signal is presented, and it is demonstrated that the integrated signal can, in practice, be accurately fitted by a single Gaussian line shape. A large number of spectra was acquired using a randomized experimental design with four independently controllable engineering variables and three discrete magnetic fields. Separate parameterizations of the results for each magnetic field in terms of the engineering variables showed that the data could already be well fitted using only the plasma current as a predictor. The fit to the ion temperature data was significantly improved when both the plasma current and filament bias voltage were used as predictors. The helium gas fill pressure had negligible predictive value for the ion temperature. (figures in this article are in colour only in the electronic version).","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45728137","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 : 2020-05-28DOI: 10.1088/2516-1067/abb4c2
I R Goumiri, K. McCollam, A. Squitieri, D J Holly, J. Sarff, S P Leblanc
Programmable control of the inductive electric field enables advanced operations of reversed-field pinch (RFP) plasmas in the Madison Symmetric Torus (MST) device and further develops the technical basis for ohmically heated fusion RFP plasmas. MST’s poloidal and toroidal magnetic fields (B p and B t) can be sourced by programmable power supplies (PPSs) based on integrated-gate bipolar transistors (IGBT). In order to provide real-time simultaneous control of both B p and B t circuits, a time-independent integrated model is developed. The actuators considered for the control are the B p and B t primary currents produced by the PPSs. The control system goal will be tracking two particular demand quantities that can be measured at the plasma surface (r = a): the plasma current, I p ∼ B p(a), and the RFP reversal parameter, F ∼ B t(a)/Φ, where Φ is the toroidal flux in the plasma. The edge safety factor, q(a) ∝ B t (a), tends to track F but not identically. To understand the responses of I p and F to the actuators and to enable systematic design of control algorithms, dedicated experiments are run in which the actuators are modulated, and a linearized dynamic data-driven model is generated using a system identification method. We perform a series of initial real-time experiments to test the designed feedback controllers and validate the derived model predictions. The feedback controllers show systematic improvements over simpler feedforward controllers.
{"title":"Simultaneous feedback control of toroidal magnetic field and plasma current on MST using advanced programmable power supplies","authors":"I R Goumiri, K. McCollam, A. Squitieri, D J Holly, J. Sarff, S P Leblanc","doi":"10.1088/2516-1067/abb4c2","DOIUrl":"https://doi.org/10.1088/2516-1067/abb4c2","url":null,"abstract":"Programmable control of the inductive electric field enables advanced operations of reversed-field pinch (RFP) plasmas in the Madison Symmetric Torus (MST) device and further develops the technical basis for ohmically heated fusion RFP plasmas. MST’s poloidal and toroidal magnetic fields (B p and B t) can be sourced by programmable power supplies (PPSs) based on integrated-gate bipolar transistors (IGBT). In order to provide real-time simultaneous control of both B p and B t circuits, a time-independent integrated model is developed. The actuators considered for the control are the B p and B t primary currents produced by the PPSs. The control system goal will be tracking two particular demand quantities that can be measured at the plasma surface (r = a): the plasma current, I p ∼ B p(a), and the RFP reversal parameter, F ∼ B t(a)/Φ, where Φ is the toroidal flux in the plasma. The edge safety factor, q(a) ∝ B t (a), tends to track F but not identically. To understand the responses of I p and F to the actuators and to enable systematic design of control algorithms, dedicated experiments are run in which the actuators are modulated, and a linearized dynamic data-driven model is generated using a system identification method. We perform a series of initial real-time experiments to test the designed feedback controllers and validate the derived model predictions. The feedback controllers show systematic improvements over simpler feedforward controllers.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49625259","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 : 2020-05-27DOI: 10.1088/2516-1067/ab9731
D. Piriaei, T. D. Mahabadi
Using a small (450 J) Mather-type plasma focus device, this research investigates the effects of cathode rod removal from the cathode array in two steps on hard x-ray emission, both in total and specifically from the plasmoid. The effect on anode rod erosion is also measured. Six hard x-ray detectors were placed around the chamber to measure the emitted hard x-rays. By reducing the number of cathode rods, some features of these hard x-rays such as peak intensity and pulse yield decreased and were deteriorated. Besides, the capability of the device for producing and reproducing the hard x-rays with roughly similar and repeatable characteristics diminished. Moreover, the anode erosion took place during the breakdown phase and by using the detectors around the chamber, similar features were obtained both for the total and the plasmoid hard x-rays, but with different scales. The cathode rod removal could violate the symmetry and uniform formation of the current sheath layer during the breakdown phase and could weaken and change the direction of the Lorentz force vector acting on the current sheath layer during the axial phase. It also causes discharge delay and decreases the axial and radial velocities of the current sheath layer which would result in a weak pinch effect and reduced number of energetic runaway electrons inside the plasma column during the pinch phase. These electrons, by colliding the anode surface, are mainly responsible for producing the great portion of the emitted hard x-ray. On the contrary and based on a different mechanism, the cathode rod removal enhances the number of the runaway electrons during the breakdown phase which increases the anode erosion and enhances the impurities that eventually leads to a weak emission of low intensity hard x-rays.
{"title":"The cathode array effects on features and reproducibility of emitted hard x-rays, and anode erosion in a small plasma focus device","authors":"D. Piriaei, T. D. Mahabadi","doi":"10.1088/2516-1067/ab9731","DOIUrl":"https://doi.org/10.1088/2516-1067/ab9731","url":null,"abstract":"Using a small (450 J) Mather-type plasma focus device, this research investigates the effects of cathode rod removal from the cathode array in two steps on hard x-ray emission, both in total and specifically from the plasmoid. The effect on anode rod erosion is also measured. Six hard x-ray detectors were placed around the chamber to measure the emitted hard x-rays. By reducing the number of cathode rods, some features of these hard x-rays such as peak intensity and pulse yield decreased and were deteriorated. Besides, the capability of the device for producing and reproducing the hard x-rays with roughly similar and repeatable characteristics diminished. Moreover, the anode erosion took place during the breakdown phase and by using the detectors around the chamber, similar features were obtained both for the total and the plasmoid hard x-rays, but with different scales. The cathode rod removal could violate the symmetry and uniform formation of the current sheath layer during the breakdown phase and could weaken and change the direction of the Lorentz force vector acting on the current sheath layer during the axial phase. It also causes discharge delay and decreases the axial and radial velocities of the current sheath layer which would result in a weak pinch effect and reduced number of energetic runaway electrons inside the plasma column during the pinch phase. These electrons, by colliding the anode surface, are mainly responsible for producing the great portion of the emitted hard x-ray. On the contrary and based on a different mechanism, the cathode rod removal enhances the number of the runaway electrons during the breakdown phase which increases the anode erosion and enhances the impurities that eventually leads to a weak emission of low intensity hard x-rays.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab9731","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45012497","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 : 2020-05-27DOI: 10.1088/2516-1067/ab9730
P. Wong, Peng Zhang, J. Luginsland
The traveling-wave tube (TWT), also known as the traveling-wave amplifier (TWA) or traveling-wave tube amplifier (TWTA), is a widely used amplifier in satellite communications and radar. An electromagnetic signal is inputted on one end of the device and is amplified over a distance until it is extracted downstream at the output. The physics behind this spatial amplification of an electromagnetic wave is predicated on the interaction of a linear DC electron beam with the surrounding circuit structure. Pierce, known as the ‘father of communications satellites,’ was the first to formulate the theory for this beam-circuit interaction, the basis of which has since been used to model other vacuum electronic devices such as free-electron lasers, gyrotrons, and Smith-Purcell radiators, just to name a few. In this paper, the traditional Pierce theory will first be briefly reviewed; the classic Pierce theory will then be extended in several directions: harmonic generation and the effect of high beam current on both the beam mode and circuit mode as well as ‘discrete effects’, giving a brief tutorial of recent theories of TWTs.
{"title":"Recent theory of traveling-wave tubes: a tutorial-review","authors":"P. Wong, Peng Zhang, J. Luginsland","doi":"10.1088/2516-1067/ab9730","DOIUrl":"https://doi.org/10.1088/2516-1067/ab9730","url":null,"abstract":"The traveling-wave tube (TWT), also known as the traveling-wave amplifier (TWA) or traveling-wave tube amplifier (TWTA), is a widely used amplifier in satellite communications and radar. An electromagnetic signal is inputted on one end of the device and is amplified over a distance until it is extracted downstream at the output. The physics behind this spatial amplification of an electromagnetic wave is predicated on the interaction of a linear DC electron beam with the surrounding circuit structure. Pierce, known as the ‘father of communications satellites,’ was the first to formulate the theory for this beam-circuit interaction, the basis of which has since been used to model other vacuum electronic devices such as free-electron lasers, gyrotrons, and Smith-Purcell radiators, just to name a few. In this paper, the traditional Pierce theory will first be briefly reviewed; the classic Pierce theory will then be extended in several directions: harmonic generation and the effect of high beam current on both the beam mode and circuit mode as well as ‘discrete effects’, giving a brief tutorial of recent theories of TWTs.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab9730","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44339246","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}
The streamer discharges and electric breakdown in insulating liquid like transformer oil are undesirable for power equipment. However, the physical processes of streamer propagation and branching events in dense liquid dielectrics are not well understood. In this paper, we develop an improved fluid model to investigate the interactions of cellulose particles with streamer propagation and branching behaviors. We elaborately select the number of cellulose particles (single or multiple particles), their size and locations to elucidate the influencing mechanisms. The simulation results show that when the heads of streamer contact with the surface of the cellulose particle, the local electric field increases sharply, hence the rise of ionization rate and velocity. The scattering electric field lines guide the streamer head away from the surface, thereby causing branching to occur. The interactions between the two split streamers allow one head to continuously propagate, while the other dies out due to insufficient ionization rate. When the particle is too small or too far away to the streamer channel, it has no pronounced impact on the streamer propagation. While placing the particle very close to or on the route of discharge channel will cause the streamer to creep on the cellulose particle and to branch more.
{"title":"How cellulose particles influence streamer propagation and branching in transformer oil: a 2D modelling perspective","authors":"Yuan Li, Yahong Li, Jia-ye Wen, Linbo Li, Luning Wang, Guanjun Zhang","doi":"10.1088/2516-1067/ab9539","DOIUrl":"https://doi.org/10.1088/2516-1067/ab9539","url":null,"abstract":"The streamer discharges and electric breakdown in insulating liquid like transformer oil are undesirable for power equipment. However, the physical processes of streamer propagation and branching events in dense liquid dielectrics are not well understood. In this paper, we develop an improved fluid model to investigate the interactions of cellulose particles with streamer propagation and branching behaviors. We elaborately select the number of cellulose particles (single or multiple particles), their size and locations to elucidate the influencing mechanisms. The simulation results show that when the heads of streamer contact with the surface of the cellulose particle, the local electric field increases sharply, hence the rise of ionization rate and velocity. The scattering electric field lines guide the streamer head away from the surface, thereby causing branching to occur. The interactions between the two split streamers allow one head to continuously propagate, while the other dies out due to insufficient ionization rate. When the particle is too small or too far away to the streamer channel, it has no pronounced impact on the streamer propagation. While placing the particle very close to or on the route of discharge channel will cause the streamer to creep on the cellulose particle and to branch more.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47289447","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 : 2020-05-19DOI: 10.1088/2516-1067/ab906c
A. I. Mahdy
We propose a mathematical model to study the effect of an external electric field on the relaxation of a Traveling Plasma Grating (TPG) that is induced by the filamentation of two femtosecond laser beams in air plasma. The main purpose of this study is to examine the role of the applied electric field on the relaxation-delay of the formed plasma grating (PG) and to investigate the consequences of this delay on the efficiency of the energy exchange between these beams. The proposed model employs two coupled 2D envelope-equations in conjunction with a kinetic electron balance and an electron energy conservation equation to study the relaxation of the induced PG in the molecular air structure. The employed equations have been numerically solved and the simulation results have revealed that the presence of the electric field widely prolongs the electron density decay period and largely extends the electron temperature relaxation time of the induced PG at different molecular structures, furthermore it increases the energy exchange ratio between the two fs beams on these air structures.
{"title":"Electric field effect on the relaxation of a plasma grating induced by two femtosecond lasers in air","authors":"A. I. Mahdy","doi":"10.1088/2516-1067/ab906c","DOIUrl":"https://doi.org/10.1088/2516-1067/ab906c","url":null,"abstract":"We propose a mathematical model to study the effect of an external electric field on the relaxation of a Traveling Plasma Grating (TPG) that is induced by the filamentation of two femtosecond laser beams in air plasma. The main purpose of this study is to examine the role of the applied electric field on the relaxation-delay of the formed plasma grating (PG) and to investigate the consequences of this delay on the efficiency of the energy exchange between these beams. The proposed model employs two coupled 2D envelope-equations in conjunction with a kinetic electron balance and an electron energy conservation equation to study the relaxation of the induced PG in the molecular air structure. The employed equations have been numerically solved and the simulation results have revealed that the presence of the electric field widely prolongs the electron density decay period and largely extends the electron temperature relaxation time of the induced PG at different molecular structures, furthermore it increases the energy exchange ratio between the two fs beams on these air structures.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48507224","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 : 2020-05-13DOI: 10.1088/2516-1067/ab8f04
Zumei Sun, L. Velásquez-García
We report the design, fabrication, and experimental characterization of the first additively manufactured, miniature, metal multi-needle ionic wind pumps in the literature. The pumps are needle-ring corona diodes composed of a monolithic inkjet binder-printed active electrode, made in stainless steel 316L, with five sharp, conical needles, and a thin plate counter-electrode, made in copper, with electrochemically etched apertures aligned to the needle array; by applying a large bias voltage across the diode, electrohydrodynamically driven airflow is produced. The influence of tip multiplexing and tip sharpening on the ion current, airflow velocity, volumetric flow rate, and kinetic conversion efficiency of the pumps was characterized under different interelectrode separations, counter-electrode aperture diameters, and applied bias voltages, while triggering a negative corona discharge. At the optimal operating bias voltage (7.4 kV), the as-printed five-needle ionic wind pumps eject air at 2.66 m s−1 and at a volumetric flow rate of 316 cm3 s−1 –a twofold larger than the flow rate of an as-printed single-needle device and with 35% higher efficiency (i.e. 0.27%). Using a two-step electropolishing procedure, the needles of the active electrode can be uniformly sharpened down to 83.4 μm average tip diameter, i.e. about one quarter of their as-printed dimension (∼300 μm). Operated under the same conditions, the electropolished five-needle pumps eject air at 3.25 m s−1, i.e. 22% higher speed compared to the as-printed devices, with the same kinetic conversion efficiency. A two-module model was built in COMSOL Multiphysics, consisting of a three-species corona discharge module and a gas dynamics module, to gain insights into the operation of the pumps and to determine trends for increasing device performance. The electrohydrodynamic (EHD) body force calculated using this model has the same periodic behaviour of the Trichel pulse current. A time-dependent EHD body force analysis was performed, and the stabilized forces averaged over a multiple of the Trichel pulse period were used to predict the large-timescale airflow. The EHD force from the corona simulation can be rescaled to calculate the flow at different bias voltages, greatly reducing the simulation time, and making possible to systematically study the relevant parameters and optimize the design of the air pump. The experimental data agree with the simulation results and the reduced-order modelling.
我们报道了文献中第一个添加制造的微型金属多针离子风泵的设计、制造和实验表征。泵是针环电晕二极管，由单片喷墨粘合剂印刷的活性电极组成，该活性电极由316L不锈钢制成，具有五个尖锐的锥形针，以及薄板对电极，该电极由铜制成，具有与针阵列对齐的电化学蚀刻孔；通过在二极管两端施加大的偏置电压，产生了电流体动力学驱动的气流。在不同的电极间间距、对电极孔径和施加的偏置电压下，表征了尖端多路复用和尖端锐化对泵的离子电流、气流速度、体积流速和动力学转换效率的影响，同时触发负电晕放电。在最佳工作偏置电压（7.4 kV）下，印刷态五针离子风泵以2.66 m s−1的速度喷射空气，体积流速为316 cm3 s−1，比印刷态单针装置的流速大两倍，效率高35%（即0.27%）。使用两步电抛光程序，活性电极的针可以均匀地削尖至83.4μm的平均尖端直径，即约为其印刷尺寸的四分之一（～300μm）。在相同的条件下操作，电解抛光的五针泵以3.25 m s−1的速度喷出空气，即与印刷设备相比速度高22%，具有相同的动力学转换效率。COMSOL Multiphysics中建立了一个两模块模型，由三种电晕放电模块和气体动力学模块组成，以深入了解泵的运行情况，并确定提高设备性能的趋势。使用该模型计算的电流体动力学（EHD）体力具有与Trichel脉冲电流相同的周期性行为。进行了与时间相关的EHD身体力分析，并使用在Trichel脉冲周期的倍数上平均的稳定力来预测大时间尺度的气流。电晕模拟产生的EHD力可以重新缩放，以计算不同偏置电压下的流量，大大缩短了模拟时间，并使系统研究相关参数和优化气泵设计成为可能。实验数据与仿真结果和降阶模型相一致。
{"title":"Miniature, metal 3D-printed, multiplexed electrohydrodynamic gas pumps","authors":"Zumei Sun, L. Velásquez-García","doi":"10.1088/2516-1067/ab8f04","DOIUrl":"https://doi.org/10.1088/2516-1067/ab8f04","url":null,"abstract":"We report the design, fabrication, and experimental characterization of the first additively manufactured, miniature, metal multi-needle ionic wind pumps in the literature. The pumps are needle-ring corona diodes composed of a monolithic inkjet binder-printed active electrode, made in stainless steel 316L, with five sharp, conical needles, and a thin plate counter-electrode, made in copper, with electrochemically etched apertures aligned to the needle array; by applying a large bias voltage across the diode, electrohydrodynamically driven airflow is produced. The influence of tip multiplexing and tip sharpening on the ion current, airflow velocity, volumetric flow rate, and kinetic conversion efficiency of the pumps was characterized under different interelectrode separations, counter-electrode aperture diameters, and applied bias voltages, while triggering a negative corona discharge. At the optimal operating bias voltage (7.4 kV), the as-printed five-needle ionic wind pumps eject air at 2.66 m s−1 and at a volumetric flow rate of 316 cm3 s−1 –a twofold larger than the flow rate of an as-printed single-needle device and with 35% higher efficiency (i.e. 0.27%). Using a two-step electropolishing procedure, the needles of the active electrode can be uniformly sharpened down to 83.4 μm average tip diameter, i.e. about one quarter of their as-printed dimension (∼300 μm). Operated under the same conditions, the electropolished five-needle pumps eject air at 3.25 m s−1, i.e. 22% higher speed compared to the as-printed devices, with the same kinetic conversion efficiency. A two-module model was built in COMSOL Multiphysics, consisting of a three-species corona discharge module and a gas dynamics module, to gain insights into the operation of the pumps and to determine trends for increasing device performance. The electrohydrodynamic (EHD) body force calculated using this model has the same periodic behaviour of the Trichel pulse current. A time-dependent EHD body force analysis was performed, and the stabilized forces averaged over a multiple of the Trichel pulse period were used to predict the large-timescale airflow. The EHD force from the corona simulation can be rescaled to calculate the flow at different bias voltages, greatly reducing the simulation time, and making possible to systematically study the relevant parameters and optimize the design of the air pump. The experimental data agree with the simulation results and the reduced-order modelling.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab8f04","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46918604","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 : 2020-05-12DOI: 10.1088/2516-1067/ab8f39
K. Barman, Deepika Behmani, Mohit Mudgal, S. Bhattacharjee, R. Rane, S. Nema
The plasma characteristics of atmospheric pressure micro-plasma jets in two different modes of excitation: low frequency (∼10 kHz), high voltage (∼15 kV) (LFHV) and high frequency (∼80 kHz), low voltage (4 kV) (HFLV), are investigated. The effect of AC electrical excitation on the plasma, depending upon wave amplitude and frequency, are looked at experimentally in the two systems. Plasma parameters such as the electron density (ne), electron excitation temperature (Texc), including optical line intensities from different species in the plasma are investigated as a function of applied external voltage, gas flow rate and operating frequency. Electrical modelling of the two different plasma systems are carried out and the results from the models are found to agree reasonably well with those of the experiments. It is found that the electron density and the temperature of the HFLV system are higher than the LFHV system at a particular gas flow rate, although the external applied voltage is higher for the LFHV system. A lower value of Texc for the LFHV system may make it suitable for medical or biological applications. Since a large electric field is created near the tip of the pin electrode in the HFLV system, therefore even though the applied voltage is lower than the LFHV system, the plasma can be easily generated. The HFLV system support a higher Texc, and such a system could be useful for material surface modification applications.
{"title":"Characteristics of atmospheric pressure micro-plasma jets in two different modes of excitation depending upon wave amplitude and frequency","authors":"K. Barman, Deepika Behmani, Mohit Mudgal, S. Bhattacharjee, R. Rane, S. Nema","doi":"10.1088/2516-1067/ab8f39","DOIUrl":"https://doi.org/10.1088/2516-1067/ab8f39","url":null,"abstract":"The plasma characteristics of atmospheric pressure micro-plasma jets in two different modes of excitation: low frequency (∼10 kHz), high voltage (∼15 kV) (LFHV) and high frequency (∼80 kHz), low voltage (4 kV) (HFLV), are investigated. The effect of AC electrical excitation on the plasma, depending upon wave amplitude and frequency, are looked at experimentally in the two systems. Plasma parameters such as the electron density (ne), electron excitation temperature (Texc), including optical line intensities from different species in the plasma are investigated as a function of applied external voltage, gas flow rate and operating frequency. Electrical modelling of the two different plasma systems are carried out and the results from the models are found to agree reasonably well with those of the experiments. It is found that the electron density and the temperature of the HFLV system are higher than the LFHV system at a particular gas flow rate, although the external applied voltage is higher for the LFHV system. A lower value of Texc for the LFHV system may make it suitable for medical or biological applications. Since a large electric field is created near the tip of the pin electrode in the HFLV system, therefore even though the applied voltage is lower than the LFHV system, the plasma can be easily generated. The HFLV system support a higher Texc, and such a system could be useful for material surface modification applications.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44242460","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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