Pub Date : 2021-03-03DOI: 10.1088/2516-1067/abf911
C. Corbella, S. Portal, M. Keidar
Spherical quartz stones of around 1 cm in diameter have been exposed to anodic arc discharges in a helium atmosphere at 300 Torr. The arc current flowing between the graphite electrodes was set either in continuous DC mode (30–150 A) or in pulsed mode at 2 Hz (220 A peak). The ablation rate in each sample was systematically measured after several seconds of arc plasma treatment. Optical emission spectroscopy (OES) diagnostics and 2D fluid simulations of the arc discharge have shed light on the heat flux transport and the heating mechanisms of the quartz crystals. A linear correlation is found between the absorbed power density and the resulting rate of penetration, which yields a maximal value of 15 cm h−1 for approximately 150 W cm−2. The linear fit on the slope provides a specific energy of 40 kJ cm−3. The incident energy flux onto the sample surface promoted a phase transition from crystalline to glassy silica, as characterized via Raman spectroscopy. This study points out the strong potential of arc plasma technology for geothermal drilling applications.
直径约1cm的球形石英石已在300托的氦气气氛中暴露于阳极电弧放电。石墨电极之间流动的电弧电流设置为连续直流模式（30–150 A）或2 Hz的脉冲模式（峰值220 A）。在电弧等离子体处理几秒钟后，系统地测量每个样品中的消融速率。电弧放电的光学发射光谱（OES）诊断和2D流体模拟揭示了石英晶体的热通量传输和加热机制。在吸收的功率密度和由此产生的穿透率之间存在线性相关性，对于大约150 W cm−2，穿透率的最大值为15 cm h−1。斜坡上的线性拟合提供了40 kJ cm−3的比能量。入射到样品表面的能量通量促进了从晶体二氧化硅到玻璃态二氧化硅的相变，如通过拉曼光谱所表征的。该研究指出了电弧等离子体技术在地热钻探应用中的强大潜力。
{"title":"Arc plasma ablation of quartz crystals","authors":"C. Corbella, S. Portal, M. Keidar","doi":"10.1088/2516-1067/abf911","DOIUrl":"https://doi.org/10.1088/2516-1067/abf911","url":null,"abstract":"Spherical quartz stones of around 1 cm in diameter have been exposed to anodic arc discharges in a helium atmosphere at 300 Torr. The arc current flowing between the graphite electrodes was set either in continuous DC mode (30–150 A) or in pulsed mode at 2 Hz (220 A peak). The ablation rate in each sample was systematically measured after several seconds of arc plasma treatment. Optical emission spectroscopy (OES) diagnostics and 2D fluid simulations of the arc discharge have shed light on the heat flux transport and the heating mechanisms of the quartz crystals. A linear correlation is found between the absorbed power density and the resulting rate of penetration, which yields a maximal value of 15 cm h−1 for approximately 150 W cm−2. The linear fit on the slope provides a specific energy of 40 kJ cm−3. The incident energy flux onto the sample surface promoted a phase transition from crystalline to glassy silica, as characterized via Raman spectroscopy. This study points out the strong potential of arc plasma technology for geothermal drilling applications.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45097694","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 : 2021-03-01DOI: 10.1088/2516-1067/abe293
I. Smetanin, Y. Kurilenkov, A. Oginov, V. Tarakanov, I. Samoylov
It is demonstrated experimentally that polydisperse Pd plasma of low energy (∼1 J) nanosecond vacuum discharge operating in a virtual cathode regime becomes an effective stochastic cavity in hard x-ray domain. A diffusion model of stochastic propagation of spontaneous x-ray radiation in the volume of randomly located reflecting clusters is developed also. The model provides qualitative explanation of both the experimentally observed effects of high-intensity bursts and partial ‘trapping’ of x-ray radiation. The x-ray burst emerges when photons are stored inside the plasma volume followed by instant release at the end of the discharge while the trapping regime corresponds to the slow developing x-ray diffusion with the characteristic time larger than the discharge duration. The results obtained are compared qualitatively with well-known concept of Letokhov’s random laser.
{"title":"Polydisperse inter-electrode plasma of Pd nanoclusters as a random cavity for x-ray spontaneous emission bursts","authors":"I. Smetanin, Y. Kurilenkov, A. Oginov, V. Tarakanov, I. Samoylov","doi":"10.1088/2516-1067/abe293","DOIUrl":"https://doi.org/10.1088/2516-1067/abe293","url":null,"abstract":"It is demonstrated experimentally that polydisperse Pd plasma of low energy (∼1 J) nanosecond vacuum discharge operating in a virtual cathode regime becomes an effective stochastic cavity in hard x-ray domain. A diffusion model of stochastic propagation of spontaneous x-ray radiation in the volume of randomly located reflecting clusters is developed also. The model provides qualitative explanation of both the experimentally observed effects of high-intensity bursts and partial ‘trapping’ of x-ray radiation. The x-ray burst emerges when photons are stored inside the plasma volume followed by instant release at the end of the discharge while the trapping regime corresponds to the slow developing x-ray diffusion with the characteristic time larger than the discharge duration. The results obtained are compared qualitatively with well-known concept of Letokhov’s random laser.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46628116","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 : 2021-03-01DOI: 10.1088/2516-1067/ab880a
David Alderman, Christopher Tremble, D. Singleton, J. Sanders, C. Jiang
Transient plasma ignition (TPI) employs highly non-equilibrium plasmas driven by nanosecond high-voltage pulses for combustion ignition. The effects of rise time and pulse repetition frequency (PRF) on combustion ignition are evaluated when transient plasmas, powered by 10-ns, kilovolt pulses, are employed to initiate combustion of lean, stoichiometric, or rich methane-dry air mixtures at atmospheric pressure. It was found that the plasmas driven by high voltage pulses with a faster rise time and PRF between 6–10 kHz enhanced combustion with higher peak pressure and/or shorter ignition delay. A mode transition in the plasma, corresponding to the combustion initiation, was observed based on voltage and current waveforms of four consecutive pulsed plasmas driven by a pulse burst at kilohertz PRFs. Although benefits in combustion ignition from a shorter rise time and optimal PRF were observed for all three equivalence mixture ratios, the highest peak pressure and shortest ignition delay were associated with the stoichiometric mixtures. In addition, the gas temperature of the transient plasma was measured by determining the rotational temperature of the 2nd positive system of nitrogen to be ∼1000 K for the first pulse and increased up to 2000 K after the application of the 4th pulse in a four-pulse burst TPI.
{"title":"Effects of pulse rise time and repetition frequency on nanosecond pulsed plasma ignition for combustion","authors":"David Alderman, Christopher Tremble, D. Singleton, J. Sanders, C. Jiang","doi":"10.1088/2516-1067/ab880a","DOIUrl":"https://doi.org/10.1088/2516-1067/ab880a","url":null,"abstract":"Transient plasma ignition (TPI) employs highly non-equilibrium plasmas driven by nanosecond high-voltage pulses for combustion ignition. The effects of rise time and pulse repetition frequency (PRF) on combustion ignition are evaluated when transient plasmas, powered by 10-ns, kilovolt pulses, are employed to initiate combustion of lean, stoichiometric, or rich methane-dry air mixtures at atmospheric pressure. It was found that the plasmas driven by high voltage pulses with a faster rise time and PRF between 6–10 kHz enhanced combustion with higher peak pressure and/or shorter ignition delay. A mode transition in the plasma, corresponding to the combustion initiation, was observed based on voltage and current waveforms of four consecutive pulsed plasmas driven by a pulse burst at kilohertz PRFs. Although benefits in combustion ignition from a shorter rise time and optimal PRF were observed for all three equivalence mixture ratios, the highest peak pressure and shortest ignition delay were associated with the stoichiometric mixtures. In addition, the gas temperature of the transient plasma was measured by determining the rotational temperature of the 2nd positive system of nitrogen to be ∼1000 K for the first pulse and increased up to 2000 K after the application of the 4th pulse in a four-pulse burst TPI.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab880a","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42699623","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 : 2021-02-17DOI: 10.1088/2516-1067/abe71e
A. Elshafiey, J. Musk, S. Pikuz, T. Shelkovenko, D. Hammer
Studies were carried out on the hybrid X-pinch (HXP) configuration for several wire materials using a 40 ns risetime, 300-kA pulsed-power generator with the goal of optimizing the HXP x-ray burst parameters for different applications. The gap distance between the conical electrodes of the hybrid X-pinch was varied from 0.5 to 5 mm for Al, Ag, Ti, and Mo using different wire diameters to maintain a consistent mass per unit length from one material to the next. It was found that 0.5–1 mm gap spacing was optimal to obtain a single x-ray burst, while the number of x-ray bursts increased with gap spacing for all materials at a rate of 1–2/mm. Time consistency studies of the first x-ray burst were carried out for Ti wire by changing the gap distance and wire diameter while observing the time of occurrence of the x-ray bursts. It was found that a 40 μm Ti wire load with a 3 mm electrode gap spacing had the highest probability to have the first x-ray burst reproducibly within a 2 ns time window. Time-resolved and time-integrated diagnostics provided information about the source size, time of occurrence, intensity, and the number of the x-ray bursts.
{"title":"Studies and optimization of hybrid X-pinches","authors":"A. Elshafiey, J. Musk, S. Pikuz, T. Shelkovenko, D. Hammer","doi":"10.1088/2516-1067/abe71e","DOIUrl":"https://doi.org/10.1088/2516-1067/abe71e","url":null,"abstract":"Studies were carried out on the hybrid X-pinch (HXP) configuration for several wire materials using a 40 ns risetime, 300-kA pulsed-power generator with the goal of optimizing the HXP x-ray burst parameters for different applications. The gap distance between the conical electrodes of the hybrid X-pinch was varied from 0.5 to 5 mm for Al, Ag, Ti, and Mo using different wire diameters to maintain a consistent mass per unit length from one material to the next. It was found that 0.5–1 mm gap spacing was optimal to obtain a single x-ray burst, while the number of x-ray bursts increased with gap spacing for all materials at a rate of 1–2/mm. Time consistency studies of the first x-ray burst were carried out for Ti wire by changing the gap distance and wire diameter while observing the time of occurrence of the x-ray bursts. It was found that a 40 μm Ti wire load with a 3 mm electrode gap spacing had the highest probability to have the first x-ray burst reproducibly within a 2 ns time window. Time-resolved and time-integrated diagnostics provided information about the source size, time of occurrence, intensity, and the number of the x-ray bursts.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47843440","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 : 2021-01-21DOI: 10.1088/2516-1067/abd958
K. Kumar, M. K. Mishra
In this paper we have discussed the consequence of superthermal electrons and negative ion concentration on the arbitrary amplitude ion-acoustic double layers (IA-DLs) for plasma comprising the hot negative and positive ions with kappa distribution electrons. The energy equation is deduced for ion acoustic waves using Pseudo potential technique. We have investigated different parametric regimes for the existence of rarefactive and compressive ion acoustic DLs. The existence of double layers in term of minimum and maximum Mach number has calculated numerically. The effect of spectral index k on the amplitude of DLs and depth of Sagdeev potential has been discussed in detail. From numerical analysis, it is found that the compressive DLs exist at low values of α and rarefactive double layer exist at higher values of α. On the other hand, the effect of ionic temperature ratio (σ 1 and σ 2) plays significant role for the formation of double layer. Our analytical work also shows that the system supports coexistence of compressive and rarefactive DLs. It is also observed that the mass ratio μ affect the basic properties of DLs. We expect that the present results may be used to explain the ion-acoustic double layer in space plasma, where two ionic species and superthermal electrons are observed NO52.35g.
{"title":"Arbitrary amplitude ion acoustic double layer in plasma with k-distributed electrons and negative ions","authors":"K. Kumar, M. K. Mishra","doi":"10.1088/2516-1067/abd958","DOIUrl":"https://doi.org/10.1088/2516-1067/abd958","url":null,"abstract":"In this paper we have discussed the consequence of superthermal electrons and negative ion concentration on the arbitrary amplitude ion-acoustic double layers (IA-DLs) for plasma comprising the hot negative and positive ions with kappa distribution electrons. The energy equation is deduced for ion acoustic waves using Pseudo potential technique. We have investigated different parametric regimes for the existence of rarefactive and compressive ion acoustic DLs. The existence of double layers in term of minimum and maximum Mach number has calculated numerically. The effect of spectral index k on the amplitude of DLs and depth of Sagdeev potential has been discussed in detail. From numerical analysis, it is found that the compressive DLs exist at low values of α and rarefactive double layer exist at higher values of α. On the other hand, the effect of ionic temperature ratio (σ 1 and σ 2) plays significant role for the formation of double layer. Our analytical work also shows that the system supports coexistence of compressive and rarefactive DLs. It is also observed that the mass ratio μ affect the basic properties of DLs. We expect that the present results may be used to explain the ion-acoustic double layer in space plasma, where two ionic species and superthermal electrons are observed NO52.35g.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43741052","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 : 2021-01-20DOI: 10.1088/2516-1067/abd530
S. Noureen, G. Abbas, M. Sarfraz, L. James
On the basis of Vlasov-Kinetic model and using Maxwell-Juttner distribution function, dispersion relation of electrostatic wave in a collisionless homogeneous relativistic electron plasma is derived. The analysis of the oscillation spectra is carried out in a weak magnetic field limit ω−kvth ≥ Ω. Approximate analytic expression for the weakly damped mode is obtained in the subluminal limiting range. It is shown that the relativistic weakly damped mode can be estimated analytically in the range where the wave phase velocity v φ becomes greater than relativistic thermal velocity of the electron but less than speed of light. Results in the non-relativistic and the ultrarelativistic cases are also discussed.
{"title":"On the frequency spectra of the electrostatic upper hybrid wave and linear Landau damping in a weakly magnetized relativistic electron plasma","authors":"S. Noureen, G. Abbas, M. Sarfraz, L. James","doi":"10.1088/2516-1067/abd530","DOIUrl":"https://doi.org/10.1088/2516-1067/abd530","url":null,"abstract":"On the basis of Vlasov-Kinetic model and using Maxwell-Juttner distribution function, dispersion relation of electrostatic wave in a collisionless homogeneous relativistic electron plasma is derived. The analysis of the oscillation spectra is carried out in a weak magnetic field limit ω−kvth ≥ Ω. Approximate analytic expression for the weakly damped mode is obtained in the subluminal limiting range. It is shown that the relativistic weakly damped mode can be estimated analytically in the range where the wave phase velocity v φ becomes greater than relativistic thermal velocity of the electron but less than speed of light. Results in the non-relativistic and the ultrarelativistic cases are also discussed.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45602952","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 : 2021-01-01DOI: 10.1088/2516-1067/ac18b9
S. Dozias, J. Pouvesle, É. Robert
Recently, Iséni reported measurements and analysis of electric field (EF) strengths adjacent to, and in propagating ionization waves (IWs) for non-thermal atmospheric pressure He plasma jets [1]. This paper [1] is almost the full copy of the 2017 ArXiv :1709.03109v1 [2] for which the authors already published a comment [3]. In this comment, we confirm first that the reported results are wrong due to an improperly aligned electric field probe, and second, that even these wrong measurements are themselves inconsistent.
{"title":"Comment on ‘Mapping the electric field vector of guided ionization waves at atmospheric pressure’, (2020) Plasma Res. Express 2 025014","authors":"S. Dozias, J. Pouvesle, É. Robert","doi":"10.1088/2516-1067/ac18b9","DOIUrl":"https://doi.org/10.1088/2516-1067/ac18b9","url":null,"abstract":"Recently, Iséni reported measurements and analysis of electric field (EF) strengths adjacent to, and in propagating ionization waves (IWs) for non-thermal atmospheric pressure He plasma jets [1]. This paper [1] is almost the full copy of the 2017 ArXiv :1709.03109v1 [2] for which the authors already published a comment [3]. In this comment, we confirm first that the reported results are wrong due to an improperly aligned electric field probe, and second, that even these wrong measurements are themselves inconsistent.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181174","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 : 2021-01-01DOI: 10.1088/2516-1067/ac0d4b
Y. Raz, E. Behar, Y. Ferber, A. Biagioni, M. Galletti, Maria Pia Anania, R. Pompili, Costa Gemma, A. Zigler
A parabolic profile plasma channel formed by an electric discharge inside a gas filled capillary are currently used to achieve optimal conditions for laser guiding and electron acceleration. Acceleration of high quality externally injected electron beam by laser induced wake field requires precise synchronization between several systems. In our experiment the measured jitter in plasma ignition was on the scale of 1 ns, providing possibility for the synchronization with high intensity laser and other auxiliary systems (e.g injectors). We confirmed the existence of a parabolic density plasma profile inside the capillary using an 84 MHz oscillator laser and found its duration to be approximately 300 ns.
{"title":"Low jitter parabolic profile low density plasma channel in 3D printed gas filled capillary","authors":"Y. Raz, E. Behar, Y. Ferber, A. Biagioni, M. Galletti, Maria Pia Anania, R. Pompili, Costa Gemma, A. Zigler","doi":"10.1088/2516-1067/ac0d4b","DOIUrl":"https://doi.org/10.1088/2516-1067/ac0d4b","url":null,"abstract":"A parabolic profile plasma channel formed by an electric discharge inside a gas filled capillary are currently used to achieve optimal conditions for laser guiding and electron acceleration. Acceleration of high quality externally injected electron beam by laser induced wake field requires precise synchronization between several systems. In our experiment the measured jitter in plasma ignition was on the scale of 1 ns, providing possibility for the synchronization with high intensity laser and other auxiliary systems (e.g injectors). We confirmed the existence of a parabolic density plasma profile inside the capillary using an 84 MHz oscillator laser and found its duration to be approximately 300 ns.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181117","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 : 2021-01-01DOI: 10.1088/2516-1067/ac2a0e
S. J. Doyle, A. Mancini, M. Agredano-Torres, J. L. García-Sánchez, J. Segado-Fernandez, J. Ayllon-Guerola, M. Garcia-Muñoz, E. Viezzer, J. Garcia-Lopez, Y. Hwang, K. Chung
The SMall Aspect Ratio Tokamak (SMART) device is a novel, compact (R geo = 0.42 m, a = 0.22 m, A ≥ 1.70) spherical tokamak, currently under development at the University of Seville. The SMART device is being developed over 3 phases, with target on-axis toroidal magnetic fields between 0.1 ≤ B ϕ ≤ 1.0 T, and target plasma currents of between 35 ≤ I p ≤ 400 kA; with phases 2 and 3 enabling access to a wide range of elongations (κ ≤ 2.30) and triangularities ( − 0.50 ≤ δ ≤ 0.50). SMART employs four internal divertor coils with two internal and two external poloidal field coils, enabling operation in lower-single, upper-single and double-null configurations. This work examines phase 3 of the SMART device, presenting a prospective L-mode discharge scenario without external heating, before examining five highly-shaped equilibria, including: two double null triangular configurations, two single null triangular configurations and a baseline double null configuration. All equilibria are obtained via an axisymmetric Grad-Shafranov force balance solver (Fiesta), in combination with a circuit equation rigid current displacement model (RZIp) to obtain time-resolved vessel and plasma currents.
小宽高比托卡马克(SMART)装置是一种新颖、紧凑(R geo = 0.42 m, a = 0.22 m, a≥1.70)的球形托卡马克，目前正在塞维利亚大学开发中。SMART器件分3个阶段开发，目标轴向环面磁场在0.1≤B φ≤1.0 T，目标等离子体电流在35≤I p≤400 kA;相位2和3可以获得大范围的伸长(κ≤2.30)和三角形(- 0.50≤δ≤0.50)。SMART采用四个内部分流器线圈，两个内部和两个外部极向磁场线圈，可在低单、高单和双零配置下运行。本研究考察了SMART装置的第三阶段，在考察五种高形状平衡(包括两个双零三角形配置、两个单零三角形配置和一个基线双零配置)之前，提出了一个没有外部加热的l模式放电场景。所有平衡都是通过轴对称的grada - shafranov力平衡求解器(Fiesta)获得的，结合电路方程刚性电流位移模型(RZIp)获得时间分辨的容器和等离子体电流。
{"title":"Single and double null equilibria in the SMART Tokamak","authors":"S. J. Doyle, A. Mancini, M. Agredano-Torres, J. L. García-Sánchez, J. Segado-Fernandez, J. Ayllon-Guerola, M. Garcia-Muñoz, E. Viezzer, J. Garcia-Lopez, Y. Hwang, K. Chung","doi":"10.1088/2516-1067/ac2a0e","DOIUrl":"https://doi.org/10.1088/2516-1067/ac2a0e","url":null,"abstract":"The SMall Aspect Ratio Tokamak (SMART) device is a novel, compact (R geo = 0.42 m, a = 0.22 m, A ≥ 1.70) spherical tokamak, currently under development at the University of Seville. The SMART device is being developed over 3 phases, with target on-axis toroidal magnetic fields between 0.1 ≤ B ϕ ≤ 1.0 T, and target plasma currents of between 35 ≤ I p ≤ 400 kA; with phases 2 and 3 enabling access to a wide range of elongations (κ ≤ 2.30) and triangularities ( − 0.50 ≤ δ ≤ 0.50). SMART employs four internal divertor coils with two internal and two external poloidal field coils, enabling operation in lower-single, upper-single and double-null configurations. This work examines phase 3 of the SMART device, presenting a prospective L-mode discharge scenario without external heating, before examining five highly-shaped equilibria, including: two double null triangular configurations, two single null triangular configurations and a baseline double null configuration. All equilibria are obtained via an axisymmetric Grad-Shafranov force balance solver (Fiesta), in combination with a circuit equation rigid current displacement model (RZIp) to obtain time-resolved vessel and plasma currents.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"375 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181635","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 : 2021-01-01DOI: 10.1088/2516-1067/ac2e0f
Vera Bracht, F. Kogelheide, Sven Gröger, P. Hermanns, Simon Böddeker, N. Bibinov, P. Awakowicz
A key to the understanding of mechanisms during plasma electrolytic oxidation (PEO) is the interaction between microdischarges and an amorphous oxide film. The PEO microdischarges, which are randomly distributed on the surface of a treated lightweight metal substrate (Al, Ti, Mg), cause material extraction and support the formation of hard and dense crystalline oxide films. Characterization of these microdischarges is a complicated task under PEO conditions, because of the stochastically temporal and spatial behavior as well as the small dimension of the microdischarges. Microdischarges at atmospheric pressure conditions can leave similar erosion traces on metallic films (Al, Ti) as PEO microdischarges on oxide films, and possibly can support a better understanding of the plasma-solid-interactions as well as microdischarge characteristics during PEO. A porous aluminum oxide film is deposited on aluminum substrates by pre-anodizing at a voltage of 250 V and is treated afterwards with a relative short (duration of 1 min) PEO process at a voltage of about 500 V or filamentary dielectric barrier discharges, namely a self-organized Dielectric Barrier Discharge (DBD) and a DBD-like plasma jet operated both with a He/N2 (95%/5%) gas flow. The gas temperature at DBD plasma conditions, measured using the rotational distribution in the emission spectra of molecular nitrogen, is low and amounts to about 400 K. Erosion traces on the surface of the oxide film caused by PEO and plasma spots of both atmospheric pressure discharges are studied by scanning electron microscopy and energy dispersed x-ray spectroscopy. Form and dimensions of erosion traces and established modifications of the material composition generated by the treatment with these DBD microdischarges under atmospheric pressure conditions are similar to those ones generated by the PEO process. Hence, a similar mechanism of these processes is supposed. For stronger evidences of the assumed PEO mechanism additional experimental studies are needed.
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