Pub Date : 2024-06-11DOI: 10.1088/1361-6595/ad51a4
B Mahdavipour and J T Gudmundsson
One-dimensional particle-in-cell/Monte Carlo collisional simulations are performed on capacitive chlorine discharges with 2.54 cm gap rf driven by a sinusoidal with voltage amplitude of 222 V at driving frequency of 13.56 MHz. The properties of the discharge, the reaction rates for creation and loss of a few key species, the electron energy probability function, and the primary electron power absorption processes are explored as the gas pressure and the inclusion of secondary electron emission processes in the discharge model is varied. Five cases are investigated, including and neglecting electron, ion, and fast neutrals induced secondary electron emission. The negative ion Cl− is almost entirely created by dissociative attachment and lost through ion-ion recombination, and therefore the capacitive chlorine discharge is recombination dominated.
在 13.56 MHz 的驱动频率下，通过电压振幅为 222 V 的正弦波，对间隙为 2.54 cm 的电容式氯放电进行了一维粒子池内/蒙特卡洛碰撞模拟。随着气体压力和放电模型中包含的二次电子发射过程的变化，探讨了放电的特性、几种关键物质的生成和损耗反应速率、电子能量概率函数和一次电子功率吸收过程。研究了包括和忽略电子、离子和快中子诱导的二次电子发射的五种情况。负离子 Cl- 几乎完全由离解附着产生，并通过离子-离子重组而消失，因此电容式氯放电以重组为主。
{"title":"On the influence of electrode surfaces on the plasma chemistry of a capacitive chlorine discharge","authors":"B Mahdavipour and J T Gudmundsson","doi":"10.1088/1361-6595/ad51a4","DOIUrl":"https://doi.org/10.1088/1361-6595/ad51a4","url":null,"abstract":"One-dimensional particle-in-cell/Monte Carlo collisional simulations are performed on capacitive chlorine discharges with 2.54 cm gap rf driven by a sinusoidal with voltage amplitude of 222 V at driving frequency of 13.56 MHz. The properties of the discharge, the reaction rates for creation and loss of a few key species, the electron energy probability function, and the primary electron power absorption processes are explored as the gas pressure and the inclusion of secondary electron emission processes in the discharge model is varied. Five cases are investigated, including and neglecting electron, ion, and fast neutrals induced secondary electron emission. The negative ion Cl− is almost entirely created by dissociative attachment and lost through ion-ion recombination, and therefore the capacitive chlorine discharge is recombination dominated.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"2015 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501067","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 : 2024-06-11DOI: 10.1088/1361-6595/ad52c0
Mostafa Salahshoor
A common feature of all types of magnetron sputtering (MS) assemblies is an effective confinement of electrons by an appropriate combination of electric and magnetic fields. Therefore, studying the motions of electrons in the fields of magnetron assemblies is of particular importance. Here, we systematically analyze the electrons motions in front of a typical DC MS cathode. We first calculate the profiles of the magnetron’s magnetic field for balanced and two types of unbalanced configurations. Then, we compute the profiles of the cathode’s electric field before the gas discharge and after the plasma formation. A semi-analytical model is utilized to compute the plasma potential. We then track the motions of electrons released from the target and electrons produced through impact ionization of the background gas in the prescribed fields. A Monte Carlo model is implemented to consider electron-gas collisions and a mixed boundary condition is employed to account for electron-wall interactions. The study analyzes the impact of field profiles on the cathode’s efficiency in trapping electron by examining electron escape from the magnetic trap and electron recapture at the target surface. It is shown that the presence of plasma in all configurations leads to a significant increase in the trapping efficiency and the ionization performance, as well as a decrease in the recapture probability. These effects are attributed to the high electric field developed in the cathode sheath. Moreover, we statistically analyze the trapping efficiency by illustrating the spatial distributions of electrons locations in both axial and radial dimensions. It is demonstrated that during their azimuthal drift motion, the electrons released from the middle region at the target surface have the smallest range of axial and radial locations, in all configurations in the absence of plasma. Finally, the impact of field profiles on the average energies of electrons is discussed.
所有类型磁控溅射（MS）组件的一个共同特点是通过适当的电场和磁场组合对电子进行有效的约束。因此，研究电子在磁控管组件场中的运动具有特别重要的意义。在这里，我们系统地分析了典型直流 MS 阴极前的电子运动。首先，我们计算了平衡配置和两种不平衡配置的磁控管磁场轮廓。然后，我们计算气体放电前和等离子体形成后的阴极电场剖面。我们利用半分析模型计算等离子体电势。然后，我们在规定的电场中跟踪从目标释放的电子和背景气体撞击电离产生的电子的运动。蒙地卡罗模型用于考虑电子-气体碰撞，混合边界条件用于考虑电子-壁相互作用。研究通过考察电子从磁性阱逸出和在靶表面重新捕获的情况，分析了场剖面对阴极捕获电子效率的影响。结果表明，在所有配置中，等离子体的存在都会显著提高捕获效率和电离性能，并降低再捕获概率。这些效应归因于阴极鞘中产生的高电场。此外，我们还通过说明电子在轴向和径向的位置空间分布，对俘获效率进行了统计分析。结果表明，在没有等离子体的所有配置中，从靶表面中间区域释放的电子在其方位漂移运动过程中，其轴向和径向位置范围最小。最后，讨论了场剖面对电子平均能量的影响。
{"title":"Electron trapping efficiency of a magnetron sputtering cathode","authors":"Mostafa Salahshoor","doi":"10.1088/1361-6595/ad52c0","DOIUrl":"https://doi.org/10.1088/1361-6595/ad52c0","url":null,"abstract":"A common feature of all types of magnetron sputtering (MS) assemblies is an effective confinement of electrons by an appropriate combination of electric and magnetic fields. Therefore, studying the motions of electrons in the fields of magnetron assemblies is of particular importance. Here, we systematically analyze the electrons motions in front of a typical DC MS cathode. We first calculate the profiles of the magnetron’s magnetic field for balanced and two types of unbalanced configurations. Then, we compute the profiles of the cathode’s electric field before the gas discharge and after the plasma formation. A semi-analytical model is utilized to compute the plasma potential. We then track the motions of electrons released from the target and electrons produced through impact ionization of the background gas in the prescribed fields. A Monte Carlo model is implemented to consider electron-gas collisions and a mixed boundary condition is employed to account for electron-wall interactions. The study analyzes the impact of field profiles on the cathode’s efficiency in trapping electron by examining electron escape from the magnetic trap and electron recapture at the target surface. It is shown that the presence of plasma in all configurations leads to a significant increase in the trapping efficiency and the ionization performance, as well as a decrease in the recapture probability. These effects are attributed to the high electric field developed in the cathode sheath. Moreover, we statistically analyze the trapping efficiency by illustrating the spatial distributions of electrons locations in both axial and radial dimensions. It is demonstrated that during their azimuthal drift motion, the electrons released from the middle region at the target surface have the smallest range of axial and radial locations, in all configurations in the absence of plasma. Finally, the impact of field profiles on the average energies of electrons is discussed.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501068","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 : 2024-06-04DOI: 10.1088/1361-6595/ad53fd
Lucas Fuster, R. Pascaud, J. Sokoloff, Gerjan J M Hagelaar, Patrick Hoffmann, Olivier Pascal, Thierry Callegari
The coupling between a microwave signal and a plasma discharge in a suspended microstrip transmission line is analytically studied. Maxwell's equations are solved in a 2D approximation to get the expressions of the electromagnetic field. The wave propagation in the guiding structure is first explored without plasma, and for several modes and frequencies. A unified characterization of the three different modes that can propagate at the interface between two dielectric media, namely the leaky waves, the pseudo-surface wave and the pure surface wave, is given in terms of of both wave vectors and electromagnetic field magnitude distribution. This analyze allow to conclude that the fundamental mode in this case is a pseudo-surface wave. Thereafter, we focus on the microwave propagation with a uniform plasma inside the guiding structure. In the non collisional limit, it appears that the plasma discharge is sustained by the so-called pure surface wave, whereas in the collisional limit, a leaky wave propagates along the plasma column. Finally, a non-uniform density profile is taken into account in the calculation. The numerical results obtained from the self-consistent simulation of the microwave-plasma coupling, in a previous work, are thus analyzed with the aid of the analytical formulas to identify the microwave coupling involved in our plasma-based microwave power limiter. The computed propagation constant from numerical data confirmed the type of coupling exhibited for a uniform electron density. Furthermore, we highlight the role of the dielectric slab, from which electromagnetic power transfer occurs into the plasma discharge.
{"title":"Microwave plasma interaction in a printed transmission line for a power limiting application : from surface-wave-sustained to leaky-wave-sustained discharge.","authors":"Lucas Fuster, R. Pascaud, J. Sokoloff, Gerjan J M Hagelaar, Patrick Hoffmann, Olivier Pascal, Thierry Callegari","doi":"10.1088/1361-6595/ad53fd","DOIUrl":"https://doi.org/10.1088/1361-6595/ad53fd","url":null,"abstract":"\u0000 The coupling between a microwave signal and a plasma discharge in a suspended microstrip transmission line is analytically studied. Maxwell's equations are solved in a 2D approximation to get the expressions of the electromagnetic field. The wave propagation in the guiding structure is first explored without plasma, and for several modes and frequencies. A unified characterization of the three different modes that can propagate at the interface between two dielectric media, namely the leaky waves, the pseudo-surface wave and the pure surface wave, is given in terms of of both wave vectors and electromagnetic field magnitude distribution. This analyze allow to conclude that the fundamental mode in this case is a pseudo-surface wave. Thereafter, we focus on the microwave propagation with a uniform plasma inside the guiding structure. In the non collisional limit, it appears that the plasma discharge is sustained by the so-called pure surface wave, whereas in the collisional limit, a leaky wave propagates along the plasma column. Finally, a non-uniform density profile is taken into account in the calculation. The numerical results obtained from the self-consistent simulation of the microwave-plasma coupling, in a previous work, are thus analyzed with the aid of the analytical formulas to identify the microwave coupling involved in our plasma-based microwave power limiter. The computed propagation constant from numerical data confirmed the type of coupling exhibited for a uniform electron density. Furthermore, we highlight the role of the dielectric slab, from which electromagnetic power transfer occurs into the plasma discharge.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"3 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141266453","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 : 2024-06-04DOI: 10.1088/1361-6595/ad53fe
Kateryna Barynova, Martin Rudolph, S. Babu, J. Fischer, D. Lundin, M. Raadu, N. Brenning, Jon Tomas Gudmundsson
The ionization region model (IRM) is applied to explore working gas rarefaction in high power impulse magnetron sputtering discharges operated with graphite, aluminum, copper, titanium, zirconium, and tungsten targets. For all cases the working gas rarefaction is found to be significant, the degree of working gas rarefaction reaches values of up to 83 %. The various contributions to working gas rarefaction, including electron impact ionization, kick-out by the sputtered species or hot argon atoms, and diffusion, are evaluated and compared for the different target materials, and over a range of discharge current densities. The relative importance of the various processes varies between different target materials. In the case of a graphite target with argon as the working gas at 1 Pa, electron impact ionization (by both primary and secondary electrons) is the dominating contributor to working gas rarefaction, with over 90 % contribution, while the contribution of sputter wind kick-out is small < 10 %. In the case of copper and tungsten targets, the kick-out dominates, with up to ∼60 % contribution at 1 Pa. For metallic targets the kick-out is mainly due to metal atoms sputtered from the target, while for the graphite target the small kick-out contribution is mainly due to kick-out by hot argon atoms and to a smaller extent by carbon atoms. The main factors determining the relative contribution of the kick-out by the sputtered species to working gas rarefaction appear to be the sputter yield and the working gas pressure.
电离区模型 (IRM) 被用于探索使用石墨、铝、铜、钛、锆和钨靶的高功率脉冲磁控溅射放电中的工作气体稀释。在所有情况下，工作气体稀释都非常显著，工作气体稀释程度高达 83%。针对不同的靶材料和放电电流密度范围，对工作气体稀释的各种贡献进行了评估和比较，其中包括电子撞击电离、溅射物质或热氩原子踢出以及扩散。各种过程的相对重要性因靶材而异。对于在 1 Pa 下以氩气为工作气体的石墨靶材，电子撞击电离（通过初级电子和次级电子）是造成工作气体稀释的主要因素，其贡献率超过 90%，而溅射风踢出的贡献率小于 10%。对于铜和钨靶来说，踢出是主要因素，在 1 Pa 时的贡献率高达 ∼ 60%。对于金属靶来说，踢出主要是由靶溅射出的金属原子造成的，而对于石墨靶来说，踢出的贡献率很小，主要是由热氩原子踢出造成的，碳原子踢出的贡献率较小。决定溅射物对工作气体稀释的相对贡献的主要因素似乎是溅射产量和工作气体压力。
{"title":"On working gas rarefaction in high power impulse magnetron sputtering","authors":"Kateryna Barynova, Martin Rudolph, S. Babu, J. Fischer, D. Lundin, M. Raadu, N. Brenning, Jon Tomas Gudmundsson","doi":"10.1088/1361-6595/ad53fe","DOIUrl":"https://doi.org/10.1088/1361-6595/ad53fe","url":null,"abstract":"\u0000 The ionization region model (IRM) is applied to explore working gas rarefaction in high power impulse magnetron sputtering discharges operated with graphite, aluminum, copper, titanium, zirconium, and tungsten targets. For all cases the working gas rarefaction is found to be significant, the degree of working gas rarefaction reaches values of up to 83 %. The various contributions to working gas rarefaction, including electron impact ionization, kick-out by the sputtered species or hot argon atoms, and diffusion, are evaluated and compared for the different target materials, and over a range of discharge current densities. The relative importance of the various processes varies between different target materials. In the case of a graphite target with argon as the working gas at 1 Pa, electron impact ionization (by both primary and secondary electrons) is the dominating contributor to working gas rarefaction, with over 90 % contribution, while the contribution of sputter wind kick-out is small < 10 %. In the case of copper and tungsten targets, the kick-out dominates, with up to ∼60 % contribution at 1 Pa. For metallic targets the kick-out is mainly due to metal atoms sputtered from the target, while for the graphite target the small kick-out contribution is mainly due to kick-out by hot argon atoms and to a smaller extent by carbon atoms. The main factors determining the relative contribution of the kick-out by the sputtered species to working gas rarefaction appear to be the sputter yield and the working gas pressure.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"16 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141266856","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 : 2024-06-04DOI: 10.1088/1361-6595/ad53ff
Biemeng Jin, Jian Chen, Guang-Yu Sun, Zhibin Wang, Haomin Sun
In a recent discovery (Phys. Rev. Lett. 129, 045001, 2022), streaming waves were found in multipactor-induced plasma discharges. However, due to the limitations of a 1D simulation setup, these waves displayed only transverse dynamics. In this letter, an extended 2D particle-in-cell/Monte Carlo model is used to simulate multipactor-induced plasma discharge above a dielectric surface. The results reveal that the streaming waves are not solely transverse but oblique, featuring both transverse and longitudinal components of the wave vector. Furthermore, it is identified that the sheath-accelerated field-emission electrons, rather than the previously reported secondary emission electrons, predominantly cause the excitation of streaming waves. The simulated wave spectrum achieves an excellent agreement with the theoretical dispersion relation. The identification of oblique streaming waves provides new insights into multipactor physics and is anticipated to inspire novel mitigation strategies for multipactor-induced breakdown processes.
{"title":"Oblique streaming waves observed in multipactor-induced plasma discharge above a dielectric surface","authors":"Biemeng Jin, Jian Chen, Guang-Yu Sun, Zhibin Wang, Haomin Sun","doi":"10.1088/1361-6595/ad53ff","DOIUrl":"https://doi.org/10.1088/1361-6595/ad53ff","url":null,"abstract":"\u0000 In a recent discovery (Phys. Rev. Lett. 129, 045001, 2022), streaming waves were found in multipactor-induced plasma discharges. However, due to the limitations of a 1D simulation setup, these waves displayed only transverse dynamics. In this letter, an extended 2D particle-in-cell/Monte Carlo model is used to simulate multipactor-induced plasma discharge above a dielectric surface. The results reveal that the streaming waves are not solely transverse but oblique, featuring both transverse and longitudinal components of the wave vector. Furthermore, it is identified that the sheath-accelerated field-emission electrons, rather than the previously reported secondary emission electrons, predominantly cause the excitation of streaming waves. The simulated wave spectrum achieves an excellent agreement with the theoretical dispersion relation. The identification of oblique streaming waves provides new insights into multipactor physics and is anticipated to inspire novel mitigation strategies for multipactor-induced breakdown processes.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"7 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141266097","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 : 2024-06-04DOI: 10.1088/1361-6595/ad5401
Surong Sun, Fei Chen, Yu-Hang Zheng, Chao Wang, Hai-Xing Wang
In this study, the discharge characteristics of air rotating gliding arc are investigated by the synchronous measurements of digital oscilloscope and high-speed camera, and emission spectrum. The discharge evolution in one complete motion cycle exhibits “breakdown-elongation-extinction” process accompanied by the jump of arc root and back-breakdown phenomenon. The discharge evolves from the unstable breakdown mode (U-B), to the transition mode and finally to the stable gliding mode (S-G) by increasing the input voltage or decreasing the tangential and axial gas flow rates. The U-B mode at the input voltage of 120 V is featured by the large reduced electric field and high electron temperature of 1.90 eV, but the arc length and existence time are very short. The S-G mode at the input voltage of 270 V has relatively low breakdown frequency of 0.33 kHz and average breakdown current of 1.31 A, implying that the arc steadily glides and rotates along the spiral electrode. The average electron temperature is 0.64 eV in S-G mode, while the arc length and existence time are longer. The rotational and vibrational temperatures of N2 state are respectively measured to 2200 K and 4400 K in U-B mode, and in S-G mode are 2600 K and 4820 K. From the evolution of emission intensities of measured excited species, it is found that the NOγ band emission intensity generally rises from U-B mode to S-G mode since the gas temperature and arc existence time rise, indicating that S-G mode may be beneficial for the vibrationally-promoted Zeldovich reactions. This study could deepen the understanding of arc characteristics in air rotating gliding arc for selecting a suitable mode to achieve better plasma performance in practical applications.
{"title":"Experimental study on the discharge characteristics of air rotating gliding arc","authors":"Surong Sun, Fei Chen, Yu-Hang Zheng, Chao Wang, Hai-Xing Wang","doi":"10.1088/1361-6595/ad5401","DOIUrl":"https://doi.org/10.1088/1361-6595/ad5401","url":null,"abstract":"\u0000 In this study, the discharge characteristics of air rotating gliding arc are investigated by the synchronous measurements of digital oscilloscope and high-speed camera, and emission spectrum. The discharge evolution in one complete motion cycle exhibits “breakdown-elongation-extinction” process accompanied by the jump of arc root and back-breakdown phenomenon. The discharge evolves from the unstable breakdown mode (U-B), to the transition mode and finally to the stable gliding mode (S-G) by increasing the input voltage or decreasing the tangential and axial gas flow rates. The U-B mode at the input voltage of 120 V is featured by the large reduced electric field and high electron temperature of 1.90 eV, but the arc length and existence time are very short. The S-G mode at the input voltage of 270 V has relatively low breakdown frequency of 0.33 kHz and average breakdown current of 1.31 A, implying that the arc steadily glides and rotates along the spiral electrode. The average electron temperature is 0.64 eV in S-G mode, while the arc length and existence time are longer. The rotational and vibrational temperatures of N2 state are respectively measured to 2200 K and 4400 K in U-B mode, and in S-G mode are 2600 K and 4820 K. From the evolution of emission intensities of measured excited species, it is found that the NOγ band emission intensity generally rises from U-B mode to S-G mode since the gas temperature and arc existence time rise, indicating that S-G mode may be beneficial for the vibrationally-promoted Zeldovich reactions. This study could deepen the understanding of arc characteristics in air rotating gliding arc for selecting a suitable mode to achieve better plasma performance in practical applications.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"82 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141268409","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 : 2024-05-21DOI: 10.1088/1361-6595/ad4416
Matjaž Panjan
A high-frame-rate camera with microsecond-level time resolution was used to make systematic investigations of plasma self-organization and spoke dynamics during individual HiPIMS pulses. The plasma was imaged for a range of argon pressures (0.25–2 Pa) and peak discharge currents (10–400 A) using an Al target. The experiments revealed that plasma evolves through three characteristic stages as the discharge current increases. In stage I, which is present from the current onset and up to ∼25 A, spokes are azimuthally long and rotate in the −Ez× B direction. The spoke behavior is similar to the one observed in DCMS discharges. The number of spokes depends on pressure and the current growth rate. At the lowest pressure (0.25 Pa) a single spoke is present in discharge, while at higher pressures (1–2 Pa) two spokes are most often observed. The spoke velocity depends on the number of spokes, current growth rate and pressure. A single spoke rotates with velocities in the 4–15 km s−1 range, while two spokes rotate in the 1–9 km s−1 range depending on the pressure and growth rate. Following stage I, the plasma undergoes a complex reorganization that is characterized by aperiodic spoke patterns and irregular dynamics. In stage II spokes are less localized, they merge, split and propagate either in the retrograde or prograde direction. After chaotic plasma reorganization, more ordered spoke patterns begin to form. Spokes in stage III are azimuthally shorter, typically exhibit a triangular shape and rotate in the Ez× B direction. In general, the spoke dynamics is less complicated and is only influenced by the pressure. Spokes rotate faster at higher pressures than at lower ones; velocities range from 9 km s−1 at 0.25 Pa to 6 km s−1 at 2 Pa. The spoke velocity in stage III is largely unaffected by the discharge current or number of spokes. Stage III can be further divided into sub-stages, which are characterized by different current growth rates, spoke sizes and shapes. In general, the spoke evolution is highly reproducible for pulses with similar discharge current waveforms.
利用具有微秒级时间分辨率的高帧频照相机对单个 HiPIMS 脉冲期间的等离子体自组织和辐条动力学进行了系统研究。使用一个铝靶，在一系列氩气压力（0.25-2 Pa）和峰值放电电流（10-400 A）条件下对等离子体进行了成像。实验表明，随着放电电流的增加，等离子体会经历三个特征阶段。在第一阶段，即从电流开始到 ∼25 A 时，辐条呈方位长条状，并沿 -Ez× B 方向旋转。辐条行为类似于在 DCMS 放电中观察到的行为。辐条的数量取决于压力和电流增长率。在最低压力（0.25 Pa）下，放电中只出现一根辐条，而在较高压力（1-2 Pa）下，最常见的是两根辐条。辐条速度取决于辐条数量、电流增长率和压力。单根辐条的旋转速度在 4-15 千米/秒之间，而两根辐条的旋转速度在 1-9 千米/秒之间，具体取决于压力和增长速度。在第一阶段之后，等离子体经历了复杂的重组，其特点是非周期性的辐条模式和不规则的动力学。在第二阶段，辐条的局部性较弱，它们合并、分裂并向逆行或顺行方向传播。在混乱的等离子体重组之后，开始形成更有序的辐条模式。第三阶段的辐条方位较短，通常呈三角形，并沿 Ez× B 方向旋转。一般来说，辐条的动力学没有那么复杂，只受压力的影响。压力较高时，辐条的旋转速度比压力较低时要快；速度范围从 0.25 Pa 时的 9 km s-1 到 2 Pa 时的 6 km s-1。阶段 III 还可进一步划分为几个子阶段，其特点是电流增长率、辐条尺寸和形状各不相同。一般来说，对于具有类似放电电流波形的脉冲，辐条的演变具有很高的重现性。
{"title":"Plasma dynamics of individual HiPIMS pulses: imaging study using high-frame-rate camera","authors":"Matjaž Panjan","doi":"10.1088/1361-6595/ad4416","DOIUrl":"https://doi.org/10.1088/1361-6595/ad4416","url":null,"abstract":"A high-frame-rate camera with microsecond-level time resolution was used to make systematic investigations of plasma self-organization and spoke dynamics during individual HiPIMS pulses. The plasma was imaged for a range of argon pressures (0.25–2 Pa) and peak discharge currents (10–400 A) using an Al target. The experiments revealed that plasma evolves through three characteristic stages as the discharge current increases. In stage I, which is present from the current onset and up to ∼25 A, spokes are azimuthally long and rotate in the −Ez× B direction. The spoke behavior is similar to the one observed in DCMS discharges. The number of spokes depends on pressure and the current growth rate. At the lowest pressure (0.25 Pa) a single spoke is present in discharge, while at higher pressures (1–2 Pa) two spokes are most often observed. The spoke velocity depends on the number of spokes, current growth rate and pressure. A single spoke rotates with velocities in the 4–15 km s−1 range, while two spokes rotate in the 1–9 km s−1 range depending on the pressure and growth rate. Following stage I, the plasma undergoes a complex reorganization that is characterized by aperiodic spoke patterns and irregular dynamics. In stage II spokes are less localized, they merge, split and propagate either in the retrograde or prograde direction. After chaotic plasma reorganization, more ordered spoke patterns begin to form. Spokes in stage III are azimuthally shorter, typically exhibit a triangular shape and rotate in the Ez× B direction. In general, the spoke dynamics is less complicated and is only influenced by the pressure. Spokes rotate faster at higher pressures than at lower ones; velocities range from 9 km s−1 at 0.25 Pa to 6 km s−1 at 2 Pa. The spoke velocity in stage III is largely unaffected by the discharge current or number of spokes. Stage III can be further divided into sub-stages, which are characterized by different current growth rates, spoke sizes and shapes. In general, the spoke evolution is highly reproducible for pulses with similar discharge current waveforms.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"94 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141152905","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 : 2024-05-16DOI: 10.1088/1361-6595/ad4588
N Yu Babaeva and G V Naidis
Characteristics of low-current stationary axially symmetric discharges in longitudinal laminar flows of atmospheric-pressure air calculated in the framework of a two-dimensional model are presented. Non-equilibrium discharge regimes, in the current range from 1 to 100 mA, are considered for gas flow velocities up to 50 m s−1. It is shown that variation of the flow velocity substantially affects the discharge characteristics, such as the width of discharge column, the electric field inside the gap, the current density etc. Validity of the obtained results is confirmed by their comparison with available experimental data.
介绍了在二维模型框架内计算的大气压空气纵向层流中低电流静止轴对称放电的特征。在 1 至 100 mA 的电流范围内，考虑了气体流速高达 50 m s-1 的非平衡放电状态。结果表明，流速的变化对放电特性有很大影响，如放电柱宽度、间隙内电场、电流密度等。通过与现有实验数据的比较，证实了所获结果的有效性。
{"title":"Simulation of low-current DC discharges in longitudinal flows of atmospheric-pressure air","authors":"N Yu Babaeva and G V Naidis","doi":"10.1088/1361-6595/ad4588","DOIUrl":"https://doi.org/10.1088/1361-6595/ad4588","url":null,"abstract":"Characteristics of low-current stationary axially symmetric discharges in longitudinal laminar flows of atmospheric-pressure air calculated in the framework of a two-dimensional model are presented. Non-equilibrium discharge regimes, in the current range from 1 to 100 mA, are considered for gas flow velocities up to 50 m s−1. It is shown that variation of the flow velocity substantially affects the discharge characteristics, such as the width of discharge column, the electric field inside the gap, the current density etc. Validity of the obtained results is confirmed by their comparison with available experimental data.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141061838","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}
Electric field measurement using electric-field-induced second-harmonic generation (E-FISHG) draws attention because of its non-invasiveness and is increasingly being applied to various discharge plasmas. However, measurement accuracy of previous studies is unclear since approximations in calibration are inadequate. Therefore, we have developed a measurement and analysis method that does not require approximations and can furthermore obtain the distribution of the electric field. To demonstrate the applicability of the proposed method to discharge plasmas, in this paper, we measure the electric field as a result of the space charge generated by DC corona discharge in atmospheric pressure air and validate the results by comparing them with those obtained using the laser-triggering method. We demonstrate that the electrostatic field and electric field resulting from the space charge can be measured with a difference of about 10% between the results obtained from the laser triggering method and E-FISHG method. The proposed method holds potential for applications in discharge plasmas.
{"title":"Electric field measurement in DC corona discharge in atmospheric pressure air using E-FISHG and laser-triggering methods","authors":"Shin Nakamura, Masataka Sogame, Masahiro Sato, Takashi Fujii and Akiko Kumada","doi":"10.1088/1361-6595/ad4670","DOIUrl":"https://doi.org/10.1088/1361-6595/ad4670","url":null,"abstract":"Electric field measurement using electric-field-induced second-harmonic generation (E-FISHG) draws attention because of its non-invasiveness and is increasingly being applied to various discharge plasmas. However, measurement accuracy of previous studies is unclear since approximations in calibration are inadequate. Therefore, we have developed a measurement and analysis method that does not require approximations and can furthermore obtain the distribution of the electric field. To demonstrate the applicability of the proposed method to discharge plasmas, in this paper, we measure the electric field as a result of the space charge generated by DC corona discharge in atmospheric pressure air and validate the results by comparing them with those obtained using the laser-triggering method. We demonstrate that the electrostatic field and electric field resulting from the space charge can be measured with a difference of about 10% between the results obtained from the laser triggering method and E-FISHG method. The proposed method holds potential for applications in discharge plasmas.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140928564","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 : 2024-05-12DOI: 10.1088/1361-6595/ad3e29
A D Pajdarová, T Kozák, T Tölg and J Čapek
Time-resolved Langmuir probe diagnostics at the discharge centerline and at three distances from the target ( , , and ) was carried out during long positive voltage pulses (a duration of and a preset positive voltage of ) in bipolar high-power impulse magnetron sputtering of a Ti target (a diameter of ) using an unbalanced magnetron. Fast-camera spectroscopy imaging recorded light emission from Ar and Ti atoms and singly charged ions during positive voltage pulses. It was found that during the long positive voltage pulse, the floating and the plasma potentials suddenly decrease, which is accompanied by the presence of anode light located on the discharge centerline between the target center and the magnetic null of the magnetron’s magnetic field. These light patterns are related to the ignition of a reverse discharge, which leads to the subsequent rise in the plasma and the floating potentials. The reversed discharge is burning up to the end of the positive voltage pulse, but the plasma and floating potentials have lower values than the values from the initial part of the positive voltage pulse. Secondary electron emission induced by the impinging Ar+ ions to the grounded surfaces in the vicinity of the discharge plasma together with the mirror configuration of the magnetron magnetic field are identified as the probable causes of the charge double-layer structure formation in front of the target and the ignition of the reverse discharge.
在使用非平衡磁控管对 Ti 靶（直径为 ）进行双极高功率脉冲磁控管溅射时，在放电中心线和距靶三个距离（ 、 、 和 ）处进行了时间分辨朗缪尔探针诊断。在正电压脉冲期间，快速相机光谱成像记录了 Ar 和 Ti 原子以及单电荷离子的光发射。研究发现，在长正向电压脉冲期间，浮动电位和等离子体电位突然降低，同时在靶中心和磁控管磁场磁空之间的放电中心线上出现阳极光。这些光斑与反向放电的点燃有关，反向放电导致等离子体和浮动电位随之上升。反向放电一直燃烧到正电压脉冲结束，但等离子体和浮动电位的值低于正电压脉冲初始部分的值。放电等离子体附近接地表面的 Ar+ 离子撞击引起的二次电子发射以及磁控管磁场的镜面配置被认为是靶前电荷双层结构形成和反向放电点燃的可能原因。
{"title":"On double-layer and reverse discharge creation during long positive voltage pulses in a bipolar HiPIMS discharge","authors":"A D Pajdarová, T Kozák, T Tölg and J Čapek","doi":"10.1088/1361-6595/ad3e29","DOIUrl":"https://doi.org/10.1088/1361-6595/ad3e29","url":null,"abstract":"Time-resolved Langmuir probe diagnostics at the discharge centerline and at three distances from the target ( , , and ) was carried out during long positive voltage pulses (a duration of and a preset positive voltage of ) in bipolar high-power impulse magnetron sputtering of a Ti target (a diameter of ) using an unbalanced magnetron. Fast-camera spectroscopy imaging recorded light emission from Ar and Ti atoms and singly charged ions during positive voltage pulses. It was found that during the long positive voltage pulse, the floating and the plasma potentials suddenly decrease, which is accompanied by the presence of anode light located on the discharge centerline between the target center and the magnetic null of the magnetron’s magnetic field. These light patterns are related to the ignition of a reverse discharge, which leads to the subsequent rise in the plasma and the floating potentials. The reversed discharge is burning up to the end of the positive voltage pulse, but the plasma and floating potentials have lower values than the values from the initial part of the positive voltage pulse. Secondary electron emission induced by the impinging Ar+ ions to the grounded surfaces in the vicinity of the discharge plasma together with the mirror configuration of the magnetron magnetic field are identified as the probable causes of the charge double-layer structure formation in front of the target and the ignition of the reverse discharge.","PeriodicalId":20192,"journal":{"name":"Plasma Sources Science and Technology","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140942204","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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