Pub Date : 2020-04-28DOI: 10.1088/2516-1067/ab8e2b
N. Noreen, A. Shiekh, I. Habumugisha, S. Zaheer, H. Shah
The growth rate of bump on tail instability propagating in unmagnetized plasma has been derived. The dispersion relation has been characterized for (r, q) distribution function with spectral indices r and q which ultimately contributes towards tails and shoulder of distribution function. The growth rate of the bump on tail instability has been estimated numerically for different ratios of temperature and number density using solar wind data and also by varying values of indices r and q . The higher value of q play the role towards decreasing the growth rate where the instability has the higher value when the number density of the superthermal electrons in the bump is higher and the temperature is low. The maximum growth rate increases with the increase in number density of electrons and decreases with the increasing temperature in the bump.
{"title":"Linear analysis of bump on tail instability with non-Maxwellian distribution function","authors":"N. Noreen, A. Shiekh, I. Habumugisha, S. Zaheer, H. Shah","doi":"10.1088/2516-1067/ab8e2b","DOIUrl":"https://doi.org/10.1088/2516-1067/ab8e2b","url":null,"abstract":"The growth rate of bump on tail instability propagating in unmagnetized plasma has been derived. The dispersion relation has been characterized for (r, q) distribution function with spectral indices r and q which ultimately contributes towards tails and shoulder of distribution function. The growth rate of the bump on tail instability has been estimated numerically for different ratios of temperature and number density using solar wind data and also by varying values of indices r and q . The higher value of q play the role towards decreasing the growth rate where the instability has the higher value when the number density of the superthermal electrons in the bump is higher and the temperature is low. The maximum growth rate increases with the increase in number density of electrons and decreases with the increasing temperature in the bump.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab8e2b","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44640849","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 : 2020-04-24DOI: 10.1088/2516-1067/ab89c9
Lintu G Laly, K. Ramachandran
Hollow cathode with gas injection in transferred arc plasma system has been used for high temperature material processes. The effect of operating parameters such as gas flow rate, electrode gap, arc current, etc on the arc behaviour at an operating pressure of 1 atm is studied numerically. The knowledge on the arc behaviour at operating pressures lower and higher than atmospheric pressure is very limited. In this work, a two dimensional axi-symmetric model is developed to simulate the behaviour of the argon arcs formed between hollow cathode with gas injection and crucible anode as well as heat transfer from the plasma to the anode at different operating pressures. The effects of gas flow rate and electrode gap on the arc behaviour and heating efficiency at different operating pressures are investigated. The arc voltage is strongly influenced by both operating pressure and electrode gap. The effect gas flow rate on the arc voltage is stronger at higher operating pressures. The movement or detachment of the arc root from the centre of the anode is strongly influenced by operating pressure and gas flow rate. Arcs formed at 0.2 atm have unique features compared to the arcs formed at higher operating pressures. The heat flux to the anode is higher where arc root is attached and the highest arc heating efficiency of 68.1% is predicted at an operating pressure of 0.2 atm, electrode gap of 15 mm and gas flow rate of 5 lpm.
{"title":"Numerical studies on the effects of operating parameters on the behaviour of transferred arc inside the crucible with gas injection through the cathode at different operating pressures","authors":"Lintu G Laly, K. Ramachandran","doi":"10.1088/2516-1067/ab89c9","DOIUrl":"https://doi.org/10.1088/2516-1067/ab89c9","url":null,"abstract":"Hollow cathode with gas injection in transferred arc plasma system has been used for high temperature material processes. The effect of operating parameters such as gas flow rate, electrode gap, arc current, etc on the arc behaviour at an operating pressure of 1 atm is studied numerically. The knowledge on the arc behaviour at operating pressures lower and higher than atmospheric pressure is very limited. In this work, a two dimensional axi-symmetric model is developed to simulate the behaviour of the argon arcs formed between hollow cathode with gas injection and crucible anode as well as heat transfer from the plasma to the anode at different operating pressures. The effects of gas flow rate and electrode gap on the arc behaviour and heating efficiency at different operating pressures are investigated. The arc voltage is strongly influenced by both operating pressure and electrode gap. The effect gas flow rate on the arc voltage is stronger at higher operating pressures. The movement or detachment of the arc root from the centre of the anode is strongly influenced by operating pressure and gas flow rate. Arcs formed at 0.2 atm have unique features compared to the arcs formed at higher operating pressures. The heat flux to the anode is higher where arc root is attached and the highest arc heating efficiency of 68.1% is predicted at an operating pressure of 0.2 atm, electrode gap of 15 mm and gas flow rate of 5 lpm.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"30 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab89c9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41302677","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 : 2020-04-23DOI: 10.1088/2516-1067/ab835d
R. Niranjan, R. Srivastava, J. Joycee, P. Mishra, K. Joshi
Samples of ferrite -austenite stainless steel (SS) have been exposed to fusion grade plasma and radiations using a medium energy plasma focus device, ‘MEPF-12’. Three different polished samples of SS (10 mm diameter ×2 mm thick) were irradiated using single and multiple ( five and ten) plasma focus discharges. Each plasma focus discharge comprised energetic and high intensity deuterium ions, energetic deuterium plasma streams and 2.45 MeV neutrons produced via D(d, 3He)n fusion reactions. At sample position, typical values of deuterium ion fluence and neutron fluence were measured to be ∼1018ions/m2 and ∼1010 neutrons/m2, respectively, in each plasma focus discharge. Post irradiations, the samples have been characterized using different techniques for study of their surface modification characteristics, specifically, crystallinity, surface morphologies and surface roughness. The XRD analysis of the SS sample exposed to single or more plasma focus discharges revealed structural phase transformation from initial mixed ferrite [α(BCC)] -austenite [γ(FCC)] phase to austenite phase. Effects of deuterium ion concentration and transient rise in surface temperature on structural phase transformation have been discussed in detail. Surface morphologies studied using SEM has revealed erosion, melting and recrystallization of surface layer along with various other defects like pores, blisters, open bubbles and so on. Measurements using surface profilometer confirmed increase in surface roughness of the samples on irradiation. Detail discussion on the variation in the surface damage features with increasing number of plasma focus discharges used for irradiating samples and its comparison with virgin sample have been included in this report.
铁素体-奥氏体不锈钢(SS)样品使用中能等离子体聚焦装置MEPF-12暴露于聚变级等离子体和辐射中。使用单次和多次(5次和10次)等离子体聚焦放电照射三种不同的抛光SS样品(直径10 mm ×2 mm厚)。每次等离子体聚焦放电由高能高强度氘离子、高能氘等离子体流和通过D(D, 3He)n聚变反应产生的2.45 MeV中子组成。在样品位置，在每次等离子体焦点放电中，氘离子和中子的典型值分别为~ 1018个离子/m2和~ 1010个中子/m2。辐照后，使用不同的技术对样品进行表征，以研究其表面改性特性，特别是结晶度，表面形貌和表面粗糙度。对单次或多次等离子体聚焦放电的SS试样进行XRD分析，发现结构相由初始混合铁素体[α(BCC)] -奥氏体[γ(FCC)]相转变为奥氏体相。详细讨论了氘离子浓度和表面温度的瞬时升高对结构相变的影响。利用扫描电镜对表面形貌进行了研究，发现表层存在侵蚀、熔化、再结晶等缺陷，同时还存在气孔、水泡、开泡等缺陷。使用表面轮廓仪的测量证实了辐照后样品表面粗糙度的增加。本报告详细讨论了辐照样品等离子体聚焦放电次数增加时表面损伤特征的变化，并与未辐照样品进行了比较。
{"title":"Pulsed fusion grade deuterium plasma induced structural phase transformation in stainless steel using medium energy plasma focus device","authors":"R. Niranjan, R. Srivastava, J. Joycee, P. Mishra, K. Joshi","doi":"10.1088/2516-1067/ab835d","DOIUrl":"https://doi.org/10.1088/2516-1067/ab835d","url":null,"abstract":"Samples of ferrite -austenite stainless steel (SS) have been exposed to fusion grade plasma and radiations using a medium energy plasma focus device, ‘MEPF-12’. Three different polished samples of SS (10 mm diameter ×2 mm thick) were irradiated using single and multiple ( five and ten) plasma focus discharges. Each plasma focus discharge comprised energetic and high intensity deuterium ions, energetic deuterium plasma streams and 2.45 MeV neutrons produced via D(d, 3He)n fusion reactions. At sample position, typical values of deuterium ion fluence and neutron fluence were measured to be ∼1018ions/m2 and ∼1010 neutrons/m2, respectively, in each plasma focus discharge. Post irradiations, the samples have been characterized using different techniques for study of their surface modification characteristics, specifically, crystallinity, surface morphologies and surface roughness. The XRD analysis of the SS sample exposed to single or more plasma focus discharges revealed structural phase transformation from initial mixed ferrite [α(BCC)] -austenite [γ(FCC)] phase to austenite phase. Effects of deuterium ion concentration and transient rise in surface temperature on structural phase transformation have been discussed in detail. Surface morphologies studied using SEM has revealed erosion, melting and recrystallization of surface layer along with various other defects like pores, blisters, open bubbles and so on. Measurements using surface profilometer confirmed increase in surface roughness of the samples on irradiation. Detail discussion on the variation in the surface damage features with increasing number of plasma focus discharges used for irradiating samples and its comparison with virgin sample have been included in this report.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab835d","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44286744","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 : 2020-04-16DOI: 10.1088/2516-1067/ab880b
Yongbin Chang, Dingyi Li
The correct cutoff variable for the integrals with Rutherford scattering cross-section is established in this paper. The traditional cutoff variables in plasma physics, such as scattering angle θ and impact parameter b, are incorrect or just partial cutoff variables for lacking the necessary cutoff on relative speed g. The correct cutoff variable is the same variable that correctly describing the singularity of the integrals. The difference of the partial cutoff variables and the correct one is compared through their contour lines in the b − g plane. With the correct cutoff, many physical results become more simplified and structured for both rigid-sphere interaction and Coulomb interaction. These physical results include the arbitrary higher order of Fokker-Planck coefficients, transition moments, and energy transfer rates for both rigid-sphere and Coulomb interactions. All the physical results depending on velocity are expressed by a set of functions q n ( k ) ( y min , u ) = 2 π ∫ y min ∞ ∫ − 1 1 e − y + xu 2 y n − x k dxdy . A useful integral formula ∫ 0 ∞ q n ( k ) ( y min , u ) u k + 2 e − u 2 ξ du = ξ k + 3 2 2 1 + ξ k − n 2 ∑ j = 0 ⌊ k / 2 ⌋ k ! Γ n + k + 1 2 − j , y min 2 1 + ξ j ! ( k − 2 j ) ! 4 ξ j , which associates q n ( k ) ( y min , u ) with incomplete gamma functions Γ j , y min 2 1 + ξ is also proved. This integral formula is the key to show that the correct cutoff constants for both rigid-sphere and Coulomb interactions are all in the form of incomplete gamma functions of different orders. In particular, the so called Coulomb logarithm ln Λ should be replaced by the exact form—the zeroth order incomplete Gamma function.
本文建立了Rutherford散射截面积分的正确截止变量。等离子体物理中的传统截止变量，如散射角θ和冲击参数b，由于缺乏相对速度g的必要截止，是不正确的或只是部分截止变量。正确的截止变量与正确描述积分奇异性的变量相同。通过b−g平面中的轮廓线比较部分截止变量和正确截止变量的差异。有了正确的截止点，刚性球体相互作用和库仑相互作用的许多物理结果变得更加简化和结构化。这些物理结果包括刚性球和库仑相互作用的Fokker-Planck系数、过渡矩和能量传递率的任意高阶。所有与速度有关的物理结果都用一组函数qn（k）（y min，u）=2πõy min∞õ−1 1 e−y+xu 2 y n−x k dxdy表示。一个有用的积分公式ξ0∞q n（k）（y min，u）u k+2 e−u 2ξdu=ξk+3 2 1+ξk−n 2∑j=0⌊k/2⌋k！Γn+k+1 2−j，y min 2 1+ξj！（k−2 j）！4ξj，它将qn（k）（y min，u）与不完全伽玛函数Γj，y min 2 1+ξ联系起来。这个积分公式是证明刚性球和库仑相互作用的正确截止常数都是不同阶的不完全伽玛函数形式的关键。特别是，所谓的库仑对数ln∧应该用精确的形式——零阶不完全伽玛函数来代替。
{"title":"The correct cutoff for Rutherford scattering cross-section","authors":"Yongbin Chang, Dingyi Li","doi":"10.1088/2516-1067/ab880b","DOIUrl":"https://doi.org/10.1088/2516-1067/ab880b","url":null,"abstract":"The correct cutoff variable for the integrals with Rutherford scattering cross-section is established in this paper. The traditional cutoff variables in plasma physics, such as scattering angle θ and impact parameter b, are incorrect or just partial cutoff variables for lacking the necessary cutoff on relative speed g. The correct cutoff variable is the same variable that correctly describing the singularity of the integrals. The difference of the partial cutoff variables and the correct one is compared through their contour lines in the b − g plane. With the correct cutoff, many physical results become more simplified and structured for both rigid-sphere interaction and Coulomb interaction. These physical results include the arbitrary higher order of Fokker-Planck coefficients, transition moments, and energy transfer rates for both rigid-sphere and Coulomb interactions. All the physical results depending on velocity are expressed by a set of functions q n ( k ) ( y min , u ) = 2 π ∫ y min ∞ ∫ − 1 1 e − y + xu 2 y n − x k dxdy . A useful integral formula ∫ 0 ∞ q n ( k ) ( y min , u ) u k + 2 e − u 2 ξ du = ξ k + 3 2 2 1 + ξ k − n 2 ∑ j = 0 ⌊ k / 2 ⌋ k ! Γ n + k + 1 2 − j , y min 2 1 + ξ j ! ( k − 2 j ) ! 4 ξ j , which associates q n ( k ) ( y min , u ) with incomplete gamma functions Γ j , y min 2 1 + ξ is also proved. This integral formula is the key to show that the correct cutoff constants for both rigid-sphere and Coulomb interactions are all in the form of incomplete gamma functions of different orders. In particular, the so called Coulomb logarithm ln Λ should be replaced by the exact form—the zeroth order incomplete Gamma function.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab880b","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49054359","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 : 2020-04-06DOI: 10.1088/2516-1067/ab8076
E. Rostomyan
A study is developed, which allows investigating weakly coupled electron beam-plasma systems in general form regardless on geometry and specific parameters. In this case the instability acquires completely new aspects. In contrast to the well-known case of strong coupling, the role of the beam natural oscillations becomes decisive. The instability is due to the growth of the beam wave of negative energy. The study shows that the space-time evolution of an initial perturbation in weakly coupled beam-plasma systems is described by partial differential equation of second order. The equation is solved. Obtained expression for the fields’ space-time distribution gives most complete information on the instability: growth rates, velocities of unstable perturbations, influence of the dissipation on the instability, its character, (absolute/convective), etc. Most of the information is unavailable by conventional methods. In particular, the results clearly show that with an increase in the level of dissipation in the plasma, the instability transforms into a new, previously unknown type of dissipative streaming instability (DSI). Its growth rate depends on dissipation more critically than the growth rate of the single known DSI.
{"title":"Peculiar behavior of the instability in systems with weak electron beam-plasma coupling","authors":"E. Rostomyan","doi":"10.1088/2516-1067/ab8076","DOIUrl":"https://doi.org/10.1088/2516-1067/ab8076","url":null,"abstract":"A study is developed, which allows investigating weakly coupled electron beam-plasma systems in general form regardless on geometry and specific parameters. In this case the instability acquires completely new aspects. In contrast to the well-known case of strong coupling, the role of the beam natural oscillations becomes decisive. The instability is due to the growth of the beam wave of negative energy. The study shows that the space-time evolution of an initial perturbation in weakly coupled beam-plasma systems is described by partial differential equation of second order. The equation is solved. Obtained expression for the fields’ space-time distribution gives most complete information on the instability: growth rates, velocities of unstable perturbations, influence of the dissipation on the instability, its character, (absolute/convective), etc. Most of the information is unavailable by conventional methods. In particular, the results clearly show that with an increase in the level of dissipation in the plasma, the instability transforms into a new, previously unknown type of dissipative streaming instability (DSI). Its growth rate depends on dissipation more critically than the growth rate of the single known DSI.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44603934","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 : 2020-03-24DOI: 10.1088/2516-1067/ab805a
M. M. Haider, S. Yasmin Swarna, Nusrat Khan, O. Rahman
A theoretical investigation has been done to find the impacts of Chandrasekhar limits (ultra-relativistic and non-relativistic) in adiabatic plasmas with the presence of superthermal ions. To do so, a dust-acoustic solitary wave (DASW) equation propagating in adiabatic degenerate plasmas has been derived employing the reductive perturbation method. The effects of the external magnetic field on the wave propagation and its instability have also been scrutinized. However, the plasma parameters, used in this present theoretical analysis, correspond to white dwarfs but it is possible to apply results for neutron stars and other compact objects.
{"title":"A study of Chandrasekhar limits in adiabatic degenerate plasmas with superthermal ions","authors":"M. M. Haider, S. Yasmin Swarna, Nusrat Khan, O. Rahman","doi":"10.1088/2516-1067/ab805a","DOIUrl":"https://doi.org/10.1088/2516-1067/ab805a","url":null,"abstract":"A theoretical investigation has been done to find the impacts of Chandrasekhar limits (ultra-relativistic and non-relativistic) in adiabatic plasmas with the presence of superthermal ions. To do so, a dust-acoustic solitary wave (DASW) equation propagating in adiabatic degenerate plasmas has been derived employing the reductive perturbation method. The effects of the external magnetic field on the wave propagation and its instability have also been scrutinized. However, the plasma parameters, used in this present theoretical analysis, correspond to white dwarfs but it is possible to apply results for neutron stars and other compact objects.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab805a","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47737259","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 : 2020-03-18DOI: 10.1088/2516-1067/ab7c82
Meraj Alam, M. Talukder
The head-on collisional phenomena concerning ion acoustic waves are investigated considering collisional plasma system comprises of pair ions and hybrid non-Maxwellian electrons. The two-sided Korteweg–de Vries (KdV) equations are derived using extended poincaré-Lighthill-Kuo (ePLK) method. The effects of superthermal index ( κ e ) related to kappa distributed electrons, nonthermal parameter ( β e ) related to the Cairn’s distributed electrons, density ratio of electron to positive ion ( n e 1 i ), and temperature ratio ( T 1 i 2 i ) of positive to negative ion on the phase velocity, spatiotemporal evolutions of amplitude, width, time dependent phase shifts and velocity of the right propagating solitons as well as the production of KdV solitons are investigated. Both the rarefactive and compressive soliton structures are produced due to head-on collision depending on plasma parameters. It is found that phase velocity is increasing (decreasing) due to the enhancement of κ e and β e ( n e 1 i ). The amplitude of right traveling soliton increases (decreases) with increasing β e ( κ e ), while κ e and β e show opposite characteristic behaviors due to the plasma parameters concerned.
考虑由对离子和杂化非麦克斯韦电子组成的碰撞等离子体系统，研究了离子声波的正面碰撞现象。利用扩展的poincar - lighthill - kuo (ePLK)方法导出了双边Korteweg-de Vries (KdV)方程。superthermal指数的影响(κe)与kappa分布式电子,非热能的参数(βe)与凯恩的分布式电子,电子的密度比积极的离子(n e 1 i),和温度的比值(T 1我2)正到负离子相速度,时空演进的振幅、宽度、与时间有关的相移和正确的传播孤子的速度以及KdV孤子的生产调查。根据等离子体参数的不同，在正面碰撞的情况下会产生屈光孤子和压缩孤子结构。由于κ e和β e (n e 1 i)的增强，相速度增大(减小)。右行孤子的振幅随β e (κ e)的增大而增大(减小)，而κ e和β e受等离子体参数的影响表现出相反的特征行为。
{"title":"Head-on collision of ion-acoustic solitons in collisional pair ions plasmas with non-Maxwellian electrons","authors":"Meraj Alam, M. Talukder","doi":"10.1088/2516-1067/ab7c82","DOIUrl":"https://doi.org/10.1088/2516-1067/ab7c82","url":null,"abstract":"The head-on collisional phenomena concerning ion acoustic waves are investigated considering collisional plasma system comprises of pair ions and hybrid non-Maxwellian electrons. The two-sided Korteweg–de Vries (KdV) equations are derived using extended poincaré-Lighthill-Kuo (ePLK) method. The effects of superthermal index ( κ e ) related to kappa distributed electrons, nonthermal parameter ( β e ) related to the Cairn’s distributed electrons, density ratio of electron to positive ion ( n e 1 i ), and temperature ratio ( T 1 i 2 i ) of positive to negative ion on the phase velocity, spatiotemporal evolutions of amplitude, width, time dependent phase shifts and velocity of the right propagating solitons as well as the production of KdV solitons are investigated. Both the rarefactive and compressive soliton structures are produced due to head-on collision depending on plasma parameters. It is found that phase velocity is increasing (decreasing) due to the enhancement of κ e and β e ( n e 1 i ). The amplitude of right traveling soliton increases (decreases) with increasing β e ( κ e ), while κ e and β e show opposite characteristic behaviors due to the plasma parameters concerned.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab7c82","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42523585","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 : 2020-03-18DOI: 10.1088/2516-1067/ab7d0f
J. Ji, J. Spencer, E. Held
Exact moments of the Landau collision operator are calculated for the irreducible Hermite polynomials written in terms of the random-velocity variable. We present closed, algebraic formulas which can be implemented in computer algebra systems. The formulas reproduce the results for the total-velocity moment expansion (J-Y Ji and E D Held, 2006 Phys. Plasmas 13 102 103) and for the random-velocity moment expansion with the small mass-ratio approximation (J-Y Ji and E D Held, 2008 Phys. Plasmas 15 102 101). For verification of the formulas, example calculations for several lowest order moments are presented. The collisional moments can be applied in the derivations of Braginskii and integral (nonlocal) closures for arbitrary relative flow velocity between electrons and ions.
对于用随机速度变量表示的不可约埃尔米特多项式，计算了朗道碰撞算子的精确矩。我们提出了可以在计算机代数系统中实现的封闭代数公式。这些公式再现了总速度矩展开的结果(J-Y Ji and E D Held, 2006 Phys.)。等离子体13 102 103)和小质量比近似下的随机速度矩膨胀(J-Y Ji, E D Held, 2008)。等离子体15 102 101)。为了验证公式的正确性，给出了几种最低阶矩的算例。碰撞矩可以应用于任意电子和离子之间相对流动速度的Braginskii和积分(非局部)闭包的推导。
{"title":"Exact irreducible moments of the Landau collision operator in the random-velocity moment expansion","authors":"J. Ji, J. Spencer, E. Held","doi":"10.1088/2516-1067/ab7d0f","DOIUrl":"https://doi.org/10.1088/2516-1067/ab7d0f","url":null,"abstract":"Exact moments of the Landau collision operator are calculated for the irreducible Hermite polynomials written in terms of the random-velocity variable. We present closed, algebraic formulas which can be implemented in computer algebra systems. The formulas reproduce the results for the total-velocity moment expansion (J-Y Ji and E D Held, 2006 Phys. Plasmas 13 102 103) and for the random-velocity moment expansion with the small mass-ratio approximation (J-Y Ji and E D Held, 2008 Phys. Plasmas 15 102 101). For verification of the formulas, example calculations for several lowest order moments are presented. The collisional moments can be applied in the derivations of Braginskii and integral (nonlocal) closures for arbitrary relative flow velocity between electrons and ions.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41865823","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 : 2020-03-06DOI: 10.1088/2516-1067/ab7b36
A. Mohamed, Mazen Mohamed Aljuhani, J. Almarashi, A. Alhazime
Cold atmospheric pressure plasma jet has attracted a great interest of researchers engaged in different areas due to its wide range of applications. In this article, the effect of adding a second grounded electrode (SGE) to the two electrodes plasma jet system was investigated. The jets system consisted of a quartz tube surrounded by two copper strips, which were separated by 40 mm. The SGE was placed below the jet nozzle by 2 mm and 5 mm from its axial. The jet characteristics with and without the SGE were investigated using plasma images, voltage-current waveforms, and emission spectra. Two current pulses per each half a cycle were measured when the SGE was used while one pulse was measured without using it. The second current pulse was much longer than the first one. Argon emission spectra were the most intense lines among all other plasma species even for the measurement out of the flow stream. The OH• emission spectra were higher in the discharge zone than those outside the discharge zone. The presence of the SGE enhanced the emission spectra for all the investigated positions above and in front of the SGE. The transition from laminar to turbulent mode was observed at lower flow rate value without using the SGE and a significant decrease in jet length was detected at 3.5 slpm with and without using the SGE. This system is scalable by using multi-SGE to form a large volume plasma, which is strongly required for biomedical and industrial applications.
{"title":"The effect of a second grounded electrode on the atmospheric pressure argon plasma jet","authors":"A. Mohamed, Mazen Mohamed Aljuhani, J. Almarashi, A. Alhazime","doi":"10.1088/2516-1067/ab7b36","DOIUrl":"https://doi.org/10.1088/2516-1067/ab7b36","url":null,"abstract":"Cold atmospheric pressure plasma jet has attracted a great interest of researchers engaged in different areas due to its wide range of applications. In this article, the effect of adding a second grounded electrode (SGE) to the two electrodes plasma jet system was investigated. The jets system consisted of a quartz tube surrounded by two copper strips, which were separated by 40 mm. The SGE was placed below the jet nozzle by 2 mm and 5 mm from its axial. The jet characteristics with and without the SGE were investigated using plasma images, voltage-current waveforms, and emission spectra. Two current pulses per each half a cycle were measured when the SGE was used while one pulse was measured without using it. The second current pulse was much longer than the first one. Argon emission spectra were the most intense lines among all other plasma species even for the measurement out of the flow stream. The OH• emission spectra were higher in the discharge zone than those outside the discharge zone. The presence of the SGE enhanced the emission spectra for all the investigated positions above and in front of the SGE. The transition from laminar to turbulent mode was observed at lower flow rate value without using the SGE and a significant decrease in jet length was detected at 3.5 slpm with and without using the SGE. This system is scalable by using multi-SGE to form a large volume plasma, which is strongly required for biomedical and industrial applications.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab7b36","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43033916","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 : 2020-03-06DOI: 10.1088/2516-1067/ab7ab8
S. Hussain, N. Imtiaz, H. Hasnain
We study the propagation properties of the small amplitude nonlinear ion acoustic solitary structure in dense electron-position-ion (e-p-i) plasmas. We consider an oblique propagation of the wave with respect to the applied magnetic field. The reductive perturbation technique is employed to derive the nonlinear Zakharov-Kuznetsov (ZK) equation which describes the propagation characteristics of the ion acoustic solitary wave structures in e-p-i plasmas. The effects of different plasma parameters including the positron concentration have been invesigated. These findings may be helpful to understand the small amplitude nonlinear solitary structures that exist in the dense astrophysical environments and in the intense-laser plasma interactions.
{"title":"Oblique propagation of nonlinear solitary structures in electron positron ion plasmas under the influence of quantizing magnetic field","authors":"S. Hussain, N. Imtiaz, H. Hasnain","doi":"10.1088/2516-1067/ab7ab8","DOIUrl":"https://doi.org/10.1088/2516-1067/ab7ab8","url":null,"abstract":"We study the propagation properties of the small amplitude nonlinear ion acoustic solitary structure in dense electron-position-ion (e-p-i) plasmas. We consider an oblique propagation of the wave with respect to the applied magnetic field. The reductive perturbation technique is employed to derive the nonlinear Zakharov-Kuznetsov (ZK) equation which describes the propagation characteristics of the ion acoustic solitary wave structures in e-p-i plasmas. The effects of different plasma parameters including the positron concentration have been invesigated. These findings may be helpful to understand the small amplitude nonlinear solitary structures that exist in the dense astrophysical environments and in the intense-laser plasma interactions.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/2516-1067/ab7ab8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43101134","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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