A. Amin, D. Aossey, B. Nguyen, Hyun-Soo Kim, J. Cooney, K. Lonngren
The spatial and temporal evolution of a sheath surrounding a planar electrode whose potential is suddenly decreased in a quasineutral plasma consisting of positive ions, negative ions, and electrons is numerically investigated. The model predicts several features observed in recent laboratory experiments directed toward the excitation and subsequent propagation of solitons in such a plasma.
{"title":"Sheath evolution in a negative ion plasma","authors":"A. Amin, D. Aossey, B. Nguyen, Hyun-Soo Kim, J. Cooney, K. Lonngren","doi":"10.1063/1.860599","DOIUrl":"https://doi.org/10.1063/1.860599","url":null,"abstract":"The spatial and temporal evolution of a sheath surrounding a planar electrode whose potential is suddenly decreased in a quasineutral plasma consisting of positive ions, negative ions, and electrons is numerically investigated. The model predicts several features observed in recent laboratory experiments directed toward the excitation and subsequent propagation of solitons in such a plasma.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115800644","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}
Numerical simulations of three‐wave interactions among Langmuir, ion‐acoustic, and electromagnetic waves by means of an efficient algorithm developed here for solving full Zakharov equations show that total electric field collapses if the electrostatic field collapses when plasma temperature is much less than 0.5 MeV and thus relativistic effects can be neglected, and that the electromagnetic wave energy generated in the high‐temperature Langmuir collapse comes to no less than one‐tenth of the Langmuir wave energy even if the mean intensity of the collapsing wave packet increases by a factor of less than 5.
{"title":"Three-wave interactions in strong Langmuir turbulence","authors":"L. Li, X. Q. Li","doi":"10.1063/1.860600","DOIUrl":"https://doi.org/10.1063/1.860600","url":null,"abstract":"Numerical simulations of three‐wave interactions among Langmuir, ion‐acoustic, and electromagnetic waves by means of an efficient algorithm developed here for solving full Zakharov equations show that total electric field collapses if the electrostatic field collapses when plasma temperature is much less than 0.5 MeV and thus relativistic effects can be neglected, and that the electromagnetic wave energy generated in the high‐temperature Langmuir collapse comes to no less than one‐tenth of the Langmuir wave energy even if the mean intensity of the collapsing wave packet increases by a factor of less than 5.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"319 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131993317","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}
Nonlinear wave–particle scattering and absorption (nonlinear Landau and cyclotron damping) of electromagnetic and electrostatic waves by high energy or relativistic electrons in a homogeneous magnetized plasma are investigated theoretically by numerical analysis of general and simplified expressions of nonlinear wave–particle coupling coefficients. It is shown that strong nonlinear absorption of the extraordinary wave can occur by nonlinear scattering into the other extraordinary waves or Bernstein waves induced by high‐energy stationary or drifting electrons, and they can be accelerated. Nonlinear absorption by Bernstein wave or ordinary wave is weaker than that by extraordinary wave. These nonlinear absorption mechanisms can compete with linear absorption in a fusion plasma, and can exceed it for a sufficiently small k∥ρb. It is verified that nonlinear scattering of extraordinary waves can induce the effective acceleration of relativistic electrons in a fusion plasma.
{"title":"Nonlinear wave–particle scattering and absorption of electromagnetic and electrostatic waves in a magnetized plasma","authors":"R. Sugaya","doi":"10.1063/1.860827","DOIUrl":"https://doi.org/10.1063/1.860827","url":null,"abstract":"Nonlinear wave–particle scattering and absorption (nonlinear Landau and cyclotron damping) of electromagnetic and electrostatic waves by high energy or relativistic electrons in a homogeneous magnetized plasma are investigated theoretically by numerical analysis of general and simplified expressions of nonlinear wave–particle coupling coefficients. It is shown that strong nonlinear absorption of the extraordinary wave can occur by nonlinear scattering into the other extraordinary waves or Bernstein waves induced by high‐energy stationary or drifting electrons, and they can be accelerated. Nonlinear absorption by Bernstein wave or ordinary wave is weaker than that by extraordinary wave. These nonlinear absorption mechanisms can compete with linear absorption in a fusion plasma, and can exceed it for a sufficiently small k∥ρb. It is verified that nonlinear scattering of extraordinary waves can induce the effective acceleration of relativistic electrons in a fusion plasma.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133117672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The presence of an electron beam in a quasioptical gyrotron cavity alters the structure of the fields from that of the empty cavity. A computer code has been written that calculates this alteration for either an electron beam or a thin dielectric tube placed in the cavity. Experiments measuring the quality factor of such a cavity were performed for the case of a dielectric tube and the results agree with the predictions of the code. Simulations of the case of an electron beam indicate that self‐consistent effects can be made small, in that almost all the power leaves the cavity in a symmetric Gaussian‐like mode, provided the resonator parameters are chosen carefully.
{"title":"Studies of self‐consistent field structure in a quasioptical gyrotron","authors":"T. Antonsen, A. Bondeson, M. Roulin, M. Tran","doi":"10.1063/1.860597","DOIUrl":"https://doi.org/10.1063/1.860597","url":null,"abstract":"The presence of an electron beam in a quasioptical gyrotron cavity alters the structure of the fields from that of the empty cavity. A computer code has been written that calculates this alteration for either an electron beam or a thin dielectric tube placed in the cavity. Experiments measuring the quality factor of such a cavity were performed for the case of a dielectric tube and the results agree with the predictions of the code. Simulations of the case of an electron beam indicate that self‐consistent effects can be made small, in that almost all the power leaves the cavity in a symmetric Gaussian‐like mode, provided the resonator parameters are chosen carefully.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"174 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114395153","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}
A sheared, relative ion–neutral flow can generate a magnetic field in an unmagnetized, weakly ionized plasma. The field generation term is ∂B/∂t=(mec/e)∇×νen(Vi−Vn) where νen is the electron–neutral collision frequency, Vi is the ion fluid velocity, and Vn is the neutral fluid velocity. The time period over which the field grows is limited by diffusion, convection, or collisional relaxation of the relative drift. Since the field generation term scales as νen/Ωe relative to the other terms in the field induction equation, the maximum field generated is found from Ωe≂few νen so that Bmax≂few (mec/e)νen. Both analytical and numerical results are presented. The computational results are based upon a two‐dimensional (2‐D) magnetohydrodynamic (MHD) code which includes the following terms: ion–neutral drag, gravity, resistivity, recombination, the Hall term, and the shear‐driven source term. The theory is applied to the generation of magnetic fields in an unmagnetized planetary ionosphere, such as Venus, and to ...
{"title":"Self‐generation of magnetic fields by sheared flows in weakly ionized plasmas","authors":"J. Huba, J. Fedder","doi":"10.1063/1.860848","DOIUrl":"https://doi.org/10.1063/1.860848","url":null,"abstract":"A sheared, relative ion–neutral flow can generate a magnetic field in an unmagnetized, weakly ionized plasma. The field generation term is ∂B/∂t=(mec/e)∇×νen(Vi−Vn) where νen is the electron–neutral collision frequency, Vi is the ion fluid velocity, and Vn is the neutral fluid velocity. The time period over which the field grows is limited by diffusion, convection, or collisional relaxation of the relative drift. Since the field generation term scales as νen/Ωe relative to the other terms in the field induction equation, the maximum field generated is found from Ωe≂few νen so that Bmax≂few (mec/e)νen. Both analytical and numerical results are presented. The computational results are based upon a two‐dimensional (2‐D) magnetohydrodynamic (MHD) code which includes the following terms: ion–neutral drag, gravity, resistivity, recombination, the Hall term, and the shear‐driven source term. The theory is applied to the generation of magnetic fields in an unmagnetized planetary ionosphere, such as Venus, and to ...","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129689706","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}
It is clear that the edge plasma plays a crucial role in global tokamak confinement. This paper is a report on simulations of a new drift wave type instability driven by conducting wall (also originally named as a ∇Te instability) [Phys. Fluids B 3, 1364 (1991)]. A 2d(x,y) fluid code has been developed in order to explore the anomalous transport in the boundary plasmas. The simulation consists of a set of fluid equations (in the electrostatic limit) for the vorticity ∇⊥2φ, and the temperature Te in a shearless plasma slab confined by a uniform, straight magnetic field Bz with two divertor (or limiter) plates intercepting the magnetic field. The model has two regions separated by a magnetic separatrix: In the edge region inside the separatrix, the model is periodic along the magnetic field while in the scrapeoff layer (SOL) region outside the separatrix, the magnetic field is taken to be of finite length with model (logical sheath) boundary conditions at diverter (or limiter) plates. The simulation results...
{"title":"Fluid simulations of conducting‐wall‐driven turbulence in boundary plasmas","authors":"X. Xu","doi":"10.1063/1.860836","DOIUrl":"https://doi.org/10.1063/1.860836","url":null,"abstract":"It is clear that the edge plasma plays a crucial role in global tokamak confinement. This paper is a report on simulations of a new drift wave type instability driven by conducting wall (also originally named as a ∇Te instability) [Phys. Fluids B 3, 1364 (1991)]. A 2d(x,y) fluid code has been developed in order to explore the anomalous transport in the boundary plasmas. The simulation consists of a set of fluid equations (in the electrostatic limit) for the vorticity ∇⊥2φ, and the temperature Te in a shearless plasma slab confined by a uniform, straight magnetic field Bz with two divertor (or limiter) plates intercepting the magnetic field. The model has two regions separated by a magnetic separatrix: In the edge region inside the separatrix, the model is periodic along the magnetic field while in the scrapeoff layer (SOL) region outside the separatrix, the magnetic field is taken to be of finite length with model (logical sheath) boundary conditions at diverter (or limiter) plates. The simulation results...","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129238038","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}
Current drive by asymmetric synchrotron radiation in high‐temperature inhomogeneous tokamaks is discussed and the global normalized efficiency as a function of the peak density and temperature and profile indices is obtained.
{"title":"Temperature dependence of synchrotron radiation current drive in inhomogeneous tokamak plasmas","authors":"I. Fidone","doi":"10.1063/1.860602","DOIUrl":"https://doi.org/10.1063/1.860602","url":null,"abstract":"Current drive by asymmetric synchrotron radiation in high‐temperature inhomogeneous tokamaks is discussed and the global normalized efficiency as a function of the peak density and temperature and profile indices is obtained.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125133086","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}
A correct approach to the problem of a reduction of the growth rate of the Rayleigh–Taylor (RT) instability in an ablation wave is demonstrated in this paper by considering a slow combustion wave in a gravitational field. It is shown that both the supplementary condition required in the model of discontinuity and the reduction of the instability growth rate can be obtained only by solving the complete system of equations, including the equation of thermal conductivity and energy release which are responsible for the wave propagation and the finite thickness of the wave front. The point is that there is no stabilization of the growth rate of RT instability by a mass flow in the limit of zero thickness of the wave front. The reduction of the growth rate can be obtained rigorously for a finite thickness of the wave front only.
{"title":"On the stability of combustion and laser‐produced ablation fronts","authors":"V. Bychkov, S. M. Goldberg, M. Liberman","doi":"10.1063/1.860601","DOIUrl":"https://doi.org/10.1063/1.860601","url":null,"abstract":"A correct approach to the problem of a reduction of the growth rate of the Rayleigh–Taylor (RT) instability in an ablation wave is demonstrated in this paper by considering a slow combustion wave in a gravitational field. It is shown that both the supplementary condition required in the model of discontinuity and the reduction of the instability growth rate can be obtained only by solving the complete system of equations, including the equation of thermal conductivity and energy release which are responsible for the wave propagation and the finite thickness of the wave front. The point is that there is no stabilization of the growth rate of RT instability by a mass flow in the limit of zero thickness of the wave front. The reduction of the growth rate can be obtained rigorously for a finite thickness of the wave front only.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122599690","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}
H. Maassberg, R. Burhenn, U. Gasparino, G. Kühner, H. Ringler, K. Dyabilin
The electron energy balance is analyzed for equivalent low‐density electron cyclotron resonance heated (ECRH) discharges with highly peaked central power deposition in the stellarators W7‐A [Plasma Phys. Controlled Fusion 28, 43 (1986)], L‐2 [Proceedings of the 6th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Berchtesgaden, 1976 (International Atomic Energy Agency, Vienna, 1977), Vol. 2, p. 115] and W7‐AS [Proceedings of the 9th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Baltimore, 1982 (International Atomic Energy Agency, Vienna, 1983), Vol. 3, p. 141]. Within the long mean‐free path (LMFP) collisionality regime in stellarators, the neoclassical electron heat diffusivity χe can overcome the ‘‘anomalous’’ one. The neoclassical transport coefficients are calculated by the dkes code (Drift Kinetic Equation Solver) [Phys. Fluids 29, 2951 (1986); Phys. Fluids B 1, 563 (1989)] for these configurations, and the particle and energy flu...
{"title":"Experimental and neoclassical electron heat transport in the LMFP regime for the stellarators W7‐A, L‐2, and W7‐AS","authors":"H. Maassberg, R. Burhenn, U. Gasparino, G. Kühner, H. Ringler, K. Dyabilin","doi":"10.1063/1.860835","DOIUrl":"https://doi.org/10.1063/1.860835","url":null,"abstract":"The electron energy balance is analyzed for equivalent low‐density electron cyclotron resonance heated (ECRH) discharges with highly peaked central power deposition in the stellarators W7‐A [Plasma Phys. Controlled Fusion 28, 43 (1986)], L‐2 [Proceedings of the 6th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Berchtesgaden, 1976 (International Atomic Energy Agency, Vienna, 1977), Vol. 2, p. 115] and W7‐AS [Proceedings of the 9th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Baltimore, 1982 (International Atomic Energy Agency, Vienna, 1983), Vol. 3, p. 141]. Within the long mean‐free path (LMFP) collisionality regime in stellarators, the neoclassical electron heat diffusivity χe can overcome the ‘‘anomalous’’ one. The neoclassical transport coefficients are calculated by the dkes code (Drift Kinetic Equation Solver) [Phys. Fluids 29, 2951 (1986); Phys. Fluids B 1, 563 (1989)] for these configurations, and the particle and energy flu...","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"366 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131582978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The current‐diffusive ballooning mode is analyzed in the tokamak plasma. This mode is destabilized by the current diffusivity (i.e., the electron viscosity) and stabilized by the thermal conductivity and ion viscosity. By use of the ballooning transformation, the eigenmode equation is solved. An analytic solution is obtained by the strong ballooning limit. Numerical calculation is also performed to confirm the analytic theory. The growth rate of the mode and the mode structure are analyzed. The stability boundary is derived in terms of the current diffusivity, thermal conductivity, ion viscosity, and the pressure gradient for the given shear parameter. This result is applied to express the thermal conductivity in terms of the pressure gradient, magnetic configurational parameters (such as the safety factor, shear, and aspect ratio), and the Prandtl numbers.
{"title":"Analysis of the current‐diffusive ballooning mode","authors":"M. Yagi, K. Itoh, S. Itoh, A. Fukuyama, M. Azumi","doi":"10.1063/1.860841","DOIUrl":"https://doi.org/10.1063/1.860841","url":null,"abstract":"The current‐diffusive ballooning mode is analyzed in the tokamak plasma. This mode is destabilized by the current diffusivity (i.e., the electron viscosity) and stabilized by the thermal conductivity and ion viscosity. By use of the ballooning transformation, the eigenmode equation is solved. An analytic solution is obtained by the strong ballooning limit. Numerical calculation is also performed to confirm the analytic theory. The growth rate of the mode and the mode structure are analyzed. The stability boundary is derived in terms of the current diffusivity, thermal conductivity, ion viscosity, and the pressure gradient for the given shear parameter. This result is applied to express the thermal conductivity in terms of the pressure gradient, magnetic configurational parameters (such as the safety factor, shear, and aspect ratio), and the Prandtl numbers.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132676928","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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