The three‐dimensional problem of the wave propagation from a point source in a moving magnetoactive plasma is considered for the case of monochromatic waves. The magnetic Reynolds number is assumed to be small, so that the potential approximation for the electric field perturbation can be accepted. The cases of subsonic and supersonic main flows are considered. The method of integral transformations is used for the solution of the problem. The high‐frequency asymptotic expansion of the solution is obtained and analyzed. For a supersonic flow, the existence of the electric and gas‐dynamic perturbations outside the classic Mach cone is established, and the properties of these perturbations are examined.
{"title":"Electroacoustic radiation from a point source in a moving magnetoactive plasma","authors":"B. Dobrydnev, I. Rutkevich","doi":"10.1063/1.860875","DOIUrl":"https://doi.org/10.1063/1.860875","url":null,"abstract":"The three‐dimensional problem of the wave propagation from a point source in a moving magnetoactive plasma is considered for the case of monochromatic waves. The magnetic Reynolds number is assumed to be small, so that the potential approximation for the electric field perturbation can be accepted. The cases of subsonic and supersonic main flows are considered. The method of integral transformations is used for the solution of the problem. The high‐frequency asymptotic expansion of the solution is obtained and analyzed. For a supersonic flow, the existence of the electric and gas‐dynamic perturbations outside the classic Mach cone is established, and the properties of these perturbations are examined.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"13 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114114755","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}
Time‐dependent high‐gain free‐electron laser equations are generalized to the strong pump regime where fast, 2π/kw, spatial oscillations can no longer be eliminated by spatial averages, and evolution of the radiation phase needs to be taken into account. The equations are solved numerically along the characteristics of the beam and the laser field for superradiant solutions in the strong pump regime using the parameters of the Electron Laser Facility (ELF) of the Lawrence Livermore National Laboratory, [Phys. Rev. Lett. 54, 889 (1985); Nucl. Instrum. Methods A 250, 144 (1986); 285, 217 (1989); Phys. Rev. A 35, 2184 (1987)]. With beam pulses short compared to the wiggler length and long compared to the cooperation length, numerical solutions show that the initial laser fields get amplified to the steady‐state level intensity in only a few bucket distances in the slippage region along the beam characteristics. The underlying mechanism for this superradiant gain gradient is due to the amplification of the in...
时间相关的高增益自由电子激光方程被推广到强泵浦区，其中快速的2π/kw空间振荡不能再被空间平均消除，并且需要考虑辐射相位的演化。利用劳伦斯利弗莫尔国家实验室的电子激光设备(ELF)的参数，沿着光束和激光场的特征对强泵浦区的超辐射解进行了数值求解。Rev. Lett. 54,889 (1985);诊断。Instrum。方法A 250,144 (1986);285, 217 (1989);理论物理。[j].生物工程学报，2004，(1)。这种超辐射增益梯度的潜在机制是由于激光的放大。
{"title":"Superradiant free‐electron lasers in the high‐gain strong pump regime","authors":"K. H. Tsui","doi":"10.1063/1.860598","DOIUrl":"https://doi.org/10.1063/1.860598","url":null,"abstract":"Time‐dependent high‐gain free‐electron laser equations are generalized to the strong pump regime where fast, 2π/kw, spatial oscillations can no longer be eliminated by spatial averages, and evolution of the radiation phase needs to be taken into account. The equations are solved numerically along the characteristics of the beam and the laser field for superradiant solutions in the strong pump regime using the parameters of the Electron Laser Facility (ELF) of the Lawrence Livermore National Laboratory, [Phys. Rev. Lett. 54, 889 (1985); Nucl. Instrum. Methods A 250, 144 (1986); 285, 217 (1989); Phys. Rev. A 35, 2184 (1987)]. With beam pulses short compared to the wiggler length and long compared to the cooperation length, numerical solutions show that the initial laser fields get amplified to the steady‐state level intensity in only a few bucket distances in the slippage region along the beam characteristics. The underlying mechanism for this superradiant gain gradient is due to the amplification of the in...","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"92 6 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":"128021343","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 theory of stochastic processes is applied to analyze the effect of magnetic‐field perturbations on the motion of classical charged particles. For arbitrary field fluctuations along the path of a particle, an approximate diffusion equation is obtained by means of the cumulant technique. The limit of white noise, in which the model is exact, and the difference between adiabatic and nonadiabatic motion are discussed. These cases relate results obtained for astrophysical plasmas and tokamak plasmas. It is shown that large longitudinal perturbations give rise to a new regime for diffusion perpendicular to the mean magnetic field.
{"title":"Test particle transport in stochastic magnetic fields modeled by stochastic processes","authors":"L. Hannibal","doi":"10.1063/1.860971","DOIUrl":"https://doi.org/10.1063/1.860971","url":null,"abstract":"The theory of stochastic processes is applied to analyze the effect of magnetic‐field perturbations on the motion of classical charged particles. For arbitrary field fluctuations along the path of a particle, an approximate diffusion equation is obtained by means of the cumulant technique. The limit of white noise, in which the model is exact, and the difference between adiabatic and nonadiabatic motion are discussed. These cases relate results obtained for astrophysical plasmas and tokamak plasmas. It is shown that large longitudinal perturbations give rise to a new regime for diffusion perpendicular to the mean magnetic field.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"30 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":"117251511","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 ponderomotive force acting on an overdense, absorbing plasma with nonlocal electric properties is calculated from first principles. On the basis of the space–time dependence of the electric field and the electron distribution function which were calculated self‐consistently, the conductivity, current, and force in the plasma are calculated. The possibility of acceleration of ions by an intense laser beam is demonstrated and the proper conditions for this to occur are pointed out.
{"title":"The ponderomotive force in an overdense, absorbing, dispersive plasma, caused by an intense laser–matter interaction","authors":"E. Gamaly","doi":"10.1063/1.860846","DOIUrl":"https://doi.org/10.1063/1.860846","url":null,"abstract":"The ponderomotive force acting on an overdense, absorbing plasma with nonlocal electric properties is calculated from first principles. On the basis of the space–time dependence of the electric field and the electron distribution function which were calculated self‐consistently, the conductivity, current, and force in the plasma are calculated. The possibility of acceleration of ions by an intense laser beam is demonstrated and the proper conditions for this to occur are pointed out.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"603 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":"134174179","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}
Radio frequency (rf) magnetic fluctuations B have been measured with loop antennas in a large pulsed discharge plasma column (ne≲1012 cm−3, kTe≲3 eV, B0≂20 G, Ar, 2×10−4 Torr, 1 m diam×2.5 m length). A 1/f‐like noise spectrum is observed in the whistler wave regime (ωce1/2ωci1/2<ω<ωce) both in the Maxwellian afterglow plasma and in the active discharge which contains energetic (45 eV) electrons. Discrete emission lines at the electron cyclotron frequency and its harmonics are found only in the presence of spiraling energetic electrons. These are naturally present in the active discharge but have also been injected as a controlled oblique electron beam into the Maxwellian afterglow plasma. In the latter case up to 15 cyclotron harmonic lines with weak amplitude decay Bz(ω) are generated in the beam flux tube. From two‐point correlation measurements it is shown that the line spectrum is due to ballistic beam modes rather than plasma eigenmodes driven unstable by the beam. The lines evolve from broadband t...
{"title":"Cyclotron harmonic lines in the thermal magnetic fluctuation spectrum of spiraling electrons in plasmas","authors":"R. Stenzel, G. Golubyatnikov","doi":"10.1063/1.860959","DOIUrl":"https://doi.org/10.1063/1.860959","url":null,"abstract":"Radio frequency (rf) magnetic fluctuations B have been measured with loop antennas in a large pulsed discharge plasma column (ne≲1012 cm−3, kTe≲3 eV, B0≂20 G, Ar, 2×10−4 Torr, 1 m diam×2.5 m length). A 1/f‐like noise spectrum is observed in the whistler wave regime (ωce1/2ωci1/2<ω<ωce) both in the Maxwellian afterglow plasma and in the active discharge which contains energetic (45 eV) electrons. Discrete emission lines at the electron cyclotron frequency and its harmonics are found only in the presence of spiraling energetic electrons. These are naturally present in the active discharge but have also been injected as a controlled oblique electron beam into the Maxwellian afterglow plasma. In the latter case up to 15 cyclotron harmonic lines with weak amplitude decay Bz(ω) are generated in the beam flux tube. From two‐point correlation measurements it is shown that the line spectrum is due to ballistic beam modes rather than plasma eigenmodes driven unstable by the beam. The lines evolve from broadband t...","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"3 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":"114623005","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 kinetic theory is developed which unifies the concept of radio‐frequency (rf) current drive and wave helicity injection. It is shown that wave helicity injection and transport can be incorporated into the more general concept of rf forces. Moreover, the part related to wave helicity has the same form as a mean field dynamo. Present result suggests that the evaluation of rf current drive by conventional methods may leave out some important effects. The theory may also simplify the study of rf influence on transport and stability.
{"title":"Radio-frequency (rf) forces and wave helicity transport","authors":"V. Chan, S. Chiu","doi":"10.1063/1.860830","DOIUrl":"https://doi.org/10.1063/1.860830","url":null,"abstract":"A kinetic theory is developed which unifies the concept of radio‐frequency (rf) current drive and wave helicity injection. It is shown that wave helicity injection and transport can be incorporated into the more general concept of rf forces. Moreover, the part related to wave helicity has the same form as a mean field dynamo. Present result suggests that the evaluation of rf current drive by conventional methods may leave out some important effects. The theory may also simplify the study of rf influence on transport and stability.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"51 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120993685","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}
An analytical model has been developed for toroidal coupling of tearing modes with different helicities in the low‐β and large aspects ratio tokamaks. A standard characteristic value problem has been naturally composed according to the structure of magnetohydrodynamic (MHD) solutions. The explicit general dispersion relation has been obtained by the asymptotic matching. The growth rates (characteristic values) and corresponding flux perturbations (characteristic functions) of the toroidal tearing mode have been derived. The toroidal coupling plays a role mainly through the correction for the ideal MHD solutions. Without loss of generality, variation tendency of growth rates has been analyzed for a toroidal tearing mode with cylindrical components m/n and (m+1)/n, the results indicate that (1) The toroidal coupling has a destabilizing effect on the tearing modes; (2) the ‘‘beating’’ of the growth rates of two components leads to strong coupling, even if the coupling parameter C is quite small, and the coup...
{"title":"Toroidal coupling of disparate helical tearing modes","authors":"Ding Li, Y. Huo","doi":"10.1063/1.860844","DOIUrl":"https://doi.org/10.1063/1.860844","url":null,"abstract":"An analytical model has been developed for toroidal coupling of tearing modes with different helicities in the low‐β and large aspects ratio tokamaks. A standard characteristic value problem has been naturally composed according to the structure of magnetohydrodynamic (MHD) solutions. The explicit general dispersion relation has been obtained by the asymptotic matching. The growth rates (characteristic values) and corresponding flux perturbations (characteristic functions) of the toroidal tearing mode have been derived. The toroidal coupling plays a role mainly through the correction for the ideal MHD solutions. Without loss of generality, variation tendency of growth rates has been analyzed for a toroidal tearing mode with cylindrical components m/n and (m+1)/n, the results indicate that (1) The toroidal coupling has a destabilizing effect on the tearing modes; (2) the ‘‘beating’’ of the growth rates of two components leads to strong coupling, even if the coupling parameter C is quite small, and the coup...","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"32 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":"122088203","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}
When the poloidal ion diamagnetic flow is of the order of the E×B drift velocity, it significantly affects the shock formation in a poloidally rotating tokamak plasma. (Here, E is the electric field and B is the magnetic field.) The poloidal density variation in both linear and shock regimes can be weakened if the poloidal ion diamagnetic flow tends to cancel the poloidal E×B flow. The magnitude of the density variation is not symmetric with respect to the direction of the E×B poloidal rotation. The resonant condition at which strong shock occurs is also modified dramatically by the diamagnetic flow. For some cases, the poloidal density variation inside the bifurcated electric field layer in the L–H transition [Phys. Rev. Lett. 42, 1408 (1982)] may not be large enough to significantly modify the plasma viscosity obtained by neglecting the compressibility effects.
当极性离子反磁流为E×B漂移速度数量级时，对极性旋转托卡马克等离子体中的激波形成有显著影响。(这里，E是电场，B是磁场。)如果极向离子反磁性流倾向于抵消极向E×B流，则线性和激波状态下的极向密度变化都可以减弱。密度变化的大小相对于E×B极向旋转的方向是不对称的。强激波发生时的共振条件也被反磁流显著地改变。在某些情况下，L-H跃迁中分岔电场层内的极向密度变化[物理学]。Rev. Lett. 42, 1408(1982)]可能不足以显著改变忽略可压缩性效应所获得的等离子体粘度。
{"title":"Effects of ion diamagnetic flow on shock formation in poloidally rotating tokamak plasmas","authors":"K. Shaing, C. Hsu","doi":"10.1063/1.860831","DOIUrl":"https://doi.org/10.1063/1.860831","url":null,"abstract":"When the poloidal ion diamagnetic flow is of the order of the E×B drift velocity, it significantly affects the shock formation in a poloidally rotating tokamak plasma. (Here, E is the electric field and B is the magnetic field.) The poloidal density variation in both linear and shock regimes can be weakened if the poloidal ion diamagnetic flow tends to cancel the poloidal E×B flow. The magnitude of the density variation is not symmetric with respect to the direction of the E×B poloidal rotation. The resonant condition at which strong shock occurs is also modified dramatically by the diamagnetic flow. For some cases, the poloidal density variation inside the bifurcated electric field layer in the L–H transition [Phys. Rev. Lett. 42, 1408 (1982)] may not be large enough to significantly modify the plasma viscosity obtained by neglecting the compressibility effects.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"12 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":"128519954","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 dynamo effect due to neoclassical tearing modes is considered. It is found that the global constraints on energy and helicity balance require a redefinition of the dynamo field in neoclassical magnetohydrodynamics. The parallel dynamo field is calculated from the boundary‐layer equations governing tearing modes. This dynamo effect can sustain a completely bootstrapped tokamak. A typical steady‐state current profile has a core region of weak pressure gradients surrounded by a region of strong pressure gradients, where the current profile is entirely due to the bootstrap effect.
{"title":"Neoclassical tearing dynamo and self‐sustainment of a bootstrapped tokamak","authors":"Y. Yuan, A. Bhattacharjee","doi":"10.1063/1.860838","DOIUrl":"https://doi.org/10.1063/1.860838","url":null,"abstract":"The dynamo effect due to neoclassical tearing modes is considered. It is found that the global constraints on energy and helicity balance require a redefinition of the dynamo field in neoclassical magnetohydrodynamics. The parallel dynamo field is calculated from the boundary‐layer equations governing tearing modes. This dynamo effect can sustain a completely bootstrapped tokamak. A typical steady‐state current profile has a core region of weak pressure gradients surrounded by a region of strong pressure gradients, where the current profile is entirely due to the bootstrap effect.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"47 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":"132072564","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 new paradigm for producing well‐confined, dense‐thermonuclear plasmas is described. The convergence of a radial beam distribution of a Penning‐trap‐confined plasma produces a dense inertially confined non‐neutral plasma. The equilibrium, stability, classical transport, and particle‐handling properties of such a concept are developed. The application of this approach to controlled fusion using a pure electron plasma to form a central virtual cathode in which ions are electrostatically confined is discussed. On one hand, extreme plasma control is required, placing the major uncertainty on issues of machine precision. On the other hand, development is characterized by the manufacture and testing of extremely small and inexpensive systems. Thus, it would seem that a timely experimental test of this concept would be ineluctable. Success at such experiments might indicate an alternate path to practical fusion applications.
{"title":"Production and application of dense Penning trap plasmas","authors":"D. Barnes, R. Nebel, L. Turner","doi":"10.1063/1.860837","DOIUrl":"https://doi.org/10.1063/1.860837","url":null,"abstract":"A new paradigm for producing well‐confined, dense‐thermonuclear plasmas is described. The convergence of a radial beam distribution of a Penning‐trap‐confined plasma produces a dense inertially confined non‐neutral plasma. The equilibrium, stability, classical transport, and particle‐handling properties of such a concept are developed. The application of this approach to controlled fusion using a pure electron plasma to form a central virtual cathode in which ions are electrostatically confined is discussed. On one hand, extreme plasma control is required, placing the major uncertainty on issues of machine precision. On the other hand, development is characterized by the manufacture and testing of extremely small and inexpensive systems. Thus, it would seem that a timely experimental test of this concept would be ineluctable. Success at such experiments might indicate an alternate path to practical fusion applications.","PeriodicalId":113346,"journal":{"name":"Physics of fluids. B, Plasma physics","volume":"14 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":"122191738","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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