摘要:

The iterative method of evaluating plasma equilibria is especially simple in a magnetic coordinate representation. This method is particularly useful for clarifying the subtle constraints of three‐dimensional equilibria and studying magnetic surface breakup at high plasma beta.

ISSN:0031-9171    

DOI:10.1063/1.864835

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Neoclassical diffusion coefficients are obtained in the collisional, small electric field regime for any bumpy closed field line device. A variational principle is used and energy scattering is included in the collision operator.

ISSN:0031-9171    

DOI:10.1063/1.864836

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The linear theory of Alfve´n ion‐cyclotron instability is extended by a rigorous treatment of plasma nonuniformity along the equilibrium magnetic field. A standard phase‐integral dispersion relation provides stability boundaries. Two ion distribution functions allow modeling of plasmas formed in various ways, including neutral‐beam injection both perpendicular and oblique to magnetic field lines. Stability results are quantitatively consistent with past and present experiments. The results further indicate that two important features of stable mirror cells in future experiments are large mirror ratios and pitch‐angle distributions that are broad or are peaked far from perpendicular to the magnetic field.

ISSN:0031-9171    

DOI:10.1063/1.864837

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A method is presented to calculate the hypothesized dynamo mean electric field required to sustain reversed field pinch (RFP) plasmas in time‐independent states such as have been observed in recent RFP experiments. It is also shown how to simultaneously calculate energy transport in terms of a phenomenological radial thermal conductivity &kgr;. It was found that the dynamo extracts energy from the central plasma in order to drive the large azimuthal current needed by the RFP. The quantitative results are only weakly sensitive to the choice of parameters. The principal predictions are the distribution of the dynamo mean electric field in the plasma and the ratio between average and peak electrical conductivity. The theory is compared with experimental RFP data, and it is concluded that the mean plasma resistivity is not much different from the classical resistivity of Spitzer.

ISSN:0031-9171    

DOI:10.1063/1.864838

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A theoretical analysis based on the magnetohydrodynamic approximation is carried out on the effect of multipole‐field suppression of the rotational instabilities excited in a high‐&bgr; plasma column. The multipole field is assumed not to penetrate into the plasma column but to exert magnetic pressure on its boundary surface in order to suppress the distortion of the plasma column. Analytical theory, which takes into account only the effects of the fundamental wave, gives the stability criterion for then=2 mode asBs≥Bs,c= 1/2 (m−1)−1/2rs‖&OHgr;‖(&mgr;0 &rgr;0)1/2, wherers, &rgr;0, and &OHgr; are the radius, mass density, and rotational angular velocity of the plasma column, respectively, 2mthe order of the multipole field,Bsthe field strength at radiusrsin the vacuum state, and &mgr;0the permeability of vacuum. Numerical calculations including the effects of the waves parasitic to the fundamental wave support the stability criterion for hexapole (m=3) and octopole (m=4) fields. For quadrupole (m=2) fields, it is shown that the stable range ofBsis limited between 0.841Bs,cand 0.856Bs,c, whereBs,cis the analytical threshold form=2.

ISSN:0031-9171    

DOI:10.1063/1.864839

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A finite Larmor radius treatment of the tilting instability for field‐reversed configurations is presented. It is shown on two accounts that such a treatment is inappropriate. First, the finite Larmor radius terms become infinite at the field null of the magnetic axis, because of the breakdown of the small Larmor radius assumption. Second, numerical computations using realistic parameters show that the magnetic moments of the ions are very poorly conserved at the tips of the flux surfaces in field‐reversed configuration equilibria. Therefore finite Larmor radius theories cannot be used reliably to explain the observed stability to tilting of field‐reversed configuration experiments.

ISSN:0031-9171    

DOI:10.1063/1.864840

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Loop‐antenna coupling to toroidal plasmas is simulated in a flat geometry by an infinitely repeated array of finite loops in order to obtain a discrete spectrum along they(azimuthal) as well as thez(toroidal) directions. The electromagnetic field of the entire configuration, including the wall, the plasma, and the Faraday shield, is analytically expressed in terms of the antenna current. The self‐consistent antenna current is determined by variational techniques which also yield the antenna impedance. Finally, the theory is specifically applied to the case of ion‐cyclotron‐wave coupling. An approach for obtaining broadband, reflectionless coupling is introduced.

ISSN:0031-9171    

DOI:10.1063/1.864841

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A numerical simulation scheme is developed to examine the nonlinear evolution of the Rayleigh–Taylor instability of a thin sheet in three dimensions. It is shown that the erosion of mass at the top of the bubble is approximately as described by two‐dimensional simulations. However, mass is lost into spikes more slowly in three‐dimensional than in two‐dimensional simulations.

ISSN:0031-9171    

DOI:10.1063/1.864842

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Experimental observations on the partial reflection of a planar ion‐acoustic soliton from a plane rigid boundary with sharp density gradients are presented. The reflected wave attenuates rapidly, forming a spherical wave front apart from a small reflector. The reflection coefficient of about 25% at the boundary has no apparent dependence on the incident wave amplitude and the sheath thickness in front of the reflector in the case of the disk reflector, while it has a dependence in the case of the mesh reflector, having even larger values of up to about 50%.

ISSN:0031-9171    

DOI:10.1063/1.864843

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Time‐resolved stimulated Raman scattering (SRS) spectra from UV laser‐produced plasmas are reported. In analyzing these spectra the theory for SRS in inhomogeneous plasma is extended. This theory is applied to obtain temporally resolved electron temperatures in the plasma corona. Typical coronal temperatures for plastic targets irradiated at 1015W/cm2range up to 1.8 keV. A comparison is made with the predictions of hydrodynamic simulations.

ISSN:0031-9171    

DOI:10.1063/1.864844

出版商:AIP    

年代:1984

数据来源: AIP