摘要:

In the near &Vthgr;‐pinch limit, a radially diffuse high‐&bgr; screw pinch may be rendered completely stable through a combination of finite ion Larmor radius effects and wall effects.

ISSN:0031-9171    

DOI:10.1063/1.863518

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The dispersion relation for the drift‐cyclotron loss‐cone mode in the presence of the lower hybrid wave is calculated using both electrostatic and finite &bgr; models. It is found that lower hybrid wave fields with frequency &ohgr;0can stabilize the mode if &ohgr;lh<&ohgr;0<&ohgr;+, or &ohgr;0<&ohgr;−<&ohgr;lh, where &ohgr;lh= &ohgr;pi/(1+&ohgr;2pe/&ohgr;2ce)1/2, &ohgr;±= [±A+(A2+4&ohgr;2lh)1/2]/2, andA= &ohgr;2lh&egr;/&ohgr;cik. If the plasma &bgr; is greater than a critical value &bgr;c, there is another stabilization region, namely, &ohgr;0≳&dgr;&ohgr;lh, where &dgr; is a numerical constant. Even though the stabilization effect is small in this region, the lower hybrid wave frequency for electron heating should be in this region in order to avoid enhancing the particle loss rate.

ISSN:0031-9171    

DOI:10.1063/1.863519

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Particle orbits in the presence of the fast wave fields are calculated. It is found that the resonant interaction of ions with the wave can be neglected at &ohgr;0= 2&ohgr;ci, provided that the wave electric field strength is less than a critical valueEc( = 4k∥T/e). The dominant effect on the dispersion relation of the drift‐cyclotron loss‐cone mode is thus found to be due to the nonresonant effects of the wave on electrons and ions. It is found that a fast wave with &ohgr;0= 2&ohgr;cidestabilizes the mode. For &ohgr;0<2&ohgr;ci, fast waves can stabilize the mode for certain values of the plasma &bgr;, which is calculated numerically.

ISSN:0031-9171    

DOI:10.1063/1.863520

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The influence of a random spectrum of lower hybrid waves on the evolution of tearing modes in a tokamak plasma is investigated. For rather modest levels of fluctuations, it is found that new tearing instabilities driven by turbulence are excited with significantly enhanced growth rates and comparable real frequencies. The growth rates for the newm= 1 andm= 2 modes vary as fractional powers of &tgr;Rand &dgr;, where &tgr;Ris the turbulence induced diffusion time and &dgr; is the ratio of Alfve´nic time to the ion gyration period.

ISSN:0031-9171    

DOI:10.1063/1.863521

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The system of time independent Vlasov and Maxwell’s equation is solved for a cylindrically symmetriczpinch including weak rotation of both electrons and ions. The solution clearly shows the effect of rotation on the density profile and azimuthal magnetic field. Limitations on the rotation frequency and radius are found by insisting on self consistency of the approximation scheme.

ISSN:0031-9171    

DOI:10.1063/1.863532

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A general procedure for examining the influence of kinetic effects on the stability of magnetohydrodynamic ballooning modes in mirror machines is presented. In particular, the basic kinetic ballooning mode equation for a nonaxisymmetric, arbitrary beta system with anisotropic pressure is derived. Considering a long‐thin equilibrium typical of the tandem mirror, it is shown that this governing eigenmode equation reduces to a simple form independent of wave‐particle resonant effects.

ISSN:0031-9171    

DOI:10.1063/1.863533

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The steady‐state, axial plasma confinement by a multiple‐mirror device is studied in the ’’viscous fluid regime,’’ &lgr;/lm≪1 (but not negligible), where &lgr; is the ion‐ion mean‐free‐path andlmis the scale length of magnetic field variations. An approximate analytical solution is obtained by averaging over the rapid variations caused by the individual mirrors and compared to a numerical solution without averaging. A smooth transition is found, with increasing values of &lgr;/lm, from sonic flow to a diffusive flow. Studies are made of the variation in density profiles and confinement times versus &lgr;/lm, mirror ratio, relative mirror width, and number of mirror cells. The viscous fluid regime is found to have the same characteristics as the ideal multiple‐mirror regime for &lgr;/lm→1.

ISSN:0031-9171    

DOI:10.1063/1.863534

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Mirror equilibria for arbitrary mirror ratio and flux‐tube eccentricity are obtained to leading order in the plasma pressure (beta expansion) in the paraxial limit (axial scale lengths long compared with radial scale lengths). The solutions are given in terms of quadratures over known functions. The theory is applied to a tandem‐mirror configuration.

ISSN:0031-9171    

DOI:10.1063/1.863535

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The internal tilting instability in a force‐free spheromak plasma in cylindrical geometry is examined. It is found that this instability, originally found in spherical geometry, also occurs in cylindrical geometry. The analysis proceeds by first demonstrating that if no mode rational surface is present in the plasma, a necessary and sufficient condition for ideal magnetohydrodynamic instability is that there exist a solution to ∇×Bm= &mgr;mBm, where Bm∼exp(im&Vthgr;), with &mgr;m<&mgr;0. Solutions to this equation are investigated using two approaches, by a series expansion and by a numerical solution of a modified set of linearized magnetohydrodynamic equations. The eigenvalue for them= 1 mode satisfies &mgr;1<&mgr;0forL/a≳1.67. Since no mode rational surface exists for this elongation, an ideal magnetohydrodynamic mode, identified as the tilting mode, is unstable for these parameters. All modes withm≳1 are shown to be stable.

ISSN:0031-9171    

DOI:10.1063/1.863536

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Magnetic field penetration into a cool, collisional, magnetized plasma has been investigated in Tormac V. Magnetic probe and laser interferometer studies reveal anomalous penetration of the applied toroidal field into a plasma with an initial parallel bias toroidal field. The applied poloidal field, however, formed a well‐defined magnetic front which was effective at sweeping up particles. Strong shear in the vacuum magnetic field does not inhibit the apparent decoupling of the applied toroidal field from the applied poloidal field.

ISSN:0031-9171    

DOI:10.1063/1.863537

出版商:AIP    

年代:1981

数据来源: AIP