摘要:

Finite aspect ratio modifications to neoclassical transport theory are considered. In the general case of arbitrary flux surface geometry, a closed set of macroscopic equations is derived. These include the equation which determines the time evolution of the flux surfaces. In the large aspect ratio case, theO (r /R )corrections to the orderO (r )1/2)R (1/2))transport coefficients, calculated previously, are obtained. In particular, an expression for the electrical conductivity is obtained which may be regarded as exact for all experimentally interesting aspect ratios.

ISSN:0031-9171    

DOI:10.1063/1.1694191

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Cross field loss of a partially ionized plasma induced by magnetic field asymmetries varies as the reciprocal of the collision frequency,&ngr;, at large&ngr;and as&ngr;at small collision frequencies. The value of the collision frequency at peak loss (≈ 40times classical for 1% field asymmetries) is a function of the asymmetry amplitude and wavelength. These observations can be accounted for in terms of an ambipolar neoclassical diffusion model taking into account field asymmetries in a shearless multipole‐like device.

ISSN:0031-9171    

DOI:10.1063/1.1694192

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A theory of electron cyclotron resonance heating in a mirror device is applied to the radio frequency induced particle diffusion into the loss cone. It is shown that the loss time is much slower than the heating time within the stochastic heating region, but that the losses are strongly enhanced over collisional losses alone. The effects of collisions in combination with the electron cyclotron resonance heating are considered and found to give additional heating beyond the adiabatic barrier, on the time scale of the 90° collisional deflection. The collisions also act, together with the radio frequency fields, to enhance the rate of loss cone diffusion. The major assumptions and results of the theory are confirmed by exact numerical calculations. Predictions of the performance of a 25 kW electron cyclotron resonance heating experiment are made.

ISSN:0031-9171    

DOI:10.1063/1.1694193

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Ion‐acoustic solitary wave (solitons) have been studied experimentally by employing a double‐plasma device. The solitary waves are found to be produced from both a single compressional pulse and a continuous wave. A rarefaction pulse also produces solitons if the pulse width is sufficiently wide. A theory based on the Schro¨dinger equation accounts for the number of solitons. Recurrence to the original state is observed when a continuous wave is launched. A simple wave‐wave coupling analysis for the recurrence of the original state is given.

ISSN:0031-9171    

DOI:10.1063/1.1694194

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Two electromagnetic waves, propagating in opposite directions, can resonantly excite electron or ion waves, if the difference frequency&Dgr;&ohgr;and wave number&Dgr;ksatisfy the linear dispersion relation of such modes. This process damps the higher‐frequency electromagnetic wave and amplifies the lower‐frequency one (nonlinear Landau damping). The amplitude of the electrostatic mode may be limited by Landau damping, trapping, or by loss of resonance due to the frequency shift of the electromagnetic modes.

ISSN:0031-9171    

DOI:10.1063/1.1694195

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Incoherent scattering of microwaves at the upper‐hybrid resonance in an inhomogeneous plane‐layered plasma is investigated. The incident and scattered waves propagate in the plane characterized by the directions of the density gradient and the externally imposed magnetic field. The frequency of the waves is close to the cyclotron frequency and therefore full account of the dispersive properties of the plasma is taken. The principal aim of the study is the investigation of collective effects on the scattered flux of energy in a toroidal machine and therefore the case of accessible resonance and frequency shift of the order of the ion frequency are specificallly considered. Except in the spectrum of the density fluctuations, thermal effects are neglected. This is the collision‐dominated case. The relevant equations are solved for the case of opaque plasma and the scattered flux of energy is estimated. The result obtained indicates that enhancement of the scattering cross section with respect to the transparent scattering is expected for&ngr;/&ohgr; ≪ 1, where&ngr;is the electron collision frequency.

ISSN:0031-9171    

DOI:10.1063/1.1694196

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Incoherent scattering of microwaves at the upper‐hybrid resonance in an inhomogeneous stratified warm plasma is investigated. The incident and scattered waves propagate in the plane characterized by the directions of the density gradient and the externally static magnetic field. Ordinary collisions are neglected and finite Larmor radius corrections in the dielectric tensor are taken into account. The structure of the incident wave field near the hybrid layer is discussed, and it is shown that the component of the incident Poynting vector along the density gradient is totally converted into Bernstein plasma waves. The energy flux of the scattered radiation is also calculated. The result obtained indicates that forT / m c2enhancement with respect to the usual high‐frequency scattering(&ohgr; ≫ &ohgr;p , &ohgr;c)is expected.

ISSN:0031-9171    

DOI:10.1063/1.1694197

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A theory is developed of ion‐acoustic resonances in inhomogeneous plasmas of the positive column type using a fluid plasma description. Poisson's equation is properly taken into account, instead of applying the usual assumption of wave quasineutrality. The order of the differential equation describing the wave is thereby increased by two and the singularity that previously occurred as a result of the presence of a sheath region is thereby removed. It is shown that ion‐acoustic resonances are confined within the plasma core, the effective boundary not being the wall, but the region in the plasma where the macroscopic ion flow velocity attains the Bohm velocity(KTe/mi)(1/2). The theoretical predictions are substantiated by a number of experiments taken from the literature and supplemented by a series of new experiments. The theory sheds new light on the problem of wave reflection from a negatively polarized wall and the damping of ion‐acoustic waves propagating in inhomogeneous plasmas.

ISSN:0031-9171    

DOI:10.1063/1.1694198

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The radial structure of the dissipative trapped ion mode is studied in order to determine the effect of shear and the possibility of finding ranges of tokamak operation which are stable to this mode even in the presence of a temperature gradient. It is found that owing to the presence of increasing numbers of resonant untrapped ions near the mode rational surfaces, wherelqis an integer, the radial wavelengths are reduced and the modes are strongly Landau damped. These effects increase with increasing shear and with increasing values ofl, the toroidal mode number. Numerical estimates of the growth rates and marginal stability conditions are obtained from eigenmode solutions of the radial differential equation and from algebraic dispersion relations which simulate the effects of the radial structure. It is concluded that if(r /q )d q / d rexceeds one, then the temperature threshold for instability is raised by approximately a factor of two from that of the no shear case. It is also proposed that even in unstable regimes, the anomalous diffusion should be less than indicated by previous estimates, since both the growth rates and wavelengths are reduced.

ISSN:0031-9171    

DOI:10.1063/1.1694199

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Injection of fast neutrals with a component of the beam velocity along the magnetic fieldB0results in a plasma having a sheared mean velocity alongB0. If this parallel velocity shearU′and the density inhomogeneity scale lengthLnare large enough so thatU ′|Ln |/(&tgr; + 1) 1/2&ugr;i > 1then a parallel Kelvin‐Helmholtz instability is excited, whereviis the ion thermal speed and&tgr;is the electron temperature/ion temperature. Magnetic shear stabilization requires a shear lengthLscomparable to or less than|Ln |, namely,&tgr;L s /3 (&tgr; + 1) < &ugr;i /U ′ < |Ln |/(&tgr; + 1) 1/2. ForU ′|Ln |/(&tgr; + 1) 1/2&ugr;i < 1, however, this parallel Kelvin‐Helmholtz instability is stabilized and only drift wave instabilities can be excited. For&tgr; ≈ 1and(M / m) 1/2 ≈ 43, the first of these drift wave instabilities is unstable forU ′/&OHgr;i > 172| (Ln / Ls)3/2 |provided|Ln /Ls| < ai /30|Ln |, while the second is stable forU ′ /&OHgr;i < 136ai /|Ls |provided|Ls /Ln | > 600andU ′ /&OHgr;i ≪ 1, whereaiand&OHgr;iare the ion gyration radius and frequency.

ISSN:0031-9171    

DOI:10.1063/1.1694200

出版商:AIP    

年代:1973

数据来源: AIP