摘要:

Self‐consistent equilibria of cylindrical beams are studied in the Vlasov framework with the assumption of a uniform canonical axial momentum for the particles. The study is restricted to beams of circular cross section without azimuthal currents, but not necessarily without axial magnetic field. Attention is focused on beams with intensities much higher than Alfve´n’s limit, which are shown to progress slowly along the axis and to flow predominantly in their external sheath.

ISSN:0031-9171    

DOI:10.1063/1.861887

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

An advantageous configuration for plasma heating with a relativistic beam utilizes an annular beam rotating about a guide magnetic field. The return current processes for such a configuration are considered. For the parameters expected to prevail in an experiment, the plasma response can be described as magnetic diffusion or critically damped magnetosonic waves, these being equivalent. Equations for the axial and angular return currents are derived and take the form of decoupled diffusion equations. The effects of pulse shape, boundary conditions, etc. are then treated. The drag force on the beam resulting from the interaction is greatly enhanced and leads to a stopping length reduction by the factor (1/2)(v∥/c)3as compared with nonrotating beams. The implications of these effects for a plasma heating application are discussed.

ISSN:0031-9171    

DOI:10.1063/1.861888

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The magnetosonic wave emission by an intense relativistic electron beam rotating within a plasma is calculated. This process follows the trapping of the beam in the plasma, and results in a transfer of approximately half the beam energy to the plasma ions. A nonlinear theory is given in accord with beam and plasma parameters of fusion interest. It is shown that dissipation balances the nonlinearity to produce a shock‐type flow resembling that of the linear theory. The primary nonlinear modification is an adjustment of the wave speed tovs=vAMs, wherev2A=B20/4&pgr;nmiandMs=1+B˜/B0is the mach number (B˜is the wave field,B0is the applied field). Estimates are made of power radiated to the waves and the resultant ion energies for some typical experimental parameters.

ISSN:0031-9171    

DOI:10.1063/1.861889

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The conditions for the generation and containment of relativistic electron beams in a tokamak discharge were studied by deliberately driving Ormak into a strong runaway regime. The experimental results show that beams with typical currents of 60 kA and mean electron energies of 3 MeV could be generated reproducibly and then contained safely overe‐folding decay times of 35 msec without damaging the machine. The experiments substantially confirm and extend the results of previous modeling studies on runaway discharges. They also implicitly define the experimental conditions for the establishment of a steady, toroidal beam‐plasma system that can be of interest for plasma physical studies.

ISSN:0031-9171    

DOI:10.1063/1.861890

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

An analysis is presented of the radiation emitted by an arbitrary source embedded in a cold, magnetoactive plasma and physically distinct from the latter. The plasma is supposed to be infinite and homogeneous; its dielectric properties are described by a dielectric tensor &egr;. Expressions for the radiation fields are derived using the technique of Fourier decomposition. An expression for the vector potential is constructed and elaborated as far as possible for anarbitrarycurrent source. The approach differs from that in previous work on technical points, the main one being the sequence in which the various integrations are carried out. The radiation flux is defined on the basis of Poynting’s vector S; a distinction is made between current sources behaving as a given function of time and randomly fluctuating sources. In the latter case an ensemble average is preferred over a time average. A comparison is made with existing treatments in the literature, and a variety of defects is pointed out. The general result for the radiation flux is then specified for cyclotron radiation from a stationary ensemble of electrons and for multipole radiation. Throughout the paper a compact notation is used based on the work of Bremmer.

ISSN:0031-9171    

DOI:10.1063/1.861891

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The oscillation mode of a laser‐produced plasma expanding into a uniform transverse magnetic field is seen to depend on the similarity parameter,N= (8&pgr;&rgr;0)1/2U0/B0.

ISSN:0031-9171    

DOI:10.1063/1.861892

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Calculations of the rf field in a sheath, like that one surrounding an antenna in an infinite plasma, show that resonances occur, yielding very high losses.

ISSN:0031-9171    

DOI:10.1063/1.861893

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The threshold and growth rate for backscattering processes in which electromagnetic waves are backscattered off bunches of plasma ions are given. Multiple backscattering processes are observed in computer simulations as the saturation mechanism of the instability.

ISSN:0031-9171    

DOI:10.1063/1.861894

出版商:AIP    

年代:1977

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.861873

出版商:AIP    

年代:1977

数据来源: AIP