摘要:

A particle simulation with plasma source is carried out on plasma structures generated by an electron emissive electrode floated in a collisionless plasma. When low‐temperature, high‐density thermal electrons are emitted, there appears a negative potential dip in front of the electrode, which is always accompanied by a low‐frequency oscillation. On the other hand, three regimes of plasma structures appear for an electron beam injection. When a high‐flux electron beam is injected, an electron sheath is generated in front of the electrode. The sheath reflects ions flowing to the electrode, providing an increase in the plasma density. When a low‐flux electron beam is injected, no electron sheath is generated. When an intermediate‐flux beam is injected, the electron sheath structure appears periodically in time. The lifetime of the sheath is proportional to the system length. These results of beam injection are almost consistent with those of a Q‐machine experiment.

ISSN:0899-8221    

DOI:10.1063/1.860589

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Comparative observations of the Vacuum Spark discharge are presented under differing electrical drive conditions but identical geometrical conditions. A 1.5 &OHgr; 120 nsec, coaxial line is used to provide maximum currents to 90 kA. The line may be operated in the usual switched mode to give a rectangular voltage and current wave form, or in the Hybrid mode, in which case the voltage builds slowly until breakdown occurs. In both modes of operation the value ofdI/dtis about 1×1012A/sec. A Nd:YAG is focused onto either electrode to initiate the discharge. With the laser focused onto the anode a low‐density plasma accompanied by intense electron beams is formed. With the laser focused on the cathode a much higher plasma density is observed in the gap, with the formation of a dense tight pinch close to the cathode, in which hot spots form at peak current. The Hybrid mode is favored for its reproducible behavior.

ISSN:0899-8221    

DOI:10.1063/1.860590

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The three‐dimensional shapes of azimuthally asymmetric non‐neutral plasmas are investigated numerically, and a simple theory is developed that predicts these shapes in many circumstances.

ISSN:0899-8221    

DOI:10.1063/1.860591

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The effects of nonlocal heat transport on stimulated scattering instabilities of electromagnetic waves are investigated employing the recently derived expression for the electron number density perturbations that are driven by the ponderomotive and thermal forces in highZicollisional plasmas. The growth rates and the threshold conditions for stimulated Brillouin and stimulated Compton scattering, as well as modulational instabilities, are obtained. It is found that the growth rates of the scattering instabilities of electromagnetic waves are considerably enhanced due to nonlocal electron heat conduction in collisional plasmas.

ISSN:0899-8221    

DOI:10.1063/1.860592

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A compact formula for fully relativistic Thomson scattering spectrum including depolarization term is presented. By rational approximation, an analytic formula with high accuracy (relative error<0.1% at 100 keV) is obtained, which is applicable to a wide range of plasmas.

ISSN:0899-8221    

DOI:10.1063/1.860593

出版商:AIP    

年代:1993

数据来源: AIP