摘要:

To clarify the characteristics of the discharge induction against the delay time of impulse application with a long gap/1/, the electron and neutral particle density in the plasma were measured. The electron density was about 1023m−3at 10 &mgr;s after firing the laser and then gradually decreases in several tens of microseconds. The rarefied air region of lower neutral particle density takes a spherical shell profile in later stages after firing the laser. From the experiments of the laser‐induced discharge, it seems that the discharge induction was greatly influenced by the electron attachment to oxygen molecules and rarefied region of the neutral particle density. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50366

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A series of laboratory experiments has been conducted to investigate the initiating effects of laser plasma channel on electrical discharge. It was confirmed that the plasma channels reduce the required electrical field strength for electrical discharges to occur by a factor of 6. A field experimental site targeting natural lightning is being prepared. The thunderstorm monitoring system and the laser and optical systems have been developed and tested against various weather conditions. The results from the laboratory experiments and field experiments will be discussed. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50367

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Dynamics of dense laser‐produced vapor plume are studied. The analysis is based on the well‐known special solution of gas dynamics equations that describes the expansion of an ellipsoidal gas cloud into vacuum. This solution is employed to explain the apparent ‘‘rotation’’ of the cloud (so called ‘‘flip‐over effect’’). The flux of atoms to the substrate and the film thickness profiles are calculated using the model. It is shown that the cloud expansion into vacuum and into an ambient gas both are unstable. For short‐wavelength perturbations, estimates of the instability growth rate are presented. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50368

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The process of the plasma discharge due to an electron beam is experimentally investigated. A pulse (∼540 &mgr;s) of an electron beam (0.5–1.5 keV, ≤20 mA) is injected into argon gas (5×10−5–5×10−4Torr) in a magnetic field (50–300 G). The discharge based on a gas break down occurs cascade‐likely in time. The gas beak down with some steps is explained by the two stream instability of an electron beam‐plasma system, from the observation of the temporal evolution of the frequency spectra (0–3.0 GHz) of the instability and the measurement of the temporal plasma density and temperature. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50370

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Electron Cycrotron Resonance argon plasma was investigated by optical methods. A luminosity distribution of Ar‐II was imaged through an interferometer filter and the luminous arch hill was observed near the ECR region, where the plasma was resonantly generated. Absorption spectroscopy using laser diode was applied to neutral metastable argon. The typical value of the density amounted at 1010particles per cm3. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50405

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Acceleration and heating of a relativistic electron beam induced by cascading nonlinear Landau damping involving three or four intense electromagnetic waves in a plasma are investigated theoretically by using relativistic Vlasov‐Maxwell equations. It is proved that a relativistic electron beam can be accelerated more effectively by the cascading nonlinear Landau damping than by usual process of two electromagnetic waves. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50406

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An intense relativistic electron beam was injected into an unmagnetized gun‐produced plasma. From spectroscopic measurements of strong high frequency electrostatic fields, it was found that this beam‐plasma system was in a strong Langmuir turbulent state. Moreover, high‐power broadband microwave radiation was observed. A result indicating relation between the turbulence and the microwave radiation is shown. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50407

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Microheterogeneous targets for plasma investigation are discussed. Microheterogeneity is obtained in the form of metal clusters dispersed inside solid material or foam as well as in the form of metallized aerogel. Microheterogeneous plasma is shown to be initiated by such targets and its behavior is analyzed. The only way to observe the long‐evolution plasma in a short laser experiment is to conserve a certain stage of plasma evolution in the target structure. Target structuring provides: 1) phase separated multi‐ion mixtures in highly non‐ideal plasmas, 2) extended corona (without any prepulse), 3) obscure stability through microinstabilities in the non‐linear growth regime. For ICF applications, underdence microheterogeneous plasma is equalizing the laser irradiation energy over the target‐in‐flight surface. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50408

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report here the remarkable result that a correspondence principle for electromagnetic radiation can exactly reproduce the apparently anomalous behavior that has been observed by a number of experimenters in the transition regime between multiphoton ionization and tunneling ionization for tenuous gases irradiated with high intensity lasers. Further, when the photon density of a laser beam of frequency &ohgr; is equated to the electron density of a plasma at its critical value (plasma frequency &ohgr;p≡&ohgr;), it turns out that the corresponding laser intensity is just the critical laser intensity derived from this correspondence principle which separates classical and quantum ranges and which has been previously identified by various experiments. The relationship between this purely classical plasma property and basic quantum and relativistic effects are discussed. It may also follow from this discussion that higher harmonic generation with fsec lasers can be explained as a photon collective effect. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50410

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

New scheme of a nuclear fusion reactor system is proposed, the basic concept of which comes from ingenious combination of hitherto developed techniques and verified facts; 1) so‐called cold fusion (CF), 2) plasma of both magnetic confinement fusion (MCF) and inertial confinement fusion (ICF), and 3) accelerator‐based D‐T (D) neutron source. Through the comparison of the characteristics among ICF, LCF, and MCF, the feasibility of the LCFs is discussed. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50411

出版商:AIP    

年代:1996

数据来源: AIP