摘要:

Multimegajoule high‐temperature high‐Zplasmas are of interest as high‐intensity radiation sources for use in a number of applications. This paper describes a possible method of generating such plasmas by means of thej × Bdriven implosion of thin metallic foil cylinders. Basic analytical guidelines are developed and the results of numerical computations are displayed. Experimental problems associated with the creation of high‐energy plasmas by this technique are discussed with some initial experimental results presented.

ISSN:0021-8979    

DOI:10.1063/1.1662066

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The interaction of a relativistic electron beam(&ngr;/&ggr;[inverted lazy s]2)with the turbulent phase of aZdischarge is examined. An enchancement in heating is observed when the electron current due to theZdischarge is in the opposite direction to the beam current and the plasma is highly turbulent. The ion energy distribution is examined for turbulent heating, beam heating, and combined beam and turbulent heating.

ISSN:0021-8979    

DOI:10.1063/1.1662067

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Plasma‐resonance light scattering has been observed from alkali metal particles condensed from atoms in a flowing inert gas. Lithium, sodium, potassium, rubidium, and cesium vapors were found to spontaneously form particles from 0.5 to more than 200 Torr inert gas pressure. Wavelengths of observed resonances agree with those calculated for spherical particles of 5–50 nm diameter. Using the resonance peak position as an indication of particle size, it has been possible to study the growth of the particlesin situ. . Particle size was found to be a function of the metal, metal vapor pressure, inert gas, inert gas flow rate, and total pressure, with prime factors being the transit time from the furnace to the observation region and metal vapor concentration.

ISSN:0021-8979    

DOI:10.1063/1.1662068

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An approximated energy equation is derived with the dissipation function expressed in terms of the loss modulus and the strain components. The equation is suitable for the analysis of the thermomechanical behavior of a viscoelastic material subjected to cyclic loadings. The material is assumed to be linear, homogeneous, and isotropic. Its mechanical properties are temperature dependent and satisfy the time‐temperature equivalence.

ISSN:0021-8979    

DOI:10.1063/1.1662069

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Using the Walsh‐Christian formulation for the isentropes of a solid having the property of maximum free‐surface velocity, we obtain the first three terms in the expansion of the Gru¨neisen parameter in terms of the compression. In addition, we determine the coefficients of the quadratic and cubic terms in the expansion of the shock velocity in terms of the particle velocity. Finally, we show that the Gru¨neisen parameter for a maximum free‐surface velocity solid furnishes an upper bound to the Gru¨neisen parameter for a given solid. Calculations are given for aluminum and copper by way of illustration.

ISSN:0021-8979    

DOI:10.1063/1.1662070

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A short (2‐nsec) pulse ruby laser has been used to make holographic interferograms of exploding‐wire events. At atmospheric pressure the interferograms exhibit both shock waves and ionization. In a vacuum the vaporization and subsequent ionization of the wire are evident. At selected times after initiation, spatial electron density profiles have been calculated via an Abel inversion, with peak densities approaching 1019cm−3.

ISSN:0021-8979    

DOI:10.1063/1.1662071

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Using 70‐ns bursts of 3‐MeV average energy electrons as the heating source, inertial thermomechanical stresses were produced inX‐cut quartz disks. The range of peak absorbed energy density was from 30 to 360 cal/g. The stress pulses propagated through the samples (direction perpendicular to thecaxis), and the ensuing rear surface motion was recorded with a laser interferometer. At the highest dose, the peak temperature produced in the absorber was calculated to exceed 1600 K, well in excess of the &agr;‐&bgr; transition temperature. Comparison of the experimental results with a model calculation, taking into account the shift of transition temperature with pressure, suggests that the phase transition occurred and that the response was not associated with a metastable state.

ISSN:0021-8979    

DOI:10.1063/1.1662072

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A new interferometer concept has been successfully applied to the measurement of dynamic response associated with thermally induced stress waves. The technique involves the use of two Michelson interferometers to simultaneously measure front and back surface displacements of a specimen exposed to an intense electron pulse. Application of the method to porous copper (86 and 70% of the theoretical density) has resulted in dynamic data over an energy range spanning elastic and plastic behavior of the porous material. These data were compared to the predictions based on a hydrodynamic model for stress wave generation and propagation in a porous medium. The results indicated semiquantitative agreement, complete agreement not being possible using a single set of porous material model parameters. The study demonstrated that some important differences exist in porous material response to constant volume heating and planar plate impact loading. Finally, the results indicated that the double interferometer technique is uniquely suited to simultaneously studying thermally generated stress and attenuation in complex materials.

ISSN:0021-8979    

DOI:10.1063/1.1662073

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Hot ion implantation as a doping technique was used for the fabrication of visible‐light‐emitting diodes with GaAs1−xPx(x= 0.38 ± 0.01). Zinc ions,p‐type dopants, were implanted inton‐type (001)‐oriented heteroepitaxially grown Ga(AsP)‐on‐GaAs substrates at 400°C with an energy of 20 keV. Then, thermal treatment at various temperatures was carried out on the sample in order to investigate the effect of annealing on the electrical properties of Zn‐implanted layers in the Ga(AsP) substrate. Thep‐type layer, which was obtained by the ion implantation of 2 × 1015Zn ions/cm2with subsequent annealing at 900°C for 40 min, was found to have an effective surface concentration of 1.7 × 1015carriers/cm2and a sheet resistivity of about 100 &OHgr;/sq. Red‐light‐emitting Ga(AsP) diodes fabricated using Zn ion implantation have usually shown an average brightness of 400–600 fL, and sometimes as high as 850 fL at a current density of 10 A/cm2. Diodes, which were formed by means of a standard Zn diffusion technique in an evacuated ampoule at 750°C for 30 min using a ZnAs2source, had an average brightness of 350–500 fL at the same current density.

ISSN:0021-8979    

DOI:10.1063/1.1662074

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A series of CuGaS2crystals were annealed in excess sulfur at temperatures between 250 and 850°C. This treatment varies the room‐temperature hole density from 5 × 1015cm−3to 2 × 1018cm−3. From the temperature dependence of the resistivity, the acceptor ionization energies of several representative samples were determined. The energy increases from 5 to 70 meV as a function of increasing resistivity.

ISSN:0021-8979    

DOI:10.1063/1.1662075

出版商:AIP    

年代:1973

数据来源: AIP