摘要:

A solution to the heat conduction equation for multidimensional composite media, with discontinuities of thermal properties, and having contact resistance at inclusion interfaces is presented. The temperature is expressed as an integral over sources and boundary surfaces in terms of a Green function. The solution is thereby reduced to solving the related eigenfunction problem for the Green function. This solution is also expressed in an alternative form utilizing a technique developed by O¨lcer which promotes faster convergence of the eigenfunction expansion in regions of discontinuities. The solution technique is summarized, and numerical results are presented for one‐dimensional layered slabs, with and without contact resistance specified at layer interfaces.

ISSN:0021-8979    

DOI:10.1063/1.334472

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A two‐dimensional model of the positive column of a glow discharge in flowing nitrogen is presented. The model is applicable to a cylindrically symmetric and axially nonuniform weakly ionized discharge. Nitrogen ionization mainly results from associative ionization occurring in the collisions of metastable molecules in thea’1&Sgr;−uandA3&Sgr;+uelectronic states. Gas heating explains the lowering of the electric field as the current increases or the flow velocity decreases. Under most conditions, vibrational deactivation results from superelastic collisions between excited molecules and electrons. Electric field, discharge voltage, vibrational and electronic populations, and gas temperature, are calculated as a function of pressure, flow velocity, diameter and length of the discharge, and current. Quantitative comparisons with available experimental data are made. Good agreement is observed for discharges at low pressures in gas flows with low Reynolds numbers.

ISSN:0021-8979    

DOI:10.1063/1.334473

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A new type of high‐power, high‐voltage vacuum opening switch is described. This switch has been used in a magnetic energy storage system with a peak current of 340 kA to produce a 2.7‐MV pulse with a risetime of ∼15 ns.

ISSN:0021-8979    

DOI:10.1063/1.334474

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Research in light‐ion‐driven inertial‐confinement fusion is emphasizing high‐voltage, nonprotonic ions to obtain improved magnetic stiffness. Target preheat by coaccelerated proton impurities is a serious concern. A method is described which should essentially eliminate protonic preheat for applied magnetic field, magnetically insulated (applied‐B) ion diodes. Briefly, the charge state of the principal ion species is changed by passing through a thin foil in the applied magnetic field. Due to the change in canonical angular momentum, the ions’ closest approach to the axis of an axisymmetric diode is different from that of the proton contaminant. This difference provides effective separation of protons from the principal species.

ISSN:0021-8979    

DOI:10.1063/1.334475

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The collective acceleration of deuterons by an intense relativistic electron beam has been studied experimentally. The accelerated ion energy spectra for various different experimental configurations has been measured using stacked foil activation analysis. The spectra extend to energies below the injected electron beam energy, and thus allow estimates of the net efficiency of the acceleration process. The effect of variations in electron beam power and applied magnetic field on the acceleration process are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.334476

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Some of the fundamental properties of the NF3etchant gas discharge were investigated. The dissociation of the parent gas molecules was inferred using mass spectrometric methods, and it was found that the discharge is much more effective at dissociating NF3than CF4. Furthermore, the percentage dissociation of the NF3was extremely large, ∼50%. Using a pulsed discharge it was possible to observe the time evolution of the dissociation products. These studies have led to a mathematical description of the dissociation and product formation kinetics.

ISSN:0021-8979    

DOI:10.1063/1.334477

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is shown theoretically how much the magnetic field influences the collision frequencies between charged and neutral particles. The magnetic fieldBfor the usual field strength does not affect the collision cross section. However, the respective charged particles gyrate around the field lines, and then the relative velocity between charged and neutral particles changes withB. Consequently, it is shown that, when the mean free path &lgr; is large compared with 2&pgr;rL, the velocity component contribution to the collision is the velocity component due to the motion along the field axis and not that due to the gyration. Here,rLis a Larmor radius.

ISSN:0021-8979    

DOI:10.1063/1.334478

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We describe a pulsed CO2laser scattering experiment set up to measure the ion temperature of a magnetically stabilized arc plasma (ne&bartil;1021m−3,Te&bartil;5 eV). Sensitivity and spectral resolution considerations led us to use heterodyne detection with a separate local oscillator and a multichannel rf frequency analyzer. The forward scattering angle is chosen to be 5° in order to match the expected ion feature spectrum to the receiver bandwidth and also to eliminate spontaneous fluctuations from the small‐klarger‐amplitude signal. Experimental scattering spectra illustrate the apparatus sensitivity to discharge current and gas mixture. Ion‐acoustic resonances are resolved as well as the spectral signatures from various mixed ion species plasmas. The ion temperature appears to be determined to ±10% onceTeandneare known from other measurements. Applications to high temperature fusion plasmas are discussed.

ISSN:0021-8979    

DOI:10.1063/1.334479

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A Langmuir probe incorporated with a boxcar averager is used to measure the temporally and spatially resolved electron density and electron temperature in a UV‐photoionization device for several gases and gas mixtures. The predominant ionization mechanism is determined. The data provides information to optimize the effectiveness of the UV preionization operation in high‐pressure lasers.

ISSN:0021-8979    

DOI:10.1063/1.334480

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The performance of externally controlled, high‐pressure, diffuse discharges as switching elements in pulse power systems is strongly determined by the recombination and attachment processes in the fill gas. To obtain high control efficiency and fast response of the diffuse discharge switch the discharge must be attachment dominated with the attachment rate coefficient increasing with field strength. An electron‐beam controlled diffuse discharge system was constructed to study the behavior of pulsed discharges in the submicrosecond range in gas mixtures containing N2as a buffer gas and small additives of electronegative gases. The results of experiments in N2plus N2O were compared with values obtained with a Monte Carlo code and a rate equation calculation.

ISSN:0021-8979    

DOI:10.1063/1.334481

出版商:AIP    

年代:1985

数据来源: AIP