摘要:

The steady state of a nonisothermal cylindrical discharge in a longitudinal magnetic field is described by three moment equations in the plasma approximation for electrons and ions. Volume generation of electron‐ion pairs by single‐stage ionization, the presence of axial current, and collisions with neutrals are considered. The theory yields radial profiles of the charged particle velocities, density, potential, electron and ion temperatures, and demonstrates similarity laws for the positive column. The results are compared with two‐moment theories and with experimental data on helium, argon, and mercury vapor found in the literature for a wide range of pressures.

ISSN:0021-8979    

DOI:10.1063/1.1662885

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The time variation of the near‐infrared radiation intensity from restrikes of exploding wires was studied for different currents and wire materials. The results show that the peak near‐infrared radiation intensity form the restrike is proportional to the first current maximum and that the radiation reaches its peak slightly after the first current maximum. By using the computed values of the particle density and the temperature of the discharge plasma, it was possible to show that the reason why the radiation from the discharge reaches its peak near the first current maximum may be that the ionized particle density in the discharge channel reaches its peak near the first current maximum.

ISSN:0021-8979    

DOI:10.1063/1.1662886

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The results of a numerical simulation of a dc gas discharge in a mixture of neon + 0.1% argon are presented. The simulation is based upon a Townsend avalanche mechanism (direct ionization) and the ion secondary effect. The effect of the delayed electron due to Penning collision (indirect ionization) in the mixture is fully accounted for. Comparisons with the experimental results of Penning and co‐workers are also made.

ISSN:0021-8979    

DOI:10.1063/1.1662887

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The hydrodynamic equations for a shock wave, propagating in a viscous material, are integrated to obtain an expression for the shock profile under steady conditions. This expression is compared with a similar one reported by other authors, and both are shown to be in reasonable agreement with the available experimental data for shock propagation in aluminum. It is also demonstrated that these expressions for the steady shock profile are different because they are based on different assumptions on the form of the shock‐vs‐particle velocity relationship. It is finally shown that the linear relation used in the present paper is in better agreement with the experimental data on velocities.

ISSN:0021-8979    

DOI:10.1063/1.1662888

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The piezoresistance response of shock‐loaded manganin wire embedded in C‐7 epoxy insulation was experimentally determined over the stress range from 4 to 94 kbar. Manganin stress gauges of this configuration have been used extensively in previous shock wave studies. Interpretation of shock profiles below 50 kbar has been hampered, however, because the relationship between change in resistance and shock stress was not well established. The results of this work show the manganin piezoresistance coefficient to be nonlinear in the low‐stress region, varying from 0.00246 &OHgr;/&OHgr; kbar at 9 kbar to 0.00291 &OHgr;/&OHgr; kbar at 40 kbar. Good agreement was observed between the shock and hydrostatic coefficients up to 9 kbar; the piezoresistance data above 40 kbar agreed with previously published high‐stress results. The nonlinear increase in the manganin piezoresistance is attributed to defects generated in the wire by plastic deformation accompanying the shock loading. The stress‐particle velocity response of the C‐7 epoxy used in the stress gauge was also characterized, with Hugoniot and release adiabat data being generated. The epoxy Hugoniot data were significantly different from previously reported data for stresses below 20 kbar.

ISSN:0021-8979    

DOI:10.1063/1.1662889

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The effective modulus of rigidity &mgr;* of dilutely dispersed systems of spherical shell structures, consisting of the shell region and the inside region, is calculated for the finite thickness of the shell, taking account of material compressibility.

ISSN:0021-8979    

DOI:10.1063/1.1662890

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Flat‐plate impact experiments were performed on polycarbonate specimens to produce various levels of fracture damage. Nucleation and growth functions for incipient shock damage were deduced from the observed damage and from measured and computed stress histories. These functions allow quantitative prediction of the shock damage produced by arbitrary stress histories in polycarbonate.

ISSN:0021-8979    

DOI:10.1063/1.1662891

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The application of a phenomenological depth‐dose theory to the exposure of negative electron resists is described in detail. The model predicts a cross‐linking ratednc/dt=(Gc/100) × (J0/e)(Va/RG)&Lgr;(f) cm−3sec−1, whereGcis the number of crosslinks produced per 100 eV lost in the polymer.Jois the incident current density,Vathe initial kinetic energy,RGthe electron Grun range, and &Lgr;(f) the depth‐dose function in terms of the normalized penetrationf=z/RG. Since theGvalue of a negative resist decreases with exposure, it is suggested that a more meaningful parameter characterizing a negative resist is the absorbed energy required to gel the polymer at the resist‐substrate interface. This interface or threshold gel energy density,Eg(i), is independent of the beam parameters and varies from about 1022eV cm−3for polyvinyl ferrocene to 3.8×1018eV cm−3for epoxidized polybutadienes. The model predicts that the threshold sensitivity should vary asVa0.75which agrees reasonably well with published experimental values. It also predicts that at a given accelerating voltage, there is a unique initial resist thickness at which the top surface and interface receive identical doses. This unique thickness turns out to be roughly the electron diffusion rangeRD. The transverse resolution or linewidth for negative resists has been investigated as a function of accelerating voltage and found to be given by twice the diffusion range. SinceRDdecreases with decreasingVa, the linewidth likewise decreases as the accelerating voltage is lowered. The optimum operating conditions for a 500‐nm resist film for electron lithography are predicted to beVa≈5 kV exposed to yield about a 400‐nm film after development. It should be noted that these conditions result in a maximum crosslink density per incident electron and a minimum linewidth. However, there may be specific applications where other sets of operating conditions are useful. A geometric model is suggested which appears to account for the observed behavior of sensitivity of negative resists.

ISSN:0021-8979    

DOI:10.1063/1.1662892

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A study has been made of the use of low‐voltage exposure of negative resists for electron lithography. Three resists have been investigatd; an esterified terpolymer, epoxidized polybutadiene, and polyglycidyl methacrylate. The optimum exposure conditions have been determined for each material, and the use of a low accelerating voltage (5 kV) found to be advantageous. The application of this technique for the pattern delineation of silicon dioxide and tungsten is described.

ISSN:0021-8979    

DOI:10.1063/1.1662893

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The elastic moduli of bulk polyethylene having a spherulitic structure are determined by the multistep method described in a previous paper. It is pointed out that the properties of the regular symmetrical spherulite are spherically isotropic (that is to say, the properties are the same in all directions tangent to a series of concentric spheres) and can be characterized by the same elastic constants as those of a cylindrical spherulite. The effective moduli of spherulitic polyethylene are then computed from the properties of individual spherulites by the self‐consistent scheme of Hershey, Kerner, and Kroner. The results agree very well with existing experimental data for Young's modulus and shear modulus. The predicted bulk modulus is found to be strongly dependent on the estimated Poisson's ratio of amorphous polyethylene.

ISSN:0021-8979    

DOI:10.1063/1.1662894

出版商:AIP    

年代:1973

数据来源: AIP