摘要:

A perturbation method for determining electric fields in an inhomogeneous magnetized plasma column is given that removes restrictions on the wavelengths present in previous treatments. The method is also applicable to finite‐amplitude wave problems.

ISSN:0021-8979    

DOI:10.1063/1.325478

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The opacity and radiative‐energy current due to line radiation is calculated for a U235plasma with a temperature range 5000–8000 °K. Also, a variation in the neutron flux of 2×1012to 2×1016neutrons/cm2 sec is considered. The plasma forms a cylinder with a diameter and height of 1 m. Because the electron states in uranium lie below 5 eV, recombination is the principal excitation mechanism. At and above 6000 °K, inversions are found and, at all temperatures, the line radiation at line center is greater than the corresponding blackbody radiation. An example of this is the 28763–5762‐cm−1transition in neutral uranium, where the Planck function at 5000 °K is 6.49×10−6ergs/cm2, and the calculated radiative‐energy current is 1.492×10−4ergs/cm2. Negligible changes in the radiative‐energy current are observed for changes in the neutron flux at a given temperature. The opacity at 5000 °K agrees with Parks’s previous calculations, and recombinational excitation explains the variation in the opacity with temperature.

ISSN:0021-8979    

DOI:10.1063/1.325479

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A new version of a diode simulation code has been written which allows for nonuniform zoning in both therandzdirections. This new flexibility enables more accurate treatment of crucial areas in the diode such as near emission surfaces and in target regions. The new code also has the ability to treat slanted surfaces such as that found in a tapered cathode diode. An interesting result of the new code is that a ’’parapotential’’ cathode pinches better than the corresponding flat cathode at the same total current.

ISSN:0021-8979    

DOI:10.1063/1.325480

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

In the present paper the authors have investigated the transient Thomson scattering of the EM pulses (having Gaussian intensity distribution in space and time) from a collisional plasma with random inhomogeneities. Because of a Gaussian intensity distribution of the pulse in a plane transverse to the pulse propagation, the electrons get redistributed and affect the scattering accordingly. When the power of the pulse is greater than the critical power for self‐focusing, the backscattered power is found to exhibit a maximum at a particular time, dependent on the parameters of the pulse and the plasma.

ISSN:0021-8979    

DOI:10.1063/1.325481

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The ionization and radiation dynamics of dense magnetohydrodynamic plasmas has been modeled in a fashion suitable for implementation in MHD computer simulation codes. It has been shown that more restrictive LTE models such as those based on the Saha equation are inadequate to describe the rapidly varying temperature and density regimes characterizing many such plasmas. Detailed collisional‐radiative models are developed which directly solve the time‐dependent rate equations characterizing atomic processes along with those equations characterizing the hydrodynamic motion of the plasma. These models are applied to analyze high‐density‐heliumZ‐pinch and lithium exploding‐wire plasmas, and they are found to yield results which compare quite favorably with experimental data.

ISSN:0021-8979    

DOI:10.1063/1.325482

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

High‐power (10–100 MW/liter) pulsed discharges in Na‐doped Xe vapor have been studied at Na densities of 1015–1016cm−3and Xe densities of 1019–1020cm−3, as appropriate for excimer‐laser use. Stable steady‐state discharges are obtained for a number of microseconds in a small‐volume cell, without use of preionization or sustainers. This stability is attributed to the observed positiveV‐Icharacteristic. Measured spectra are interpreted to yield Na excited‐state densities, and the implications for a potential excimer laser are discussed.

ISSN:0021-8979    

DOI:10.1063/1.325491

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Ranges of 10–30‐keV deuterons implanted into amorphous C, and polycrystalline Al, Ni, and Zr have been measured via the D(3He,&agr;)1H nuclear reaction. The finite depth resolution, which has been determined separately, was taken into account in the evaluation of the data. Monte Carlo computer calculations have been carried out for comparison with the experimental results. Generally, good qualitative agreement is observed.

ISSN:0021-8979    

DOI:10.1063/1.325492

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The adiabatic single‐crystalline elastic constants of pure niobium, Nb‐Zr, Nb‐Hf, and Nb‐W alloys were determined in the temperature range 77–298 °K. An unusual temperature dependence was noted in the Nb‐rich alloys which may be related to the shape of the Fermi surface. Zr and Hf alloying additions decrease the value ofC′, which indicates decreasing bcc lattice stability. The values of the elastic anisotropy ratioC44/C′ follow the behavior predicted by Fisher, which indicates that the elastic shear moduli are closely related to the filling of thedband. The Debye temperatures &Vthgr;Dwere calculated, and W additions tend to increase &Vthgr;D, while Zr and Hf lower &Vthgr;D.

ISSN:0021-8979    

DOI:10.1063/1.325493

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Complete high‐pressure single‐crystal structure determinations have been performed up to 90 kbar on ruby (Al2O3with less than 0.05 wt&percent; Cr2O3) using an automatic diffractometer. The rhombohedral lattice constantaRis found to decrease linearly within the given error limits fromaR=5.136±0.004 toaR=5.075±0.005 A˚ at 90 kbar. The rhombohedral angle &agr;R=55.30°±0.06° as well as the atom‐position parametersu(Al, Cr) =0.3520±0.0004 for Al (or Cr) andu(0) =0.556±0.003 for oxygen remain constant up to at least 86 kbar. These results are in very good agreement with earlier measurements up to 25 kbar by Schiferl and Jamieson as well as with the Birch and Murnaghan equations of state with the literature values of the isothermal compresssibilityK0and its pressure derivativeK′.

ISSN:0021-8979    

DOI:10.1063/1.325494

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

During the drawing of optical fibers, the maintenance of a uniform fiber diameter is a difficult task. Parameters affecting the diameter variations are the temperature and viscosity distributions within the neck‐down region, the neck‐down shape, and the fiber drawing tension. A physical model is presented that predicts the neck shape and temperature distribution within the neck‐down region during the drawing of a high silica rod into a fiber. The model is formulated by an iterative technique to obtain solutions from the coupled equations of momentum and energy for given fiber‐drawing conditions. It is demonstrated that the predicted values of the viscosity, neck shape, and drawing tension agree well with those of measured values.

ISSN:0021-8979    

DOI:10.1063/1.325495

出版商:AIP    

年代:1978

数据来源: AIP