摘要:

The ion acoustic‐wave response to an impulse excitation applied to an antenna is examined experimentally. Dispersion is found to determine the radiation characteristics.

ISSN:0021-8979    

DOI:10.1063/1.329238

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Volume‐produced H−ions have been extracted from a multicusp ion source. In addition, a molybdenum converter is installed in the source to generate surface‐produced H−ions. Without cesium, the production of H−ions by the surface process is very small compared with those generated by volume production. However, the presence of cesium can greatly enhance the surface production yield. The energy spectrum shows that the surface‐generated H−ions contain two distinct groups when cesium is added to the discharge. The energy of one group is essentially that of the sheath potential and appears to be produced by a desorption process. The second group of H−ions has a slightly higher energy and appears to be formed by a reflection process. Different types of converter materials have also been tested.

ISSN:0021-8979    

DOI:10.1063/1.329239

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The breakdown voltages of some electron attaching gases and gas mixtures have been calculated from their fundmental properties such as ionization and attachment cross sections, the momentum transfer cross section, the drift velocity or the mean energy of electrons. The calculated breakdown voltages in SF6, N2O, SF6+N2, and SF6+N2O gas mixtures, on the basis of Maxwellian electron energy distribution, agree very well with the measured values. The good agreement between the calculated and measured values shows that the mean energies of electrons in SF6+N2corresponds to that of SF6up to 90% concentration of N2in the mixture, whereas the mean energies of electrons in SF6+N2O mixtures correspond to that of the majority gas.

ISSN:0021-8979    

DOI:10.1063/1.329240

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Warburg’s law, which describes the distribution of the current density over the plane electrode for a point to plane steady corona discharge, is derived. The derivation is based on a model using hyperboloid point to plane geometry with a constant charge carrier mobility model and a time independent potential. The derived relation is shown to be in exact agreement with the empirical law when the calculations are done for an infinite plane electrode.

ISSN:0021-8979    

DOI:10.1063/1.329241

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The paper gives a survey of numerical values of the most important parameters at the copper arc‐cathode root and in the cathode‐fall region. The radius and the temperature of the arc‐cathode root, the electron current fraction, the electric field, the thickness of the cathode‐fall region, and the atom density in this region are theoretically calculated and shown as a function of the arc current. Furthermore, there is a short section describing the suggestion that after neutralization of ions on the boiling surface of the cathode root, all of the resulting atoms may be reflected away into the cathode‐fall region.

ISSN:0021-8979    

DOI:10.1063/1.329196

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The removal of electrode material by electric discharges in a dielectric liquid is usually performed with a short interelectrode gap (about 50 &mgr;m) and short discharge durations (20–2000 &mgr;s). It is therefore virtually impossible to measure the anodic and cathodic voltage drops of such discharges. However, considering that there is a direct relation between the amount of electrode material removed and the electric energy provided in the anodic (or cathodic) region, an indirect determination of those voltage drops is obtained by comparison of experimental results concerning mass loss at the electrodes and the molten volume computed after a linearized heat‐conduction model. The results obtained are in agreement with the measured value of the total interelectrode voltage drop.

ISSN:0021-8979    

DOI:10.1063/1.329197

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The detailed properties of strain distributions in Ne+, B+, and He+implanted magnetic bubble garnet materials are accounted for by calculating the nuclear energy loss as a function of depth. The calculation is based on stopped ion distributions for ZnS, with suitable corrections made for differences in material density. The constant of proportionalityKbetween strain and nuclear energy loss, and the density ratiolare determined for each ion by comparing calculated strain distributions with experimental results obtained previously using an x‐ray diffraction technique. It is found thatKis roughly the same for all three ions, 0.016±0.003 (eV/A˚3)−1, and that the average valuel= 0.79±0.08 is consistent with the actual density ratiol= 0.72. Good agreement is found in additional examples of both single and multiple implants (±10% relative error). Finally, a procedure for selecting the incident energies and dosages required to produce a uniformly strained layer for bubble device applications is described, and then demonstrated by achieving a 0.4‐um‐thick layer with (1.07±0.09)% strain, using a double B+implant.

ISSN:0021-8979    

DOI:10.1063/1.329198

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Cholesteric and nematic liquid‐crystal electro‐optic cells are described which function as both UV shutters and as tunable fluorescent emitters ( shutter cells ). Two‐color displays of blue‐green, blue‐red, or green‐red are achieved in the double‐layered structure of the shutter cell with an external passive fluorescent element. Contrast ratios of about 5 in these two‐color pairs are achievable by electrically switching the shutter cell. Display characteristics for several fluorescent guest materials are measured and their dependence on various system parameters is discussed. Multicolor fluorescent displays are made by using a triple‐layered structure of shutter cells and passive elements.

ISSN:0021-8979    

DOI:10.1063/1.329199

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Theoretical and experimental contrast ratios are compared for homogeneous‐to‐homeotropic liquid‐crystal cells containing fluorescent dye molecules activated by ultraviolet light. Two‐color fluorescent displays are described in which one  active  fluor dissolved in the liquid crystal is used as a UV shutter to switch a passive fluor external to the cell. Contrast ratios of about 8 have been achieved simultaneously for both colors, if two polarizers are used and about 7, if only one polarizer is employed.

ISSN:0021-8979    

DOI:10.1063/1.329200

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Depth distributions, range‐energy curves, and the Pearson IV moments are given for Cr implantation into crystalline GaAs and Si as a function of ion energy from 40 to 600 keV at 4×1013cm−2fluence, and as a function of ion fluence from 4×1012to 2×1016cm−2at 300‐keV ion energy. The nature of the redistribution of these Cr profiles upon annealing at 840 °C for 20 min in both GaAs and in Si are shown and agree qualitatively in the two materials. Two general types of redistribution occur for 4×1013cm−2fluence, one for ion energies below and one for energies above about 100 keV.

ISSN:0021-8979    

DOI:10.1063/1.329201

出版商:AIP    

年代:1981

数据来源: AIP