摘要:

The plasma potential of 13.56‐MHz low‐pressure argon glow discharges has been measured for various modes of applying the rf power in a geometrically asymmetric planar system. The plasma potential is determined from the energy distribution of positive ions incident on the grounded electrode. The voltages on the excitation electrode (target electrode) are carefully measured and the capacitive sheath approximation is used to relate these measured voltages to the measured plasma potential. This approximation is successful in most of the situations encountered in this low‐pressure (20 mTorr) relatively low‐power density regime. The effects of superimposing dc voltages on the excitation electrode are discussed.

ISSN:0021-8979    

DOI:10.1063/1.335396

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Experiments were performed measuring beam current, magnetic field, and energy of a 400‐keV relativistic electron beam propagation in air in a 7.6‐cm‐diam glass guide tube, the same covered with a conducting screen, and in a 3.4‐m‐diam chamber. Nose‐erosion rates, current neutralization, and stability data are given at various pressures. A propagation window exists between pressures of 270–1070 Pa. At the lower pressures, propagation is limited by nose erosion, whereas at higher pressures, propagation is limited by instability of the tail. The conducting screen stabilizes the tail of the beam, extending the high‐pressure end of the window to ∼6000 Pa. Rectilinear propagation within 5 mrad occurs in the large chamber at 270–800 Pa.

ISSN:0021-8979    

DOI:10.1063/1.335397

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Calculations of high‐explosive (HE) driven plasma opening switches have been extended to two dimensions. The goal of our calculations is to determine the role of mixing in the resistance increases that are observed experimentally. We have not included a magnetic field, but have looked at the hydrodynamics of the interface between the cool HE detonation products and the hot plasma. Our calculations indicate that significant mixing can occur if perturbations exist along the interface. We estimate the sensitivity of our results to the wavelength and amplitude of these perturbations.

ISSN:0021-8979    

DOI:10.1063/1.335399

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The contribution of the ionization from the two metastable and the two resonance levels of argon to the total ionization rate in a low‐pressure argon positive column is investigated theoretically and experimentally. A simple yet self‐consistent discharge model is developed by coupling the balance between the electron total production and loss rates to the steady‐state rate balance equations for the excited states. The predictions of this model, i.e., the maintenance field for the positive column and the populations in the individual excited states as a function of the gas pressure and the discharge current are compared with the experiment (0.05<p<1 Torr; 0.2<I<20 mA; &fgr;=2.6‐cm‐i.d. discharge tube). It is shown that stepwise ionization becomes predominant for pressures larger than a few tenths of a Torr even for the lowest currents of this experiment. The predicted values of the maintenance field are considerably lower than those that would be required to sustain the discharge by ground‐state ionization and compare favorably with the measurements. The calculated populations in the metastable states also compare reasonably well with the experiment. The discrepancies are, however, quite large in the case of the resonance levels owing, presumably, to the lack of accuracy of the theoretical escape factors for the resonance radiation.

ISSN:0021-8979    

DOI:10.1063/1.335400

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Up to now, the production of plasma columns through the propagation of electromagnetic surface waves had been reported essentially in the microwave range (200 MHz–10 GHz), with tube diameters that extend from 0.5 to 40 mm. Such plasmas can be obtained at much lower frequencies, at least down to 27 MHz. We also present larger plasma column diameters, up to 124 mm, as well as column lengths up to 6 m. The surface wave dispersion and the axial electron density distribution observed under these new conditions are well described by the cold plasma model.

ISSN:0021-8979    

DOI:10.1063/1.335401

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The influence of In diffusion on resistance stability of AuIn2thin‐film resistors was studied and the mechanism for resistance change was clarified. When resistors with In concentration below that of AuIn2were in contact with Pb‐In‐Au alloy interconnection lines, In diffused from the Pb alloy into the resistors. This diffusion caused grain growth in the In‐diffused zone, in addition to a phase change from an AuIn and AuIn2mixture to AuIn2single phase. The In‐diffusion‐induced grain growth decreased film resistivity because resistivity is mainly determined by grain‐boundary scattering. When the resistor was preannealed before being connected to interconnection lines to saturate grain growth, excellent resistance stability was obtained even though In concentration shifted by ∼2 wt. % below AuIn2stoichiometry.

ISSN:0021-8979    

DOI:10.1063/1.335348

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

SnOxfilms with different values ofxwere deposited by rf sputtering. Secondary emission yield &dgr;, physical density &ggr;, and electrical resistivity &rgr; of the films were investigated. Higher values of &dgr; than those of bulk SnO and SnO2were found. From the experiment it results that &dgr;, &ggr;, and &rgr; increase with the increase ofx. The crossover energyEc, the primary electron energy for &dgr;=1, decreases withx. Analysis of the experimental data and theory leads to the conclusion that the main factor which determines the maximum secondary electron emission yield &dgr;mis the ratio between the escape probability and the work function.

ISSN:0021-8979    

DOI:10.1063/1.335503

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Microwave energy stored in a superconducting cavity is released to an output circuit in a short time by a gas discharge switch which is different from previous works. Output pulse of 350 times the input cw power fed to the cavity is obtained. A cw microwave is incident on a superconducting lead cavity of TE011cylindrical mode with resonant frequency 2.868 GHz and unloadedQof 3.8×106. A small semicircular glass tube with two electrodes and with rarefied helium gas is set inside the cavity. Pulsed discharge current of the order of 100 A and time width 0.4 &mgr;sec produces high‐density plasmas which may be equivalent to a metal loop antenna. Large microwave output pulses of time width 0.17 &mgr;sec are produced. It is suggested that the apparatus may be extended to millimeter microwave pulse production.

ISSN:0021-8979    

DOI:10.1063/1.335381

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The maximum supercurrent through a long and narrow Josephson junction has been calculated numerically as a function of an applied magnetic field for various feed current distributions. The results have been shown to depend drastically on the mode of the current feed. In particular, the real nonuniform distribution &eegr;ov(x) of the current corresponding to the overlap geometry of the junction is nearly equivalent to the mixturey&eegr;un+(1−y)&eegr;inwith the factoryapproaching unity as the junction length increases: (1−y)=Cy(L/&lgr;j)−0.5,Cy&bartil;1.7. In contrast with the static properties, the shape of the zero‐field step in the long junctionI‐Vcurve appears to be almost independent of the mode of the current feed, because of averaging of the Lorentz force by the travelling Josephson vortices.

ISSN:0021-8979    

DOI:10.1063/1.335383

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The hydrostatic piezoelectric coefficientdhhas been measured for biaxially‐oriented poly(vinylidene fluoride) transducers using pressure pulses having peak values of 1.8×107Pa (2600 psi) and a pulse width of approximately 10 ms. For these measurements, the sample was placed in an oil pressure chamber at room temperature and the pressure pulse was initiated by dropping a 16‐kg mass onto a plunger in the chamber. Since adiabatic compressional heating accompanies the pressure pulse, temperature compensation of the transducer was necessary. This was achieved by incorporating a thermocouple in the bilaminate configuration of the transducer and by amplifying the thermocouple signal appropriately to account for the pyroelectric response due to adiabatic heating, which was approximately 15% of the transducer signal. The calculation ofdhshows that the response of the bilaminate transducer is linear up to 1.8×107Pa (2600 psi).

ISSN:0021-8979    

DOI:10.1063/1.335384

出版商:AIP    

年代:1985

数据来源: AIP