摘要:

Three methods were used to obtain electron density as a function of radius in a magnetically confined, low‐pressure argon arc. The first utilized the phase shift of a reflected 35‐kMc/sec microwave, and the second determined density from the ion saturation current to a Langmuir probe. The third determination utilized the broadening of the H &bgr; line emitted by a small quantity of added hydrogen. Agreement among the three methods is satisfactory; the electron density at the axis of this discharge is of order 1014cm−3, in agreement with results obtained by others for discharges of similar type.

ISSN:0021-8979    

DOI:10.1063/1.1713990

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A direct electrical method for measuring the velocity of a flowing plasma is based upon the polarization voltage induced when a plasma flows transversely to an applied magnetic field. A method has been developed to allow the estimation of certain background signals and the determination of allowable measurement currents arising from plasma and probe properties. Applications for this technique of ionized gas velocity measurements are indicated.It was found that an ac magnetic field of the order of 5 G would give a sufficient signal to determine the gas velocity of a plasma jet as compared to a dc field of the order of 100 G. Gas stream velocities produced by a low‐power argon plasma jet were found to vary from 1000 to 3000 m/sec depending slightly on the mass flow rate and predominantly on the ambient pressure.

ISSN:0021-8979    

DOI:10.1063/1.1713991

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The performance of a ruby laser amplifier is described and compared with a theoretical model. The ruby laser amplifier was driven by aQ‐switched laser oscillator with a stable output, whose properties are due, in part, to a newly developed output coupler and a spinning roof‐top prism forQ‐spoiling. From the theoretical amplifier model, a relation between the population inversion and the energy stored in the system supplying the xenon flash lamps is derived and fitted to the particular laser configuration by a single parameter established by the laser threshold. Experimentally, the gain of the 15‐cm (6‐in.) ruby amplifier saturates at values between 5 and 7, apparently caused by complete pumping of the system rather than limited by the energy input to the flashlamp pump.

ISSN:0021-8979    

DOI:10.1063/1.1713992

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The edges of planar thin‐film strips of tin are shown to limit the supercurrent carrying capacity of the films in some cases. This edge effect is demonstrated by means of a special structure which provides two current flow‐paths through the same film. The film strip edges are included in only one of these two paths. Detailed results are given for a 4400‐Å film of tin in which dc critical currents near the Silsbee limit are observed when the edges are excluded. Including the edges reduces the critical current for this film by more than 30%. It is suggested that an evaporation process can probably be developed which leads to films which will not exhibit this edge effect. The special structure would provide a useful tool for this process development, and it can also be adapted to serve as an improved gate for thin‐film cryotrons.

ISSN:0021-8979    

DOI:10.1063/1.1713993

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The secondary electron yield from fission fragments has been measured directly using an ultrahigh‐vacuum diode containing uranium which was operated in a nuclear reactor. The current measured in this diode consisted of contributions from the positively charged fission fragments, secondary electron emission induced by fission fragments, and photoelectrons generated by gamma radiation. The secondary electron yield &Dgr; was determined from the secondary electron current and the computed fission fragment emission rate. For a thick (>one range) uranium‐nickel (5.7 wt. % nickel) alloy the value of &Dgr; is 207±10.

ISSN:0021-8979    

DOI:10.1063/1.1713994

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A fractional monolayer film of ions is formed by the adsorption of a gas onto a metal substrate. These ions form a discrete dipole layer, the potential across it being the change in electron work function of the surface. As additional ions are brought to the surface, they penetrate only a fractionfof the potential across the dipole layer.In this work the penetration coefficientfvalid for the entire range of coverages is derived for two limiting types of films, immobile and mobile. By considering thermal effects, a penetration coefficient for partially mobile films is also derived. The values obtained for the penetration coefficient are applicable to any substrate‐adsorbate system.The theoretical expressions for the penetration coefficient are evaluated for cesium on tungsten and compared with the data of Taylor and Langmuir.

ISSN:0021-8979    

DOI:10.1063/1.1713995

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A description of the visual characteristics of some constricted discharges in the rare gases using dc, rf, and microwave excitation is given. These discharges require power inputs of from 20 to greater than 100 W/cc. The results of a series of spectroscopic and electrical measurements made on these discharges indicate the range of plasma parameters encountered. Gas temperatures were measured using the intensity distribution of the spectra of several diatomic molecules. The gas temperature falls in the range from 2000° to 3000°K, but atomic excitation levels are not in equilibrium at this temperature. The charge density is around 1014/cc from continuum intensity, line broadening, and electrical measurements. The electron energy distribution is Maxwellian with an average electron energy which falls between 1 and 2 eV. Thus, these plasmas lie between ``thermal'' and ``cold'' plasmas in their properties. The recombination process probably has contributions from both dissociative recombination and dielectronic recombination with an over‐all recombination coefficient of about 2×10−11cm3/sec.

ISSN:0021-8979    

DOI:10.1063/1.1713996

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The macroscopic properties of the rare gas constricted discharges are discussed. For the rf excited discharge an equivalent circuit for the electrode coupling has been found, comprising a capacitor with the electrode and plasma forming the plates and the discharge tube wall the dielectric. An explanation for the observed striations is advanced, based upon the existence of voltage standing waves at the plasma resonance frequency. A numerical analysis based on an energy balance indicates that these discharges should have a finite radius, in this case smaller than the discharge tube radius. It is necessary to require that the electron energy distribution be Maxwellian near the center of the discharge and that deviation from this energy distribution causes the sharp boundary observed for the heavier rare gases. For the microwave discharge it is pointed out that it is necessary to include the electromagnetic field equations in the analysis and that this requirement naturally leads to a maximum radius for asingledischarge channel which is much smaller than for the rf‐excited case. This, in turn leads to an explanation of the multicolumn effect observed.

ISSN:0021-8979    

DOI:10.1063/1.1713997

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The characteristics of the ``synchrotron light'' emitted by electrons in the NBS 180‐MeV electron synchrotron were studied in detail. The electron beam cross section was approximately 1×2 mm. The angular distribution and polarization properties were determined for the visible radiation; photoelectric techniques resulted in a more critical comparison of the experimental results to the theoretical predictions than heretofore possible. Doubts raised by previous work regarding the symmetry of the radiation with respect to the orbital plane have been allayed. Characteristics of the radiation in the extreme ultraviolet are calculated for the NBS machine, and applications of this source for physical experiments are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1713998

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Multimode laser oscillation in the presence of internal resonator modulation is discussed. Modulation of the dielectric constant (&egr;) is shown to lead to frequency modulation of the laser light while modulation of the losses (or gain) leads to amplitude modulation. The results are discussed with particular reference to recent experiments and proposals involving modulation inside laser resonators. The mathematical formalism is that of normal‐mode parametric interactions.

ISSN:0021-8979    

DOI:10.1063/1.1713999

出版商:AIP    

年代:1965

数据来源: AIP