摘要:

The formation of argon plasma in crossed electric and magnetic fields in a cylindrical diode with an incandescent cathode has been studied by means of the delay time of the anode current pulse and photon pulse (corresponding to the optical transitions) and the shape of the voltage collapse. The working conditions were: pressurep=10−5–10−3Torr, anode voltageUa=800 V, and maximum magnetic fieldBmax=1200 Gs. Photoelectrical recording of spectral lines was performed with a monochromator in the wavelength range 3600–6000 A˚, and the total optical spectrum was recorded simultaneously on a photoplate in a separate spectrograph in the wavelength range 2000–10 000 A˚. The delay time of the anode current pulse and photon pulse are approximately the same and are in the millisecond range. The delay time of the photon pulse does not depend on the wavelength. Simultaneously the spectral lines of the working gas (A II), residual gas (O II), and tungsten (W I) appear. Tungsten atoms appear at the moment of breakdown as a result of ion bombardment of the cathode. Neutral atomic lines of the working gas (A I) have not been observed. Radial analysis shows that the delay time of the photon pulse does not depend on the radius. Spectroscopic results have been analyzed in terms of excitation and ionization processes during the formation time. The shape of the voltage collapse suggests the streamer breakdown mechanism.

ISSN:0021-8979    

DOI:10.1063/1.327973

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An experimental study is presented for the dependence of the breakdown voltage and the prebreakdown current on the crossed electrical and magnetic fields in vacuum. The magnetic field is varied in the range 0–250 G and the gap separation 0.5–3 cm. Bruce profiled copper electrodes which have been prebaked either in vacuum or hydrogen were employed. The breakdown voltage and the prebreakdown current are presented as functions of the magnetic flux density at fixed gap separation as well as at fixed flux density as functions of the gap separation. Comparison is made between these functions and curves calculated from the theory of the magnetic perturbation of the field emission from protrusions covered with semiconducting oxide layers and good agreement is obtained.

ISSN:0021-8979    

DOI:10.1063/1.327974

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The results of a diode fed by a medium energy pulsed electron gun are reported. Brief explanations of several behaviors of the electron emission from cold cathodes and electron flow in the diode region with energy in the range of 20–100 keV are presented.

ISSN:0021-8979    

DOI:10.1063/1.327975

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A method for calculating the diffracting efficiency of the convex curved‐crystal spectrograph is presented. Experimental data and calculated values are given for elastically curved potassium acid phthalate (KAP) and plastically curved LiF. The calculation method accounts for extinction and anomalous scattering effects. The principal area of application is expected to be diagnostics of the x radiation emitted by hot plasmas.

ISSN:0021-8979    

DOI:10.1063/1.327976

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Simple equations are used to infer approximate values of the major parameters of an unusual plasma which was used by Rashleigh and Marshall to accelerate 3‐g macroparticles to high velocities (5.9 km/s). Subject to the assumptions made here, these results indicate that for the applied current of 300 kA and generated pressure of 1.1×108N/m2, the temperature of the ionized copper plasma was 4413 kK and the electron number density was (81)×1025m−3. It is recommended that future experiments of this type should incorporate instrumentation techniques which can provide direct experimental evidence on these parameters.

ISSN:0021-8979    

DOI:10.1063/1.327977

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Liquid crystal alignment on thin films obliquely deposited by electron beam evaporation of SiO2is reported. Films deposited at a glancing angle of 5° give high tilt alignment ?45°, while increasing the deposition angle to 30° gives zero tilt alignment. Scanning electron microscope (SEM) pictures relate surface topography to alignment. The material and temperature dependence of tilt are reported. The tilt is constant through the nematic‐smecticAtransition.

ISSN:0021-8979    

DOI:10.1063/1.327978

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

High‐resolution diffraction utilizing an analytical electron microscope has been employed to identify small (∼500 A˚‐diam) precipitates attached to line dislocations in gallium arsenide. The results show that the precipitates consist of crystallites of elemental hexagonal arsenic embedded within the gallium arsenide matrix. Precipitates were observed in a range of semi‐insulating, p‐type, and n‐type material and were not dependent on the presence of specific additional dopants for their occurrence. The way in which the particles may originate is discussed.

ISSN:0021-8979    

DOI:10.1063/1.327979

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The effect of gamma ray irradiation on the density, refractive index, thermal expansion, and helium permeability of a variety of commercial borosilicate glasses has been measured for doses between 108and 1011rad. The radiation‐induced densification of these glasses for a constant dose can vary by as much as factor of 30 and appears to increase with increasing boron content of the glass. The refractive index also increases with dose and appears to be related to the change in density via the Lorentz‐Lorenz equation. The thermal expansion coefficient decreases with increasing dose for any given glass, and appears to vary inversely with the density change on a universal plot of change in thermal expansion coefficient versus change in density. Although the helium permeability was only measured for a few of the glasses, it appears that it is unaffected by radiation‐induced compaction of the glass. These effects are believed to result from the phase‐separated morphology of these glasses and from the less rigid nature of the network of one of these phases.

ISSN:0021-8979    

DOI:10.1063/1.327980

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

For amorphous SiO2and Si3N4the Auger spectra were measured and an interpretation of the Si(LVV) spectra is given based upon electron energy‐level schemes, derived from electron energy‐loss spectroscopy results obtained at the same samples. For Si‐nitride the effect of oxygen content (O/N from 0.02 to 1) and Ar+ion bombardment was studied and it is shown that discrepancies between the spectra of different authors are mainly due to these effects.

ISSN:0021-8979    

DOI:10.1063/1.327981

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Soft x‐ray vacuum ultraviolet spectroscopy (10–600 eV) has been used to study relativistic electron beam energy deposition in 6‐&mgr;m Au foils mounted in two different anode geometries. Experimentally determined thermal electron temperatures of 173 eV and 306 eV are in agreement with calculations assuming electron energy deposition rates of 5×1013W/g and 1014W/g for the two geometries. These results are consistent with electrons multipassing through the thin foils several times.

ISSN:0021-8979    

DOI:10.1063/1.327982

出版商:AIP    

年代:1980

数据来源: AIP