摘要:

An arc model for a high‐pressure sodium lamp is developed which relates the position of the peaks of the self‐absorbed 3S‐3Psodium resonanceDline to the operating densities and pressures of sodium and mercury. Vapor pressure equations for a Na‐Hg amalgam are derived and used to relate the pressures to the temperature and molar ratio of the amalgam reservoir. Allowing for change in amalgam composition due to preferential evaporation of Hg, the amalgam and vapor pressure data are then related to the total amounts of Na and Hg in the arc tube. In order to obtain agreement with experimental data forD‐line widths between 25 and 200 A˚, it is found necessary to maintain the distinction between the two doublets of the NaDline. In addition, it is shown that the effect of the temperature profile is practically negligible in relating the peak shifts to the average Na and Hg densities.

ISSN:0021-8979    

DOI:10.1063/1.334482

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Experimental results on the collective acceleration of ions using a relativistic electron beam (0.5 MeV, 30 kA, 60 ns) are presented. A gas cloud consisting of either H2, He, or N2gas was used as the ion source. Ion species, charge state, and energy were measured. Ions were accelerated as derived from the hydrogen and helium gas sources but not from the nitrogen gas source. In almost all shots significant numbers of hydrogen and carbon impurity ions were accelerated. The electron beam exhibited asymmetric propagation characteristics in the region immediately downstream from the anode.

ISSN:0021-8979    

DOI:10.1063/1.334483

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Etching of silicon and SiO2has been investigated in a dc plasma discharge confined by a multipolar surface magnetic field layer. The reactive plasma is produced by primary ionizing electrons drawn from heated tungsten filaments and confined by permanent magnets. Electrical probe measurements show that a uniform high‐density plasma (1010–1011cm−3) is sustained in SF6‐O2at very low pressure (0.2–2.0×10−3Torr). Substrates are biased independently of plasma production by a low‐frequency alternating voltage (0–400 V) applied to the substrate through a blocking capacitor. Anisotropic profiles are etched into Si in SF6‐20% O2with etch rates in excess of 1 &mgr;m/min at 2×10−3Torr. The etch rate increases with increasing primary electron current (up to 3 A) and energy (up to 60 eV), gas pressure (up to 2.0×10−3Torr), substrate bias voltage, and the addition of up to 20% O2. For higher ionizing electron energies (>60 eV) and higher gas pressure (>2.0×10−3Torr), etching is partially blocked by residue formation. The etch anisotropy depends mainly on substrate bias, increasing for higher values of bias voltage. The Si:SiO2etch selectivity is typically 10–20, becoming large with decreasing substrate bias and plasma ion density.

ISSN:0021-8979    

DOI:10.1063/1.334484

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this paper we report a technique for generating a large, homogeneous volume of ionized gas and for making time‐resolved measurements of its electron density. We also report absolute photoionization coefficients for a number of molecules. These coefficients will allow calculation of peak electron densities obtained in other ionization‐related experiments. In our technique, the beam from a rare‐gas halogen laser photoionizes organic molecules that have been seeded into a buffer gas. Ionization is accomplished by the absorption of two photons. We have analyzed the electron densities produced by photoionization with a microwave interferometer that measures the electron density in the ionized gas with a time‐resolution of a few nanoseconds. Some of the organic molecules photoionized in this work produce electron‐ion pairs with an efficiency more than five orders of magnitude higher than commonly used laboratory ionization sources such as ArF laser photoionization of NO. We have also studied the effect of attaching gases on the ionized mixtures and have demonstrated that addition of as little as 10 Torr of SF6can reduce the peak electron density observed by a factor of 103.

ISSN:0021-8979    

DOI:10.1063/1.334485

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Seven donors (Si, S, Ge, Se, Sn, Te, and Pb) and nine acceptors (Be, Mg, Cr, Mn, Fe, Cu, Zn, Cd, and Hg) have been implanted into liquid‐encapsulated Czochralski InP(Fe). For each dopant, the first four moments of the density profile have been extracted by fitting Pearson IV distributions to secondary ion mass spectrometry data. The results suggest that, when implanting into indium phosphide at reduced energies not too far from 1, the mean will be 1/5 larger than the theoretical prediction and the standard deviation will be twice the theoretical prediction.

ISSN:0021-8979    

DOI:10.1063/1.334432

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Channeling‐radiation spectra produced by planar‐channeled, 30.5‐MeV electrons in Type‐Ia and Type‐IIa natural diamonds have been measured and are compared with previous results for 54.5‐MeV electrons. Because of the presence of platelets precipitated along the (100) planes in the Type‐Ia diamond, the energies of the (100) spectral peaks are shifted downward relative to those for the Type‐IIa diamond. We have developed a model to explain this effect.

ISSN:0021-8979    

DOI:10.1063/1.334433

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Quasi‐isentropic (QI) compression can be achieved by loading a specimen with a low strain rate, long rise time uniaxial strain wave. Recent experimental data show that the quasi‐isentrope of 6061‐T6 aluminum lies a few percent above the principal Hugoniot, that is, at a given specific volume, the QI stress exceeds the principal Hugoniot stress. It has been suggested that this effect is due to material strength. Using Hugoniot data, shock‐reshock, and shock‐unload data for beryllium and 6061‐T6 aluminum, we have constructed the quasi‐isentropes as functions of specific volume. Our results show that the QI stress exceeds the principal Hugoniot stress above a Hugoniot stress of 8.4 GPa in beryllium, and between Hugoniot stresses of 3.8 and 21.4 GPa in aluminum. The effect is due to strength and implies that the QI yield strength can be large. Our calculations show that the QI yield strength is 0.9 GPa in aluminum at a QI stress of 9 GPa, and 5.2 GPa in beryllium at a QI stress of 35 GPa.

ISSN:0021-8979    

DOI:10.1063/1.334434

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Free standing, doubly supported micromechanical beams which are fabricated from films with built‐in compressive strain fields buckle at critical geometries. Experimental determination of the onset of buckling for known geometries leads to a direct measurement of the strain level in the films. This idea is supported by appropriate theory for experimental structures which form clamped, doubly supported beams with constant cross section and varying lengths. Application to low pressure chemical vapor deposition polysilicon leads to the conclusion that strain fields of 0.2% reduce to 0.05% during annealing.

ISSN:0021-8979    

DOI:10.1063/1.334435

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Shock‐induced luminescence from lithium niobate has been studied in the stress range 1.6–21.0 GPa. Both fast‐framing photography and five‐channel optical pyrometry were used to observe the luminescence. The framing photography showed that the emission pattern is heterogeneous for stresses just above the dynamic yield point. A further increase of the stress resulted in a pattern which was essentially homogeneous to within the experimental spatial resolution of about 30 &mgr;m. Narrowband filters and photomultiplier tubes were used in the optical pyrometry experiments. A broadband spectrum with a peak near 700 nm was observed. A plot of the energy dissipated by the shock versus shock stress correlates very well with a plot of the 700‐nm intensity versus shock stress. The mechanism for light emission in lithium niobate appears to be closely related to the dynamic yielding process.

ISSN:0021-8979    

DOI:10.1063/1.334436

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Resonances in the current‐voltage characteristics of interferometers with two Nb‐NbOx‐Pb window junctions have been experimentally investigated. The data are compared with the theoretical curves computed both for the voltage and for the magnetic field dependence of the resonance amplitudes. Very good agreement is found in all the range of values of the damping parameter &Ggr;=I0R/Vr, whereVris the resonant voltage andI0andRare the maximum Josephson current and the parallel resistance of each junction. New features that cannot be explained in terms of the existing theory have been observed in devices with larger values of the parameter &bgr;=2&pgr;LI0/&Fgr;0, whereLis the loop inductance, and &Fgr;0is the flux quantum.

ISSN:0021-8979    

DOI:10.1063/1.334437

出版商:AIP    

年代:1985

数据来源: AIP