摘要:

During Ti:LiNbO3integrated optical waveguide fabrication the (Ti0.65Nb0.35)O2forms at temperatures ranging from 700 to 950 °C, after the Ti oxidation which occurs owing to Ti reaction with oxygen atoms of the surrounding atmosphere and/or of LiNbO3substrates. The (Ti0.65Nb0.35)O2compound has been characterized using scanning electron microscopy, secondary ion mass spectrometry, Auger electron spectroscopy, Rutherford backscattering in channeling conditions, and x‐ray diffraction. Results show that the (Ti0.65Nb0.35)O2phase grows epitaxially on bothZ‐ andY‐cut substrates, the quality depending on both annealing atmosphere and film thickness. The film behaves as a real source for Ti diffusion and consequently is consumed at increasing annealing temperatures and/or times. We did not observe Li‐Ti‐O compounds, although a small amount of Li was detected in the surface layer.

ISSN:0021-8979    

DOI:10.1063/1.331687

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A thin film thermoelectric device was used to study gas‐solid transient heat transfer under conditions identical to those used for photoacoustic measurements. Although the species and pressure dependence agreed qualitatively with conventional theory, quantitatively our measured heat exchange is about a factor of two larger. We attribute the discrepancy to the neglect gas viscosity.

ISSN:0021-8979    

DOI:10.1063/1.331688

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We report the confined compression strengths and Young’s moduli of coal and roof rock from the Upper Freeport seam, Lucerne No. 6 Mine, Homer City, Pennsylvania, the Lower Kittanning seam, Kitt No. 1 Mine, Phillipi, West Virginia, and the Soldier Canyon seam, Soldier Canyon Mine, Price, Utah. A total of 210 tests to failure in biaxial compression were performed at confining pressures of 0.1, 3.0, and 10.0 MPa. The strengths increase by a factor of 2–3 over the confining pressure range, while the Young’s moduli are about constant. Standard deviations are 10–30% of the mean, emphasizing the need to do many tests. Failure in all three coals is brittle, progressing from dilational to multiplane shear to single‐plane shear on increasing confining pressure. Strengths and moduli could not be correlated with such macroscopic inhomogeneities as large cracks, voids, and compositional changes.

ISSN:0021-8979    

DOI:10.1063/1.331689

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The generalized formulas have been derived for the curvature radius and layer stresses caused by thermal strain in semiconductor multilayer structure with different elastic moduli and growth temperatures. Several special forms and applications are given.

ISSN:0021-8979    

DOI:10.1063/1.331690

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Observations show that the frequency of breakdown of the tube, when it is immersed in a 60‐Hz alternating field, is determined by the potential drop along the tube, an effect which can be explained by assuming that the tube wall acts as a lossless guide for the breakdown discharge.

ISSN:0021-8979    

DOI:10.1063/1.331691

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The operation of a pinch‐reflex diode as an intense pulsed ion‐beam source has been scaled up to the multiterawatt PITHON generator. Ion beams with currents of 1 MA at 1.8 MeV have been extracted in a 130 kJ, 100‐ns pulse. The corresponding ion production efficiency is 60%. Power losses were observed in interfacing the coaxial diode to the biconic vacuum feed of the generator. By using smaller area diodes, the average current density at the anode source was increased to 20 kA/cm2. Proton and deuteron beams were studied in both planar and spherical diode geometries. The ion beam is focused predominantly by self‐magnetic fields for planar diodes and predominantly by electrode shaping for spherical diodes. Current densities exceeding 150 kA/cm2were achieved with spherical diodes. The spatial evolution of the anode and cathode plasmas was studied by laser holographic interferometry. As the peak of the power pulse is approached, plasmas were observed to expand from the electrodes in fairly uniform profiles with steep density gradients and to accelerate across the vacuum gap. After peak power, anode plasma fluctuations and a high‐velocity (30 cm/&mgr;s) axial plume develop; the latter expands radially coincident with collapse of the power pulse.

ISSN:0021-8979    

DOI:10.1063/1.331692

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Microwave energy coupling to nitrogen for breakdown conditions has been investigated. The experiments were performed in 25‐Torr nitrogen using a 35‐GHz 1‐&mgr;s microwave pulse focused to 33 kW/cm2. The plasma created during breakdown was observed to travel towards the source with a velocity of 4.6×106cm/s. Spectroscopic measurements using a nitrogen‐helium mixture indicate the average electron density over a 2‐cm chord to be 4.4×1012cm−3, and the electron temperature to be 3.8 eV. Microwave cutoff was observed photographically, and suggests the peak electron density to be the collisional critical density. Computer simulations were also performed, and their results are in accord with the experimental results.

ISSN:0021-8979    

DOI:10.1063/1.331733

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

In the horizontal operation of dysprosium‐thallium and scandium‐sodium iodide lamps, the internal surface of the upper portion of the arc tube is etched, causing precipitation on the side and lower portions. This precipitation produces spheroidal outgrowths on the side internal surface and closely bunched fibers on the lower internal surface. These deposits are examined by electron beam microanalysis and micro x‐ray diffraction analysis, and are construed to be amorphous SiO2. The transport of silica is found to occur also in a furnace experiment, where dysprosium iodide is heated in an evacuated silica tube held at 750–1150 °C.

ISSN:0021-8979    

DOI:10.1063/1.331734

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We investigate theoretically and experimentally the possibility of energy deposition enhancement when a relativistic electron beam interacts with a high density plasma. The beam‐plasma instability is studied taking into account the angular spread of the beam, the electron‐ion collisions, and the density gradients. The beam (500 kV, 250 kA, 50 ns) interacts with a thin CH2foil. Contrary to previous experiments, the plasma expansion from the foil target is found to be symmetric. The maximum temperature estimated by x‐ray diodes is 13 eV. The measured parameters (temperature, density, gradients), together with the theoretical study, show that the beam‐plasma instability is ineffective in the expanding target.

ISSN:0021-8979    

DOI:10.1063/1.331736

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Weakly focused pulsed‐CO2‐laser radiation has been examined as an ignition source for low‐pressure (85–100 Torr), near‐stoichiometric fuel/oxygen mixtures containing the following fuels: ethylene, methyl fluoride, methanol, ethanol, dimethyl ether,p‐dioxane,n‐propyl nitrate, and iso‐propyl nitrate. The data analysis includes characterization of the spatially dependent ir absorption in the test cell, calculation of appropriate medium temperatures from the absorbed laser energy, and correlation of observed ignition delay timestigwith the calculated temperatures. Effects of hydrodynamic motion on the pressure, density, and temperature profiles of the irradiated samples were modeled using a computer code for two‐dimensional wave propagation. Code predictions are in accordance with experimental pressure‐time histories obtained using a piezoelectric transducer. Minimum ignition temperatures ranged from 590 K for the iso‐propyl nitrate/O2system to 1645 K for CH3F/O2. The observed functional relationship betweentigand temperatureTwas generally of the form ln tig=A/T+B, whereAandBare constants. This relationship follows the form predicted by thermal and degenerate chain ignition theories, viz., ln tig=Eact/RT+constant, whereEactcorresponds to an overall activation energy. Using this relation, derived activation energies are 86, 57, 42, 47, ∼40, 13, and 12 kcal/mole for the CH3F/O2, CH3OCH3/O2, CH3OH/O2, C2H5OH/O2, C4H8O2/O2,n‐propyl nitrate/O2, and iso‐propyl nitrate/O2mixtures, respectively. These results are in reasonable agreement with available data from shock‐tube and hot air stream injection techniques. In contrast, an anomalous, threshold‐like effect was observed for laser ignition of C2H4/O2. The applicability of ignition schemes of this type to time‐resolved kinetic spectroscopic studies is briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.331737

出版商:AIP    

年代:1983

数据来源: AIP