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Journal of Applied Physics

Issue 8 • Date Aug 1983

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Displaying Results 1 - 25 of 78
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Total internal reflectance optoacoustic spectroscopy

    Page(s): 4251 - 4253
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    When radiation undergoes total internal reflection at a solid–gas interface, an exponentially decaying wave, known as the evanescent wave, propagates into the gas. If the incident radiation is amplitude modulated and the gas has an absorption at the wavelength of the radiation, the optoacoustic effect can be produced by absorption of energy from the evanescent wave. Experiments with 10.6 μ radiation internally reflected in an NaCl prism show the amplitude of the optoacoustic signal (in SF6) to be linearly proportional to the product of the square of the electric field amplitude and the penetration depth of the evanescent wave as given by Fresnel’s equations. The amplitude of the optoacoustic signal in a 100‐μl detection cell is found to increase linearly with the mole fraction of SF6 in He over the range from 10-5 to 10-2. View full abstract»

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  • Wideband heterodyne detection in the far infrared with extrinsic Ge photoconductors

    Page(s): 4254 - 4259
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    The heterodyne performance of Ge photoconductors doped with shallow impurities was investigated using optically pumped far infrared lasers. Two lasers operating on the 67‐μm NH3 Raman line generated difference frequencies from 0–100 MHz. An additional frequency point at 1.155 GHz was produced with two methanol‐isotope lasers at 118 μm. For three detectors with different doping levels IF bandwidths of 141, 63, and 8 MHz were measured using local oscillator powers of a few milliwatts. The detector gain and quantum efficiency were calculated from shot noise measurements. For impedance matched operation the calculated noise equivalent power (NEP) values are 2×10-18 W Hz-1 for the fastest detector and 6.5×10-19 W Hz-1 for the slowest detector. View full abstract»

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  • Characterization of laser‐produced plasma x‐ray sources for use in x‐ray radiography

    Page(s): 4260 - 4268
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    We report the absolute conversion efficiency ξx from the incident laser light energy to x‐ray photons for laser‐produced plasmas. Potential x‐ray backlighting (radiography) line sources having photon energies from 1.4 to 8.6 keV are studied as a function of laser wavelength, pulsewidth, and intensity. The laser intensity and pulsewidth range from 1014 to 1016 W/cm2, 100 ps to 2 ns and include incident wavelengths of 1.06, 0.53, and 0.35 μm. We found that K‐shell x‐ray line emission ξx : (1) decreases with increasing x‐ray energy, (2) decreases with increasing laser intensity, (3) decreases rapidly with pulselength, and (4) moderately increases with decreasing laser wavelength. On the contrary, for Au M band emission, at a fixed laser intensity and pulsewidth, ξx significantly increases (∼25×) upon decreasing the laser wavelength from 1.06 to 0.35 μm. View full abstract»

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  • Pulsed ion beam generation with cryogenic‐anode diode

    Page(s): 4269 - 4274
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    Magnetically insulated ion diodes with a cryogenically refrigerated anode are proposed and their characteristics are examined. Proton beams of 7 A/cm2 and deuteron beams of 5 A/cm2, with energy of about 80 keV are extracted from a refrigerated H2O or D2O anode with good reproducibility and reasonable repetition rate. View full abstract»

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  • Vibrational relaxation and laser extraction in rare gas halide excimers

    Page(s): 4275 - 4279
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    Recent experiments have demonstrated that the finite rate of vibrational relaxation in the formation of KrF affects the saturation characteristics of the KrF(B) state during extraction of laser light. We have assembled a collisional radiative model using calculated Einstein A coefficients for the lowest twenty KrF states and an approximate calculation of the rate of vibrational energy transfer between KrF and a buffer gas. The model describes the flow of excitation through the vibrational levels of KrF, and demonstrates the effects of vibrational relaxation on KrF(B) saturation and spectra. The results of these calculations agree qualitatively with the published experimental results. In addition, we find that, due to the relaxation kinetics of KrF, Kr2F, a major absorber, is not truly saturable. View full abstract»

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  • The nonlinear generation of a steady magnetic field in a conducting sphere placed in an oscillatory magnetic field

    Page(s): 4280 - 4284
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    It is shown that the nonlinear ‘‘Hall’’ force generated in a conducting sphere placed in an oscillatory (ac) magnetic field has a nonzero curl. It, therefore, drives a poloidal current which has a steady (dc) component and a second harmonic component. A general analytic expression for the dc toroidal magnetic field generated by the Hall current is obtained for the weakly nonlinear case: ωce/ν ≪1, where ωce =eB/m is the electron cyclotron frequency in the ac magnetic field and ν is the effective collision frequency. The dc magnetic field is evaluated numerically (using the general analytic formulae) for the special case where the applied ac magnetic field is uniform. View full abstract»

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  • A high‐energy, laser accelerator for electrons using the inverse Cherenkov effect

    Page(s): 4285 - 4288
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    A laser method for accelerating electrons is described, based on the inverse Cherenkov effect in a gas. The laser fields are in the form of a cylindrical cone of plane waves on whose axis travel the electrons, with the cone angle and the gas refraction index such that each electron sees constant fields in time. Expressions are obtained relating the overall energy transfer to total laser power and wavelength, and to gas index and interaction length. With laser powers now available, energy increments of tens of GeV are possible. For comparative purposes, a related alternative scheme involving electrons in vacuum and evanescent laser fields is also analyzed. It is found that the method applies particularly well to adding energy to the electron bunches produced by large microwave accelerators, as collision effects are less troublesome at high injection energies. View full abstract»

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  • Wiggler‐free free electron waveguide laser in a uniform axial magnetic field: Single particle treatment

    Page(s): 4289 - 4294
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    A wiggler‐free free electron laser operating in a waveguide is analyzed by using a single particle treatment. The use of either a TE or a TM mode is shown to enhance the gain for a resonant frequency much higher than the cyclotron frequency. It is demonstrated that a source of a submillimeter radiation, based on this analysis, may have output power comparable to that of a wiggler‐type free electron laser. View full abstract»

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  • Analysis of space charge in photonic tubes

    Page(s): 4295 - 4301
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    Temporal resolution in fast photonic tubes, e.g., streak tubes, frame tubes, and photodiodes, is enhanced by using a high electric field at the photocathode. However, at relatively high irradiance, the tube performance is degraded in both temporal and spatial resolution. It is generally assumed that the degradation is due to space charge. It is well known that space charge depresses the electric field in the immediate region of the cathode. For zero initial‐energy electrons, the electric field at the photocathode decreases with increasing space charge and becomes zero when the full space‐charge‐limit current is extracted from the cathode; however, photoelectrons from real cathodes have finite energy distributions that can change the polarity of the cathode field from accelerating to retarding at high irradiance. By utilizing appropriate photoelectron energy distribution functions, we will first calculate the electric field at the cathode‐grid region for high irradiance and then examine the perturbing effects upon the resolution in the photonic tube. View full abstract»

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  • New class of gain guiding laser with a tapered‐stripe structure

    Page(s): 4302 - 4304
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    A new class of gain guiding laser with a tapered‐stripe structure has been developed which exhibits a linear dependence of light output on cw current, a stable single‐lobe far‐field pattern along the junction at the power level of more than 10 mW, and an amount of astigmatism below 20 μm. It is also shown that a thin active layer thickness is desirable to achieve a stable lateral mode. The main feature of the tapered‐stripe structure is that it offers an additional degree of freedom in controlling the beam spot size and the radius of curvature of the phase front separately, by varying the widths as well as the length of the tapered stripe. View full abstract»

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  • Photolithography experiments using forced Rayleigh scattering

    Page(s): 4305 - 4313
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    Phase conjugate wavefront generation by degenerate four‐wave mixing has been used to project images with spatial resolution greater than 500 line pairs per millimeter. The nonlinear medium, a solution of rhodamine 6G in acetone, produced the images by forced Rayleigh scattering. These images were bright enough to expose photoresist in 30 sec and their quality was adequate for fine‐line lithography and consistent with theoretical expectations. View full abstract»

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  • Experimental study of the Scholte wave propagation on a plane surface partially immersed in a liquid

    Page(s): 4314 - 4322
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    This study shows that as a pseudo‐Rayleigh wave propagates on the surface of a semi‐infinite elastic plane solid, partially immersed in a liquid, a new repartition of the energy appears at the liquid–solid interface. Two interface waves are generated: a generalized Rayleigh wave (or leaky Rayleigh wave) and a Scholte wave (or pseudo‐Stoneley). We show that for values of the angle of immersion θi less than θi,mR/2+π/4 (where θR is the Rayleigh angle), the amplitude of the Scholte wave depends strongly on the wetting and on θi. In this angular region the leaky Rayleigh wave does not disturb the Scholte wave propagation. For θi≫θi,m the experimental records present an oscillating behavior that we have attributed to the superposition of the pseudo‐Stoneley wave and the generalized Rayleigh wave specularly reflected by the air–liquid interface. View full abstract»

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  • Surface acoustic wave measurements using an impulsive converging beam

    Page(s): 4323 - 4329
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    A method for velocity and attenuation measurement of leaky surface acoustic wave on small areas of a solid surface was developed. This technique uses an impulsive converging beam generated with an acoustic lens. Reflected waves from a sample consisted of the axial wave and the leaky surface wave separated in time domain. From the time interval between these waves, the velocity of the leaky surface wave is determined using an expression derived along with ray optics. Because time interval measurements do not require any mechanical scanning, they can be done without special attention paid for mechanical precision of the scanning system, enabling rapid and simple measurement. Since the impulsive wave has a broad frequency spectrum, spectroscopic analysis of leaky surface wave is also possible. Frequency dependent attenuation measurement of leaky surface acoustic waves on heat treated steels and velocity dispersion measurement of leaky surface wave on titanium nitride film on tool steel are demonstrated. View full abstract»

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  • Thermal profiles and thermal stresses introduced on silicon during scanning line shaped beam annealing

    Page(s): 4330 - 4337
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    The evaluation of thermal profiles and introduction of defects due to thermal stesses induced on 〈100〉 silicon during the annealing carried out by the scanning of a line shaped e‐beam source, has been performed. The computation of the temperature profiles along the sample for different beam scan speed and incident power has been used to evaluate the two‐dimensional map of the thermal stresses induced over a 4×2 cm2 silicon sample 〈100〉 oriented. The computed stresses were then compared with the yield stress of the material at the actual annealing temperature. The topographic distribution of the thermal stresses shows quite a complicated trend changing drastically from compressive to tensile as a function of beam position along the sample; it can be concluded that the introduction of defects takes place mainly at the edge of the sample which is irradiated last. An experimental check of our computations has been performed by using a fast multiscanning electron beam along a line, joined to a mechanical translation of the sample through the scanned region. Pyrometric temperature measurements performed during the irradiation confirm our computed temperature profiles, whereas both sheet resistivity measurements and x‐ray topography show that the introduction of defects actually takes place in the region of the sample and at the irradiation conditions foreseen by the present computation. View full abstract»

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  • Time‐dependent behavior of high‐pressure mercury discharges

    Page(s): 4338 - 4347
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    A numerical model has been developed for studying the time‐dependent behavior of cylindrical high‐pressure mercury discharges. The model makes it possible to calculate time‐dependent plasma parameters such as temperature profiles, arc conductance, etc. for arbitrary supply voltage waveforms and frequencies. The model is based on an expansion of the heat flux potential into a series of Bessel functions of zero order. An analytical approximation for the local net emission has to be provided for the model. It has been evaluated as a function of lamp diameter, mercury pressure, axis temperature, and temperature profile by calculating the radiation transport in the mercury lines. The calculated wall temperature and luminous flux as well as the calculated time‐dependent lamp voltage, current, and arc temperature profiles are compared with corresponding measurements. View full abstract»

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  • Two‐dimensional numerical simulation of an inductively driven imploding foil plasma

    Page(s): 4348 - 4353
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    A 1.9‐MJ capacitor bank with intermediate inductive energy storage for pulse shortening has been used to implode a thin cylindrical sheath in a z‐pinch geometry. Theoretical investigations of two‐dimensional axisymmetric effects in the r‐z plane, which lead to a thickening of the sheath, have been made using a two‐dimensional magnetohydrodynamics code. The results of several calculations are presented which demonstrate how imperfections in the initial sheath geometry affect development of the acceleration‐driven magnetohydrodynamic Rayleigh–Taylor instability. View full abstract»

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  • The formation of double‐valued sheaths in thermionic converters

    Page(s): 4354 - 4358
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    A theory for the sheath in an ignited thermionic converter is presented. The theory includes the effect of the velocity spread of the particles but the charge‐particle collisions are neglected. Conditions for the appearance of a virtual emitter are given. The theory is compared with a beam approximation theory and a hydrodynamic theory. All three theories give almost the same condition for the appearance of a virtual emitter in an ignited thermionic converter. View full abstract»

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  • Two‐temperature modeling of the free‐burning, high‐intensity arc

    Page(s): 4359 - 4366
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    In this paper a two‐temperature model (Te ≫Th) is applied to a free‐burning, high‐intensity, atmospheric pressure argon arc. With appropriate boundary conditions and nonequilibrium thermodynamic and transport properties, solutions of the conservation equations are obtained for the entire arc, except for the electrode sheath regions. Significant temperature discrepancies between electrons and heavy particles are found in the arc fringes. The elevated electron temperatures in the arc fringes lead to a rearrangement of the current density distribution which, in turn, has some effect on the temperature as well as on the velocity field in the arc core. Comparisons of the results of this study with spectrometric temperature measurements show better agreement than with results based on a one‐temperature model. View full abstract»

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  • Longitudinal voltage distribution in transverse rf discharge waveguide lasers

    Page(s): 4367 - 4373
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    The longitudinal variation in the voltage across a waveguide channel, excited by a transverse radio‐frequency discharge has been analyzed in terms of simple transmission line theory. It is shown that the voltage variation follows a cosine curve for the waveguide structure in the absence of a discharge, and that this behavior is only slightly modified when a discharge is running. The voltage may exhibit variations of 30% for cases where the relevant waveguide length is only one tenth of the effective rf wavelength. However, it is shown that this variation may be reduced to below 5%, by the use of multiple feed points or by appropriate inductive termination of the line. Experimental results are in good agreement with theoretical predictions. View full abstract»

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  • Ion implantation of Si and Be in Al0.48In0.52As

    Page(s): 4374 - 4377
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    Electrical characterization of (Al,In)As ion implanted with Be and Si following low and high dose multiple energy implant schedules, and annealed between 740 and 815 °C with a pyrolytic silicon dioxide cap is reported. Only very low activation of Be is achieved (≪3%). Silicon activation is considerably higher (≫40%) and increases with increasing anneal temperature. However, a high concentration n‐type surface layer is found on samples annealed at 815 °C. This surface layer is not found on similarly annealed samples which were not implanted, or which were implanted with phosphorus. View full abstract»

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  • Effects of keV electron irradiation on the avalanche‐electron generation rates of three donors on oxidized silicon

    Page(s): 4378 - 4381
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    After keV electron beam irradiation of oxidized silicon, the avalanche‐electron‐injection generation rates and densities of the bulk compensating donor, the interface states, and the turnaround trap all increase. Heating at 200 °C can anneal out these three donor‐like traps, however, it cannot restore the generation rates back to their original and lower pre‐keV electron irradiation values. The experimental results also indicate that all three traps may be related to the same mobile impurity species whose bonds are loosened by the keV electrons and then broken or released by the avalanche injected electrons. View full abstract»

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  • Shock‐induced radiation spectra of fused quartz

    Page(s): 4382 - 4385
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    An optical multichannel analyzer is applied to observe shock‐induced radiation spectra of fused quartz in the 23–31 GPa shock‐pressure range. Characteristics of sample‐driver interface strongly influence both intensity and profile of the observed spectra. Brightness and color temperature are determined by an integration of spectral radiance and a fit to the greybody radiation spectrum, respectively. The resultant brightness and color temperature are lower and considerably higher than those estimated by the theoretical calculation, respectively. Some broad but strong line spectra are, however, superimposed onto the continuous greybody radiation spectrum even though the influences of the interface are reduced as much as possible. The line spectra are probably caused by electroluminescence and/or triboluminescence. View full abstract»

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  • High pressure measurements on photopumped low threshold AlxGa1-xAs quantum well lasers

    Page(s): 4386 - 4389
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    Data are presented on the continuous (cw) 300 K photopumped laser operation of a low threshold Alx′Ga1-x′As–GaAs (x′∼0.30) single quantum well heterostructure (quantum well size Lz∼60 Å) subjected to high pressure (0–11 kbar) in a simple opposed anvil apparatus. Beyond ∼11 kbar where the central Alx′Ga1-x′As waveguide region undergoes a direct–indirect transition, and the waveguide confinement begins to weaken and deep levels tend to become important, the laser threshold increases rapidly and ‘‘quenches’’ cw 300 K operation. Pulsed 300 K photopumped laser operation of an undoped 121‐period AlxGa1-xAs–GaAs (x∼0.5) superlattice in the pressure range from 0–11 kbar is shown for reference. The pressure coefficients of the quantum well heterostructure and the superlattice lasers are comparable (∼11 meV/kbar). View full abstract»

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  • Gold as a reliable internal pressure calibrant at high temperatures

    Page(s): 4390 - 4397
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    Energy‐dispersive x‐ray diffraction measurements on a mixture of powdered NaCl and Au were carried out at high temperatures up to 600 °C (at atmospheric pressure) and also at simultaneously high temperatures and high pressures (to 425 °C and 10.2 GPa). A modified diamond‐anvil high pressure cell with a mini resistance‐wire heater was used in conjunction with the synchrotron radiation at the Stanford Synchrotron Radiation Laboratory. The temperature of the sample was measured directly by a precalibrated Pt‐Pt 10% Rh thermocouple adjacent to the sample. The pressure of the sample was determined by measuring the molar volume changes in NaCl and deriving the pressure through an equation of state. The measured thermal expansion from 25 °C up to 600 °C for NaCl and Au at 1 atm can be expressed by second‐order polynomials: V/V0(NaCl)=1+(1.08±0.05)×10-4 (T-25)+(7.5±1.1)×10-8 (T-25)2 and V/V0(Au) =1+(4.26±0.85)×10-5 (T-25)+(5.0±20)×10-9 (T-25)2, where T is in °C. These results are in excellent agreement with previously published data. The measured molar volume ratios of Au at simultaneously high temperatures and high pressures have been found to be in good agreement (within 0.2%) with the values based on the calculated isochores from shock wave data. The pressures determined from the compression of Au at high temperature are compatible with those based on the compression of NaCl (within 2.7% at pressures up to 10.2 GPa). These results enhance the reliability and the scope of the use of Au as an internal pressure calibrant at high temperatures. View full abstract»

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Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

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Editor
P. James Viccaro
Argonne National Laboratory