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Journal of Applied Physics

Issue 2 • Date Feb 1979

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Displaying Results 1 - 25 of 116
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Thermodynamic limits to nonlinearity: Lossless energy‐storing systems

    Page(s): 569 - 573
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    The nonlinearity of the relationship between the extensive and the intensive variables of an ideal energy‐storing thermodynamic system in equilibrium is expressed in terms of the higher‐order moments of the extensive variable, and is thus shown to have both an upper and a lower bound. The bounds are proportional to the size of the system and for most practical systems the upper bound is more restrictive. As an illustration, the bound is applied to the nonlinearity of varactor diode capacitors, and the lower bound is shown to be far from the presently achieved nonlinearity. View full abstract»

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  • A solid rotor iron‐free asynchronous machine

    Page(s): 574 - 581
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    Solid rotor iron‐free asynchronous machines are important for the achievement of high‐speed motors with high power‐to‐weight ratios. This paper presents a theoretical study of these machines, based on Maxwell’s relations, which is carried out using simplified two‐dimensional models. Results are compared to experimental measurements. View full abstract»

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  • The relation of the yield stress of high‐pressure anvils to the pressure attained at yielding and the ultimate attainable pressure

    Page(s): 582 - 588
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    Using a sensitive microprofilometer, the onset of yielding in the anvils of a supported opposed anvil device can readily be determined. If the pressure at which yielding occurs is measured, the yield stress of the anvil material can be obtained. This is illustrated for 3% cobalt cemented tungsten carbide. The reverse is also true and can be used as the basis for obtaining the transition pressures of a material that transforms to a conducting phase at a pressure near which yielding of the anvil material commences. This is illustrated for the gallium phosphide transition which is found to be near 18 GPa based on the commencement of yielding in boron carbide anvils. Moreover, the yield stress or Knoop hardness can be used as the basis for obtaining the ultimate attainable pressures in supported opposed anvil devices. Based on the measured yield stress of a maraging steel, and the experimental observation that the bismuth transition is near or at the ultimate attainable pressure of this steel in a supported opposed anvil device, the III–V transition is found to be near 7.7 GPa. Based on the Knoop hardness and the previously mentioned observation, this transition is found to be near 7.5 GPa. Based on the measured yield stress of a 3% cobalt cemented tungsten carbide anvil, the ultimate pressure attainable in a supported opposed anvil device is found to be about 18 GPa and in any case less than 19 GPa. Inasmuch as the gallium phosphide transition occurs near the limit of the ultimate attainable pressure with such tungsten carbide pistons, the transition pressure of gallium phosphide to a conducting phase under the stress state present there is near 18 GPa. Based on the ultimate attainable pressure in boron carbide pistons the completion of the transition of sulfur to a conducting phase is found to be less than 33 GPa. The yielding of supported opposed diamond anvils with dislocation densities of ∼5×104/cm2 or more is expected to- be in the neighborhood of 50 GPa. The onset of this yielding could be used as the basis for determining approximately the transition pressure of silicon carbide to a conducting phase at an estimated value of 64 GPa. View full abstract»

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  • Isotope separation by jet‐background interaction

    Page(s): 589 - 594
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    Separation measurements have been made for neon isotopes penetrating a nitrogen jet over a broad range of flow regimes. The products of the jet‐background interaction were collected by molecular probes which projected through the jet orifice from the plenum into the background chamber. The separation profiles are in excellent agreement with a very simple physical model of the penetration process. This model can be used to predict the performance of any isotopic separation experiment and has been shown to agree with another investigator’s argon and SF6 data. The amount of separation is adjustable, does not appear to be limited, and thus can be arbitrarily large. The apparatus required is particularly simple to construct. View full abstract»

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  • Evaluation of beam distribution parameters in an electron storage ring

    Page(s): 595 - 598
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    The motion of a charged particle in a linear electromagnetic device can often be analyzed by using the transport matrices. For an electron storage ring, this technique has been applied to yield fruitful results such as the trajectory of the particle distribution center and the beam sizes and shapes in phase space. Coupling effects among the horizontal, vertical, and longitudinal motions are included in a straightforward manner. View full abstract»

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  • Measurement of the width of the inverted Lamb dip in H2CO at 3.51 μm

    Page(s): 599 - 601
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    The width of the inverted Lamb dip in H2CO at 3.51 μm [51,5 (ground state) →60,6(v5=1)] was measured by using a low‐noise He‐Xe laser in an axial magnetic field as the light source. To measure the dip width it was necessary to determine first the range of the magnetic field strength and the maximum frequency deviation of the laser frequency modulation. Based on these results, the power‐broadening characteristics were measured. Finally, the relation between the dip width free from the power broadening and the pressure of H2CO was obtained. The dip width (HWHM) was Δνh= (123±24)+(155±31) PF (kHz), where PF represents the H2CO pressure expressed in Pascal. View full abstract»

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  • Radio transmission in an elliptical tunnel with a contained axial conductor

    Page(s): 602 - 605
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    Electromagnetic transmission in a straight cylindrical tunnel with imperfectly conducting walls is considered when the cross section is in elliptical form. The presence of a thin axial conductor is also allowed for in the boundary‐value formulation. The general matrix solution is simplified by invoking the quasistatic approximation which is shown, at least for circular tunnel geometry, to be valid for frequencies up to 20 MHz. The results of the quasistatic calculations indicated that the attenuation rate of the dominant mode is relatively insensitive to the ellipticity if the cross‐section area and the cable‐to‐wall separation is kept constant. View full abstract»

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  • Continuum modeling of electromagnetic waves in composite wave guides

    Page(s): 606 - 609
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    A continuum mixture theory with microstructure is developed for electromagnetic wave propagation in laminated waveguides. The theory leads to simple governing equations for the actual composite which retain the integrity of the propagation process in each constituent but allow them to coexist under derived interactions. The utility of the resulting equations is demonstrated by studying the response of the composite to harmonic excitations. In this case the dispersion relations are found to correlate well with some derived exact solutions. View full abstract»

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  • An ultrahigh‐Q isotropically sensitive optical filter employing atomic resonance transitions

    Page(s): 610 - 614
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    A new resonance principle in optical filters has been utilized to simultaneously permit realization of wide field‐of‐view (∼2π sr) and very narrow acceptance bandwidths, approaching 0.01 Å. A light signal is transmitted through an outer bandpass filter into a resonantly absorbing atomic vapor, resulting in a fluorescence signal at a different wavelength which is transmitted through an inner bandpass filter. The outer and inner bandpass filters have no common transmission band, resulting in complete blockage of all optical signals (background noise) that are not resonantly shifted in wavelength by the intervening atomic vapor. This ’’resonance filter’’ principle is experimentally verified, and system parameters are discussed for filters utilizing potassium, rubidium, or cesium vapor at nine wavelengths between 420 and 532 nm. View full abstract»

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  • Computer simulation of exposure and development of a positive photoresist

    Page(s): 615 - 623
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    This paper applies a theoretical process model developed by Dill et al. to the polychromatic exposure systems. Exposure and development of a positive photoresist are treated with computer simulation for both contact printing and projection printing. Optical interference within resist film and the effect of it on the development condition are investigated theoretically. The results for the two printing systems are compared in order to clarify the differences between contact exposure and projection exposure. It was made clear that (1) the optical interference still has a considerable influence on the condition imposed on the photolithographic process even in the polychromatic exposure environment and (2) the projection exposure with two spectral lines is more sensitive to such parameters as the thicknesses of resist film and the underlying oxide layer than the contact exposure with three spectral lines. View full abstract»

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  • Double‐pulse excitation experiments on the Ca+ cyclic laser

    Page(s): 624 - 627
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    The total energy output of a Ca+ laser oscillating on the 866.1‐ and 854.2‐nm emision lines in a double‐pulse laser system as a function of the delay time between pulses has been measured. A very significant increase in the output energy occurs as the delay time between the discharges is decreased, reaching a maximum value at about 90 μsec for the discharge conditions employed. This improvement in performance is attributed to the difference between the destruction rates of the Ca+ ions in the 3d 2D3/2 and 3d 2D5/2 laser terminal states and that of the 4s 2S1/2 Ca+ ion ground state and to the fact that the initial discharge produces a considerable concentration of Ca+ ions which persist until the second discharge occurs. The consequences of this observation to the construction of a high‐repetition‐rate laser are discussed. View full abstract»

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  • Rotational population transfer in HF

    Page(s): 628 - 636
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    Population transfer in HF by both collisional and radiative processes was measured by ir‐laser double‐resonance experiments. In three kinds of experiments populations pumped to a specific rotational level were followed: out of the pumped level, to the levels above, and to the levels below. The rates of loss from the pumped level and transfer to the lower levels were strongly affected by lasing between rotational levels. Data for gain and laser intensity were incorporated into a kinetic rate model to evaluate transfer rates. View full abstract»

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  • uv preionized thallium‐mercury discharge

    Page(s): 637 - 640
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    Stable glow discharges have been demonstrated in thallium‐mercury gas mixtures at mercury densities of 3×1019 and temperatures of 500–900 °C. These discharges have shown themselves to be highly efficient in producing excited Tl (72S1/2) atoms and Tl‐Hg B2J1/2 excimer molecules. Discharge efficiency as high as 30±10% in producing Tl (72S1/2) and Tl‐Hg B2J1/2 points to the possibility of the creation of a Tl‐Hg excimer laser operating at similar efficiencies. These highly efficient discharges are thought to be due to very fast transfer of energy from mercury excimers into Tl‐Hg. The transfer cross section from excited molecular mercury to Tl (72S1/2) and Tl‐Hg excimers is found to be approximately 1.2×10-14 cm2. View full abstract»

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  • Oscillator strengths and laser effect in Na2Nd2Pb6(PO4)6Cl2 (chloroapatite), a new high‐Nd‐concentration laser material

    Page(s): 641 - 646
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    Chloroapatite (Na2Nd2Pb6(PO4)6Cl2), a Nd3+ compound with 3.4×1021 ions cm-3 has been shown recently to possess a high fluorescence efficiency. Measurements on single‐crystal samples show that the oscillator strengths and the fluorescence quenching are both slightly smaller than in Nd pentaphosphate (NPP). Laser effect with longitudinal Ar* laser excitation is reported for the first time in this material on two lines at 1.0585 and 1.0675 μm, which have orthogonal polarizations and equal thresholds, in agreement with fluorescence spectra. The laser threshold (absorbed power for a given total cavity loss) is nearly equal to that of a NPP crystal in the same cavity. View full abstract»

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  • CO2 TEA laser discharge development—A high‐speed‐camera investigation

    Page(s): 647 - 652
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    Discharge development processes, such as homogeneous glow formation, glow‐to‐filamentary arc transition, and arc formation, of moderate volume CO2 TEA laser medium with external ultraviolet (uv) volume preionization are studied by a high‐speed‐camera technique. The framing records in this paper supplement the earlier streak ones of CO2 TEA laser discharges of Sakai et al. The records show that instability appears as a bright spot at the cathode in the middle of the uniform glow stage, then propagates in the anode direction, keeping the shape of a bright spot or changing into a bright filament. This propagation continues even after termination of the volume‐dominated glow. The discharge development is found, from an understanding of the current waveform, to be considerably sensitive to the CO2, N2, and He composition ratio, and the pulse‐forming network and other characteristics are also studied. The glow‐to‐arc transition mechanism and the dominant contributor to suppress arc formation are discussed. View full abstract»

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  • Single‐transverse‐mode LiNdP4O12 slab waveguide laser

    Page(s): 653 - 659
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    Argon‐laser‐pumped single‐transverse‐mode laser operation was obtained with a three‐dimensionally confined LiNdP4O12 slab waveguide laser, in which one endface was cylindrically polished and directly coated with a laser mirror. The threshold, the output power, and the oscillating transverse modes were theoretically analyzed, both for transverse pumping and for longitudinal pumping, considering the spatial distribution of the pump beam and the laser beam. The necessary conditions for the pump sources to obtain a TE00 single‐transverse‐mode oscillation were determined on the supposition of the diode pumping. View full abstract»

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  • Acoustic emission in liquid crystals

    Page(s): 660 - 663
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    Acoustic emission in liquid crystals has been experimentally assessed. The emission has been studied as a function of temperature for different mesophases. The effect is attributed to the release of elastic energy involved in the defect dynamics inside the material. View full abstract»

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  • Contrast and imaging performance in the scanning acoustic microscope

    Page(s): 664 - 672
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    Several articles have been written on the subject of scanning acoustic microscopy. Nevertheless, apart from some specific papers dealing with reflection microscopy, little has been said about the various contrast mechanisms involved in the process of image formation, and the effects of parameters such as acoustic antireflection coatings on the lens surface and absorption in the water on the quality of the recorded image. This paper is devoted to an analysis of these problems. It is shown that in the amplitude mode of operation, the acoustic microscope acts as a phase contrast microscope and is sensitive to the local phase gradients in the object. Furthermore, it is shown that the effect of an acoustic antireflection coating on the lens surface is to substantially reduce the side lobe amplitude of the focal distribution at the expense of a slight increase in the width of the main lobe. Experimental observations agree with theory. View full abstract»

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  • Variational formulations for heat conduction problems

    Page(s): 673 - 678
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    By introducing suitable parameters, it is demonstrated that the heat conduction effect resembles an elastic deformation. The difference is that the mechanical stress variation induces an inertia effect, while the heat stress variation generates a diffusion effect. Guided by this resemblance, a compatible Lagrangian formulation and its complementary form are derived for the heat conduction problems. The results are similar to Biot’s variational principles. The advantages of using the complementary form for the approximate solutions are also discussed. Temperature distributions in a semi‐infinite solid with prescribed wall temperatures and with described heat flux are considered as illustrative examples. View full abstract»

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  • Effects of free‐stream velocity and pressure gradients on MHD boundary‐layer control

    Page(s): 679 - 682
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    A steady two‐dimensional MHD boundary‐layer flow on a flat plate with varying hydrostatic pressure and free‐stream velocity along the plate and a uniform transpiration through the plate is considered. The momentum boundary‐layer thickness is found to increase substantially with injection and negative flow‐shape factors. However, it decreases with increasing magnetic interaction numbers. Transpiration, flow‐shape factor, as well as magnetic interaction number strongly affect the shearing stress at the wall. Injection and retarding free‐stream velocity will enhance the chances of a flow separation, while the magnetic interation number will do just the opposite. View full abstract»

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  • ac cataphoresis measurements

    Page(s): 683 - 689
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    Light spectrometric investigations of ac‐excited binary noble‐gas mixtures show ac cataphoretic phenomena. Time‐averaged and discrete‐time analysis techniques are used in studies of He‐Ne, Ne‐Ar, and Kr‐Xe mixtures. Enhancement of the readily ionized gas component can occur either at the discharge tube ends or at the center. Time‐dependent analyses indicate the importance of ionization waves when ac cataphoretic segregation is detected. The dependence of enhancement on various discharge parameters is reported. View full abstract»

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  • Study of plasma expansion in a vacuum diode by the spectroscopic method

    Page(s): 690 - 695
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    New results on the plasmas produced by an e‐beam in a vacuum diode are presented. In the near‐uv range, we measure the plasma expansion speeds by the Doppler‐shift and by the time‐of‐flight methods. The maximum observed speed of 2.4×107 cm/sec for the C+3 ions leads us to estimate the electric field which is probably in the range of 1–6 kV/cm and may exist for tens of nsec. Some aspects of the spectral characteristics, the collective field effect, and the partition of the discharge energy are discussed in connection with recent literature. View full abstract»

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  • Cyclotron maser instability for intense solid electron beams

    Page(s): 696 - 701
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    The cyclotron maser instability for a solid relativistic electron beam propagating parallel to a uniform axial magnetic field B0?z is investigated. The stability analysis is carried out within the framework of the linearized Vlasov‐Maxwell equations. It is assumed that ν/?≪1, where ν is Budker’s parameter and ?mc2 is the electron energy. Stability properties are investigated for the choice of equilibrium distribution function in which all electrons have the same value of total perpendicular energy, the same value of axial velocity, and a step‐function distribution in canonical angular momentum. The instability growth rate is calculated including a determination of the optimum value of the beam radius R0 for maximum growth. It is found that the maximum growth rate for a solid beam is comparable to the maximum growth rate for a hollow beam. View full abstract»

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  • Interaction of a relativistic electron beam with surface waves

    Page(s): 702 - 704
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    The electromagnetic surface modes at the interface between two plasma media are studied and the excitation of these surface waves in a plasma by a relativistic electron beam is discussed. Under the resonance condition ω?kzvb, it is shown that an electron beam crossing a plasma can excite a surface electromagnetic wave at the plasma frequency ω=ωp. 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