Showing papers on "Power density published in 1976"

Target heating during ion implantation

Abstract: The temperature of ion‐implanted silicon wafers has been measured as a function of time using an infrared pyrometer. Ion beam power density was varied from 0.10 to 200 W cm−2, and the target temperature was measured in the range from 100 °C to the silicon melting point. The resulting heating and cooling curves have been analyzed using a model which includes the effects of ion beam heating, radiative cooling, conductive cooling, and reradiation from the surroundings. For the system studied, conductive cooling in vacuum is less reliable and generally less effective than radiative cooling, unless conductive grease can be used. The model has also been generalized to the case of a group of wafers being scanned cyclically by the ion beam, and the calculated temperatures have been compared with experimentally measured values. Implanting N wafers cyclically is not equivalent to dividing the input power density by N, because the time required for the wafers to cool is typically less than the time between scans. Ho...

Instabilities during high‐field electrical conduction in solids

Abstract: Measurements of the time and voltage dependence of dc and ac currents in insulators and semiconductors and the evaluation of results of other authors on corresponding measurements using metallic samples reveal that critical power densities Nk1≈10−8 W/mm3 and Nk2≈10−5 W/mm3 separate three different ranges of charge transport loading of solids in the frequency range 0⩽f⩽50 Hz. The loading state of a solid is described macroscopically by the average electric power density and microscopically by the local value of the power density j↘⋅E↘. In semiconductors and insulators electrical breakdown or transition to a strongly localized and highly conducting state is unavoidable if an overcritical power density N≳10−5 W/mm3 is supplied. This locally quite limited and highly conducting state exists in the prebreakdown range wherein Nk2

Apparatus for fluid treatment by electron emission

Abstract: Improved efficiencies in the treatment of a fluid such as oxygen or an oxygen containing gas by electron emission so as to produce a product such as ozone may be achieved by regulating the manner in which energy is used within a fluid treatment cell and the circuit used to power such a cell. Such a cell normally consists of two electrodes separated from one another by a dielectric layer and an air gap. The apparatus used to power such a cell preferably includes a power supply, a timing generator, transistors for releasing power from the power supply to a transformer at periodic intervals, diodes for permitting power to be reconveyed from the transformer to the power supply, an inductance either built into or associated with the secondary of the transformer, this secondary being connected across the terminals of the cell. With this circuit energy is stored in the cell and in both of the inductances as power is supplied. Such energy is used on the reversal of the polarity of the cell before power is released to the cell. This promotes efficiency in terms of the amount of power consumed per unit of power produced.

High-power density experiments in a shock-tunnel MHD generator

Abstract: An experimental MHD generator facility is described, in which cesium-seeded argon is used as a working medium. The heating of the gas is realized by compression in a shock tunnel. The enthalpy input into the generator is 5 MW. The test time is 5 msec. The objective of the experiments has been the achievement of electrical energy extractions as high as expected from one-dimensional channel computations. The effects of voltage drops and short-circuiting of the Hall field on the power output are discussed, and the performances of a 3 l and a 10 l channel are examined. In both cases, agreement between the experiment and the theoretical model was found. The 10 l channel yielded an enthalpy extraction of 24 percent with an electrical power density of 140 MW/m/sup 3/.

Conditioning of nuclear reactor fuel

Abstract: A method of conditioning the fuel of a nuclear reactor core to minimize failure of the fuel cladding comprising increasing the fuel rod power to a desired maximum power level at a rate below a critical rate which would cause cladding damage. Such conditioning allows subsequent freedom of power changes below and up to said maximum power level with minimized danger of cladding damage.

Mathematical Model of a Lithium‐Water Electrochemical Power Cell

Abstract: A mathematical model has been developed which describes the operation of a lithium‐water, electrochemical power cell. The current density, current efficiency, powder density, and specific energy are calculated as functions of cell potential, lithium hydroxide concentration, temperature, electrolytic solution flow velocity, position along the flow channel, spacing between electrodes, and flow channel width. Anode to cathode contact pressure is not included in this initial model. A large dependence of power density on concentration is predicted. For example, at an concentration of 2M, a power maximum of 394 mW/cm2 is calculated, and in the power maximum is calculated to be 25 mW/cm2. Temperature and flow velocity show similar but smaller effects.

Half-life of /sup 242/Pu from precise low-temperature heat capacity measurements

Abstract: Heat capacity measurements on three pure compounds, PuF/sub 3/, PuF/sub 4/, and PuO/sub 2/, made from 99.91 at.% /sup 242/Pu, have been used to evaluate the power produced by radioactive decay. The mean specific power was found to be (0.12099 +- 0.00024) mW per gram of plutonium in the samples. The contribution of nuclides other than /sup 242/Pu to the power was calculated to be (5.15 +- 0.11) ..mu..W per gram of plutonium, and so the specific power of pure /sup 242/Pu is (0.115 94 +- 0.000 26) mW g/sup -1/. A correction for the (5.50 x 10/sup -4/) % spontaneous fission branching reduces the specific power due to ..cap alpha.. decay to (0.11591 +- 0.00026) mW g/sup -1/. Combining this value of the specific power with the total disintegration energy of (4.9823 +- 0.0012) MeV, we obtain (3.763 +- 0.009) x 10/sup 5/ years as the ..cap alpha.. half-life of pure /sup 242/Pu. (AIP)

Fusing Mechanism of Nichrome Thin Films

Abstract: (1) Conduction electrons in nichrome have a short mean-free path. This maximizes E2R heating and precludes electromigration in the direction of electron flow as a fusing mechanism. (2) Transmission electron microscopy is the only effective analytical tool to characterize the programmed fuse gap structure. (3) Nichrome fuses program by molten metal (nickel, chrome) ions moving in the presence of an electric field. The final structure resembles a frozen splash and is described by fluid dynamics. (4) Thermal analysis coupled with empirical programmed fuse data indicate a threshold power density for fusing. If this power density is exceeded, which can be assured if the programming time utilized is as specified, the fuse gap will be wide and reliable. If this power density threshold is only matched, it is possible to create a marginal fuse. (5) Life test results indicate programmed PROM reliability is equivalent to devices of the same complexity that do not utilize fusible links.

Multifactor optimization of a carbon dioxide gasdynamic laser. II. Specific power optimization

Abstract: Methods for calculation of the output power of a carbon dioxide gasdynamic laser are discussed. The optimal conditions are found for maximum specific power on the assumption of one-dimensional flow of an inviscid gas ignoring changes in the chemical composition. The optimization is performed simultaneously with respect to the initial temperature, pressure, gas composition (carbon dioxide, nitrogen, helium, water vapor), nozzle profile, and resonator characteristics. The shape of the surface in the multidimensional space of the parameters being optimized is found. The nature of changes in the parameters near the optimal points is investigated.

Optical energy extraction from electron‐beam‐initiated H2–F2 mixtures

Abstract: An oscillator, based on electric discharge in an SF6‐H2 mixture and yielding 400‐nsec pulses, was used to probe an HF amplifying medium produced by electron‐beam initiation of H2‐F2 mixtures. The oscillator produced 17 lines of the P1, P2, and P3 transitions. The oscillator power density at the input to the amplifier was about 2×104 W/cm2 at the time the H2‐F2 mixture was initiated. The power gain of the amplifier was estimated to be 500. Results indicate that with 17 lines from the v′=1, v′=2, and v′=3 vibrational levels of HF, about 6% of the generated energy can be extracted by the oscillator beam. The results of the experiment have also beem compared with a model calculation.

Induced electromagnetic field and absorbed power density inside a human torso

Abstract: The electric field and abscetbed power density inside a typical human torso 1.7 m in height induced by EM waves with frequencies ranging from 10 to 500 MHz have been theoretically quantified. Some numerical examples are given. The strongest internal electric field and absorbed power was found to be induced by an EM wave of about 80 MHz with the incident electric field parallel to the torso height.

Cylindrical Waveguide Applicators with Uniform Power Flow Distribution

Abstract: Design of a cylindrical waveguide applicator with a uniform power density distribution over the available cross section is described. The applicator consists of an annular layer of loss-less dielectric placed in contact with the walls of a circular waveguide. The dielectric concern of this layer is higher than that of the material to be heated and a suitable thickness leading to uniform power density distribution can be calculated.

Space-to-earth power transmission system

Abstract: A preliminary analysis was conducted to establish the requirements of a space-to-earth microwave power transmission system. The need for accurate phase control on the transmitter was established and methods for assessing the impact of power density and thermal constraints on system performance were demonstrated. Potential radio frequency interference was considered. The sensitivity of transmission system scale to variations in power source, transportation and orbital fabrication and assembly costs was also determined.

Optimization and limiting characteristics of CO2 lasers

Abstract: It is shown that the limiting characteristics of CO2 lasers are determined mainly by two parameters: the specific power of the electric discharge, referred to the square of the active medium pressure, and the product of the pumping time and the gas pressure. An investigation is made of the dependence of the efficiency and the radiation pulse shape over a wide range of the parameters. For the first time it is noted that the energy from the lower laser level can be given to the upper vibrational states of the symmetric and deformed modes, which allows high radiation density, ∼0.2 J/cm3 · atm, to be achieved, as is shown by calculation. Because of energy redistribution in the asymmetric mode the limiting gain coefficient in C02 lasers is ∼0.12 cm−1.

Dependence of the transmission coefficient of passive switches on the power density of exciting neodymium laser radiation

Abstract: An investigation was made of the dependences of the transmission coefficients of solutions of a polymethine dye, a dye based on a nickel complex, and bromated phthalocyanine on the density of the incident power in the form of picosecond and nanosecond neodymium laser pulses. The relaxation times of the excited states of the investigated dye molecules were determined. Excitation with nanosecond light pulses induced additional absorption in the investigated dye solutions.

Temperature effects on the nonlinear absorption of radiation by optical mixing in a plasma

Abstract: An analysis of the heating of plasma with arbitrary temperature and density inhomogeneity by parallel or antiparallel laser beams is presented. The average power density absorbed by a warm plasma due to the excitation of electron plasma waves at the beat frequency is determined as a function of the frequency mismatch. Formulas for the absorption efficiency of a plasma with both temperature and density variation along the beams are derived. Linear and parabolic temperature distributions are considered explicitly.

A Microwave Radiation Monitor

Abstract: A microwave radiation monitor designed for rapid measurement of microwave power density in the field is described. The instrument incorporates a broad-band spiral antenna whose design is based on a knowledge of the field pattern of a circular loop antenna. The power induced in the spiral by the radiation raises the temperature of a microbead thermistor in an electric circuit. This rise in temperature is a measure of the power density which is indicated directly on a meter.

De-Icing Using Lasers,

Abstract: : The feasibility of employing a laser to de-ice remote surfaces was investigated. A Nd:Glass laser, wavelength 1.06 micrometers, and a Ruby laser, wavelength 6943 A were used to irradiate ice grown upon six types of substrates -- asphalt, brass, concrete, aluminum, steel, and stone. It was found that a single pulse, delivered to the interface between the ice and its substrate at a power density of 10 to the 8th power to 10 to the 9th power watts/sq cm, produced fractures 0.1 to 2 cm in diameter for all substrates. If the initial fracture could be propagated by suitable scanning of the optical beam over the interface, the ice could be disrupted and thus removed from the substrate. The technique could also be a useful adjunct to de-icing methods that depend upon the existence of an initial crack. The process of producing the initial fracture was found to be limited by the thickness of the ice, the bubble content of the ice, and the focusing system.

Measurement of Power and Energy

Abstract: For the measurement of power in d.c. circuits a wattmeter is not necessary since power is then the product of ammeter and voltmeter readings. For the a.c. circuit this is only true if the power factor is unity, and for all other conditions a wattmeter is essential since such an instrument indicates true power, that is supply voltage × current × cosine of phase angle between voltage and current

Electromagnetic Non-Perturbing Microprobes

Abstract: Since 1971, the Microwave Department of the 'Centre d'etudes et de recherches de Toulouse' is effecting research on the problem of measuring temperature and power density in electromagnetic fields. The possibility of obtaining a dielectric microprobe not interfering with electromagnetic waves was studied.

V-groove power junction field-effect transistor for v.h.f. applications

Abstract: A new high-power, high-frequency junction field-effect transistor with a nonplanar V-shaped channel fabricated by preferential etching of ?100? silicon is described. The structure of this transistor is very simple, requires only three photolithographic masking steps and results in a very high packing density. A device having an effective channel length of 2 ?m was fabricated. This transistor exhibits a low-frequency transconductance of 9.6 mS/mm, a cutoff frequency of 0.9 GHz and an output power density of 25 W/mm2 of chip area.

High Power Density MHD Generators.

Abstract: : Operating parameters were calculated for MHD generators operating at power densities in the channel of 500 MW/cu m and with power outputs of 30 - 35 MW (nominal). Liquid-fueled generators, using hydrocarbon fuels such as JP-4 or RP-1 and oxygen, and solid fuel generators were investigated. Designs of both liquid and solid fuel generators are described, and estimates of their weights and sizes are given. Operation of generators at power densities of 1000 MW/cu m was investigated. Assessments of feasibility and risks involved in achieving high power density operation are made. A development plan for construction of flightweight high power density MHD generator power supplies is presented. (Author)