Showing papers on "Power density published in 1973"

Optical third-harmonic generation in alkali metal vapors

Abstract: This paper considers third-harmonic generation in phase-matched mixtures of alkali metal vapors and inert gases. Calculations show that the combination of near-resonant nonlinear susceptibilities, the ability to phase match, and the relatively high UV transparency of these vapors should allow high conversion efficiency for picosecond laser pulses with a peak power of 108-109W. Calculations of the nonlinear susceptibility and of the ratio of xenon atoms to metal vapor atoms which is necessary to achieve phase matching are given for each of the alkalies as a function of incident laser wavelength. Processes that limit the allowable peak power density and energy density are discussed and guides for determining the metal vapor pressure, cell length, and beam area are given.

Concept for a high-power-density mirror fusion reactor

Abstract: A concept for a minor-type fusion reactor based on recent advances in neutral-beam technology is shown to have improved plasma stability, a much higher power density, and a somewhat higher factor of energy gain Q, as compared with previous concepts using the magnetic-mirror principle, (auth)

Thermal limitation for CW output power of a Gunn diode

Abstract: CW output power of a sandwich-type Gunn diode was calculated numerically as functions of diode area and input power density It was shown that output power has a maximum against diode area and that the maximum power as well as the corresponding diode area increases steeply as the power dissipation density decreases within a reasonable nl product range The latter relation still holds when the temperature rise of the active layer is limited within a certain value For an X-band Gunn diode with room temperature efficiency of 6% and mounted on a cylindrical copper heat sink, the available power with a temperature rise of 170°C was about 1W when input power density was 2 × 104 W/cm2 (nl ⋍ 1 × 1012 cm−2), while the available power was about 0·25 W when input power density was 4 × 104 W/cm2 (nl ⋍ 2 × 1012 cm−2)

Method and apparatus for balancing an ultrasonic detection system

Abstract: A method and apparatus for equalizing the sensitivity of an ultrasonic detection system of the type using Doppler frequency in which a test unit generates a spectrum of energy of different frequencies, and transmits the spectrum through transducers located in the areas to be protected, to create, at a receiving transducer, an average standing-wave power density proportional to the total traveling-wave power density. The average standing-wave power density is measured to provide a means of equalizing detection sensitivity.

Life tests of a thermionic converter

Abstract: The ES-6-3 six-element thermionic assembly has been tested in a reactor for 2670 h. During the tests the electrical power of the assembly decreased from 550 W, corresponding to a specific power of ∼7 W/cm2, to 75 W. A stepwise decrease in assembly power was observed following any reduction in reactor power; this is attributed to short-circuiting of individual elements, to irreversible increase in temperature of the collectors, and to possible increase in heat loss from the emitter.

''Semiclassical'' bremsstrahlung calculations

Abstract: The quantum calculation leading to the bremsstrahlung power density which varies as the square root of the plasma temperature T is reasonably successful in predicting the x-ray production when electrons bombard metal targets. It is expected to be useful in other cases where interaction times are small, such as when electrons stream through neutral gases, or when plasmas are sufficiently dense so that the number of particles in a Debye sphere is small. In the case of rarefied plasmas, for which there is no corresponding quantum treatment, common practice is to begin with classical orbit theory and either cut off in impact parameter or in frequency in order to obtain a power density which also varies as T/sup 1/2. We show that all such semiclassical'' treatments for rarefied plasmas are either physically or mathematically inconsistent; that the usual cutoffs in impact parameter do not lead to the expected T/sup 1/2 power density in the temperature range from O.01 eV to 1 keV; and that the spectrum of the power density obtained by cutting off at the de Broglie wavelength contains frequencies in excess of the usual one-photon emission limit. (auth)

A parametric study of the performance of a TEA CO2 laser

Abstract: An investigation into the operating characteristics of a double discharge TEA CO2 laser is presented, the object of which is to optimize the available focused power density. The existence of an operating regime of enhanced peak power but degraded energy is noted and qualitatively explained.

Method and means for reducing the power density of an internal cyclotron beam

Abstract: A method and apparatus for reducing the power density of the internal beam in an isochronous cyclotron at its extraction radius or an internal target wherein the internal beam in its orbits near and at the extraction or target radius is spread axially by applying to it a time-varying electrostatic field tuned to the natural axial oscillation frequency of the beam in such orbits.

Calculated power distribution of a thermionic, beryllium oxide reflected, fast-spectrum reactor

Abstract: A procedure is developed and used to calculate the detailed power distribution in the fuel elements next to a beryllium oxide reflector of a fast-spectrum, thermionic reactor. The results of the calculations show that, although the average power density in these outer fuel elements is not far from the core average, the power density at the very edge of the fuel closest to the beryllium oxide is about 1.8 times the core avearge.

High-power density hydrazine fuel cells

Abstract: : A hydrazine-oxygen fuel cell was operated under moderate conditions of temperature and concentration at power densities up to 600 watts per square foot (1000 amperes per square foot at 0.6 volt). At this output, a power efficiency of 32% was obtained at 70C at less than molar hydrazine concentration. Power efficiencies exceeding 48% were obtained over a power density range from 40 to 200 watts per square foot by matching the temperature and hydrazine concentration optimally to the electrical load. The three major components of cell polarization were examined. Critical resistance losses were minimized by use of a 0.010-inch asbestos matrix which was more than adequate to prevent leakage of oxygen to the anode at moderate differential pressures. A projected cell thickness of 0.1 inch and a power density of 200 watts per square foot correspond to a calculated stack power-volume ratio of 16 kilowatts per cubic foot. (Modified author abstract)

Circuits for Power Density Reduction in TRAPATT Diodes

Abstract: Experiments have been performed using a single frequency tuned coaxial cavity for a TRAPATT oscillator. It is shown that increasing the bias source impedance results in a lowered dissipated power density. In general the efficiency will also be lowered, but if for each case the r.f. load is increased to the highest value permitted with respect to premature avalanching an efficiency which is approximately independent of the bias resistance is obtained. Using this technique it has been possible to decrease the dissipated power from an initial value of about 100 to less than 15 W. Results on the effect of waveshaping by higher harmonic loading are also presented. The starting mechanism in TRAPATT oscillators is also studied and shown to consist of an interaction between successively reflected bias pulses and wave trains of IMPATT oscillation.

Characteristics of radioisotope power sources in an ocean environment

Abstract: The results of this study show that lightweight radioisotope heat sources can be considered for use undersea with little shielding necessary for electronics packages in close proximity to the heat ...