Showing papers on "Power density published in 1978"

Planar magnetron sputtering

Abstract: The technology is reviewed with emphasis on implementation. PM sputtering is characterized by cathode potentials of 300–700 V and sputtering gas pressures of 1‐15 mTorr (0.1–2 Pa). Deposition rates are proportional to power density, which in turn is primarily limited by the thermal conductivity and cooling efficiency of the target. rf operating characteristics are similar to dc, but plasma plus target impedance is somewhat higher. For both rf and dc PM sputtering higher power (or current) densities are achievable at lower target potentials than for conventional sputtering. Permanent magnets and electro‐magnets have been used to produce closed electron‐trapping field patterns adjacent to the surface of both circular and rectangular planar targets. Plasma intensity and target erosion is a maximum where the magnetic field lines are parallel to the cathode surface. Deposition uniformity can be achieved by substrate motion combined with optimized magnet geometry. For a given material at equivalent deposition r...

On power estimation in maximum entropy spectral analysis

Abstract: A conceptually simple method for power estimation in maximum entropy spectral analysis, based on evaluation of complex residues of the spectral density estimator, is suggested. Numerical integration of the peaks of the power density function is thus avoided. The agreement in simple cases with conventional estimates is demonstrated, and the explicit performance is analyzed in detail in a series of examples. The close connection between the residue power estimate and the estimate proposed recently by Pisarenko is pointed out. The method is particularly suitable for spectral decomposition of low noise time series with several harmonic components, because it allows a direct listing of frequency and power estimates, provides an indication of the purity of the obtained harmonic components and enhances the resolution of the maximum entropy spectral density estimator. Computing facilities with modern program libraries are required for efficient use of the method.

Method and apparatus for evaporating materials in a vacuum coating plant

Abstract: A method and apparatus for evaporating materials in a vacuum evaporator by bombarding a material to be evaporated with electrons generated by a low voltage arc discharge sustained between a hot cathode and an anode comprising, locating the hot cathode in a chamber which is separated from an evaporation chamber wherein the hot cathode chamber communicates with the evaporation chamber through an aperture, connecting the material to be evaporated as the anode in the evaporation chamber, continuously introducing a gas into the hot cathode chamber while evacuating the evaporation chamber to maintain a pressure differential therebetween, and concentrating the beam of electrons by a magnetic field so as to obtain on the surface of the anode a power density sufficient for evaporation.

Analysis of Power Density Distribution in Microwave Ovens

Abstract: The power density distribution and the input admittance of the microwave oven are evaluated theoretically. The experimental results for the power density distribution show a good agreement with the...

Power density in direct nuclear‐pumped 3He lasers

Abstract: The interaction of neutron beams with He-3 gas is of interest for nuclear pumped lasers. The effects of spectral dependence of the neutron beam, neutron attenuation in the gas-filled laser tube, and transport of the charged-particle He-3(n, p)He-3 reaction products are treated in detail. An expression for the energy density as a function of position within the tube, tube radius, operating pressure, and neutron fluence is given. The maximum energy density within the optical cavity is achieved when the tube radius is 3.26/P where P (atm) is the operating pressure. The variation of radius by 50% above and below optimum will change the energy density at most by 10%, although performance degrades quickly for radii outside this range. If the optimum tube radius is used for each operating pressure, then the power density on the centerline (kW/cu cm) is given as 9.3 x 10 to the -18th power times the operating pressure times flux in a thermal neutron environment of flux (n/sq cm sec).

Gain, fluorescence and energy extraction characteristics of photostabilised atmospheric pressure UV nitrogen lasers

Abstract: The authors report on a detailed investigation of the gain, fluorescence and energy extraction characteristics of photopreionisation-stabilised atmospheric pressure UV nitrogen lasers excited at pump powers of up to approximately 5*109 W cm-3. The lasers provide specific power outputs of approximately 6 MW cm-3.

Efficient second harmonic generation in a KDP crystal pumped with picosecond YAG:Nd3+ laser pulses of 0.5 Hz repetition frequency

Abstract: Frequency doubling in a KDP crystal, pumped with single pulses of 30 psec duration, was optimized. It was found that, under picosecond pumping conditions, there was a definite optimal relationship between the length of a crystal and pump power density. The energy efficiency of conversion to the second harmonic was 92% for a pump power density of 8×109 W/cm2 in a crystal 14 mm long.

Phase and power density distributions on plane apertures of reflector antennas

Abstract: Complex coordinates are used under the assumptions of geometrical optics to study the relations between phase and power density distributions on plane apertures of reflector antenna systems. No symmetry assumptions are made and the results form a generalisation of existing work in the field. The synthesis of a dual reflector system to produce given aperture phase and power distributions when illuminated by a point source of prescribed power density is shown to depend on the solution of a particular partial differential equation of the Monge-Ampere type. Finally it is shown that even in cases of symmetry the use of complex coordinates simplifies the design equations.

Device and method for noresonantly Raman shifting ultraviolet radiation

Abstract: A device and method for nonresonantly Raman shifting broad band uv excimer laser radiation, which enhances preselected Stokes signals by varying the pressure of the Raman scattering medium, the focal interaction length of the incident radiation within the Raman scattering medium and its power density level. Gaseous molecular H2, D2, CH4 (methane), HD and mixes thereof, and liquid N2 are used as the Raman scattering medium to frequency shift the outputs of high power KrF and ArF lasers. A cable fed discharge with an unstable resonant cavity configuration is utilized to produce the output laser power levels required for operation.

Electric power from laser fusion - The HYLIFE concept

Abstract: A high yield lithium injection fusion energy chamber is described which can conceptually be operated with pulsed yields of several thousand megajoules a few times a second, using less than one percent of the gross thermal power to circulate the lithium. Because a one meter thick blanket of lithium protects the structure, no first wall replacement is envisioned for the life of the power plant. The induced radioactivity is reduced by an order of magnitude over solid blanket concepts. The design calls for the use of common ferritic steels and a power density approaching that of a LWR, promising shortened development times over other fusion concepts and reactor vessel costs comparable to a LMFBR.

NUWMAK: an attractive medium field, medium size, conceptual tokamak reactor

Abstract: A new conceptual design of a medium field tokamak reactor shows that such systems can have high power density, a high degree of modularity, and moderate size. The design, called NUWMAK, is especially attractive from the viewpoints of system accessibility, low levels of long term radioactivity, and minimum penetrations. The power density (10 MW/m/sup 3/) and electrical power output (660 MW) are chosen as typical of a full scale reactor operating in a base-loaded mode. The plasma has a noncircular D shape and a toroidal ..beta.. of 6%. Plasma heating is by RF at omega = 2 omega/sub CD/ (92 MHz) based on the fast magnetosonic mode. The TF coil set is unique in that just 8 superconducting coils are used. A set of 16 small water cooled copper trim coils that do not encircle the vacuum chamber correct the field ripple to below 2%. The blanket is constructed of the titanium alloy, Ti-6A1-4V, and is designed to minimize thermal cycling, to provide internal energy storage, and to eliminate the need for an intermediate heat exchanger. A lithium-lead eutectic, Li/sub 62/ Pb/sub 38/, with a melting point of 464/sup 0/C is used as the tritium breeding and thermal energy storagemore » material.« less

Generation of Anomalous High Energy Picosecond X-Ray Pulse from Laser-Produced Plasma

Abstract: Dynamical behavior of X-ray emission from laser-produced plasma has been extensively studied up to the power density of 1016W/cm2 It has been observed that the intensities of emitted hard X-ray pulses with picosecond time duration are anomalously enhanced as if it has a threshold laser intensity Strong anomalies in spatial distribution of emitted X-ray are found out in the direction perpendicular to the plane of laser polarization Sometimes intense "spots" were created on the X-ray photographic films These results are attributed to the relativistic effect caused by the electron streaming due to oscillating two stream instability at critical density surface of the plasma

Lighttwater type power reactor and its operation method

Abstract: PURPOSE:To increase a power density by arranging a square grid pattern of a number of fuel rods having a small outer diameter in the central area of a number of fuel assemblies forming a core and having an equal outer size and by arranging a less number of fuel rods having a large outer diameter in the circumferential area therethereof.

A fully implanted V-groove power MOSFET

Abstract: This paper presents a microwave V-Groove Silicon Power MOSFET (VMOS) with drain to source breakdown voltage of 100V and drain current capability of 0.5A, and a forward transconductance of 150 millimho. A gain-bandwidth product (f T ) of 1.5 GHz has been measured. The power density of this enhancement device is about 20KW/cm2of the active area. A refractory metal scheme has been used for improved device reliability. Ion implantation has been utilized in processing the device in order to obtain process control and good threshold voltage uniformity. A theoretical model of the device has been developed, and experimental data are compared with simple theory.

Imaging conditions for electron‐beam micromachining

Abstract: In electron‐beam micromachining the highest attainable power density in the substrate material is required for material removal. The application of the Zr/W(100) thermal field emitter combines the advantages of a low electron energy for a minimum electron penetration range in the substrate and a high current density in the final spot. The range of final electron spot sizes considered is from 10 to 100 nm. The spot size on‐axis, as well as off‐axis when scanning the beam, is mainly limited by chromatic aberration. A considerable improvement of the power density, up to about 108 W/cm2 at 3 kV, is obtained by using a high beam current collection efficiency and a symmetrical imaging system of unit magnification. Therefore, a power density of more than 1013 W/cm3 for most of the substrate materials results, allowing operation times of less than 1 μs per image element. A proposed illumination system for electron‐beam micromaching with a working distance of 4 mm is outlined. The intention is to replace the electron optics of a SEM by the proposed illumination system for micromaching purposes.

Power density and electrical efficiency in closed cycle MHD generator with fully ionized seed.

Abstract: Effects of a reduced seed concentration on performances of a nonequilibrium MHD generator are investigated by calculating power densities and electrical efficiencies for both Faraday and Hall generators. It is shown that high electrical efficiencies and high power densities are obtained simultaneously by suppressing the ionization instability with reduced seed fractions (10−4 ∼10−5) when values of the effective electrical conductivity and the effective Hall parameter recover to above 50% of their ideal ones. Results also indicate that argon is more suitable for a working fluid than helium in the case of a reduced seed concentration.

Advanced Photovoltaic Synchronous-Orbit Spacecraft Power Systems

Abstract: The state-of-the-art of photovoltaic power systems, for use in synchronous-orbit spacecraft, is characterized, including solar array, battery, and power control component performance. Advanced developments in each of these areas are reviewed, and performance improvement projections are made for the 1980-1990 time period. It is estimated that photovoltaic power system specific weight could improve from a present value of 126 kg/kW to approximately 43 kg/kW in 1985. These performance predictions are compared to nuclear system performance projections over the same period. The analysis indicates that advanced photovoltaic power systems will exhibit specific weights lower than isotope and nuclear reactor systems for power levels up to approximately 25 kW. At higher power levels, batteries with higher energy density would be required to compete with the projected performance of advanced nuclear systems. N this paper, we review state-of-the-art performance characteristics of synchronous-orbit power system components, discuss technology advancements, extrapolate overall system performance into the 1980-1990 time period, and finally, make alternative power system comparisons. Power subsystem performance improvement areas include solar array power density, battery energy density, and power control electronics power density. These components typically comprise 15-20% of total spacecraft weight. Increased spacecraft payload weight allocation and total system capability improvement will result from power system weight reduction.

Method of and apparatus for laser machining

Abstract: PURPOSE:To obtain stable shape in machining through removal or fusing of a rise formed around the portion of the workpiece machined with a laser beam irradiated thereon at a power density below the evaporation threshold value of the workpiece after removal machining is accomplished with a laser beam converged and irradiated thereon.

Surface damage caused by laser radiation to solid transparent dielectrics

Abstract: The dependence of the threshold power density of laser radiation on the diameter of a focal spot is calculated for the surface damage of solid transparent dielectrics. The calculation is carried out on the assumption that this dependence is governed by the development of thermal instabilities at absorbing inhomogeneities. The results obtained explain physically the experimental data, particularly the observed increase in the surface breakdown threshold when the surface of a dielectric is subjected to a preliminary treatment.

High Power Magnetohydrodynamic System

Abstract: : During this phase a lightweight, high performance hot gas flow train using liquid oxygen and JP-4 was designed and component modeling completed. The magnetohydrodynamic channel/diffuser performance parameters which were used as the design criteria were an output power of 30 MWe, a specific energy extraction of 1.0 MJ/kg, and a specific power density of 200 MWe/cu.m. To achieve these performance requirements, the required characteristic velocity efficiency of the combustion system was greater than 99%. During this program a limited amount of development testing was completed using a heat sink combustor and a diagnostics channel. These tests measured the combustor characteristic velocity efficiency and the gas electrical conductivity, as well as pressures, vibrations, and temperatures. The results of the development test program, which verified the design assumptions used to achieve the performance requirements, were a characteristic velocity efficiency of nearly 99% and a gas electrical conductivity at the magnetohydrodynamic channel inlet of 15 mhos/m.

Nitrogen laser emitting ultraviolet radiation of high specific power at a high pulse repetition frequency

Abstract: A study was made of the characteristics of a transverse-discharge molecular nitrogen laser (λ =337.1 nm). When the length of the discharge chamber was 190 mm, the average output power was 210 mW. The specific average and pulse powers exceeded 40 mW/cm3 and 40 kW/cm3, respectively. Stimulated emission was observed at pulse repetition frequencies in excess of 2 kHz. The high specific power and high pulse repetition frequency were achieved in a laser discharge chamber whose walls were made of a ceramic characterized by a high thermal conductivity and were in contact with a relaxing plasma.

Comments on ''Power conversion of energy fluctuations''

Abstract: The equations used by Yater to calculate dc power conversion of energy fluctuations are shown to contain mistakes which prohibit their use in general calculations. Corrected equations are presented which converge to known results in the limit of large capacitances: Yater's conversion-efficiency equations do not. Calculations with the present equations are used to demonstrate that the high conversion efficiencies approaching the Carnot cycle do occur, but only for circuit situations where the power output is considerably below the maximum obtainable fluctuation power and where the circuit capacitances are impractically small (approx. = 3 x 10/sup -19/ F). Conversion efficiencies at the maximum output power are considerably smaller than the Carnot-cycle limit. No net power conversion is predicted for practical circuit capacitances.

Meteorological effects on Schottky-barrier solar cells

Abstract: The effect of different meteorological conditions on Schottky-barrier solar-cell outputs has been investigated, using a model for an n-type solar cell. Similar results to those for p-n junction cells have been obtained, namely that although the output power density is reduced, a much higher conversion efficiency is possible when the solar cell is illuminated with diffuse radiation. The effect of the density of interfacial states, and the metal work function, upon the J/V characteristics and on the conversion efficiency is shown to be an important feature of Schottky-barrier solar cells.

Diagnostic Techniques in Combustion MHD Flows

Abstract: The U.S. national program in MHD electric power generation is predicated on the direct firing of pulverized coal, using MHD as a topping cycle for a regular steam plant. Extensive system studies predict the thermal efficiency of a large combined MHD/Steam plant will be in the range 50 – 55 % compared with 35 – 40 % for a conventional steam plant. The basic idea is to burn a fossil fuel at a very high temperature (~ 3000 K), seed it with an easily ionizable material (K, Cs) and expand the resulting combustion products plasma through a nozzle into a generator channel at high (usually subsonic) velocity u ⩽ cs ~ 1000 m/s. The generator channel is immersed in a strong transverse magnetic field B, and is fitted with electrodes in the walls for electric power take off. The induced electric field in the plasma is E = u × B, the induced current density is J~σE, where σ is the electrical conductivity, and the generated power density is P~J · E~σu2B2.

Finite element analysis of a twenty-five megawatt power tube and a high-energy water-cooled heat sink for fusion research

Abstract: The finite element method is used to calculate the thermal stress behavior of structures with up to 30 kW/cm/sup 2/ of surface energy bombardment. Analysis of structures by this method in the early design stage can be done at relatively low cost and offers a reduction in design and development times. Further, the method permits the analysis of structures with nonlinear properties, such as temperature-dependent thermal conductivity or radiation-induced swelling. The method is applied (1) to a power tube anode capable of dissipating two megawatts of power and (2) to a beam dump for use in a Tokamac Fusion Test Reactor with a power density of thirty kW/cm/sup 2/.

Microwave Radiation-Pattern Measurements in the Presence of Biological Specimens

Abstract: Power density is used extensively as an index of hazard to living systems from microwave radiation. To assess this, the biological effect observed in test specimens is related to power density, as measured in the absence of the specimen. The usefulness of power density as a biologically meaningful parameter has often been questioned and other alternatives have been proposed. In this paper, the authors show the restricted applicability of power density as an indicator of both biological hazard and beneficial effects caused by microwave fields. Power density measurements, at X-band microwave frequencies, were carried out in an anechoic chamber. Measurements were conducted in the absence and in the presence of biological specimens (animals and plant vegetation), with the aid of an isotropic microwave probe. Dramatic differences in the radiation patterns were observed, attributable to the large disturbance introduced by the biosystem on the imposed electromagnetic fields. Thermographic analysis (IR scanning) and microwave radiometry complemented the investigation.

Energy sources and conventional magnets

Abstract: A power supply for an EPR toroidal field magnet is described It is concluded the main network can supply the necessary power estimated to be of the order of 1 GW The power system response to fault conditions in the experiment is discussed The utilization of the power dissipated in the magnet is desirable and is referred to in connection with the cooling system arrangements

MHD conversion of solar energy

Abstract: Low temperature plasmas wherein an alkali metal vapor is a component are uniquely suited to simultaneously absorb solar radiation by coupling to the resonance lines and produce electrical power by the MHD interaction. This work is an examination of the possibility of developing space power systems which take advantage of concentrated solar power to produce electricity. It is shown that efficient cycles in which expansion work takes place at nearly constant top cycle temperature can be devised. The power density of the solar MHD generator is lower than that of conventional MHD generators because of the relatively high seed concentration required for radiation absorption and the lower flow velocity permitted to avoid total pressure losses due to heating.