Showing papers on "Power density published in 1983"

Thermoelectric energy conversion with solid electrolytes.

Abstract: The alkali metal thermoelectric converter (AMTEC) is a device for the direct conversion of heat to electrical energy. The sodium ion conductor beta"- alumina is used to form a high-temperature regenerative concentration cell for elemental sodium. An AMTEC of mature design should have an efficiency of 20 to 40 percent, a power density of 0.5 kilowatt per kilogram or more, no moving parts, low maintenance requirements, high durability, and efficiency independent of size. It should be usable with high-temperature combustion, nuclear, or solar heat sources. Experiments have demonstrated the feasibility of the AMTEC and confirmed the theoretical analysis of the device. A wide range of applications from aerospace power to utility power plants appears possible.

High-power, subpicosecond 10-microm pulse generation.

Abstract: Two-picosecond, 10-μm pulses, generated by optical semiconductor switching, have been regeneratively amplified in a multiatmosphere TE CO2 gain module. Pulses have been produced with a peak circulating energy of ~15 mJ and a power density in the gain medium in excess of 1012 W/cm2. A plasma-breakdown wave, traveling with the regeneratively amplified pulse, combined with anomalous dispersion in the NaCl windows, has permitted compression of these pulses to less than 1 psec in duration.

The power density of a surgical laser beam: its meaning and measurement.

Abstract: This paper discusses the fundamental concepts of matter, energy, power, and power density, with specific emphasis on the power density of a laser. It points out that a laser beam does not have a single, unique value of diameter within which all of its radiation is confined. Therefore, a computation of power density requires both a value of diameter, and the value of the fraction of total power which is transmitted within that diameter. Some possible means of measuring diameter, power, and power density are presented.

Hyperthermia by magnetic induction: experimental and theoretical results for coaxial coil pairs

Abstract: High-frequency magnetic induction for producing elevated temperatures in human tumors can be accomplished with several electrode arrangements. We describe the physical characteristics of a coaxial pair of electrodes or current loops placed on either side of the body. This electrode arrangement can improve the depth of power deposition within the body relative to that obtained with an electrode circumferentially encircling the body or a single surface applicator ("pancake coil"). We report results of measured and calculated magnetic field distributions and power density distributions obtained with a coaxial pair. The effect of varying load geometry upon the power density distribution was shown to be significant in several static phantom experiments. Electrode geometry was also important, as shown by calculations of power deposition as a function of electrode diameter in a simple model of body tissue conductivities. The power density was found to diminish at given depths as the electrode diameter decreased. Finally, values of magnetic fields were measured during treatment of human subjects with a coaxial electrode pair and were found to vary significantly from subject to subject. This resulted from variation in the geometry and electrical characteristics of tissues among subjects, and indicates the difficulty of formulating a standard accurate model for use with this magnetic induction technique.

Test results on plasma direct converters

Abstract: The power carried out through the ends of a mirror fusion reactor by escaping plasma can be converted directly into electricity by a plasma direct converter. Test results from three plasma direct c...

High‐power KrF laser transmission through optical fibers and its application to the triggering of gas switches

Abstract: The fundamental transmission characteristics of KrF laser radiation (248 nm) through the step‐index‐type fused quartz fiber have been determined. For the step‐index‐type fused quartz fiber used the transmission loss is about 0.5 dB/m at power densities up to 3.9 MW/cm2 and 2 dB/m at 100 MW/cm2. One of the applications of this intense UV KrF laser transmission via optical fibers is the development of a gas insulated spark‐gap switch trigger by a KrF laser through a 2‐m‐long optical fiber. As a result, at a voltage 90% of the self‐breakdown voltage and at an illumination power density of 1.2 MW/cm2, a full trigger jitter of less than 5 ns is realized and it corresponds to a 1‐σ jitter of less than 1 ns. The illumination energy is as low as 10 μJ/shot.

Large area electron beam annealing

Abstract: We have achieved wide area (38 cm2) electron beam annealing of ion implanted silicon wafers using a glow discharge electron beam with electron energies between 3 and 7 keV. A continuous beam 7 cm in diameter with a power density up 90 W/cm2 was used to anneal the 7‐cm‐diam central portion of boron‐implanted (30 keV, 5×1015 atoms/cm2) n‐type 〈100〉 silicon wafers 10 cm in diameter. Annealing was obtained without redistribution of the original dopant profile using a 15‐selectron beam exposure. Due to the high electron beam power density achieved over a large area, one can uniformly anneal an entire wafer in a single exposure without sample or beam scanning.

Contact glass for use with high power lasers--geometrical and optical aspects. Solution for the angle of the anterior chamber.

Abstract: A new mirror contact glass for irradiation of pathological structures within the angle of the anterior chamber with high power lasers is described. The new contact glass is distinguished by its optimized optical characteristics. Due to its spherical front surface, tipping movements, as necessary in inspection and aiming manoeuvres, have no significant influence on the focus diameter. That the imaging quality is independent of the contact glass manipulations is seen as essential for laser surgical tasks with high power lasers, since changes in the focus diameter critically affect the power density at the focus and thus the intensity of the microsurgical effects. The increased spatial reliability of the laser-induced microexplosion is thought to be a further merit of the new contact glass.

A unique fast atom source for mass spectrometry applications

Abstract: An alternative source for the generation of fast atom beams developed for fast atom bombardment mass spectrometry is described The principle of operation is based on a Capillaritron ion source described elsewhere Easy to operate with any gas and requiring low maintenance, the source should prove extremely useful for the analysis of high molecular weight compounds Residual ions are separated from fast atoms, produced by a novel charge transfer geometry, before the beam emerges from the source Power calorimetry was utilized as the diagnostic technique to quantify and evaluate the fast atom beam parameters Using 8 kV Xenon beams, measurements of ion currents and power density fluxes were made with and without ion beam deflection It was determined that the power contribution due to fast atoms in an undeflected beam can vary from 40% to 80% of the total power delivered to a target depending on the gas flow rate and ion beam energy In one case, it is shown that 42% of the total power imparted to a probe consisted of fast Xenon atoms corresponding to a deposition at the target of 16 mW cm−2 Below a certain gas flow rate, depending on the gas, the power density was determined to be flow rate dependent Above this value, the peak power density is constant and limited to further increases by space charge effects in the ion beam A sample spectrum using a fast atom Capillaritron source installed on a Hewlett-Packard 5985B quadrupole mass spectrometer is shown

Non-LTE Analysis of Soft X-Ray Spectrum from Laser-Irradiated Gold Plasma

Abstract: Soft X-ray spectrum from laser-irradiated Au plasma is analyzed by 1-D hydrodynamic Lagrangian code with a non-LTE model and a multi-group radiation transport code and is compared with the experimental results. The physical meaning of the experimentally obtained spectrum is clarified and the total emitted power density proves to have maximum value at a certain combination of ion density and electron temperature.

Power density flattening in fusion-fission hybrid reactors

Abstract: A number of approaches to the design of fusion-fission hybrid reactor blankets having a flat power distribution and constant energy multiplication are described. These include the use of reflectors, lithium control, spectral shift control, and inherent control. These approaches are illustrated for natural-uraniumfueled, light-water-moderated blankets.

A DYE LASER SOURCE OF MONOCHROMATIC UV‐B and UV‐C RADIATIONS FOR BIOLOGICAL ACTION SPECTROSCOPY

Abstract: We have used a flashlamp driven tunable dye laser as a radiation source for observing UV-C and UV-B action spectra of two eukaryotic microorganisms. The general nature of the irradiation system and various operating parameters are described. The laser produces the high power output required for UV-B action spectroscopy; it is tunable throughout the UV-B range with the very narrow bandwidth required for high resolution action spectra. The peak power density does not appear to reach the threshold of ‘two photon’ biological effects, a concern when using pulsed lasers for action spectroscopy. The laser is somewhat more expensive and considerably more difficult to operate compared with arc-monochrometer systems; it is generally equal or greater in UV-B power and has distinct advantages in tunability and bandwidth of the spectral output.

Method of measuring reactive acoustic power density in a fluid

Abstract: A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas.

ICRF heating experiments on JIPP T-II

Abstract: Data of JIPP T-II ICRF heating experiments are presented The experiment covers three typical cases: the low-concentration hydrogen minority case, the high-concentration hydrogen minority case, and the 3He-minority case The best heating efficiency is obtained for the 3He-minority case It is shown through power balance analysis that the two H-minority cases are different in the wave energy deposition profile The difference is explained by the presence of a local cavity mode in the high-concentration minority case The ion temperature stops rising at a power density level of 065 W-cm−3 for the hydrogen minority experiments No such deterioration is found in the case of the 3He minority experiment up to a power density level of 045 kW-cm−3 This is the maximum possible to attain within the maximum power injection (180 kW) up to which the experiment is conducted An analytic solution of the Fokker-Planck equation is derived in order to interpret the deterioration of the heating efficiency

Plasmon-resonant aerosols for space optics

Abstract: We identify a cloud of plasmon-resonant particles as an ultimate low-power third-order nonlinear-optic medium that may be suitable for configuring large holographic optical elements in space. We compute the third-order susceptibility and the saturation power density of such a cloud in a space environment. We find that electrostatic repulsion of the particles because of charging by the background plasma dominates as the effective internal pressure of the cloud. The pump-power density required for configuring a space hologram in a cloud of plasmon-resonant particles for 100-μm radiation under ideal conditions is computed to be ~1 W/m2 for a background plasma density and an electron temperature of 108 cm−3 and 1 eV, respectively. The scaling behavior of the pump-power density with the radiation wavelength and the cloud thickness is exhibited and compared with results for nonresonant particles.

Optical monitoring for rate and uniformity control of low power plasma-enhanced CVD

Abstract: Plasma‐enhanced CVD requires close control of the plasma power density for reproducibility of both deposition rate and spatial uniformity in a radial‐flow reactor. Frequently the low rf power levels needed are not adequately controlled by the output power control of the relatively high power rf generator found in most commercial multipurpose plasma etch/deposition systems. This paper describes very simple and inexpensive broadband optical monitoring of the plasma emission for improved control sensitivity. The technique has the advantage of directly monitoring the plasma intensity, avoiding effects of variable power transmission losses between the rf generator and the plasma. Application to the control of low power plasma‐enhanced CVD of ‘‘SiO2’’ from Ar:SiH4:N2O plasmas, where the monitor signal is almost entirely due to near infrared Ar emission, is described.

Performance demonstration of a high-power space-reactor heat-pipe design

Abstract: Performance of a 15.9-mm diam, 2-m long, artery heat pipe has been demonstrated at power levels to 22.6 kW and temperatures to 1500/sup 0/K. The heat pipe employed lithium as a working fluid with distribution wicks and arteries fabricated from 400 mesh Mo-41 wt % Re screen. Molybdenum alloy (TZM) was used for the container. Peak axial power density attained in the testing was 19 kW/cm/sup 2/ at 1465/sup 0/K. The corresponding radial flux density in the evaporator region of the heat pipe was 150 W/cm/sup 2/. The extrapolated limit for the heat pipe at its 1500/sup 0/K design point is 30 kW, corresponding to an axial flux density of 25 kW/cm/sup 2/. Sonic and capillary limits for the design were investigated in the 1100 to 1500/sup 0/K temperature range. Excellent agreement of measured and predicted temperature and power levels was observed.

Optically Pumped Laser Operation of InGaAsP/InGaP Double Heterostructures Grown by Metalorganic Chemical Vapor Deposition

Abstract: InGaAsP/InGaP double heterostructures have been grown on GaAs(100) substrates by low pressure metalorganic chemical vapor deposition. We have carried out a lasing experiment with a cleaved sample of ~200 µm width by optical pumping. At high excitation levels, we have observed a stimulated emission of a wavelength of 717 nm at 150 k. The threshold power density is estimated to be about 4.5×104 W/cm2 at this temperature. We also mention the room-temperature lasing operation of similar double heterostructure samples.

Heat flow in thermally addressed liquid-crystal displays

Abstract: Thermal addressing of both smectic and nematic liquid-crystal displays by melting has recently been demonstrated and is very promising. We present a theoretical and experimental investigation of the heat flow characteristics and suggest suitable combinations of power density and pulse length. In addition, we demonstrate a simple method of measuring the thermal diffusivity of the liquid crystal.

Continuous tokamak operation with an internal transformer

Abstract: A large improvement in efficiency of current drive in a tokamak can be obtained using neutral beam injection to drive the current in a plasma which has low density and high resistivity. The current established under such conditions acts as the primary of a transformer to drive current in an ignited high-density plasma. In the context of a model of plasma confinement and fusion reactor costs, it is shown that such transformer action has substantial advantages over strict steady-state current drive. It is also shown that cycling plasma density and fusion power is essential for effective operation of an internal transformer cycle. Fusion power loading must be periodically reduced for intervals whose duration is comparable to the maximum of the particle confinement and thermal inertia time scales for plasma fueling and heating. The design of neutron absorption blankets which can tolerate reduced power loading for such short intervals is identified as a critical problem in the design of fusion power reactors.

Detection of megagauss spontaneous magnetic fields in a laser plasma created by λ=0.53 μ radiation

Abstract: Spontaneous magnetic fields of 1.5–2 MG intensity were recorded in the corona of a laser plasma created by λ=0.53 μ radiation of 3×1014 W/cm2 power density.

Engineering Aspects of Lower Hybrid Microwave Injection into the Alcator C Tokamak

Abstract: The authors describe here the RF system currently installed on Alcator C that is being used to inject in excess of 1 MW of net RF power into the tokamak plasma during lower hybrid heating and current drive studies. This system provides for RF power and phase monitoring in each of the individual waveguides of the two 16 waveguide launching arrays, and also for fault protection both at the waveguide arrays and klystrons. Using this system good waveguide-plasma coupling has been obtained and net RF power densities of 9 kW/cm/sup 2/ have been injected by the waveguide array without microwave arcing.

Method and device for determining the local power density in bodies affected by electromagnetic losses in the event of heating using pulsed radio-frequency power

Abstract: In the application of microwave hyperthermy there is the problem of determining the local temperature distribution as far as possible without introducing probes. Instead of the normally customary CW hyperthermy, the first step is to apply the same mean power in the form of short pulses. The short pulses generate in the body measurable mechanical shockwaves, even in the case of relatively low mean power densities (cf. microwave hearing effect). The mechanical shockwaves thus generated can be detected using suitable microphones on the surface of the body, and can then be evaluated for the purpose of reconstructing the local source distribution and thus of reconstructing the RF power density distribution.

Ion-Beam Processing of Ion-Implanted Si

Abstract: Substrates can undergo major temperature excursions during ion implantation if they are not well heat sunk. At power densities on the order of 50 watts per cm−2 radiatively cooled Si will melt in a matter of seconds. Such power densities can be maintained over a few sq. cms with many of the beams produced by even the moderate current machines currently used for doping Si and the III-V’s. We have made use of this fact to study pulsed ion-beam annealing of implanted Si. Two types of studies have been carried out. In the first, 5–20 sec proton irradiations were done at power densities of 3–35 watts cm−2 to produce sample temperatures of 500 to 1100°C. 2×1016 cm−2 280 keV B, BF2, As and P implants were annealed in this manner. Sheet resistances, ρs, versus power density curves were obtained for each ion and compared to psρs vs T data obtained for furnace annealed companion samples. In the second study the 2×1016cm−2 280 keV implants were carried out at progressively higher current densities so that the dopant beam itself raised the sample temperature to 500–1000°C. For each ion (other than B) it was possible to obtain power densities which resulted in self-annealing implants whose sheet resistances were as low as those obtained with the optimal furnace anneal. Details of the experiments, electrical and physical properties of the pulsed ion-beam annealed layers and device applications will be presented in this paper.

Coupling Properties of Phased Waveguides in LHRF Heating Experiment in JFT-2 Tokamak

Abstract: A phased array of four waveguides was used as the wave launching system in an LHRF heating experiment in the JFT-2 tokamak. The coupling properties, particularly the reflection coefficient were investigated up to a power of 250 kW. The lack of dependence of the reflection on the phase difference Δ at the high power of 70 kW obtained in an early experiment with an aluminium launcher is well explained by a theory in which the dissipation due to discharge is taken into account. After the launcher was improved in order to suppress the discharge, the reflection depended on Δ even at a high power of 100 kW. Also, the reflection depended on the power density up to 16 MW/m2. This result agrees with these obtained from a linear theory in which a small modification due to ponderomotive force is incorporated.

Harmonic power flow studies. Volume I. Theoretical basis

Abstract: This is the first volume of a two volume final report for the Electric Power Research Institute, contract RP1764-7. The work described here is the development of an electric power flow algorithm capable of handling nonlinear loads and resulting harmonic signals. In particular, as few simplifying assumptions as possible are made in order to retain accuracy - particularly in the calculation of harmonic signal amplitudes near resonance, light loading conditions, in cases of interference, and in other instances of interest.