Showing papers on "Power density published in 1972"

Forced‐convective‐flow carbon monoxide laser

Abstract: Forced convective flow has been applied to a CO laser, resulting in an order‐of‐magnitude enhancement of the output power density over what can be achieved from the same laser under diffusion‐dominated operation. A 1‐m‐long 2.5‐cm‐diam‐bore laser has produced 400 W of cw emission at 20% electrical efficiency.

Electrical CO‐mixing gas‐dynamic laser

Abstract: An electric‐discharge CO‐mixing laser is described in which N2 is vibrationally excited in an electrical discharge and then mixed with cold CO in a supersonic expansion providing a population inversion between CO vibrational bands. Continuous output is achieved from an optical cavity established transverse to the flow. Maximum laser power obtained to date is 45 W, corresponding to an efficiency of 4% and a volumetric power density of 6 W/cm3.

High Power Laser Welding

Abstract: A review of recent developments in high power, carbon dixoide laser welding is presented. Deep penetration welding in stainless steel to 0.5-in. thick, high speed welding in thin gage rimmed steel and gas shielded welding in Ti-6Al-4V alloy are described. The effects of laser power, power density, focusing optics, gas-shielding techniques, material properties and weld speed on weld quality and penetration are discussed. It is shown that laser welding performance in thin materials is comparable to that of electron beams. It is further shown that high quality welds, as evidenced by NDT, mechanical and metal-lographic tests, can be achieved. The potential of the laser for industrial welding applications is indicated.

Optimum Charged Aerosols for Power Conversion

Abstract: Charged aerosols capable of efficient power transduction in power conversion devices are discussed These charged aerosols comprise charged liquid droplets, submicron solids, or large molecules in a carrier gas To achieve efficient transduction, the charged particles must have an optimum ratio of the radius to the number of charges This optimum ratio is derived for various operating conditions Processes and devices are described for producing charged particles having an optimum ratio Elongated conductive particles, such as elongated liquid rodlike submicron microcrystals or long molecules, may be employed to increase the apparent dielectric constant and decrease the space charge of the conversion space, and thus increase output current and power density A mathematical‐physics analysis provides optimum ratios r/N as a function of relative gas density and a lumped parameter The conditions for five cases are distinguished and discussed

Some effects of the rhodamine laser radiation on absorbing materials

Abstract: The first investigations were made of the damage to absorbing materials caused by the radiation generated in a rhodamine 6G laser in the form of structure-free pulses. The laser was pumped by flashlamps and its output was in the form of 55-?sec pulses of 12?J energy. The maximum radiation power density was 3 ? 106 W/cm2. This radiation produced a quasistationary supersonic plasma jet with a relatively large angle of divergence. A static shock wave was formed in this jet. The dome-shaped configuration of this wave was determined by the geometry of the plasma jet. High-speed spectroscopic cinematography established that the spectrum was excited mainly in the static shock wave. The discontinuous structure of the plasma jet was probably due to the explosive (bulk) nature of the evaporation of a solid. The frequency of ejection of plasma bunches from lead was ~1 MHz (this was achieved using laser radiation of ~3 ? 106 W/cm2 power density). The velocity of the plasma jet was determined. The pressure in the interaction zone was estimated. Some features of the effect on the absorbing materials were analyzed.

Thermal runaway in semiconductor laser windows.

Abstract: A small perturbation model is used to obtain analytical expressions for the critical or runaway power density for laser windows constructed of semiconductor materials. These equations are used to compute the critical power density for several realistic window installations taking account of the finite value of realizable convection cooling coefficients. Computations were prepared for silicon transmitting 4.0-μ radiation and for germanium at 10.6 μ. In this way it is shown that power densities are principally limited by the effectiveness of cooling from the face of the window, that is, the surface perpendicular to the laser beam. Since convection cooling coefficients are small the transmission of high power densities through semiconductor windows is therefore contingent upon finding more effective means to cool the window from the face. Finally, a simplified calculation was made in an attempt to account for nonuniformity of the incident laser beam. The results show the nonuniformity reduces the runaway power for a given window, but not severely.

Double-Discharge TEA Laser Beams

Abstract: The energy and power density distributions of a multi-transverse-mode laser beam are predicted from a simple theoretical model. The corresponding experimental verifications show a good agreement for both the near- and far-field behavior of these beams. Finally, a method for optimizing the peak power density in the focal volume of a converging element is suggested.

Fusion of workpieces

Abstract: 1,268,044. Seaming. BRITISH OXYGEN CO. Ltd. 22 May, 1969 [29 May, 1968], No. 25742/68. Heading B5K. [Also in Division B3] In continuous seam or spot, T-joint or, as shown, lap joint, continuously-energized laser beam welding of metal or non-metal workpieces 4, 6, the power density of the beam 2 at the area of incidence on the first encountered workpiece 4 is arranged to be above a threshold level at which it heats the workpieces primarily by conduction and to be below a ceiling level at which it vaporizes the workpiece metal to such an extent that there is insufficient of said metal left to form a weld. The depth of the molten pool 8 produced is greater than the thickness of the workpiece 4 so that the pool extends into the workpiece 6. The width of the pool is less than its depth. The power density is determined by laser power output and/or beam focusing. In an example, a continuously-operated carbon dioxide laser of 400 W. output is used for continuous lap joint welding of two steel plates, each of 0.015 inch thickness. The pool 8 has a depth of three times its width. The incident power density exceeds 1 x 10 4 MWm- 2 .

Method for producing spike-free electron beam partial penetration welds

Abstract: A technique is provided for prevention of "spiking" in electron beam partial penetration welds which involves pulsing the electron beam so as to prevent achievement of steady state conditions which cause such spiking. The rate of pulsing required is determined by the electron beam oscillation frequency which is a function of total beam power, beam power density, welding speed, and the properties of the particular material being welded.

Electron heating effect on power balance in mirror reactors

Abstract: The use of auxiliary power to heat the electrons in a mirror reactor is considered. In this manner the electron temperature is raised so that the ion cooling rate is reduced and the ion confinement is improved. The power required to raise the electron temperature is estimated using the charged particle power balance equation. The merit of this scheme is shown to depend on the efficiency for heating the electrons, as well as the ion injection energy. It is shown to be beneficial for ion injection energies <100 keV, provided the efficiency for heating the electrons is greater than the ion injection efficiency.

Out-of-core Evaluations of Uranium Nitride-fueled Converters

Abstract: Two uranium nitride fueled converters were tested parametrically for their initial characterization and are currently being life-tested out of core. Test method being employed for the parametric and the diagnostic measurements during the life tests, and test results are presented. One converter with a rhenium emitter had an initial output power density of 6.9 W/ sq cm at the black body emitter temperature of 1900 K. The power density remained unchanged for the first 1000 hr of life test but degraded nearly 50% percent during the following 1000 hr. Electrode work function measurements indicated that the uranium fuel was diffusing out of the emitter clad of 0.635 mm. The other converter with a tungsten emitter had an initial output power density of 2.2 W/ sq cm at 1900 K with a power density of 3.9 W/sq cm at 4300 h. The power density suddenly degraded within 20 hr to practically zero output at 4735 hr.

Window for high power gaseous lasers

Abstract: In a gas laser capable of ultra high power, a cylindrical mirror mounted to receive the laser beam, diverge it, thereby lowering the power density. A cylindrical lens, acts as the seal and window, receives and transmits the beam causing it to reform outside of the container without the need of further optics.

Joule-heating power dissipation in a type-II superconductor tube.

Abstract: The theoretical analysis of the Joule-heating power density in a specific hollow cylinder of a NbZr superconductor is presented. It is seen that the power density, which is the primary source of internal heating neglecting localized annihilation heating, can have a very complicated behavior, especially in the circular region. Rough estimates of the relative temperature changes are made, and the locations at which instabilities are more likely to initiate are considered.

Electrical CO mixing gas dynamic laser

Abstract: An electric‐discharge CO‐mixing laser is described in which N2 is vibrationally excited in an electrical discharge and then mixed with cold CO in a supersonic expansion providing a population inversion between CO vibrational bands. Continuous output is achieved from an optical cavity established transverse to the flow. Maximum laser power obtained to date is 45 W, corresponding to an efficiency of 4% and a volumetric power density of 6 W/cm3.

The Behavior of Input‐Power Density in Exploding‐Wire Restrikes

Abstract: The input power per unit volume of the restrike channel of thin exploding wires reaches its maximum slightly before the electrical conductivity has reached its maximum. In its turn, the electrical conductivity reaches its maximum before the current and the total power input, ui, have reached their maxima but slightly after the ledge observed on the voltage oscillograms. The reason why the input power per unit volume and the electrical conductivity reach their maxima much earlier than the current and the total power input reach theirs seems to be closely connected with the magnetogasdynamics of the restrike channel, which have not yet been satisfactorily treated because of the complexity of the problem.

Application of the Spatial Spectral Power Density to the Calculation of Resolution Limits

Abstract: Resolution as a function of aperture length in the presence of phase errors is investigated with the aid of the spatial power spectral density Numerical calculations are made for power spectra thought to be appropriate for phase errors due to atmospheric turbulence Both Gaussian and uniform illumination are considered, and the results obtained here are compared with those reported by Brown and Riordan [2]