摘要:

The time evolution of ground‐ and metastable‐state copper atom concentrations and the laser energy in a bust‐mode CuBr laser were measured as a function of temperature, buffer gas species, and repetition rate within the burst. The concentrations were measured by monitoring the absorption of the 244.2‐ and 510.6‐nm atomic copper lines. The optimum time separations of the electrical pulses within the burst were found to be 80 and 235 &mgr; for helium and argon buffer gases, respectively. A correlation was found between the time dependences of the laser energy and ground‐state density within the burst. Accumulation was found to occur in the copper atom ground state but not in the metastable2D5/2level.

ISSN:0021-8979    

DOI:10.1063/1.325615

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The correlation structure of the lengths of two disjoint time intervals of the stationary point process obtained by detecting a Gaussian field with Lorentzian spectrum is studied for some special cases.

ISSN:0021-8979    

DOI:10.1063/1.325616

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Quantitative data on the plasma and chemical changes in a pulsed glow discharge in CO2have been obtained using a geometrically stable, chemically inert discharge cell. With resistively‐ballasted electrodes it was possible to achieve uniform glow discharges over a relatively large range of pressure and the yield of decomposition products was measured as a function of energy deposited at various initial charging voltages. These experimental results were compared to those predicted by numerical solution of the Boltzmann transport equation by integrating a derived yeild per unit energy,Y(E/N), over the duration of the excitation pulse. Good agreement between experiment and theory was obtained for pressures over 400 Torr but significant deviations were noted at lower pressures.

ISSN:0021-8979    

DOI:10.1063/1.325617

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A field theory for the reflectivity of a generalized Rayleigh wave from a single shallow groove etched on a LiNbO3substrate is presented. The scattering properties are studied by using a perturbation approach. Induced equivalent acoustic and electric sources which produce the reflected and scattered waves are determined. Calculated reflection coefficient agrees well with known experiments.

ISSN:0021-8979    

DOI:10.1063/1.325618

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The grating transducer, the dual of the meander line, is studied and its performance compared with a meander line for the excitation of magnetoelastic surface waves. A LiNbO3‐YIG‐LiNbO3epoxy‐bonded composite is used to experimentally study both transducer geometries at 50 MHz. It is found that the grating transducer offers no significant improvement in performance over the meander line. Both types of transducers have large conversion losses because of large Ohmic resistance to radiation resistance ratios. Practical considerations of an allowable metalization thickness for the transducers and spatially nonuniform demagnetizing fields in the substrate permit only modest reductions in the conversion losses of either type of transducer situated on materials such as YIG.

ISSN:0021-8979    

DOI:10.1063/1.325619

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The parametric mixing and harmonic generation of surface acoustic waves (SAW) has been treated by a new formalism in which the nonlinear wave equation and boundary conditions are rigorously satisfied at the sum and difference frequencies. The key features are analytical expressions for the spatial structure of modes which can be synchronously driven by volume forces and surface‐boundary conditions. After a propagation distance of a few acoustic wavelengths, the acoustic fields evolve into a linearly growing normal‐mode SAW. Equations are derived from which the nonlinear interaction cross sections can be evaluated and numerical results are given for a number of materials. Good agreement was obtained between experiment and theory fory‐xandx‐y&agr;‐quartz in the limit that the piezoelectricity is neglected.

ISSN:0021-8979    

DOI:10.1063/1.325621

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The nonlinear interaction between bulk acoustic waves at a surface to produce surface acoustic waves is analyzed theoretically. In this analysis both the nonlinear wave equation and boundary conditions are rigorously satisfied by the total acoustic fields. Shear‐wave incidence is treated in detail for isotropic fused quartz and numerical cross sections are evaluated for different angles of incidence. Maximum surface‐wave generation is predicted for geometries corresponding to bulk waves, shear or longitudinal, traveling parallel to the surface.

ISSN:0021-8979    

DOI:10.1063/1.325622

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Recently we have reported a method to measure mass and temperature simultaneously using a single rotatedY‐cut quartz crystal coated with a pair of electrodes and a tab. In this paper we will discuss some modifications by which the performance of the method may be strongly improved. A first improvement is achieved by choosing a particular crystal cut (yxl, −20°<&fgr;<20°), and a second improvement is achieved by the introduction of a small gap between the front electrode and the tab. We will present an analysis of the errors in the determination of mass and temperature, which may result from calibration and experimental errors, as a function of the crystal cut and the thickness of the crystal. The results from this analysis are compared with experimental results for three different crystal cuts (yxl, &fgr;=−15°, 0°, +15°). We found that in the presence of a temperature change of 0.1 °C, a mass change of 5 A˚ (copper) could be measured with an accuracy of 3%, while in the presence of a mass change of 500 A˚ (copper) a temperature change of 0.005 °C could be measured within 11.3%. Some suggestions are given to increase the relatively small mass range, i.e., 3000 A˚ (copper), of the method.

ISSN:0021-8979    

DOI:10.1063/1.325623

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A solution to the heat equation is given which describes a cylindrical body uniformly heated along its axis. The application considered is the determination of bulk and surface absorption coefficients of the sample material from temperature‐vs‐time measurements when the heat source is a weakly absorbed narrow light beam. Under certain conditions, the full solution can be greatly simplified and the inference of absorption coefficients thus facilitated; these conditions are discussed and specified quantitatively. Equivalent results for rectangular samples are also given. The utility of the analysis is illustrated by several experimental examples.

ISSN:0021-8979    

DOI:10.1063/1.325691

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A new ultrasonic technique for studying dewetting and cumulative internal damage in filled polymers such as solid rocket propellants has been developed. The ultrasonic measurements correlate well with volume‐dilatation data in tension. Ultrasonic assessment of damage has also been performed for uniaxial compression and shear strain fields. Experimental results show that for a filled polymer a universal relation exists between acoustic measures of damage and the maximum principal strain for fairly general states of strain. A quantitative physical model relating the observed ultrasonic effects to specific damage events is presented. Estimates of the vacuole size and number density, arising from dewetting, obtained by applying this model to experimental data are in excellent agreement with independent microscopic observations. Time‐dependent void growth at constant strain has also been monitored by means of the ultrasonic technique.

ISSN:0021-8979    

DOI:10.1063/1.325692

出版商:AIP    

年代:1979

数据来源: AIP