摘要:

A new type of acoustic imaging device, which scans a large array of piezoelectric detectors is described. Scanning is carried out by a signal traveling along an acoustic surface wave delay line. The device can be electronically focused, and has given images of objects 20 cm from the detector array, illuminated with a 5‐MHz acoustic wave, with a definition of 1 mm.

ISSN:0003-6951    

DOI:10.1063/1.1654755

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The piezoelectric response of impact‐loadedz‐cut lithium niobate is investigated to determine whether the material can be used as a time‐resolving nanosecond‐resolution stress gauge. The material is found to have appropriate properties for stresses up to 15 kbar. A gauge from this material should prove particularly useful for measurements of stress pulses resulting from the absorption of pulsed radiation in solids.

ISSN:0003-6951    

DOI:10.1063/1.1654756

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Experimental observations of diffusional broadening of the Mo¨ssbauer resonance in polycrystalline solids have generally been analyzed on the basis of a liquidlike model which neglects the restriction of atomic jumps to crystallographically determined directions. A calculation based on the theoretical results of Chudley and Elliot for single crystals, averaged over all directions, shows that a substantial correction to the liquidlike result is required. Application of this correction, along with a simple assumption about the correlation factor largely eliminates the existing discrepancies between theory and experiment.

ISSN:0003-6951    

DOI:10.1063/1.1654757

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The velocity and attenuation of a surface acoustic wave on a piezoelectric semiconductor may be controlled by adjusting the bias of a reverse‐biased distributed diode. With the proper choice of resistivity and operating frequency, changes in velocity of 1% and attenuation of 300 dB/cm may be achieved inc‐axis cadmium sulfide for bias voltages under 30 V. Theoretical behavior is presented and initial experimental results are summarized.

ISSN:0003-6951    

DOI:10.1063/1.1654758

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The depth profiles of helium implanted into copper foils have been observed experimentally by a proton backscattering technique. Carbon and oxygen on the front and rear surfaces of the foils have also been resolved. The mean depth of the helium implanted at 50, 100, and 150 keV is in agreement with projected range calculations, though the rms spread in the distributions is smaller than predicted. The shape of the profiles is the Gaussian form expected from single energy implants with no evidence of tails extending deep into the foils. Detection sensitivity is greater than 1 at.% for He in Cu under the experimental conditions investigated. The mean depth (peak) of the implanted helium distributions can be determined to within ± 100 Å.

ISSN:0003-6951    

DOI:10.1063/1.1654759

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Evaporated cadmium sulfide thin‐film resistors have been fabricated which exhibit remarkable strain sensitivity. Electrodes are arranged in sandwich fashion so that electrons flow perpendicular to the plane of the CdS layer. The layers are doped and heat treated so that nominal unstrained resistivities are of the order of 3 × 105&OHgr; cm. Tensile and compressive strain in the plane of the film causes the resistance to increase and decrease, respectively, by as much as a factor of 15.

ISSN:0003-6951    

DOI:10.1063/1.1654760

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Damage in the germanium output mirror of a TEA CO2laser shows a periodicity of 10.6 &mgr;m, the laser wavelength. A mechanism is proposed in which scattered and cavity radiation interfere. An interference mechanism is confirmed by experiments outside of the laser cavity. Periodic damage is obtained in thin films irradiated at angles other than the normal where the fringe spacing is modified.

ISSN:0003-6951    

DOI:10.1063/1.1654761

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Beam guiding and focusing have been observed for CO2laser propagation in a high‐density low‐temperature annular plasma. A TEA laser was fired along the axis of a cylindrical plasma column of densities in the 1016–1017‐cm−3range. Several radial density profiles were investigated. Beam guiding and focusing were observed when the density had a minimum on the axis. A density maximum on‐axis refracted the beam toward the tube walls, and intense ``hot spots'' resulting from apparent filamentation inside the plasma were recorded.

ISSN:0003-6951    

DOI:10.1063/1.1654762

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Measurements of the effects of polycrystallinity and lattice disorder on the intrinsic laser‐induced damage fields of transparent solids are reported. Extreme lattice disorder such as present in a highly amorphous material such as fused quartz causes the damage field to increase, whereas less severe disorder does not measurably affect the breakdown strength. This is consistent with an electron avalanche intrinsic damage mechanism.

ISSN:0003-6951    

DOI:10.1063/1.1654763

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The laser‐induced damage thresholds of two different dielectric thin‐film coatings increased with decreasing spot size and were invariant for spot sizes greater than 150 &mgr;m. A simple model has been suggested that the distribution and nature of coating defects have played an important role in this spot‐size dependence, e.g., the probability of the laser beam striking a defect site will be greater for larger spot sizes and that damage in materials can be distinguished as defect damage and intrinsic damage.

ISSN:0003-6951    

DOI:10.1063/1.1654764

出版商:AIP    

年代:1973

数据来源: AIP