摘要:

A 2.2‐kton nuclear explosive was detonated underground at one end of a 122‐m long, 1‐m i.d. horizontal tunnel at the Nevada Test Site. The purpose of the experiment was to study the hydrodynamic flow of energy down a tunnel from a nuclear explosive. This report describes the experimentation utilized to record luminosity of the shock front for the first 15 &mgr;sec and time of arrival of the shock front at specific positions along the tunnel. The observed temperature, determined from shock‐luminosity data and the blackbody radiation assumption, dropped from 11.8 to 2.3 eV at times of 3.2 and 18 &mgr;sec respectively after the peak energy output of the nuclear explosion. The shock wave traversed the 122 m in approximately 4 msec, with a velocity ranging from about 13 cm/&mgr;sec near the shot point to approximately 1 cm/&mgr;sec at the far end.

ISSN:0021-8979    

DOI:10.1063/1.1658733

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

GaAs and GaP thin film and bulk samples have been irradiated with neutron fluences of 1018nvt and the effect on the optical absorption edge and free carrier region determined. In the case of both GaAs and GaP films, which exhibit bulk or near bulk optical properties before irradiation, large optical absorption edge shifts of ∼0.3 and ∼1.5 eV, respectively, are caused by the neutron bombardment. These optical absorption edge shifts can be ``annealed out'' by high‐temperature vacuum annealing; in the case of the GaAs films, isochronal annealing points to a Frenkel‐pair annihilation mechanism. Bulk samples of GaAs and GaP, similarly irradiated, exhibit smaller optical edge shifts than the films with substantially different quantitative behavior. High‐temperature vacuum annealing of the bulk samples also results in a recovery of normal optical properties.

ISSN:0021-8979    

DOI:10.1063/1.1658734

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

We discuss in detail the imaging properties of nonlinear image upconverters. Three‐dimensional image conversion is shown to be possible. The dependence on the system parameters of the converted image's resolution, location, and chromatic aberration is treated. Image conversion with object and pump beams of the same frequency is experimentally demonstrated and the experimental techniques discussed.

ISSN:0021-8979    

DOI:10.1063/1.1658735

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The optical properties of &bgr;′ phase CoAl, CoGa, and NiGa were studied as functions of composition and photon energy in the spectral region from 0.7 to 6.3 eV. Similar investigations were conducted on NiAl between 0.7 and 2.0 eV. The specimens were prepared by a mechanical polishing technique that was shown, by the use of annealing studies, to produce surfaces from which reliable optical data could be taken. Measurements were made by the use of two polarimetric techniques on a reflectometer that was designed by the authors. The results of the optical measurements indicate that some of the investigated alloys show free electron behavior in the infrared, although the limited spectral region of investigation did not permit the authors to apply the Drude free electron theory to the data with confidence. The possible presence of hybridized plasma oscillations is indicated by structure in the loss function. The prominent optical absorption structure which is displayed by these materials in the visible and ultraviolet regions of the spectrum, and which indicates the presence of interband transitions, has been interpreted by the use of a simple rigid band model.

ISSN:0021-8979    

DOI:10.1063/1.1658736

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The ultimate strength of thin single crystals of cadmium has been measured. The crystals were initially completely free from dislocations and other imperfections, in so far as this could be established by observations with the electron microscope. They were grown from the vapor in an atmosphere of argon and had surfaces parallel to {0001} and{011¯0}planes,[2¯110]axes, and uniform rectangular cross sections. The crystals were strained in the electron microscope with a pneumatic tensile device, and the maximum elastic strain which they would sustain was determined directly from measurements of diffraction patterns. The near‐perfect crystals failed at measured elastic strains between 3.8% and 4.5% along the[2¯110]direction. The corresponding normal stress was also measured directly with the tensile device. When the elastic strain along the[2¯110]axis of tension is 4%, the resolved shear stress on the glide systems which could be activated varies betweenG/11 andG/15, whereGis the relevant shear modulus. This is within the range of estimated theoretical maximum strengths of crystals for deformation by a homogeneous shear process.

ISSN:0021-8979    

DOI:10.1063/1.1658737

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Electroabsorption (EA) measurements on ZnS crystals were performed. The electric fields were applied parallel to the polar c‐axis. In single‐crystal regions the EA was found to be independent of the sense of the electric field. On the other hand, in those crystals which contain various polytypes and stacking faults and exhibit an anomalous photovoltaic effect the EA was strongly dependent on the sense of the electric field with respect to the crystallographic polarity. From the spectral and field dependencies of the EA it was concluded that there exist in these crystals internal fields which are uniquely related to the crystallographic polarity. The sense of the electric fields in the various structures was determined. The strength of the fields was found to depend on the structure composition of the crystals; fields up to 105V/cm were estimated. The existence of opposing internal fields, as found in this work, verifies the assumption of several authors in explaining the anomalous photovoltaic effect in ZnS crystals.

ISSN:0021-8979    

DOI:10.1063/1.1658738

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The efficiency of converting focused laser radiation into kilovolt x rays by means of a high‐zplanar plasma has been calculated. For electron temperatures of several keV, the rapid expansion of the plasma limits the effective absorption and reradiation times to a few tenths of a nanosecond. This short time limits the fractional degree of ionization to 30%–60%, depending on the temperature, for heavy target ions such as gold, and in this case the predominant ions have ionization energies less than the electron temperature. For plasma temperatures of 3 up to 10 keV the total radiation output will range from 6 down to 2 times that of plasma bremsstrahlung alone. The conversion efficiency is relatively insensitive to the laser frequency and to the plasma temperature, and amounts to 2%–5%. Overall efficiency for a Nd‐glass laser system turns out to be about 10−3.

ISSN:0021-8979    

DOI:10.1063/1.1658739

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A low‐frequency oscillation excited when a low‐pressure mercury dc discharge is illuminated near the first thermal Tonks‐Dattner resonance with a moderately powerful microwave field has been investigated. It was found to be a relaxation oscillation involving enhanced ionization and coupling of the plasma column to the microwave circuit.

ISSN:0021-8979    

DOI:10.1063/1.1658740

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The ion‐burst excited by a pulsed mesh grid in a plasma is studied experimentally in connection with the sheath structure. The energy distribution of the ions participating in the burst is found to be a broad one. The attenuation of the peak amplitude of the response is confirmed to be due to collisionless damping. The shape of the ion‐burst is accounted for by the application of the Child‐Langmuir law which gives the approximate potential profile of the sheath around the grid. The potential is also measured by using ion transit time effects in the sheath.

ISSN:0021-8979    

DOI:10.1063/1.1658741

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The techniques of atomic‐absorption and emission spectroscopy have been used to detect atoms ejected from an aluminum cathode which is sputtered in a glow discharge in argon. The rate of deposition of the sputtered material is measured using a piezoelectric microbalance which is capable of measuring deposition rates as small as 9.2×10−8G min−1. The use of atomic‐absorption spectroscopy is shown to be a sensitive and reliable method for the study of the sputtering process. Experimental results indicate that some of the sputtered material in the glow discharge exists in the form of ``molecules.'' However, the absolute numbers of sputtered atoms has not been determined due to uncertainties in the tabulated values of atomic‐transition probabilities.

ISSN:0021-8979    

DOI:10.1063/1.1658742

出版商:AIP    

年代:1970

数据来源: AIP