摘要:

It is shown theoretically and experimentally that the presence of thermal conductance between a pyroelectric material and its environment affects significantly its measured dielectric loss. Depending on the details of the heat exchange with the environment, this thermal contribution to the measured dielectric loss tangent can be larger than the intrinsic loss tangent of the material, i.e., loss due to domain wall motion, defects, and impurities. In detectors fabricated from LiTaO3, temperature fluctuations due to this thermal conductance, known as temperature noise, are observed to limit the normalized detectivity (D*).

ISSN:0003-6951    

DOI:10.1063/1.89116

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A surface wave memory device in which a light pulse emitted from a GaAs laser diode is used to store surface wave signals is described. The storage of 87‐MHz surface wave signals in surface states in silicon is obtained by using a light pulse with a duration of 0.5 nsec. Pulse compression experiments are also demonstrated by storing linear FM chirp signals with this method.

ISSN:0003-6951    

DOI:10.1063/1.89117

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The behavior of MBBA nematic liquid cells under an applied shear is studied at high frequency. It is shown that hydrodynamic roll instabilities can be excited. The rolls develop in a direction perpendicular to the shear motion of the cell plates. Interference between two roll patterns can be obtained with nonparallel glass plates of the cell.

ISSN:0003-6951    

DOI:10.1063/1.89118

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Measurement of thermionic electron emission values for pointed LaB6single‐crystal emitter cathodes has shown that ⟨110⟩ axial orientations yield emission values ten times higher than ⟨100⟩ orientations at 1545 °K. Minimum values were obtained for the ⟨510⟩ directions. These findings seem encouraging in achieving perhaps two orders of magnitude higher emission fluxes as compared to tungsten emitters.

ISSN:0003-6951    

DOI:10.1063/1.89119

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Results of a numerical simulation model are given for the magnetic field produced by an impurity grain embedded in a dense inhomogeneous plasma.

ISSN:0003-6951    

DOI:10.1063/1.89120

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Exploding wire loads have been used for several years to generate a hot dense plasma. For a generator with a rise time of tens of nsec and an impedance of 1 &OHgr; or less, the inductance of the wire load and the tendency of current to flow outside the wire limits the energy that can be transferred to the wire. An array of several wires has now been used to lower the inductance and improve the energy transfer.

ISSN:0003-6951    

DOI:10.1063/1.89121

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The range statistics for C, F, Ne, Al, and Si in Si recently published by Gibbons, Johnson, and Mylroie (GJM) are significantly different from the predictions of the LSS theory. This difference exists because in their calculation GJM made use of measured electronic stopping powers (Se) for channeled ions. The scaling procedure employed by GJM builds into their calculation the pronouncedZ1oscillations observed in theSeof channeled ions. Use of the measured electronic stopping powers was limited to N, O, P, Cl, Ar, and the above mentioned ions in Si. In order to make an experimental check of the scaling procedure employed the range‐energy curve for19F in Si has been measured between 100 and 550 keV. The following observations can be made: (1) The experimental range‐energy curve for19F is in good agreement with LSS calculations and (2) the measured ranges are significantly less than the predictions of Gibbons, Johnson, and Mylroie. These results are interpreted as strong evidence against the validity of scaling Eisen’s measurements of the electronic stopping power for channeled ions over to random trajectories.

ISSN:0003-6951    

DOI:10.1063/1.89122

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Spectral information on turbulent fluid flow can be obtained from the rate statistics of tracer particles imbedded in the flow. In particular, the particle velocity correlation function can be measured by a laser technique with a single focused beam, which also provides a means to assess the lag behavior of the particles. The method offers significant simplifications of commonly used instrumentation.

ISSN:0003-6951    

DOI:10.1063/1.89099

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A method is proposed for laser separation of certain isotopes with nonzero nuclear spin which relies only on the angular‐momentum selection rules for the absorption of circularly polarized light.

ISSN:0003-6951    

DOI:10.1063/1.89100

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The photovoltaic properties of Schottky barrier solar cells made from thin films (100–1000 A˚) of the organic dye hydroxy squarylium have been studied. Amorphous and polycrystalline films, prepared by evaporation and solution casting, have strong absorption over the entire visible spectrum. The highest power conversion efficiency measured under AMO white light was 0.1% (0.14 mW/cm2input intensity); this decreased to 0.02% at 135 mW/cm2. The decrease in &eegr; with intensity is characteristic of organic materials, but is usually much more pronounced. For 8500‐A˚ monochromatic light the quantum efficiency was as high as 2.3% and the conversion efficiency was 0.2% (1 mW/cm2).

ISSN:0003-6951    

DOI:10.1063/1.89101

出版商:AIP    

年代:1976

数据来源: AIP