Certifying hot and cold test chambers

Measurement Techniques -     

Large-Amplitude Ultrasound Systems

Large amplitudes are required in many ultrasound systems. Vibrational systems of rod type are used for that purpose. The selection of materials for large-amplitude ultrasound systems is considered. A manufacturing technology for ultrasound vibrational systems is proposed.     

Correlation between the reliability of laser diodes and the crystal perfection of epitaxial layers estimated by high-resolution x-ray diffractometry

The dependence of the degradation of high-power quantum-well GaAs/AlGaAs laser diodes, grown by molecular-beam epitaxy, on the crystal perfection of the individual layers of the heterostructure is investigated. The crystal perfection of the layers is estimated by highresolution x-ray spectrometry. A numerical fit of the diffraction-reflection curves is performed using the Debye-Waller static factor. It is shown that considerably higher crystal perfection of laser heterostructures can be obtained by using as the waveguide layers binary AlAs/GaAs superlattices instead of the solid solution AlGaAs. Fiz. Tekh. Poluprovodn. 33, 634–638 (May 1999)     

Mathematical simulation of gravitational waves in the ocean in the approximation of “shallow water”

Problems of the behavior of gravitational waves in the approximation of “shallow water” — motion of a solitary wave over the water surface, exit of a wave to the shore, passage of a solitary wave over a submerged rock — are solved. The solution of the first problem showed that in modeling the motion of a solitary (soliton-type) wave the “shallow water” approximation breaks down at a ratio of water depth to wavelength equal to 0.3. An analysis of the results of solution of the second problem indicates that the “shallow water” approximation cannot be used for calculation of the height of a wave in its exit to the shore but it can be used for estimation of the distance from the shore where the wave is turned over. It follows from the solution of the third problem that the “shallow water” approximation is suited only for obtaining a qualitative picture of the distortion of the profile of a wave in its motion over a rock.     

1D GaAs Detector Arrays for Digital X-ray Imaging

1D imaging arrays of GaAs x-ray detectors are designed, fabricated, and tested. Each array consists of 64 detectors arranged with a pitch of 0.4 mm. In x-ray testing, an almost linear relationship is found between the detector response and the tube current. Zero detector cross coupling is observed in scanning an x-ray beam along any array.     

Photovoltaic X-ray detectors based on epitaxial GaAs structures

A new type of the photovoltaic X-ray detector based on epitaxial p ⁺-n-n′-n ⁺ GaAs structures is proposed, which provides for a high efficiency of charge carrier collection in a nonbiased operation regime at room temperature. The GaAs structures were grown by vapor phase epitaxy on heavily doped n ⁺-GaAs substrates. The X-ray sensitivity range covers the effective energies from 8 to 120 keV. The maximum output signal in the short-circuit regime is 30 μA min/(Gy cm²). The detector response to γ-radiation from a ¹³⁷Cs[660 keV] radioactive isotope was measured.     

Gas chromatography investigations of thermodynamics of adsorption of organic compound vapors on carbon adsorbent modified by β-cyclodextrin derivatives

The adsorption of organic-compound vapors of various structures and polarities on carbon adsorbent modified by permethylated and perbenzylated β-cyclodextrin is investigated using gas chromatography. The obtained thermodynamic properties are compared for adsorption on initial carbon adsorbent and two modified adsorbents. The influence of molecular structure of the studied sorbates and substituent groups in cyclodextrin molecules on adsorption is considered.