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  • Articles  (14)
  • 78.70  (8)
  • 72.40  (6)
  • 1985-1989  (14)
  • 1950-1954
  • 1987  (14)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (14)
  • Technology
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  • Articles  (14)
Source
Keywords
Publisher
Years
  • 1985-1989  (14)
  • 1950-1954
Year
Topic
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (14)
  • Technology
  • Physics  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Applications of accelerator-based low-energy positron beams in atomic physics (1987)
    Springer
    Applied physics 43 (1987), S. 235-245 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 34.90 ; 36.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Applications of LINAC-based positron beams in atomic physics are described. The following broad subject areas are treated; e+ mobility and momentum transfer cross section determinations, angularly resolved and integral cross sections for e+-atomic processes plus charge transfer (Ps formation) type experiments, experiments with tunable positronium beams and experiments with thermal Ps sources. In addition, some discussion is given concerning the use of channel electron multiplier arrays (CEMAs) in conjunction with charge coupled devices (CCDs) as position sensitive detectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00635178
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  • 2
    Electronic Resource
    Electronic Resource
    A high-intensity58Co slow-positron beam and applications to probe near-surface disorder (1987)
    Springer
    Applied physics 43 (1987), S. 269-274 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 07.77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Properties and performance of a magnetically-guided, high-intensity, ultra-high-vacuum slow-positron beam are reviewed. Basic positron behaviour in solids is briefly described. Results from various58Coβ + sources in conjunction with a backscattering W(110) moderator are presented. We discuss research applications to probe depth distribution of open-volume lattice defects. Two experimental methods capable of yielding information on defects within ∼500 Å and ∼1 μm from the surface, respectively, are considered. Results are shown on defect distribution in ion implanted metals and semiconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00635182
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  • 3
    Electronic Resource
    Electronic Resource
    Antihydrogen formation through positron-antiproton radiative combination (1987)
    Springer
    Applied physics 43 (1987), S. 287-293 
    Details
    ISSN: 1432-0630
    Keywords: 07.77 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In this paper the production of a beam of antihydrogen atoms through the capture of positrons by antiprotons in an arrangement of merged parallel beams is considered. The achievable luminosity is estimated on the basis of available antiproton and positron intensities. The scaling of the luminosity with various parameters is investigated. It is argued that an intense beam of antihydrogen can be obtained if antiprotons and positrons are stored, recirculated and cooled. While the number of stored antiprotons which can be achieved at present is already high, schemes for the accumulation of slow and cooled positrons have to be developed. Possible ways are pointed out. The fact that a high number of both species of charged particles can be accumulated, stored, and recirculated, compensates largely for the low capture cross-section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00635185
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  • 4
    Electronic Resource
    Electronic Resource
    Transient negative photoconductivity in silicon doped with gold (1987)
    Springer
    Applied physics 43 (1987), S. 205-208 
    Details
    ISSN: 1432-0630
    Keywords: 72.40 ; 72.20 ; 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A transient negative photoconductivity phenomenon observed in silicon doped with gold atoms by an appropriate diffusion condition has been investigated. The transient negative photoconductivity could be observed with a diode doped with gold atoms under intrinsic light-pulse illumination. In the recovery process of the transient negative photoconductivity to a steady-state dark level, two kind of time constants were observed, which may be related with the emission of electrons from gold level. A dependence of the magnitude of the peak value on the ambient temperature was observed; a qualitative explanation is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615977
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  • 5
    Electronic Resource
    Electronic Resource
    Positron-lifetime study of vacancy annealing in neutron-irradiated GaAs (1987)
    Springer
    Applied physics 42 (1987), S. 125-127 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron-lifetime measurements have been used to study the annealing of vacancies in neutron-irradiated GaAs. The vacancies which are interpreted as defects in the Ga sublattice disappear in a single annealing stage (at 500°C in GaAs doped with Si or Zn, and at 600°C in Cr-doped GaAs).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616721
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  • 6
    Electronic Resource
    Electronic Resource
    Theoretical characterisation of a superlattice avalanche photodiode (1987)
    Springer
    Applied physics 42 (1987), S. 173-177 
    Details
    ISSN: 1432-0630
    Keywords: 72.15 ; 72.40 ; 78.55 ; 79.20 ; 85.40 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A superlattice avalanche photodiode using III–V materials is expected to be used in long-distance fiberoptic communication systems in the 1.3 to 1.55 μm wavelength range. Theoretical studies have been made on the effective ionization rates of electrons and holes of the device, I–V characteristic and the frequency response characteristic of the Al x Ga1−x As/GaAs superlattice p+-i-n+ structure. It is observed that theα/β ratio of the device increases with the field and the bandwidth of the response curve increases with decrease in the dc multiplication gain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620596
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of optical radiation in a photo-DOVATT (1987)
    Springer
    Applied physics 42 (1987), S. 311-315 
    Details
    ISSN: 1432-0630
    Keywords: 70.20 ; 72.40 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Avalanche photodetectors are very important solid-state detectors currently used in long-distance and wide-band optical communication systems, due to their faster speed of response compared to other solid-state photodiodes. Furthermore, it has been found that by using heterostructures one can improve both multiplication gain and quantum efficiency of such a device. DOVATT is a heterojunction impatt device in which there is one avalanche zone followed by two drift zones at different scattering limited velocities. The device is very useful for generation of high power in the X-band. The present paper examines the effect of optical radiation on such a device. Studies have been made on the frequency-response characteristics of the device. The results show that the device has the potentiality of becoming a powerful photodetector in optical communication systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616569
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of the photoionization threshold of the deep donor in Al0.33Ga0.67As:Si (1987)
    Springer
    Applied physics 44 (1987), S. 245-247 
    Details
    ISSN: 1432-0630
    Keywords: 61.70T ; 71.55F ; 72.40 ; 78.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoionization of the DX center in Si-doped A10.33Ga0.67As has been studied by means of photoconductivity. The optical cross-sectionσ nd 0 shows a threshold atħω=200 meV and relative maxima (shoulders) around 400, 600, 950, and 1700 meV. The results throw doubt on the validity of the large lattice relaxation model, generally accepted for this class of centers. They can be well accounted for by the small relaxation model, recently proposed by the authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616697
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  • 9
    Electronic Resource
    Electronic Resource
    A field-assisted moderator for low-energy positron beams (1987)
    Springer
    Applied physics 42 (1987), S. 111-116 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 72.90 ; 79.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new positron field-assisted (FA) moderator based on the drift of positrons across a cooled silicon crystal is proposed. Using estimates for both theβ + implantation profile and attainable drift velocities, the efficiency of drift to a slow e+ emitting surface is calculated using a diffusion equation which incorporates terms describing positron drift and annihilation. It is conjectured that efficiencies of up to 10% can be achieved. The use of epitaxially grown metallic suicide contacts to facilitate the application of the electric field is described and the consequences of using such contacts are fully discussed. Applications of the FA transmission mode moderator described here to produce timed brightness enhanced beams are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616719
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrathin-layer (AlAs) m (GaAs) m superlattices withm = 1,2,3 grown by molecular beam epitaxy (1987)
    Springer
    Applied physics 43 (1987), S. 75-79 
    Details
    ISSN: 1432-0630
    Keywords: 68.55 ; 78.65 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Ultrathin-layer (AlAs) m (GaAs) m superlattices withm = 1, 2, and 3 were grown by molecular beam epitaxy and characterized by x-ray diffraction and photoluminescence measurements. The appearance of distinct satellite peaks around the Bragg reflections demonstrate the formation of high-quality layered crystals. The observed luminescence shows a maximum at 2.033 eV form = 3, and the emission energy decreases form = 2 andm = 1 as well as for them = 4 superlattice. This result for the monolayer superlattice is in good agreement with recent theoretical calculations, and it shows that the (AlAs)1(GaAs)1 superlattice represents a new artificial semiconductor material with novel electronic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615210
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  • 11
    Electronic Resource
    Electronic Resource
    Carrier frequency-dependent intrinsic parameters in an ion-implanted silicon photo-MESFET (1987)
    Springer
    Applied physics 44 (1987), S. 361-364 
    Details
    ISSN: 1432-0630
    Keywords: 72.40 ; 78.55 ; 85.30 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Carrier frequency-dependent intrinsic parameters of an ion-implanted silicon photo-MESFET have been analysed theoretically. The internal gate source capacitanceC gs is found to increase with increasing carrier frequency under the normally OFF condition and the change is small under the normally ON condition. Also, the internal drain-source resistanceR ds increases with frequency at a fixed flux density and wavelength of operation. The ion-implanted photo-MESFET could become useful as optically controlled switching device in digital circuits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00624604
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  • 12
    Electronic Resource
    Electronic Resource
    Positron annihilation study of ordering processes in rare-earth cobalt permanent magnets (1987)
    Springer
    Applied physics 42 (1987), S. 287-289 
    Details
    ISSN: 1432-0630
    Keywords: 75 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The ordering process in 1/5 and in 2/17 Sm-Co permanent magnets was followed by positron annihilation lifetime and Doppler broadening measurements. No correlation between magnetic hardness and positron annihilation parameters was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616564
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  • 13
    Electronic Resource
    Electronic Resource
    Effect of visible light intensity on the dielectric behaviour of mercuric iodide (1987)
    Springer
    Applied physics 43 (1987), S. 123-130 
    Details
    ISSN: 1432-0630
    Keywords: 77.40 ; 72.40 ; 77.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The electrical and dielectric properties of mercuric iodide were studied at room temperature under various intensities and colours of light in the frequency range 1 Hz–10 kHz. In the high-frequency region (〉40 Hz), the real part of the dielectric constant (ɛ′) is almost constant with frequency (f), colour and intensity of light. At lower frequencies,ɛ′ varies nearly as 1/f and monotonically increases with intensity (I) of the yellow (or green) light, whereas it is almost constant with red light intensity. This behaviour is discussed in the view of the different polarization contributions. The imaginary part of the dielectric constant (ɛ″) was found to vary as 1/f over the frequency range studied. This behaviour was observed whether the crystal was in dark or illuminated implying that the roomtemperature ac dark- or photo-conductivity (σ) is independent of frequency. The observed variation ofσ with intensity of yellow (or green) light was found to follow anI 1/2 dependence and a weaker dependence for the red light. the red light. The conductivity behaviour is discussed in the view of the current theories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617964
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  • 14
    Electronic Resource
    Electronic Resource
    The positron beam at the stuttgart pelletron accelerator and its applications toβ +γ positron lifetime measurements (1987)
    Springer
    Applied physics 43 (1987), S. 261-267 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 07.77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A slow-positron source has been installed in the therminal of an electrostatic 6.5 MeV accelerator and provides a monoenergetic positron beam in the few-MeV range. It will be used to operate a “fast” positron lifetime spectrometer based onβ + γ coincidences. The properties of the beam, the expected performance of the spectrometer, its advantages over conventionalγγ lifetime measurements, a number of intended applications, as well as recent positron-electron scattering experiments and plans for positron channelling and channelling-radiation studies are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00635181
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