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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3819-3825 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In a hybrid slow positron beam, extraction of the positrons from the magnetic field (∼1 T for the PSI beam) to field-free space is a necessary operation. A theoretical and experimental demonstration is given which shows that the following proposed beam extraction method works as predicted: magnetic transport of the slow positrons down to field strengths of ∼100 G and passage through an aperture grid of ∼10 cm diameter in a field termination shield followed by some brightness enhancement stages. The simulation and measurement of the magnetic-field distributions along the beam axis show a steep drop down of the field from ∼100 G to a few gauss within 1 cm of shield thickness and a quasiuniform spreading of the transverse field strength across the grid opening. Measurement of transmission and divergency (transverse energy) of the beam exiting the extraction aperture confirmed theoretical estimations and ray tracing calculations for the aperture design used to be of the order of 75% and 20 eV, respectively. These data as a function of field strength and beam energy are used for optimization of the final extraction aperture design ((approximately-greater-than)85% transmission) to be used in the PSI high intensity beam facility. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two differently heat treated samples of Fe-0.8 wt% Cu and a sample of pure iron, subjected to a fast fission fluence of 0.5×1019 neutrons/cm2 have been investigated by means of measurements of the peak height of the 2 γ-angular correlation distribution as a function of annealing temperature up to 750 °C. The results can be explained by assuming irradiation enhanced precipitation of small Cu-clusters in a supersaturated solid solution. These particles exhibit on their surfaces vacancy-like defects having the ability to trap positrons. A correlation has been observed between peak height and microhardness behaviour suggesting that both radiation induced hardening and embrittlement are due mainly to enhanced precipitation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Wir untersuchten das Diffusionsverhalten von Cäsium und Silber in den technischen Hochtemperatur-Werkstoffen Nimocast 713 LC, Nimonic 86, Inconel 625 und TZM. Proben mit polierten Oberflächen wurden zwischen 700 und 1050° C im Vakuum während 170 bis 5500 h bei einem Csund Ag-Partialdruck von 10−6 Torr beladen. SIMS Nachfolgeexperimente mittels einer Ionenmikrosonde wurden an einer großen Anzahl solcher Proben ausgeführt. Dabei wurden die Multielement-Tiefenprofile in quantitative Konzentrations-Tiefenprofile transformiert unter Zuhilfenahme des LTE-(Local-Thermodynamic-Equilibrium)-Modelles von Anderson und Hinthorn. An einigen Proben wurden auchγ-spektroskopische Konzentrationsbestimmungen von radioaktivem, eindiffundiertem Cäsium mit den SIMS-Mes-sungen verglichen. Die quantitativen Konzentrations-Profile wurden mit einem einfachen Diffusionsmodell korreliert, wobei gute Übereinstimmung der Cs-Diffusionsparameter mit jenen in elementarem Nickel bzw. Molybdän gefunden wurde.
    Notes: Summary In order to study the diffusion behaviour of caesium and silver in the technical high-temperature alloys Nimocast 713 LC, Nimonic 86, Inconel 625 and TZM, corresponding samples with polished surfaces were vacuum annealed between 700 and 1050° C for times between 170 and 5500 hr at Cs and Ag partial pressures of 10−6 mm Hg respectively. Post-exposure ion-microprobe mass analysis (IMMA) of a series of such samples, resulted in layer-stripping by sputtering and multielement depth profiles. The data were interpreted quantitatively with a physical model called the local thermodynamic equilibrium (LTE) model, and in some cases with the aid ofγ-spectroscopy with use of radioactive tracing materials. The results are discussed in terms of a comparison between the two approaches, and the quantitative concentration profiles are being used in a study of the diffusion behaviour in such systems. Good agreement with existing Cs diffusion data in pure nickel or molybdenum has been achieved.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 21 (1975), S. 47-74 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Simultaneous measurements of oscillatory magnetostriction amplitudes and de Haas-van Alphen torque amplitudes have been made in molybdenum in magnetic fields up to 22 kOe. From these results we determined the uniaxial stress dependence of various extremal cross sections of the electron lenses in the fifth band. The lenses along an axis parallel to the stress are approximately ten times more sensitive to distortion than the lenses in a plane perpendicular to the stress direction. The experimental values are in agreement with the results obtained with Pettifor's energy-independent model Hamiltonian, describingd electrons only. We found that this model gives a good description of thed-band structure and its stress dependence provided the hybridization is taken into account. The validity of the rigid-band description is discussed in detail in terms of Pettifor's model.
    Type of Medium: Electronic Resource
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