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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 51-58 
    ISSN: 1573-4862
    Schlagwort(e): eddy current testing ; magnetic particle testing ; magnetic sensor ; ferromagnetic resonance ; microwave frequency ; surface flaws ; NDE
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Mathematik
    Notizen: Abstract This article presents some results obtained in the characterization of surface flaws by means of probes using ferromagnetic resonance of yttrium iron garnets (FMR probes). These experiments on artificial flaws show that FMR probes operate like eddy current probes for nonmagnetic materials and like magnetic field sensors for magnetic ones. Consequently, the working distance is larger for magnetic materials (1000–1500 µm) than for nonmagnetic ones (100–300 µm). FMR probes have good sensitivity to narrow flaws, good spatial discrimination, and are sensitive to flaw width and depth. Vector analysis allows the separation of distance and flaw effect by phase analysis on nonmagnetic materials. On magnetic materials this phase separation does not exist and another procedure is suggested. These results, and in particular those obtained on ferromagnetic materials, point to the possibility of replacing some eddy current or magnetic particle inspections by tests with ferromagnetic resonance probes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Hyperfine interactions 129 (2000), S. 319-335 
    ISSN: 1572-9540
    Schlagwort(e): nuclear magnetic moments ; Bohr–Weisskopf effect ; hyperfine structure ; parity nonconservation in atomic interactions ; Knight shift ; QED
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Nuclear magnetic moments provide a sensitive test of nuclear wave functions, in particular those of neutrons, which are not readily obtainable from other nuclear data. These are taking added importance by recent proposals to study parity non-conservation (PNC) effects in alkali atoms in isotopic series. By taking ratios of the PNC effects in pairs of isotopes, uncertainties in the atomic wave functions are largely cancelled out at the cost of knowledge of the change in the neutron wave function. The Bohr–Weisskopf effect (B–W) in the hyperfine structure interaction of atoms measures the influence of the spatial distribution of the nuclear magnetization, and thereby provides an additional constraint on the determination of the neutron wave function. The added great importance of B–W in the determination of QED effects from the hfs in hydrogen-like ions of heavy elements, as measured recently at GSI, is noted. The B–W experiments require precision measurements of the hfs interactions and, independently, of the nuclear magnetic moments. A novel atomic beam magnetic resonance (ABMR) method, combining rf and laser excitation, has been developed for a systematic study and initially applied to stable isotopes. Difficulties in adapting the experiment to the ISOLDE radioactive ion beam, which have now been surmounted, are discussed. A first radioactive beam measurement for this study, the precision hfs of 126Cs, has been obtained recently. The result is 3629.515(∼0.001) MHz. The ability of ABMR to determine with high precision nuclear magnetic moments in free atoms is a desideratum for the extraction of QED effects from the hfs of the hydrogen-like ions. We also point out manifestations of B–W in condensed matter and atomic physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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