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  • 1
    Electronic Resource
    Electronic Resource
    Neutron irradiation study of Nd-Fe-B permanent magnets made from melt-spun ribbons (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5305-5307 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radiation-induced changes in the magnetization of sintered Nd-Fe-B permanent magnets are known to vary widely among specimens produced by different manufacturers. Samples of Nd-Fe-B MAGNEQUENCH magnets, which are made from melt-spun ribbons, have not been studied and show a much reduced sensitivity to neutron irradiation than do sintered Nd-Fe-B magnets. All melt-spun ribbon-based MAGNEQUENCH magnets, i.e., epoxy-bonded, hot-pressed, and die-upset magnets, show essentially the same slow decrease in magnetic remanence with neutron dose. Measurements of the open-circuit remanence Br/Br 0 at various times during the irradiation show a decay of only 1.5% of the preirradiated value for the MAGNEQUENCH magnets after 1 h of irradiation, or a dose of 1.4×1016 neutrons/cm2, compared to a 4.6% drop in remanence for the best sintered Nd-Fe-B magnet (Sumitomo 30H) with the same irradiation dose. Moreover, after 5.3 h of irradiation, the remanence drops by only 3% for the MAGNEQUENCH magnets. Magnets made from melt-spun ribbons are thus the least sensitive to neutron irradiation so far measured for Nd-Fe-B permanent magnets, but are somewhat more sensitive than samarium-cobalt magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342400
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  • 2
    Electronic Resource
    Electronic Resource
    Radiation-induced changes in magnetic properties of Nd-Fe-B permanent magnets (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3537-3537 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The high remanence and intrinsic coercivity of Nd-Fe-B magnets make them desirable for use in accelerators. Use in a radiation environment requires that the sensitivity of these magnets to radiation be determined and the mechanisms responsible be understood. We present results comparing the relative radiation sensitivity of a number of commercially available Nd-Fe-B magnets. Small samples of these magnets were irradiated to examine the decay of remanence. Our results show that the sensitivity to radiation varies widely among magnets from different vendors, indicating that microstructure and possibly composition play key roles in determining the loss of remanence. We examined optically the microstructure of several of the magnet materials and report on the correlation between microstructure and radiation-induced changes in magnetic properties. Samples were neutron irradiated at the Omega West Reactor in a neutron flux of 4×1012 n/cm2 s at a temperature of 350 K (77 °C). At various time intervals during the irradiation, samples were removed from the reactor and the open-circuit remanence measured. We also measured the quadrant II demagnetization curve of large samples before and after neutron irradiation to monitor changes in remanence and intrinsic coercivity. In general, these samples showed a decrease in the remanence and an increase in the intrinsic coercivity. We also present results comparing the relative decay of remanence for the large cylindrical samples having three different length-to-diameter ratios. This illustrates the effect of the demagnetizing field in determining the rate of remanence decay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340734
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  • 3
    Electronic Resource
    Electronic Resource
    Proton radiation damage in superconducting EuBa2Cu3Ox and GdBa2Cu3Ox (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 417-419 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sintered samples of EuBa2Cu3Ox and GdBa2Cu3Ox with x(approximately-equal-to)7 have been irradiated at 90 °C with 800 MeV protons. The superconducting transition temperature decreases 1.7 K/1017 pcm−2 for both materials. The critical magnetization current density, characterizing intragranular conduction, increases a factor of 3 at zero field and relatively larger factors for finite magnetic fields at 7 and 75 K for fluences on the order of 1017 pcm−2. No and only minor differences between irradiated and unirradiated specimens were seen in calorimetric and transmission electron microscopy analyses, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100607
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  • 4
    Electronic Resource
    Electronic Resource
    Neutron-induced microwave loss in ceramic YBa2Cu3O7−δ (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2462-2464 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An increase by over three orders of magnitude from 0.58 mΩ to 1.17 Ω was observed at 4.0 K in the 3 GHz microwave surface resistance of ceramic YBa2Cu3O7−δ following exposure to neutrons. The transport resistivity of an unirradiated pellet was linear in temperature down to Tc with a room-temperature value of 2.13 mΩ cm and a resistivity extrapolated to 4.0 K of 0.53 mΩ cm. Following irradiation, the resistivity rose with decreasing temperature from a room-temperature value of 1.5 Ω cm to a maximum at around 45 K with little change evident at Tc . These results, in conjunction with eddy current, susceptibility, iodometric titration, and thermally stimulated luminescence measurements on irradiated and unirradiated samples, collectively suggest that the effect of neutron irradiation has been to decrease intergranular coupling without the development of an insulating phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103256
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