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Shull, R.

Paper Title Page
THPLS130 Thermal Neutron Demagnetization of NdFeB Magnets 3589
 
  • R.W. Klaffky
    DOE/OFES, Germantown, Maryland
  • R.M. Lindstrom
    NIST, Gaithersburg, Maryland
  • B. Maranville, R. Shull
    National Institute of Standards and Technology, Gaithersburg, Maryland
  • B.J. Micklich, J.H. Vacca
    ANL, Argonne, Illinois
 
  At the Advanced Photon Source at Argonne National Laboratory, NdFeB insertion device magnets have shown losses of magnetization on a few straight sections where the largest electron beam losses occur due to limiting vacuum chamber apertures. In the worst case, these magnetization losses were evident after a three month operational period. To isolate the effect that thermal neutrons have on these magnets, the magnetization and coercivity were studied for two NdFeB grades as a function of dose from 7.5 x 10(12) to 6 x 10(13) neutrons/cm2. After saturation, the remanent magnetization was found to decrease linearly with the logarithm of the dose. At a dose of 7.5 x 10(12) neutrons/cm2.sec, there was already a 43 percent magnetization loss for the N45 grade and a 15 percent loss for the N48 grade. There was no apparent change in coercivity with dose. The change in remanent magnetization is a consequence of boron thermal neutron capture through the 10B(n,alpha)7Li reaction, which generates MeV energy alpha particles and lithium ions.