skip to main content


This content will become publicly available on February 27, 2019

Title: Demagnetization of Nd 2Fe 14B, Pr 2Fe 14B, and Sm 2Co 17 Permanent Magnets in Spallation Irradiation Fields

Prompted by the need for radiation-resistant permanent magnets for insertion devices (IDs) of high-brilliance next-generation synchrotrons such as the National Synchrotron Light Source II, the demagnetization of Nd 2Fe 14B and Pr 2Fe 14B was studied after exposure to a mixed irradiating field. Degradation and damage of the permanent magnetic material by components of electromagnetic showers induced in magnets by intense high-energy electron beams will alter the magnetic field structure of the IDs. Plate-like Nd 2Fe 14B magnets were irradiated to 1.8 Grad dose and were evaluated against Pr 2Fe 14B magnets irradiated to a lower dose of 20 Mrad. In addition, annular Sm 2Co 17 and Nd 2Fe 14B magnets integrated within a ferrofluidic feedthrough (FFFT) rotary seal were also irradiated to dose levels of 2 Grad for Sm 2Co 17 and 20 Mrad for Nd 2Fe 14B. Post-irradiation measurements of the magnetic intensity revealed that severe demagnetization exceeding 85% occurs in Nd 2Fe 14B magnets after only 50 Mrad dose and over 87% for Pr 2Fe 14B after 10 Mrad dose. The annular-shaped Sm 2Co 17 magnets of the FFFTs were almost insensitive to irradiation up to a dose of 2 Grad. Annular-shaped Nd 2Fe 14B magnets alsomore » showed resistance to demagnetization, a direct consequence of the annular shape which is characterized by the removal of the stronger demagnetizing field present at the center of a disk-like magnet. As a result, the sensitivity of boron-based permanent magnets to neutron energy (thermal versus fast) was also assessed via specifically designed experiments and discussed.« less
ORCiD logo [1] ;  [1] ;  [2] ; ORCiD logo [3] ;  [3] ;  [3]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  3. Michigan State Univ., East Lansing, MI (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0018-9464
Grant/Contract Number:
Accepted Manuscript
Journal Name:
IEEE Transactions on Magnetics
Additional Journal Information:
Journal Volume: 54; Journal Issue: 5; Journal ID: ISSN 0018-9464
Institute of Electrical and Electronics Engineers. Magnetics Group
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
43 PARTICLE ACCELERATORS; irradiation-induced demagnetization; permanent magnets; radiation damage
OSTI Identifier: