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Title: Performance degradation of ferrofluidic feedthroughs in a mixed irradiation field

We present ferrofluidic feedthrough (FF) rotary seals containing either NdFeB or SmCo-type permanent magnets that have been considered for use in the target and beam dump systems of the Facility for Rare Isotope Beams (FRIB). To evaluate their performance under irradiation three FF seals were irradiated in a mixed field consisting of fast neutrons, protons and γ-rays to an average absorbed dose of 0.2, 2.0, and 20.0 MGy at the Brookhaven Linac Isotope Producer facility (BLIP). The radiation types and energy profiles mimic those expected at the FRIB facility. Degradation of the operational performance of these devices due to irradiation is expected to be the result of the de-magnetization of the permanent magnets contained within the seal and the changes in the ferrofluid properties. Post-irradiation performance was evaluated by determining the ferrofluidic seal vacuum tightness and torque under static and dynamic conditions. The study revealed that the ferrofluidic feedthrough seal irradiated to a dose of 0.2 MGy maintained its vacuum tightness under both static and rotational condition while the one irradiated to a dose of 2.0 MGy exhibited signs of ferrofluid damage but no overall performance loss. Lastly, at 20 MGy dose the effects of irradiation on the ferrofluid propertiesmore » (viscosity and particle agglomeration) were shown to be severe. Furthermore, limited de-magnetization of the annular shaped Nd 2Fe 14B and Sm 2Co 17 magnets located within the irradiated FFs was observed for doses of 0.2 MGy and 20 MGy respectively.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [2] ;  [1] ;  [2] ;  [2] ;  [2]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Michigan State Univ., East Lansing, MI (United States). Facility for Rare Isotope Beams (FRIB)
  3. Michigan State Univ., East Lansing, MI (United States). Facility for Rare Isotope Beams (FRIB) and National Superconducting Cyclotron Laboratory NSCL
Publication Date:
Report Number(s):
BNL-113600-2017-JA
Journal ID: ISSN 0168-9002; TRN: US1701565
Grant/Contract Number:
SC00112704; SC0000661
Type:
Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 841; Journal ID: ISSN 0168-9002
Publisher:
Elsevier
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
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Neutron irradiation; De-magnetization; Radiation damage; Ferrofluidic feedthrough; Performance; Static torque; Rotational torque; Leak rate
OSTI Identifier:
1347294
Alternate Identifier(s):
OSTI ID: 1397766