High Speed Spin Testing of Reinforced 2212 Coils for High Field NMR Magnets

Area of Science:

• Materials Science
• Superconductivity
• Magnet Technology

Background:

• Bismuth-2212 (Bi-2212) superconductors offer excellent performance in high magnetic fields.
• Mechanical reinforcement of Bi-2212 is crucial for realizing its potential in high-field Nuclear Magnetic Resonance (NMR) magnets (> 1 GHz-class).
• Conventional tensile tests are insufficient for evaluating coil performance under the high Lorentz stresses experienced in operational magnets.

Purpose of the Study:

• To simulate the high-field magnet environment for testing reinforced Bi-2212 coils.
• To assess the mechanical integrity of Bi-2212 coils under high hoop stress conditions.
• To validate a novel spin-testing method for superconductor coils.

Main Methods:

• Coils wound on a 60-mm diameter mandrel were spun at speeds up to 100,000 rpm.
• Spin testing was conducted at Barbour-Stockwell (BSI) facilities to simulate high Lorentz stresses.
• Hoop stress generated by spinning was calculated to evaluate conductor yield strength.

Main Results:

• Spinning coils at 100,000 rpm generated approximately 700 MPa of hoop stress.
• This hoop stress level is sufficient to exceed the yield strength of the reinforced Bi-2212 conductor.
• The study is in its early stages, funded by NIH over 3 years.

Conclusions:

• Spin testing provides a viable method to simulate high-field magnet stresses on superconductor coils.
• This technique allows for the evaluation of coil-level factors like thermal contraction and stress concentrations.
• The reinforced Bi-2212 conductor shows promise for high-field NMR magnet applications, pending further testing.