Fabrication and Testing of a Bi-2223 Test Coil for High Field NMR Magnets

Area of Science:

• Materials Science
• Superconductivity
• Magnet Technology

Background:

• The Committee on Opportunities in High Magnetic Fields (COHMAG) challenged the development of 30 T NMR magnets in 2005.
• The National High Magnetic Field Laboratory (NHMFL) is exploring high-temperature superconductors (HTS) to meet this challenge.
• Investigated HTS include REBCO, Bi-2212, and a reinforced Bi-2223 conductor (Type HT-NX).

Purpose of the Study:

• To evaluate the performance of the reinforced Bi-2223 (Type HT-NX) conductor for high magnetic field NMR applications.
• To assess the feasibility of operating the conductor at high hoop stress and total strain levels.
• To determine the operational limits and stability of a test coil fabricated from Type HT-NX.

Main Methods:

• Fabrication of a test coil using a 240 m length of Type HT-NX conductor.
• Testing the coil in a 14 T background field.
• Operating the coil to 19.5 T with a total applied strain of 0.8% and a coil current density of 243 A/mm².
• Performing 20 current cycling tests from half to full design current.

Main Results:

• The Type HT-NX coil successfully operated to 19.5 T in a 14 T background field.
• The coil sustained a total applied strain of 0.8% and a current density of 243 A/mm².
• No degradation was observed after 20 current cycling tests, indicating excellent stability and mechanical integrity.

Conclusions:

• The reinforced Bi-2223 (Type HT-NX) conductor shows significant promise for constructing high-field NMR magnets.
• The conductor can withstand high mechanical stress and strain, crucial for demanding magnet applications.
• The demonstrated performance and stability suggest feasibility for achieving the 30 T NMR magnet goal.