No-Insulation (NI) Winding Technique for Premature-Quench-Free NbTi MRI Magnets

• Published in: IEEE transactions on applied superconductivity Vol. 22; no. 3; p. 4501004
• Main Authors: Seungyong Hahn, Dong Keun Park, Kwangmin Kim, Bascunan, J., Iwasa, Y.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.06.2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Charging; Coils; Electrical engineering. Electrical power engineering; Electromagnets; Exact sciences and technology; Magnetic resonance imaging; Magnets; MRI; NbTi; Nickel; Niobium base alloys; no-insulation; premature quench; quench-free; stability; Stability analysis; Superconducting magnets; Superconductivity; Various equipment and components; Voltage; Voltage measurement; Winding; Windings; Wire; Thermal stress; Performance evaluation; High performance; Bias temperature instability; MRI; Magnet; quench-free; Experimental study; Nuclear magnetic resonance imaging; NbTi; Critical current; Delay time; no-insulation; premature quench; stability; Machine windings
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2011.2178970

This paper describes and discusses a No-Insulation (NI) winding technique that, based on experiment results of two test NbTi coils, promises to significantly improve stability and ease protection of high performance magnets; if applied to those used in marketplace MRI magnets, it may eradicate premature quenches that still afflict these magnets, though much less frequently than in the past. The key idea is that a single turn in an NI winding can, upon a quench, share the copper stabilizers of neighboring turns through turn-to-turn contacts. To demonstrate the main features of the NI technique, two test coils (Φ30 mm) were wound with insulated (INS) and no-insulation (NI) NbTi wires, respectively. The results presented in this paper include: 1) charge-discharge test results and field analyses showing that the NI field performance is essentially identical to that of the INS coil except a charging delay; and 2) charging test results where coil voltages were measured during critical current tests to imply that the NI coil is charged more stably than its INS counterpart.