A versatile 4K insert for characterization of the superconducting joints.

Abstract

A multi-coil superconducting magnet is the heart of any modern Magnetic Resonance Imaging (MRI) scanner. The superconducting magnet in MRI produces a highly homogeneous field (±5 ppm) and stable field (<0.1 ppm/h) in its imaging volume. The temporal field stability depends on the electrical resistance of the inter-coil joints and the electrical resistance of the joint between the coil and the superconducting switch. To establish the joint technology, a 4K test rig is required for testing the sample joints. This paper briefly discusses the details of the versatile 4K insert recently developed at IUAC for the characterization of the superconducting joints using the field-decay measurement technique. It can measure the joint resistance up to ∼10-15 Ω in a straight or spiral joint configuration with lengths up to 150mm. The maximum current that can be induced on the test coil is more than 600A for the field-decay measurement. The behavior of the joint resistance can also be studied in the presence of a 1.5T background field. We have characterized many superconducting joints using this versatile 4K insert. The joints between two different conductors can also be studied using this 4K insert. The lowest joint resistance measured is 8 × 10-15 Ω at zero field. The joint resistance is also measured in the presence of the background field.