Ultrasonic Imaging of Mechanical Degradation In Superconducting Magnets

Superconducting magnets are a key component in particle accelerators and other devices. However, a phenomenon of “training” has baffled superconducting magnet designers for over 50 years. Training usually refers to a process of gradually improving maximal current that the superconducting high-field magnet can sustain. At the maximal current the magnet would develop resistance and quickly release is stored energy in a process called “quenching”. Repetitive quenching typically leads to a gradual increase of the quench current. Since in practice dozens of quenches may be needed to reach the magnet design current, training is a costly and time-consuming procedure that every newly constructed magnet has to undergo prior to its intended use. Reduction of training is thus one of the key standing problems in the field. It is believed that mechanical degradation of coil materials such as epoxy impregnation cracking and de-lamination along the conductor interfaces play a crucial role in defining length of training and performance limitations. An ability to non-destructively localize and identify these mechanical flaws in magnets would provide a valuable insight for magnet designers and help them to better understand and mitigate training. Present project aims at developing such diagnostic capability using ultrasonic diagnostics. Proposed Solution: Ultrasonic testing is a proven technique for non-destructively evaluating and imaging flaws within a wide range of complex structures, and the proposing small business has extensive experience solving challenging NDE problems using novel ultrasonic methods. For this project, the proposing firm will partner with a national research laboratory to explore various ultrasonic approaches including high-frequency, conventional, “bulk wave” ultrasound as well as lower-frequency “guided wave” ultrasound in both pulse-echo and through-transmission test configurations scanning from the outside of the magnet and from within the core. The proposing team will leverage superconducting magnet specimens with known mechanical flaws as well as the subject matter expertise available at the research institution to develop practical solutions for this application. Phase I Objectives: The primary objective of the proposed SBIR/STTR effort is to develop an ultrasonic scanning method(s) applied from within the magnet core and from outside the magnet shell that is capable of characterizing the presence, location, extent, type, and severity of the mechanical degradation. The research institution will provide access to superconducting magnet specimens with varying degrees of mechanical degradation as well as invaluable subject matter expertise on the design and operation of the magnets. The small business will utilize a variety of bulk wave and guided wave scanning methods to identify the best solution for imaging the degradation in the magnets; this will include synthetic aperture focusing scans, phased array scans, and through-transmission guided wave scans. The research institution will conduct pre-/post-test visual imaging to characterize the mechanical degradation and compare this to the ultrasonic results. A prototype scanner will be developed based on the most successful technique(s). The proposing team has used a similar approach to successfully solve various non-destructive testing challenges in previous SBIR/STTR projects. Commercial Applications & Other Benefits: The phenomenon of “training” has baffled superconducting magnet designers for over 50 years and is a costly and time-consuming procedure that every newly-constructed magnet must undergo prior to its intended use. Reduction of training is thus one of the key standing problems in the field. An ability to non-destructively localize and identify these mechanical flaws in magnets would provide a valuable insight for magnet designers and help them to better understand and mitigate training. Reducing superconducting magnet training could yield significant cost reductions for manufacturers. This benefit would not only be applicable to DOE applications in high-energy physics, such as fusion reactors and particle accelerators, but also to the many applications of superconducting magnets in the public sector. These applications include medical MRI machines, NMR equipment, mass spectrometers, magnetic separation processes, and superconducting maglev trains, among others.