Topic 32b: Ultrasonic Waveguide Reflectometry for Quench Detection

Statement of the Problem: The pragmatic use of High-temperature superconductors (HTS) and HTS magnets are critical to the operation of high-end fundamental physics research, development of fusion energy sources, energy efficient generators and systems, medical applications, and many other expected applications. These modern systems can operate at higher magnetic fields and elevated temperatures enabling more practical, compact systems, but one of key challenges associated with HTS is a slow propagation of the normal zone that complicates early detection of thermal runaway (quench). Traditional approaches such as voltage-based techniques are often insensitive to early indications of quench due to modern systems requiring field ramping rates up to several Tesla a second (T/s) causing additional plasma currents which impose strong time-varying ac magnetic fields on the conductor, leading to additional inductive voltage noise which further complicates voltage-based quench detection. How the problem will be addressed: We propose unique non-voltage quench detection based upon mechanical stress wave propagation. Over the last ten years, Etegent has been developing a new sensing technology which utilizes the propagation of stress waves through a solid metallic (or other solid materials) waveguide. This approach is akin to fiber-optic sensors except rather than transmitting optical energy via an optical fiber, the vibrational (ultrasonic) energy is transmitted through a solid fiber-like waveguide. Like fiber-optic sensors, the waveguide can be built into a monitored object to measure local variation of strain or temperature, but unlike fiber-optic sensors, mechanical waveguides are constructed of robust materials, and operate at much lower frequencies, eliminating the need for expensive, complex, and highly sensitive receivers and data processing equipment. This approach is expected to be both robust to the challenging environment of HTS, while providing additional quench detection sensitivity. Phase I Plan: During Phase I, Etegent will work with our partner, Lawrence Berkeley Laboratory, Accelerator Technology & Applied Physics Division we plan to evaluate the suitability and practical limitations of a mechanical stress waveguide temperature sensor. The plan includes testing the sensor at cryogenic temperatures, integrating the sensor into high temperature superconductor cables, and developing an actionable plan to further the development. Commercial Applications and Other Benefits: Cryogenic distributed temperature sensing technology have many potential benefits in additional to HTS magnet quench detection. HTS-based infrastructure such as superconducting grid and machinery such as HTS-based motors and generators can equally benefit from this technology. Beyond the quench detection application, a broader use is anticipated in space and rocket applications, cryogenic thermal monitoring in a variety of industrial and future transportation applications, medical equipment, cryo-electronic devices and quantum computing