Dynamic magneto-optical imaging of transport current redistribution and normal zone propagation in YBa₂Cu₃O_7−δcoated conductor

Abstract

YBa 2 Cu 3 O 7−δ (YBCO) coated conductors carry high critical current density with the potential for low cost and thus have a broad range of potential applications. An unresolved issue that could inhibit implementation, however, is a lack of understanding of the current redistribution and normal zone propagation behavior in the event of a thermal disturbance (quench). In this work, we for the first time present the real-time, dynamic observation of magnetic field redistribution during a thermal disturbance via magneto-optical imaging with a high speed, high resolution CCD (charge coupled device) camera. The optical images are converted to a two-dimensional, time-dependent data set that is then analyzed quantitatively. It is found that the normal zone propagates non-uniformly in two dimensions within the YBCO layer. Two stages of normal zone propagation are observed. During the first stage, the normal zone propagates along the conductor length as the current and magnetic field redistribute within the YBCO layer. During the second stage, current sharing with the Cu begins and the magneto-optical image becomes constant. The normal zone propagation velocity at 45 K, I = 50 A (∼50% I c ), is determined as 22.7 mm s −1 using the time-dependent optical light intensity data.

The effects of superconductor–stabilizer interfacial resistance on the quench of a current-carrying coated conductor

“…However, these are interesting phenomena in their own right and it would be worthwhile to try to observe and study them experimentally. Their detection can be made by conventional electric methods of detection, but a more spectacular result could be obtained with the help of the real-time magneto-optical imaging [21,24].…”

Dynamic magneto-optical imaging of superconducting thin films

“…High-speed magneto-optical imaging and current calculation has been used to investigate dynamic effects such as the relaxation of current distribution in a YBCO strip after a current pulse [20] (though this was limited by a relatively long exposure time), the response to a high frequency AC transport current [21] and the dynamic processes of a thermal quench [22].…”

C-Term Faraday Rotation in Metallocene Containing Thin Films

“…V is the wavelength-dependent Verdet constant, which characterizes the effectiveness of a material to produce a Faraday rotation. Faraday rotators have found many applications, , most specifically in optics, − magnetic field sensing, , and MO imaging. − It is anticipated that MO materials will be cornerstones of new optical technologies, and achieving superior Faraday rotators is key to realizing emerging applications including high-performance magnetic field sensing that may enable biomagnetic imaging of nerve impulses . The development of new and improved MO technologies has been limited by the lack of inexpensive, fabricable, optically transparent materials exhibiting large Verdet constants.…”