Title: Spatial modulation of Joule losses to increase the normal zone propagation velocity in (RE)BaCuO tapes,
Abstract: This paper presents a simple approach to increase the normal zone propagation
velocity in (RE)BaCuO thin films grown on a flexible metallic substrate, also
called superconducting tapes. The key idea behind this approach is to use a
specific geometry of the silver thermal stabilizer that surrounds the
superconducting tape. More specifically, a very thin layer of silver stabilizer
is deposited on top of the superconductor layer, typically less than 100 nm,
while the remaining stabilizer (still silver) is deposited on the substrate
side. Normal zone propagation velocities up to 170 cm/s have been measured
experimentally, corresponding to a stabilizer thickness of 20 nm on top of the
superconductor layer. This is one order of magnitude faster than the speed
measured on actual commercial tapes. Our results clearly demonstrate that a
very thin stabilizer on top of the superconductor layer leads to high normal
zone propagation velocities. The experimental values are in good agreement with
predictions realized by finite element simulations. Furthermore, the
propagation of the normal zone during the quench was recorded in situ and in
real time using a high-speed camera. Due to high Joule losses generated on both
edges of the tape sample, a "U-shaped" profile could be observed at the
boundaries between the superconducting and the normal zones, which matches very
closely the profile predicted by the simulations.