AC Losses of Roebel Cables with Striated 2G REBCO Strands

We present experimental data on the ac losses in Roebel cables with striated 2G REBCO strands. Electromagnetic measurements by pick-up coils were carried out at different temperatures between 10 K and 85 K at frequencies between 2 Hz and 20 kHz in transverse ac fields up to 0.5 T. The Roebel cable samples were assembled from laser cut 2G REBCO strands, which consist of striated filaments prepared with laser scribing. Measurements at different temperatures show that the Roebel cables with striated strands have a lower losses by a factor of strand filament number over the whole temperature range. For analysis, a semiquantitative approach for unstriated Roebel was found to work satisfactorily. However, the Striated Roebel cables appears to have a different field penetration from those of the unstriated Roebel. The coupling current among the filaments has a time constant shorter than 0.1 ms and do not appear to increase in the striated Roebel cables, hence insignificant for most magnets related applications.