conductors by striation and selective electroplating

Transcription

1 Fully-filamentized HTS coated conductors by striation and selective electroplating V. Selvamanickam, I. Kesgin, X. Cai and G. Majkic Department of Mechanical Engineering Texas Center for Superconductivity University of Houston, Houston, TX, USA Project funded by SuperPower Inc. Coated Conductors for Applications, Heildelberg, Germany, November 13-16,

2 Multfilamentary coated conductors for low ac loss applications Filamentization of coated conductors is desired for low ac loss applications. Maintaining filament integrity uniform over long lengths (no Ic reduction) Minimum reduction in non superconducting volume (narrow gap) and fine filaments Striated silver and copper stabilizer (minimize coupling losses) 4mm ac loss (W/m) Ag Hz unstriated 5.1 x B ac rms (T) Substrate A fully filamentized coated conductor would need to have µm of copper stabilizer striated! Cu multifilamentary HTS

3 One approach to make fully-filamentized coated conductor Ag 1. Coat photoresist on silver REBCO Photoresist Substrate 2. Transfer pattern from mask to 3. Electroplate copper photoresist 4. Remove remaining photoresist Cu 5. Wet etch silver and HTS X. Zhang and V. Selvamanickam, US 7,627,356

4 One approach to make fully-filamentized coated conductor Cu Ag HTS substrate 100 μm Cu 1 mm Fully-filamentized coated conductor demonstrated, but still involves etching X. Zhang and V. Selvamanickam, US 7,627,356

5 A bottom-up approach make fully- filamentizedi coated conductor Mechanical scribing of buffer layer, then deposit REBCO and Ag and Cu selectively l REBCO Buffer Stack Substrate Substrate Substrate 500 µm G. Majkic, I. Kesgin, Y. Zhang, Y. Qiao, R. Schmidt, and V. Selvamanickam, AC Loss Filamentization of 2G HTS Tapes by Buffer Stack Removal, IEEE Trans. Appl. Supercond. 21, 3297 (2011) 5X ac loss reduction without Ag or Cu

6 Another bottom-up approach make fully- filamentized coated conductor with no material removal Inkjet deposited insulator stripes Substrate with buffer X. Cai, I. Kesgin, R. Schmidt, Y. Chen and V. Selvamanickam, Completely Etch-free Fabrication of Multifilamentary Coated Conductor Using Inkjet Printing and Electrodeposition, IEEE Trans. Appl. Supercond. (submitted) 6

7 Reel-to-reel inkjet printing of insulator stripes on buffered substrate 7

8 Selective epitaxial REBCO in between inkjet printed insulator stripes 8

9 Selective Ag electroplating on epitaxial REBCO in between inkjet printed insulator stripes 9

10 Lowered ac losses in filamentized conductor made with no material removal 10-fold reduction in ac loss in 12-filament conductor made with no material removal 10

11 Fully-filamentized conductor by mechanical scribing and selective electroplating REBCO Buffer Stack Oxide Layer Ag Hastelloy Hastelloy Electroplated Cu Mechanical Scribing + oxygenation Selective Cu Electroplating Non-striated 12-filament, 12 mm wide Ag 12 mm wide sputtered tape tape 12-filament tape with electroplated l t Cu Mechanical Scribing Oxygenation + ED Cu 11

12 Significant ac loss reduction in full-filamentized conductor with copper stabilizer Critical current of standard 16 conductor = 207 A Critical current of 12-filament 12 conductor = 197 A 10 W/m) ac loss ( Critical current of 12-filament conductor after 10 µm copper 6 stabilizer = 200 A 4 AC loss of 12-fiament conductor at 60 Hz is 11 times lower than that of unstriated conductor without copper stabilizer and 13 times lower with copper stabilizer, at higher fields T 0.02 Multfilamentary Standard Multfilamentary + Cu Standard + Cu ac field frequency (Hz)

13 Investigated selectively electroplated copper thickness & coupling effects S1 S2 S3 S4 S5 S6 ~10 µm ~20 µm ~30 µm ~44 µm ~36 µm ~33 µm Fully coupled Mechanically scribed, no oxidation and Cu plated No filamentization 13

14 Sideways growth of electroplated copper reduces groove width between filaments S1 Groove Oxide Filament Copper S3 Groove Oxide Filament Copper 40 µm Filament Copper 15 µm No coupling Mechanically scribed, oxidized and Cu plated (~ 10 µm) No coupling Mechanically scribed, oxidized and Cu plated (~ 30 µm) 14

15 Partially and fully-coupled filamentized tape with copper stabilizer S4 S5 Filament Copper Groove partial Cu Groove Copper Filament Copper Partially coupled Mechanically scribed, oxidized and Cu plated (~ 44 µm) Fully coupled Mechanically scribed, no oxidation and Cu plated (~ 33 µm) 15

16 No significant loss contribution up to 30 µm stabilizer in fully-filamentized conductor at 40 Hz 40 Hz Non-striated B-I with Ic=195 A Striated B-I with Ic=195 A 15-fold ac loss reduction even with 30 µm Cu stabilizer Lower ac loss reduction with 40 µm Cu stabilizer 16

17 No significant loss contribution up to 30 µm stabilizer in fully-filamentized conductor even at 400 Hz 400 Hz 17

18 15-fold ac loss reduction in fully-filamentized conductor with up to 30 µm stabilizer ~15 times 40 Hz Magnetic Electrical Coupling + eddy current Reduction is still more than 12-fold but decreases in 400 Hz (heating effects) Loss ratio: ac loss of filamentized conductor S3/ac loss of non-striated conductor S6 18

19 5-fold ac loss reduction at 40 Hz even in partially-coupled filamentized conductor with 44 µm stabilizer Magnetic Almost 5 times 40 Hz Electrical Coupling + eddy current Striation becomes ineffective at 400 Hz Loss ratio: ac loss of filamentized conductor S4/ac loss of non-striated conductor S6 19

20 Fully-coupled filamentized conductor with 36 µm stabilizer shows comparable ac loss at 40 Hz and higher loss at 400 Hz Weak effect of 40 Hz Electrical Coupling Striation 400 Hz Losses increases beyond S6 due to Magnetic + Electrical coupling Loss ratio: ac loss of filamentized conductor S5/ac loss of non-striated conductor S6 20

21 Summary Selective electroplating has been proven to achieve fully-filamentized coated conductor even with thick copper stabilizer. Coated conductor with up to 30 µm copper stabilizer can be fully-filamentized without any coupling. 15-fold ac loss reduction achieved compared to reference non-striated coated conductor with ~ 30 µm copper stabilizer Coated conductor with 40 µm copper stabilizer can be fully-filamentized with partial coupling (due to sideways growth of copper across groove) 5-fold ac loss reduction achieved at 40 Hz even with partial coupling compared to reference non-striated coated conductor Fully-filamentized coated conductor with no coupling can be achieved even with thicker copper stabilizer using wider grooves Fully-coupled filamentized conductor (conductive material in groove) shows higher ac loss than non-striated conductor: in this case striation makes the situation worse! 21