LTSW 2020 Progress in 2G cable development at Brookhaven Technology Group U.S. DOE Office of Science SBIR Phase II award DE-SC0018737 Slowa Solovyov, Zachary Mendelson, and Paul Farrell Brookhaven Technology Group Inc., Stony Brook, NY 11794 www.brookhaventech.com LSTW 2020, Berkeley, CA February 26-29 2020 1
Goal: l: defec ect — to tole lera rant, nt, low AC AC loss s cable le ▪ Single-filament magnets proven difficult to protect against burnout ▪ Substrate prevents efficient current sharing, especially in narrow, low AC loss cables ▪ Multifilamentary cable is far more expensive than a single tape BTG exfoliated filament stack 2G wire stack Sharing current path Sharing current path Buffer Substrate Multi-strand cable Twisted strand LSTW 2020, Berkeley, CA February 26-29 2020 2
Lesso sons ns learned ned: : Multi-fila ilame menta ntary ry stac ack k cable Nichrome cladding Copper stabilizer Solder YBCO What did we learn: ✓ Active solder layer (large grain) is essential, but thickness need to be controlled ✓ Edge damage by a CO2 CW (Kern HSE) laser is too high for 1 mm filaments ✓ Handling < 2 mm wide filaments is very difficult LSTW 2020, Berkeley, CA February 26-29 2020 3
Ap Approac ach: : one pass s slic icin ing-ca cabl blin ing Scan-head ▪ Narrow filaments are not-respooled ▪ All processing done on wide tape Raster 1.06 µm beams ▪ The cable is fused post-winding Stack twist Feed spool Stack bundling Cable spool Human handling of only wide, 46 - 100 mm, tape LSTW 2020, Berkeley, CA February 26-29 2020 4
Contro rolli lling g solder er layer r thick ckne ness ss with h cus ustom tom ai air level elin ing Pre-heated air supply Air flow ▪ Dip-coating produces active surface ▪ However HTS can tolerate low temperature, < 240 o C Tape motion ▪ Without leveling the solder layer is too thick Air flow ✓ Air – assist allows coating heat-sensitive HTS tape at low solder temperature LSTW 2020, Berkeley, CA February 26-29 2020 5
Operati ation on of air-assi assiste sted d solder er coate ater Copper tape Solder coating, 5 m Air blades o C 80 260 x4 reduction of the coating thickness o C 240 70 o C 220 Coating thickness ( m) 60 50 40 30 o C Air-assist, 240 20 Solder bath, 230 o C 10 0 0.0 0.5 1.0 1.5 2.0 Tape speed (cm/s) LSTW 2020, Berkeley, CA February 26-29 2020 6
Pa Parallel lel laser er slici icing g using ng fiber er laser er Collimator Laser fiber Scanhead Tape positioning setup Laser fiber Laser power supply Optical table Torque controller ✓ Fiber laser - scanhead system for parallel slicing of filaments LSTW 2020, Berkeley, CA February 26-29 2020 7
Comparis rison on of ns-pul ulse sed d and conti ntinu nuou ous s wave e slic icing ng Pulsed fiber laser CW CO2 laser Heat damage ✓ Fiber laser enables much narrower cut width and reduced heat damage zone LSTW 2020, Berkeley, CA February 26-29 2020 8
Multi-filam lament ent slicin cing-ca cabl bling ing system stem Scan head Idlers Tape positioning Torque motors LSTW 2020, Berkeley, CA February 26-29 2020 9
Pa Paralle lel l slic icin ing g of the tape by scan anned ed laser er beam beam Laser beam 10 mm tape Tape support Sliced filaments LSTW 2020, Berkeley, CA February 26-29 2020 10
Laser er powe wer optim imiza izatio tion n for the movin ing g tape Laser power 70%, 100 KHz, 0.1 m/s 90%, 100 KHz, 0.1 m/s 60%, 100 KHz, 0.1 m/s 10 m cut width ✓ Optimum power allows confining the edge damage 10 – 20 m area LSTW 2020, Berkeley, CA February 26-29 2020 11
Ed Edge view w of the movin ing g tape cut 60%, 100 KHz, 0.1 m/s 100%, 100 KHz, 0.1 m/s LSTW 2020, Berkeley, CA February 26-29 2020 12
Laser beam Tape positioning Filaments Priming spool Air cooling LSTW 2020, Berkeley, CA February 26-29 2020 13
Th Thermal al image e of tape slici cing ng to 10 1 mm filam amen ents ts x5 2 mm x10 1 mm LSTW 2020, Berkeley, CA February 26-29 2020 14
Ef Effec ect t of slici icing g on the tape e I c 0.40 77 K self-field 0.35 10 mm Voltage, V (mV) 0.30 5 2 mm slices x2 5 mm 0.25 0.20 Uncooled 10, 1 mm slices 0.15 x5 2 mm Air-cooling 10, 1 mm slices 0.10 Air-cooled 10 1 mm slices x10 1 mm 0.05 1 V/cm 10 mm wide 0.00 0 200 400 600 800 Applied current, I (A) ✓ Air cooling is helpful is reducing the superconductor damage in a dense cut situation LSTW 2020, Berkeley, CA February 26-29 2020 15
Pa Parallel lel slici icing g cabling ing, , 1 mm strand and ✓ Tension control is critical for cut overlap LSTW 2020, Berkeley, CA February 26-29 2020 16
0.10 Co Conclus lusion ion and futu ture re wo work: k: 0.08 Two filaments Single filament one break Voltage, V (mV) 0.06 ▪ Developed thin solderble coating 0.04 3 filaments, 2 breaks ▪ Demonstrated parallel slicing and cabling 0.02 -6 V/cm 10 ▪ 80% Ic retention for 1 mm slices 0 50 100 150 200 250 300 350 Applied current, I (A) IR absorption of water Splicing: . Fiber laser ▪ Distributed splices allows for infinite length ▪ Rapid fusion ensured low resistivity Narrower filaments ▪ Further reduce heat damage by In water In air liquid cooling ▪ Shorter pulse length LSTW 2020, Berkeley, CA February 26-29 2020 17
Commerci cial aliz izati ation on: : applic icatio ation n of exfo folia liation on tech chno nolo logy gy for quantum tum signal al lines Solution: YBCO-Kapton, high density superconducting cable With ultra-low thermal loss Existing IBM system Signal cable LSTW 2020, Berkeley, CA February 26-29 2020 18
Ad Advanta ntages es of the exfo folia liated ted YB YBCO CO-Ka Kapto pton High Tc (due to compression) High carrier density (substrate side) 35 10 Imaginary signal component ( V) 30 Real signal component ( V) 8 G10 25 6 20 Stainless steel 4 15 10 2 5 0 0 86 88 90 92 94 Temperature (K) First prototype delivered and tested RT, 25 dB insertion loss at 5 GHz 77 K, -0.1 dB loss LSTW 2020, Berkeley, CA February 26-29 2020 19
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