Technology Group U.S. DOE Office of Science SBIR Phase II award - - PowerPoint PPT Presentation

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

LTSW 2020

Goal: l: defec ect—to tole lera rant, nt, low AC AC loss s cable le

2G wire stack BTG exfoliated filament stack

Buffer Substrate

Sharing current path Sharing current path

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▪ 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 Twisted strand Multi-strand cable

Lesso sons ns learned ned: : Multi-fila ilame menta ntary ry stac ack k cable

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Copper stabilizer Nichrome cladding 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

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Feed spool Scan-head Raster 1.06 µm beams Cable spool Stack bundling Stack twist

▪ Narrow filaments are not-respooled ▪ All processing done on wide tape ▪ The cable is fused post-winding

Ap Approac ach: : one pass s slic icin ing-ca cabl blin ing

Human handling of only wide, 46 - 100 mm, tape

Contro rolli lling g solder er layer r thick ckne ness ss with h cus ustom tom ai air level elin ing

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Tape motion Air flow Air flow Pre-heated air supply

✓ Air –assist allows coating heat-sensitive HTS tape at low solder

temperature

▪ Dip-coating produces active surface ▪ However HTS can tolerate low temperature, < 240oC ▪ Without leveling the solder layer is too thick

Operati ation

• n of air-assi

assiste sted d solder er coate ater

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Solder bath, 230oC Air blades

0.0 0.5 1.0 1.5 2.0 10 20 30 40 50 60 70 80

260

• C

240

• C

220

• C

Coating thickness (m) Tape speed (cm/s)

Air-assist, 240

• C

x4 reduction of the coating thickness Copper tape Solder coating, 5 m

Pa Parallel lel laser er slici icing g using ng fiber er laser er

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Torque controller Optical table Laser power supply Laser fiber Tape positioning setup Scanhead Collimator

✓ Fiber laser - scanhead system for parallel slicing of filaments

Laser fiber

Comparis rison

• n of ns-pul

ulse sed d and conti ntinu nuou

• us

s wave e slic icing ng

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Heat damage

Pulsed fiber laser CW CO2 laser

✓ Fiber laser enables much narrower cut width and reduced heat damage zone

Multi-filam lament ent slicin cing-ca cabl bling ing system stem

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Torque motors Idlers Tape positioning Scan head

Pa Paralle lel l slic icin ing g of the tape by scan anned ed laser er beam beam

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Sliced filaments 10 mm tape Laser beam Tape support

Laser er powe wer optim imiza izatio tion n for the movin ing g tape

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60%, 100 KHz, 0.1 m/s 90%, 100 KHz, 0.1 m/s 70%, 100 KHz, 0.1 m/s 10 m cut width

✓ Optimum power allows confining the edge damage 10 – 20 m area

Laser power

Ed Edge view w of the movin ing g tape cut

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60%, 100 KHz, 0.1 m/s 100%, 100 KHz, 0.1 m/s

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Filaments Air cooling Tape positioning Priming spool Laser beam

Th Thermal al image e of tape slici cing ng to 10 1 mm filam amen ents ts

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x5 2 mm x10 1 mm

Ef Effec ect t of slici icing g on the tape e Ic

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200 400 600 800 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Air-cooled 10 1 mm slices Air-cooling 10, 1 mm slices 5 2 mm slices 77 K self-field Uncooled 10, 1 mm slices

Voltage, V (mV) Applied current, I (A)

10 mm wide

1 V/cm

10 mm x2 5 mm x5 2 mm x10 1 mm

✓ Air cooling is helpful is reducing the superconductor damage in a dense cut

situation

Pa Parallel lel slici icing g cabling ing, , 1 mm strand and

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✓ Tension control is critical for cut overlap

Co Conclus lusion ion and futu ture re wo work: k:

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.

Splicing:

▪ Distributed splices allows for infinite length ▪ Rapid fusion ensured low resistivity

Narrower filaments

▪ Further reduce heat damage by liquid cooling ▪ Shorter pulse length

In air In water Fiber laser IR absorption of water

50 100 150 200 250 300 350 0.02 0.04 0.06 0.08 0.10

Two filaments

• ne break

3 filaments, 2 breaks

Voltage, V (mV) Applied current, I (A)

Single filament

10

• 6 V/cm

▪ Developed thin solderble coating ▪ Demonstrated parallel slicing and cabling ▪ 80% Ic retention for 1 mm slices

Commerci cial aliz izati ation

• n:

: applic icatio ation n of exfo folia liation

• n

tech chno nolo logy gy for quantum tum signal al lines

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Existing IBM system Signal cable Solution: YBCO-Kapton, high density superconducting cable With ultra-low thermal loss

Ad Advanta ntages es of the exfo folia liated ted YB YBCO CO-Ka Kapto pton

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86 88 90 92 94 5 10 15 20 25 30 35 Stainless steel Real signal component (V) Temperature (K) G10 2 4 6 8 10 Imaginary signal component (V)

High Tc (due to compression) High carrier density (substrate side) First prototype delivered and tested RT, 25 dB insertion loss at 5 GHz 77 K, -0.1 dB loss