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Improvement of Industrial wires: MgB 2 and HTS conductors. René Flükiger. Dept. Applied Physics (GAP) University of Geneva, Switzerland. Now : CERN Associate. Outlook. * Overview: recent progress on various conductor types for possible application in wind mill generators
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Improvement of Industrial wires: MgB2 and HTS conductors René Flükiger Dept. Applied Physics (GAP) University of Geneva, Switzerland Now: CERN Associate SOWIT, Rome, 24.10.2011
Outlook * Overview: recent progress on various conductor types for possible application in wind mill generators * Y or R.E. based coated conductors * Conductors produced by P/M techniques: - Bi-2223, Bi-2212 (very brief) - MgB2 wires * Problems to be solved * Conclusions SOWIT, Rome, 24.10.2011
Systems to be used at T = 77 K R.E.BaCuO tapes SOWIT, Rome, 24.10.2011
Requirements to a REBaCuO tape Current density * Carry optimized current in REBaCuO (dopants) Mechanical * Substrate strong enough at high temperature to stand the formation of REBaCuO * Tape as a whole strong and flexible enough to be wound into cable and coils at 300 K * Tape must withstand longitudinal and transverse stresses during operation Electrical stability * Carry excess current in Ag layer and in in Al, Cu,……. outer layers Thermal stability * Enable heat transfer to the coolant AC losses * Modify architecture to minimize AC losses (Roebel, striations) SOWIT, Rome, 24.10.2011
Many ways lead to REBaCuO coated conductor tapes Coating with liquid (metal organic deposition) MOD (AMSC) Adsorb vapors (metal organic chemical vapor deposition, MOCVD (SuperPower) Adsorb metal atoms from vacuum (pulsed laser deposition), PLD (Bruker, SEI) (electron beam evaporation):RCE (SuNAM) SOWIT, Rome, 24.10.2011
REBaCUO tape of SuperPower 2G wire based on IBAD MgO and MOCVD process < 0.1 mm D. Hazelton et al., ASC 2010 SOWIT, Rome, 24.10.2011
Summary: Fabrication width, production rate SEI: Fabrication width 30 mm, No indication about production rate AMSC: Fabrication width 40 mm, Goal: 100 mm width, lengths: > 500 m > 1’000 km/year of 4 mm tape SuperPower: Fabrication width 12 mm, Lengths: 1’400 m July 2010: > 150 km/year(?) Fujikura: Fabrication width 10 mm, lengths:> 1’000 m 2009: PLD/CeO2 (60 m/h), IBAD MgO (≤1,000 m/h), Y2O3 (500m/h), Al2O3 (150 m/h), GdBaCuO (15 m/h) SuNAM: Fabrication width 12 mm, lengths: > 100 m (planned: 2’000 m) Nov. 2009: Homoepitactic (70m/h),LMO buffer (50 m/h) Goal: 2,000 km/year (assuming 100% yield) Bruker: Fabrication width 40 mm, lengths: ≤ 100 m (planned: > 1’000 m) Goal: line speed (ABAD) 30 m/h and PLD (70 m/h) SOWIT, Rome, 24.10.2011
What remains to be done ? *Higher Jc values: - higher homogeneity over whole length - thicker layers - enhanced pinning by nano-additives - reduced anisotropy by nano-additives * Reduced ac losses SOWIT, Rome, 24.10.2011
Higher critical current density Enhanced layer thickness Fujikura reports 6 mm thick layer with 1’040 A/cm-w (Deposition time not reported) M. Igarishi et al., EUCAS 2009 (Fujikura) SOWIT, Rome, 24.10.2011
2008: BaZrO3 was demonstrated in MOCVD o achieve dramatic in-field performance improvements SOWIT, Rome, 24.10.2011
Higher critical current density Enhancement of Jc for fields out-of plane: the minimum Jc is the decisive one for applications Further progress still to expect SuperPower, 77K/1T AMSC, 77K, 1 T V. Selvamanickam and J. Deckow, DOE Peer Review 2010 M. Rupich, J. McCall, C. Thieme, DOE Peer Review, 2010 SOWIT, Rome, 24.10.2011
Effect of tensile stress on Jc SOWIT, Rome, 24.10.2011 Flükiger, Les Diablerets, 29.6.-1.7.2011
Systems to be used at T ≤ 40 K Bi- basedsystems: Bi-2223, Bi-2212 (?) Use of cryorefrigerators SOWIT, Rome, 24.10.2011
The system Bi-2223 Data from K.I. Sato, Sumitomo SOWIT, Rome, 24.10.2011
The system Bi-2212 Recent results of D. Larbalestier et al. (Tallahassee): Application of cold isostatic pressure on Bi-2212 wires SOWIT, Rome, 24.10.2011
// ⊥ Jc doubled after CIP treatment New data of D. Larbalestier (Peter Lee plot) SOWIT, Rome, 24.10.2011
Disadvantages of Bi based systems: • * In presence of fields above 0.5 T only operational at T ≤ 30K • * Costs of Ag will always be an obstacle (in particular with the • future tendency of material costs) • * Low mechanical strength (tensile and compressive) • Advantages of Bi based systems: • * High thermal stability SOWIT, Rome, 24.10.2011
The system MgB2 Use of cryorefrigerators at T ≤ 20K Large scale applications: * LINK (CERN) * Poloidal fieldcoils ? * Ignitor ? SOWIT, Rome, 24.10.2011
Preparation of MgB2 wires by 3 different P/M techniques SOWIT, Rome, 24.10.2011
Comparisonbetweenex situ and in situ binary MgB2 wires Available literature values for round wires; tapes have higher Jc values SOWIT, Rome, 24.10.2011
MID process (Japan) SOWIT, Rome, 24.10.2011
MgB2 wires:muchlighthaneveryother s.c. wires Advantages of ex situ technique * Longer lengthsproduced (> 2 km) * Higher homogeneity over wholelengths Advantage of in situ technique * Possibility of doping (higher values at high fields) SOWIT, Rome, 24.10.2011
Densification of Multifilamentary MgB2 wires SOWIT, Rome, 24.10.2011
Binary Fe/MgB2 wire 1.0 mm 1.0 mm Drawn to a square cross section After cold densification Densification pressures for MgB2 wires: 1 – 1.5 GPa R. Flükiger, M.S.A. Hossain, C. Senatore, SuST 22(2009)095004 SOWIT, Rome, 24.10.2011
Mechanism of densification effects in MgB2wires MgB2 is a forgiving material: No cracks at limit between unpressed and pressed filament SOWIT, Rome, 24.10.2011
Monofilamentary MgB2 wires with malic acid additives Highest values known so far for in situ MgB2 wires SOWIT, Rome, 24.10.2011
Homogeneousareal change of all densified filaments SOWIT, Rome, 24.10.2011
4.2 K SOWIT, Rome, 24.10.2011
The exponential n factor: strong enhancement SOWIT, Rome, 24.10.2011
Densification of long MgB2 wire lengths Two independent hydraulic systems: 40t/16t Control of the 4 anvils: * independent pressure set * independent time of pressure Very high exerted pressures: 1 – 1.5 GPa (several times higher than an extrusion machine) Pressure sequence: 2.3 s Traveling distance between pressing steps: 14 mm Pressing length: 70 mm Total densified length (estimated): 300 m/day Densified lengths of 1 km / day: possible after modifications SOWIT, Rome, 24.10.2011
Conclusions: MgB2 * Jc of in situ wires: enhanced by a factor 2.3 * There is still a potential for improvement of Jc. * Costs a factor 50 to > 100 lower than for HTS superconductors At B < 3 T (generators): Differencesbecomemuchsmallerbetween various techniques Densification: applicable on any P/M system: *Bi-2212 (under work) *Future s.c. systems * To improve: thermal stabilization SOWIT, Rome, 24.10.2011
Reduction of AC losses * Roebel technique, * Striations, * Roebel + striations SOWIT, Rome, 24.10.2011