ADVANCES IN INDUSTRIAL PRODUCTION OF Mg. B 2 WIRES Giovanni Grasso Columbus Superconductors Sp. A
Aknoweledgements o S. Brisigotti, A. Tumino, S. Berta, R. Penco, D. Pietranera, L. Rostila – Columbus Superconductors Sp. A o A. Malagoli, V. Braccini, M. Vignolo, C. Ferdeghini, M. Putti – CNR/INFM o D. Nardelli, R. Marabotto, M. Modica, A. Pellecchia – ASG Superconductors Sp. A o A. Ballarino, L. Rossi – CERN o A. Morandi, S. Imparato - Univ. Bologna o N. Magnusson, M. Runde - SINTEF o B. Coppi, F. Bombarda – MIT o R. Musenich - INFN
Outline o o o Considerations on Mg. B 2 The ex-situ manufacturing process Main properties Industrial production Applications Conclusions
Current situation o Superconductivity is a wonderful phenomenon, but its today’s applications are still confined to MRI-NMR, R&D, current leads and ‘big physics’ o 2 G HTS material is expected to modify soon this scenario, but its complexity and limitation is currently delaying its positive effect on the industrial market of superconductivity o What can we expect more from Mg. B 2?
Applications o Making a good superconducting product is a formidable interdisciplinary problem Wire performance Cryogenics Wire cost Engineering Look Cables FCL MRI Dedicated MRI
Mg. B 2 Very simple crystal structure Polycristalline materials carry large currents Very high current densities observed in films Moderately high Tc Tc of 39 K Good mechanical properties Mg. B 2 presents very promising features Factor of 10 larger than in bulks; room for large improvement in wires still available from R&D Potentially high critical field Low cost – low weight Mg. B 2 precursors: 150 €/Kg today Mg. B 2 mass density: 2. 5 kg/dm 3 Larger than 60 Tesla at low T
Superconducting wires presently available on the market LTS MTS HTS
Considerations on Mg. B 2 o Mg. B 2 development makes industrial sense if: -it can reach intermediate properties than those of Nb. Ti and Nb 3 Sn at 4. 2 K -it can reach a current density of 100 A/mm 2 in a field of 4 -6 Tesla and temperature of 10 K and above o Both results should be compatible with low wire cost (<10$/k. A▪m) and good mechanical properties (R&W), εcr > 1%
The ex-situ process + B Mg Mg. B 2 Advantages: High Mg. B 2 packing density (>80%) Short sintering time (100 -300 s) High εcr of 1% with Monel 400 sheath Good control of Mg. B 2 particle size Sustain high annealing temp. up to 800°C No need of Niobium sheath Fine particle size can be used Disadvantages: Dedicated cold working and sintering equipment have to be used Sintering of Mg. B 2 occurs at high temp. above 850°C Mg. B 2 grain growth and ‘cleaning’ occurs
Fabrication of Mg. B 2 wires by the ex-situ P. I. T. method used 325 mesh 99% purity + B amorphous 95 -97% purity tube filling 1. 3 g/cm 3 Mg mixing wire drawing to 2 mm reaction at 900°C in Ar Mg. B 2 cold rolling reaction at 900 -1000°C in Ar
Fabrication of Mg. B 2 wires by the ex-situ P. I. T. method advantages Ø Straightforward multifilament processing Ø Significant homogeneity over long lengths Ø Allows careful control of the Mg. B 2 particle size and purity disadvantages Ø Need of hard sheath materials and strong cold working Ø Jc is very sensitive to the processing route Ø More tricky to add doping and nanoparticles effectively Reliable method for exploring long lengths manufacturing
Going from flat tape to round-square wires cleans up conductor anisotropy, and the field dependence of Ic improves accordingly. However, the use of clean Mg. B 2 leads to sharp drop of jc(B)
Enhancements in the P. I. T. ex-situ method Possible routes: Commercial precursors B Mg Mg. B 2 B Mg. B 2 Mg Doped boron Mg. B 2(dope B(doped) d) + Commercial Mg. B 2 Mg B + dopant + Home made boron Mg. B 2 High energy ball milling tube filling + wire drawing to 2 mm B + cold rolling Mg B 2 O 3 reaction at
Requirements for applications High field performance demonstrated in R&D wires by many groups
Columbus Superconductors o Has its own production facilities in Genoa with leading capability to produce and supply Mg. B 2 wires on a commercial basis since two years – most used for MRI so far o o o The new plant is operational for a wire production readily scalable up to 2 -3’ 000 Km/year if requested by the market in 3 -6 months time Wire unit length today up to 4 Km in a single piece Total plant area 3’ 400 m 2 – 60% of it in use today Total production for MRI so far exceeded 400 Km of fully tested wires Mg. B 2 compound production now implemented into the owned area Increased interest from customers developing power applications
Columbus wires o Production of Mg. B 2 wires in our Company is expected to grow twice each year for the next three years o Because of the higher volumes and optimized manufacturing methodologies, from 2012 it is expected that the conductor price would have reached its final target value within 20÷ 40%
Monolithic design -1 o Two basic monolithic wire designs for magnet application are currently under development and parallel production A) B) Currently produced in three sizes (w x t): 2. 5 x 1. 5, 2 x 1, 1. 5 x 0. 7 mm
Monolithic design -2 o Type A): Standard Columbus Mg. B 2 wire with one ring of superconducting filaments – Iron barrier between the filaments and the Copper core o Type B): Newer Mg. B 2 wire with no Iron barrier between the filaments and the Copper core – higher engineering critical current and no Iron content in the conductor, Mg. B 2 filaments more near to the neutral plane to enhance resistance to bending – long lengths under development o Drawback of the monolithic wire design: Copper fraction hard to be varied significantly
Expected wire performance evolution with respect to time Type A) wire Time Process Je (A/mm 2) at 12 K, 2 T Je (A/mm 2) at 12 K, 4 T Now Carbon doping 200 130 End 2010 Ball milling 300 200 End 2011 Improved Boron 450 350 2012 High pressure process 700 500 q For type B) wire we do expect 10% higher Je q Je calculated overall (entire wire cross section) q Je at first approx is independent from the overall wire cross section S, i. e. Ic can be calculated by Ic=Je x S q For approximate numbers at 20 K, just divide magnetic field by a factor of two ( i. e. Je at 20 K, 2 T ~ Je at 12 K, 4 T)
Wire unit length/strength o Currently Columbus can treat about 4 dm 3 of material in one step o This means a single batch length of 2 Km for the 2 x 1 mm wire, or 4 Km for the 1. 5 x 0. 7 mm wire o Scaling up by a factor of two is expected by modifying actual equipment o Further scaling up by a factor of four is expected by purchasing of additional equipment – subcontracting initial drawing to Fornaci o Wires are conceived for R&W device manufacturing; minimum bending diameter with no degradation is approximately 100 times the conductor thickness o Maximum tensile strain with no degradation is about 200 MPa
Other wire configurations o These conductors are conceived for conventional magnet application o Different wire designs can be produced according to customers request (low AC-losses, high filaments count, wire-in-channel, etc. ) Sandwich conductor is becoming our best proposal for a magnet wire – f. f. of 30%, adjustable Copper fraction, lower cost, higher overall je, easier than WIC for Mg. B 2
Production process and costs Cost estimate Manpower Raw material cost Metallurgical phase Chemical phase 10% B + + Mg 90% + reaction at 900°C in Ar Mg. B 2 The production process is composed by two phases, a chemical one followed by a metallurgical one Such process is very effective in producing very homogeneous, long conductors, and it is easily scalable to long length manufacturing, reducing than the manpower costs dramatically B + Mg Ni Manpower expected at same level than Nb. Ti when production will increase Costs of Boron and Magnesium are small compared to other materials Currently, wire costs are driven by Nickel sheath Replacing with stainless or low-carbon steel will help in dropping the cost down to the same level of Nb. Ti when production will exceed 5’ 000 km/year
Demonstrators of Columbus Mg. B 2 Technology Texas Center for Superconductivity 1 Tesla cryogenic-free solenoid magnet INFN-Genova 2. 35 Tesla dipole magnet for particle accelerators ASG Superconductors Open-Sky MRI Recent R&W magnets made with our Mg. B 2 wires many more to come soon SINTEF Norway Induction heater Ansaldo Breda CRIS 1 Tesla cryogenic-free solenoid magnet Cesi Ricerca LNe Fault current limiter Chinese Academy of Science 1. 5 Tesla cryogenicfree solenoid magnet
The MRI system “MR Open” Main Magnet Parameters Nominal Field 0. 5 T Peak Field on the Conductor 1. 3 T Nominal Current 90 A Number of Pancakes 12 Conductor Length (total) 18 Km Inductance 60 H Overall Dimensions 2 x 2 x 2. 4 m Patient Available Gap 0. 6 m Weight 25000 Kg First commercial system installed in hospital 6 magnet systems produced this year – 2 to 4 systems will be shipped to customers worldwide by end of the year
Superconducting junction Mg. B 2 Columbus Superconductors standard production tapes. Persistent mode operation (R<1014 Ohm) on few turns samples (260 mm diameter): -Single joint: up to 300 A @20 K, self-field -Double joint: up to 200 A @20 K, self-field -Latest results show that joints with 300 A at 25 K, > 500 A at 20 K critical currents are achievable In progress: s. c. switch Persistent mode operation solenoid
New Induction Heater design =90% New design with DC induction heating Objectives of ALUHEAT are: • to dramatically reduce energy consumption and life-cycle costs in one of the large-scale electrotechnical components with poorest energy efficiency and at the same time improve the production quality • To validate the technical and economical feasibility of the new concept by building a 200 -300 k. W aluminium billet induction heater and test it in an industrial aluminium extrusion plant
Construction of the heater Mg. B 2 based coils have been already realized and tested individually: 32 double pancakes with 550 m each, and the magnet will be operated at 20 K, 1. 5 T Cryogenic system has been recently tested – One of the two superconducting coils has been tested successfully to rated current – the full system will be tested in beginning of 2010
Design of an Mg. B 2 feeder system to connect groups of superconducting magnets to remote power converters First test of the 3 k. A cable successfully completed at CERN using our strands – Ic exceeded 11 k. A at 4. 5 K and self field, probably reaching the optimal target of 3 k. A up to 30 K
20 k. V distribution system DC resistive FCL design based on Mg. B 2 Nominal Rate 25 MVA Nominal Voltage 20 k. V Quenching current 1225 A Inductance 5 m. H Quenched resistance 5 Cross section Number of Mg. B 2 filaments Superconducting section Stabilization material Sheath material Quenched resistance per unit length 2. 30 1. 10 mm 2 8 19. 1 mm 2 Cu Steel 0. 1 /m
Racetrack magnet for particle accelerators – MARIMBO project The magnet reached about 2. 5 Tesla in cryogenic-free conditions Magnet was R&W with a layer by layer structure
Ignitor – italian fusion project 30 K He gas cooled copper conductors are currently expected to be used in this machine Parameters Major Radius Unit m Aspect ratio Elongation Triangularity Symbol Value R 0 1. 32 0. 47, a, b 0. 86 A 2. 8 k 1. 83 d 0. 4 Toroidal magnetic field BT 13 T Toroidal current Ip 11 MA Maximum poloidal field Bp, max 6. 5 T 3. 44 T 9 MA Edge safety factor (@11 MA) qy 3. 6 Confinement strenght Plasma Surface Plasma Volume S 0 V 0 38 34 10 MA T m 2 m 3 ICRF heating (140 MHZ) PRF 6 (*) MW Minor radius Mean poloidal field Poloidal current Iq m
Mg. B 2 cable conductor for Ignitor
Conclusions o Mg. B 2 industrial production is making a substantial progress o A first commercial product has been already introduced into the market (LHe-free MRI) o Many more prototypes and demonstrators are currently under development worldwide o Low-cost and mechanical strength are essential requests for Mg. B 2 to be competitive o In-field performance still needs to be improved in order to enable effective Nb 3 Sn replacement in high-field magnets
Thank you for your attention!
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