mgb 2 wire performance giovanni grasso may 20 th , 2008
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MgB2 wire performance
Giovanni GrassoMay 20th, 2008
CoworkersCoworkers BASIC R&D
CNR-INFM: A. Malagoli, V. Braccini, C. Bernini, C. Fanciulli, M. Tropeano, M. Vignolo, C. Ferdeghini, M. Putti
CONDUCTOR DEVELOPMENTColumbus Superconductors: S. Brisigotti, A. Tumino, D. Pietranera, E. Demencik, S. Berta, R. Penco
POWDERS DEVELOPMENTFerrania Technologies: S. Magnanelli, A. Gunnella
MAGNET DEVELOPMENTASG Superconductors: R. Marabotto, M. Modica, D. Damiani, D. Nardelli
MgB2: this new material represents the natural evolution for applied superconductivity of today and tomorrow
Superconductivity in MgB2 was publicly announced in January 2001 by Japanese scientists
From then on MgB2 represents the known binary material showing superconductivity at the highest temperatures to date
As virtually all superconductors used in large-scale industrial applications are binary materials (NbTi, Nb3Sn), it appeared immediately evident that MgB2 might have represented a new option
So far researchers worldwide produced literally hundreds of scientific manuscripts focused on this surprising discovery
Helium (liquid) is a natural resource available in limited quantities and it represents a bottleneck to industrial developments using superconductivity : MgB2 is a convenient solution to that
Preamble
Important parameters for industrial applications
Material Tc Hc2 ( T= 4.2 K) ξ (nm)Mass
Density
Nb-Ti 9 K 10 T 5 6.0 g/cm3
Nb3Sn 18 K 28 T 5 7.8 g/cm3
MgB2 39 K 60 T 5 2.5 g/cm3
YBCO 90 K > 50 T << 1 c 5.4 g/cm3
BSCCO 110 K > 50 T << 1 c 6.3 g/cm3
World market
MgB2 is an HTS with
properties and price
more near to an LTS
The questions are: how much of the current and future LTS and HTS market MgB2 will grab?and how big will the new market generated by MgB2 be?
C
riti
cal
Cu
rren
t D
ensi
ty,
A/m
m²
10
100
1,000
10,000
100,000
0 5 10 15 20 25 30Applied Field, T
Nb-Ti: Max @4.2 K for whole LHC NbTistrand production (CERN-T. Boutboul)
Nb-Ti: Max @1.9 K for whole LHC NbTistrand production (CERN, Boutboul)
Nb-Ti: Nb-47wt%Ti, 1.8 K, Lee, Naus andLarbalestier UW-ASC'96
Nb-37Ti-22Ta, 2.05 K, 50 hr, Lazarev et al.(Kharkov), CCSW '94.
Nb3Sn: Non-Cu Jc Internal Sn OI-ST RRP1.3 mm, ASC'02/ICMC'03
Nb3Sn: Bronze route int. stab. -VAC-HP,non-(Cu+Ta) Jc, Thoener et al., Erice '96.
Nb3Sn: 1.8 K Non-Cu Jc Internal Sn OI-STRRP 1.3 mm, ASC'02/ICMC'03
Nb3Al: JAERI strand for ITER TF coil
Nb3Al: RQHT+2 At.% Cu, 0.4m/s (Iijima et al2002)
Bi-2212: non-Ag Jc, 427 fil. round wire,Ag/SC=3 (Hasegawa ASC-2000/MT17-2001)
Bi 2223: Rolled 85 Fil. Tape (AmSC) B||,UW'6/96
Bi 2223: Rolled 85 Fil. Tape (AmSC) B|_,UW'6/96
YBCO: /Ni/YSZ ~1 µm thick microbridge,H||c 4 K, Foltyn et al. (LANL) '96
YBCO: /Ni/YSZ ~1 µm thick microbridge,H||ab 75 K, Foltyn et al. (LANL) '96
MgB2: 4.2 K "high oxygen" film 2, Eom etal. (UW) Nature 31 May '02
MgB2: Tape - Columbus (Grasso) MEM'06
2212round wire
2223tape B|_
At 4.2 K UnlessOtherwise Stated
1.8 KNb-Ti
Nb3SnInternal Sn
2 KNb-Ti-Ta
Nb3Sn1.8 K
NbTi +HT
2223tape B||
Nb3SnITER
Nb3Al: ITERMgB2
film
YBCO µ-bridge
H||c
YBCO µ-bridge
H||ab 75 K
MgB2
tape
Nb3Al:
RQHT
Critical currents of technical superconductors at 4.2 K
Superconductors choice is ‘in principle’ quite wide,but jc is not the only important parameter for selection
Low costLow cost
HandlingHandling
SC joints,AC losses,n-factor,etc.
SC joints,AC losses,n-factor,etc.
PerformanceB,TPerformanceB,T
Little investmentfor end-usersto test it on theirproducts
Little investmentfor end-usersto test it on theirproducts
MgB2
superconductor
Driving forces for MgB2
• Low cost and wide Low cost and wide availability of the raw availability of the raw materials, particularly in materials, particularly in EuropeEurope
• Excellent chemical and Excellent chemical and mechanical compatibility mechanical compatibility with various elements (Ni, with various elements (Ni, Fe, Ti, Nb, Ta, Cr, although Fe, Ti, Nb, Ta, Cr, although not with Cu)not with Cu)
• Potential for very good Potential for very good performance at high fields performance at high fields ( thin films show H( thin films show Hc2c2 > 60 T > 60 T ! )! )
• Low anisotropy and Low anisotropy and potential for persistent potential for persistent mode operation (high n-mode operation (high n-value, low current decay value, low current decay at medium magnetic at medium magnetic fields)fields)
About our today’s structure
The new plant is ready and operational for a wire production scalable up to 3’000 Km/yearWire unit length up to 5 Km single piecesTotal plant area 3’400 m2 – 50% only used today
R&D
Powderproduction
7 engineers7 workers2 consultantsIndirect activities to ASG
3 employees
2 professors3 senior researchers4 Postdocs2 PhD students
Columbus Superconductors activities involve about 30 people
Fabrication of MgB2 wires by the ex-situ P.I.T. method used
+
B Mg MgB2amorphous
95-97% purity
325 mesh99% purity
mixing
tube filling1.3 g/cm3
reaction at900°C in Ar
wire drawing to 2 mm cold rolling reaction at900-1000°C in Ar
Straightforward multifilament processing Significant homogeneity over long lengths Allows careful control of the MgB2 particle size and purity
Need of hard sheath materials and strong cold working Jc is very sensitive to the processing route More tricky to add doping and nanoparticles effectively
Reliable method for exploring long lengths manufacturing
advantagesadvantages
disadvantagesdisadvantages
Fabrication of MgB2 wires by the ex-situ P.I.T. method
MicrostructureMicrostructure
Transverse cross section area:
• MgB2 0.21 mm2 (total area)• Cu 0.35 mm2
• Fe 0.19 mm2
• Ni 1.54 mm2
Composite wire:
99.5% pure Nickel matrix
14 MgB2 filaments
OFHC 10100 Copper core
99.5% pure Iron barrier
Dimension 3.6 mm x 0.65 mm ( w x t )
Standard batch length: > 1700 m
Cu Fe NiMgB2
Constant improvement of conductors Constant improvement of conductors from production: Ifrom production: Icc at 20K of 1.7 at 20K of 1.7
Km tapesKm tapes
20K
1.2T
1.4T
1.6T
1000 1005 1010 1015 1020 1025 1030
10
20
30
40
50
60
70
80
n -factor at 1.4T and 16K, 20K, 24K
16K
20K
24K
1.4 Tn-
fac
tor
Conductor #
Ic at 20K, 1 T always >> 90 An-factor at 20K, 1 Tesla >> 30Minimum bending diameter: 65 mmMaximum tensile strain: 150 MPa
A total of 50 lengths of 1.7 Km each have been successfully produced and tested until Nov. 2006
They have been used for two Open MRI systems
Optimisation of the wires fabrication by varying sheaths, Optimisation of the wires fabrication by varying sheaths, geometry of the conductor,…geometry of the conductor,…
Wire B37 filamCu stab
Monel
Cu
Wire C19 filamno Cuup to 61
Ni
Going from flat tape to round-square wires cleans up conductor anisotropy, and the field dependence of Ic improves accordingly
P.I.T. e-situ methodP.I.T. e-situ method+
BB MgMg MgBMgB22
B2O3
Home made boron
MgB2+
B Mg
+B Mg MgB2
Commercial precursors
Commercial MgB2
Possible routes: Possible routes:
High High energenergy ball y ball millinmillin
gg
B
Doped boronMgB2(doped)
+
dopant
+B(doped) Mg
tube filling wire drawing to 2 mm cold rollingreaction at
900-1000°C in Ar
Progress in the Ic of the flat tape conductor in multi Km-length
Time Process 20K, 1 Tesla 20K, 2 Tesla
2006 Standard, 8.5 % filling factor 200 65
Beginning 2007 Improved cold working 250 75
End 2007 Controlled atmosphere 330 80
Today Increased filling factor to 10.5% 390 95
Mid 2008 Improved MgB2 reaction path 500 150
End 2008 MgB2 ball milling and doping >> 500 >250
3.6 x 0,65 mm
2.3 mm2
With Monel sheath minimum bending radius 30 mm
MgB2 grains are covered by 5 nm of MgO layer within 2 hours of exposition of powders to air ( this layer has a thickness ~ ξ )
Working in Oxygen-cleaner conditions is mandatory!
Critical current improvement followed by inert-atmosphere handling
Ic is improved by a factor larger than 2 at virtually all fields just by inert atmosphere powder handling during the entire process
10000 20000 30000 40000 50000
10000
100000
1000000
Jc (
A/c
m2
)
B (Gauss)
CG152a T=730°C CG148a T=745°C CG125a T=752°C CG127a T=760°C CG126a T=768°C CG155a T=737°C
MgB2 powder synthesis temperature
Wires T=5K
730 740 750 760 770 7800
20000
40000
60000
Fili
Jc (
A/c
m2
)
T set (°C)
Jc vS T @ 5K-4,5T
SQUID
1.0E+03
1.0E+04
1.0E+05
1.0E+06
0 1 2 3 4 5
Magnetic Field (T)
Mag
net
ic J
c [A
/ cm
2 ] Jc@5K
1.0E+03
1.0E+04
1.0E+05
1.0E+06
0 1 2 3 4 5Magnetic Field (T)
Mag
net
ic J
c [A
/ cm
2 ] Jc@5K
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 0.2 0.4 0.6 0.8 1H / Hk
Fp
/ F
p m
ax
Effect of synthesis temperature
Decreasing synthesistemperature
Point Defect Pinning
Grain Boundaries Pinning
Decreasing synthesistemperature
Not controlled atmosphere Glove box
0
0.2
0.4
0.6
0.8
1
1.2
0 0.2 0.4 0.6 0.8 1H/Hk
Fp
/Fp
ma
x 5K 5K
The effect of high energy ball milling is evidentTo increase the milling time (up to a certain value) – the tightness of the jars needs to be improved on longer times
-1x106 0 1x106 2x106 3x106 4x106 5x106 6x106 7x106 8x106 9x106 1x107
0
5000
10000
15000
20000
25000
30000
35000
36x360
0x0
72x360
72x300
72x240
36x300
36x240
Jc (
A/c
m^
2)
rpm^2 x h
B=4.5TT=5K
Giara da 500ml in SSBPR=8.4
new
Milling
0.0 2.0x106 4.0x106 6.0x106 8.0x106 1.0x107
0
1x104
2x104
3x104
4x104
5x104
6x104
7x104
13
12
1110
9
87
6
5
43
2
1
1=(0x0)2=(180x5)3=(180x24)4=(300x15)5=(240x36)6=(180x72)7=(300x36)8=(240x72)9=(180x144)10=(300x72)11=(180x256)12=(360x72)13=(360x36)Jc
(A
/cm
^2)
rpm^2 x t
B=4 T T=5 K
Milling
0 10000 20000 30000 40000 50000102
103
104
105
106
Jc (
A/c
m^2
)
B (Gauss)
180x144 BPR 14 300x36 BPR 8.4 300x36 BPR 17
50g MgB2
Milled with different BPR
Carbon additions can be also introduced during ball milling. Because it does not enter MgB2 in a very uniform way by such a process, it is benificial if it is added to a very low levels.
Doping with ex-situ is underway
Doping with nanosized SiC is effective provided that it is added to the Boron powders prior to MgB2 synthesis
Further improvement is expected while SiC is added to optimized milling process
Control of powder production Control of powder production process is crucial to achieve process is crucial to achieve
optimal particle sizeoptimal particle size
1000 nm1000 nm
450 nm450 nm
30 μm30 μm30 μm
CommercialMgB2 MgB2 from
commercial Boron
MgB2 from own Boron
T = 20 K
SQUID measurements
What is necessary to do to meet current wire demands?
Some applications do not need better powders than today’s production (dedicated low-field MRI, FCL, CERN), only more engineered conductors are preferrable – strong activity is ongoing to reach targets over long lengths
Fully non-magnetic, high resistive matrix, twisted, for low-AC loss applications
What is necessary to do to meet current wire demands?
Most of the applications do need better powders than today’s production in very large quantities, as well as more engineered conductors are preferrable – the last point has been already addressed – wires are twisted with no degradation, and electrically insulated with different techniques as braiding, wrapping, etc.
All wires produced in Km-class length with no degradation
• Boron• Magnesium• Other metals and alloys constituents of the wire
Compound Typical batch of today (x Kg)
Amorphous Boron (97%) 250 €
Magnesium source (-325 mesh) 100 €
Pure Nickel 80 €
Pure Iron 1 €
Cu OFHC 10 €
SS 304 4 €
Materials cost estimate
In a wire we have:
60% Ni
15% Cu
15% MgB2
10% Fe
Materials cost target for large production volumes:
below 1 €/m
MgB2 wire technologies
• The production of long length of MgB2 wires has been demonstrated in the past years, with supply to ASG and other customers of about 150 Km of conductor
• In 2008 the wire production will be of about 200-300 Km, although our production capability, considering some additional limited investment, can be raised to >1’000 Km/year in 3-6 months time in the present production plant
• Survey of different technologies to produce wires (in-situ, ex-situ), and different ways to produce and improve B and MgB2 powders is always active
• Most of today’s effort is concentrated on reliability demonstration and on scaling-up technologies as much as possible in-house in order to produce enhanced MgB2 in relevant quantities (> 10 Kg/day) using cost-effective technologies
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