status and perspective of the nb al development in …...large scale application fusion, accelerator...
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Status and perspective of the Nb3Al development in Japan
Workshop on Accelerator Magnet Superconductors, Mar. 22-24, 2004
T. TakeuchiNat. Inst. Materials Sci. (NIMS)
K. TsuchiyaHigh Energy Accel. Res. Organ. (KEK)
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-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
0.8
0.9
1.0B*
c2/B*c2m
Nb3Ge
V3Si Nb3Sn(Ta,H)
Nb3Sn(Ti,Hf,Ga)
V3Ga
Nb3Al
by EkinIntrinsic Strain (%)
better strain tolerancehigher Bc2(4.2K): 30 T
Advantages of RHQT Nb3Al over Nb3Sn
Large scale applicationFusion, Accelerator
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Advantages of RHQT Nb3Al over HTS
• Easy superconducting joint• Large n-value• Tolerance to stress and strain
• High-field NMR spectroscopy
Application
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Specification of Nb3Al conductor for NMR uses
• Rectangular • Stabilizer (Cu clad)• Nb matrix (superconducting) • DC (filament diameter, spacing)• Optimization of Jc (4.2K) at 21 T
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Explored processes to achieve stoichiometrywithout grain coarsening
∼55
2600
600
1000
1400
1800
2200
100 20 30 40 50 60 70 80 90 100
Nb
Nb 3
Al
Nb2Al
NbA
l 3Tem
pera
ture
(° C
)Atomic Percent AluminumNb Al
∼28
2469°C
2060°C±10
1940°C
1680°C1590°C
42
661.4°C
660.45°C
32
II
I II'
Manufacture: binary reaction, Al dimension: < 100nm
Cu or Nb rodNb sheet
Al sheet
Diffusion process (750oC x 50h)
RHQT process (1900oC + 800oCx10h) New process (TRUQ, DRHQ)
11-14 T, off-stoichiometryCu-matrix JR
12-23 T, stacking faultsNb-matrix JR
21-25 T
Advanced A15 Compounds• Nb3Al• Nb3Ga• Nb3(Al,Ge)
Off-stoichiometry at LT
RHQT technique(rapid-heating, quenching and transformation)
stoichiometrywithout grain growth
Case of Nb3Al
New approachNew approach
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Joule Heating+
Quenching
Precursor:Nb/JR Nb/Al
Nb/Nb(Al)ss
Winding+
Transformation
Cu/Nb/Nb(Al)ss
Cu cladding
Cu/Nb/Nb3Al
Extrusion + Drawing
bcc supersaturated solid solution
stoichiometryfine grain
Cu or Nb rodNb sheet
Al sheet
Jelly-roll
Nb rod
Rapid Heating, Quenching and Transformation process
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Long-length of RHQ processing
• Plateau region (150oC): optimum• Insensitivity to unwanted
temperature scatter• Uniformity of SC properties along a
long-length of wire
1.00 1.05 1.101
10
100
17.0
17.5
18.0
18.5
4.2 K
24T
23T
22T
21T
20T
19T
Crit
ical
Cur
rent
Den
sity
(A/
mm
2 )
Normalized Heating Current iRHQ
M9-4Current: 30mA
Crit
ical
Tem
pera
ture
(K)
bccA15+σ bcc Al-poor bcc + liquidbrittle ductile (not brittle) ductile
two phase extendedsolid solution
partialmelting
completemelting
→ Tmax
1910oC 2060oC10.5 A
25at%Al
20 25 30
98
100
102
104
106
108
110
I RHQ(T
max
) (A)
at.% Al
bcc
Liquid
optimum
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0.00
0.01
0.02
0.03
0.04
0.05
0.06
0 200 400 600 800 10000
2
4
6
8
10
12
Wire diam.: 1.35 mmφNb/Nb3Al ratio: 0.81Fil. No.: 132Fil. diam.: 89 µm
RHQ Duration (s)
(a) Current variation
Shun
t Vol
tage
(V)
(b) Voltage variation
Volta
ge b
etw
een
Elec
trode
s (V
)
Nb matrix
Filament
0 50 100 150 200 250 300
100
150
200
250
300
17.0
17.2
17.4
17.6
17.8
18.0
Crit
ical
Tem
pera
ture
(K)
Crit
ical
Cur
rent
(A)
Position along a 300 m length of conductor (m)
[email protected] K 21T 20T 19T
Tc
Distributions of Tc and Jc along a 300 m length of wire
Standard deviation of Jc (4.2K&21T) : 5 %
・Constant current power supply
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Deformability of Nb(Al)ss at RT
0 2 4 6 8 10 12 140
200
400
600
800
1000
1200600oC 500oC
400oC300oC
without pre-annealing
Sample #1 (1.275mmφ, 0%RA) Temperature: 20oC Strain Rate: 6.25 x 10-4 sec-1
Stre
ss (M
Pa)
Tensile Strain (%)
Cu
Nb(Al)ss
Nb sheath
0.3mm
0 20 40 600
100
200
300
400
Cu-cladding JR Nb 3Al
Jc21T
J c (A
/mm
2 )
Reduction in Area, R.A. (%)
0
100
200
300
21 T4.2 K
I c (A
)
Ic21T
Incorporation of Cu stabilizerby mechanical cladding
Jc improvement
Tensile test at room temperature
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Temperature ramp-up rate at transformation annealing
19 20 21 22 23 24 25
4.2 K
40%RA800oCx10h
B (T)
Ramp Rate 1h/800oC 2h/800oC 4h/800oC 6h/800oC 10h/800oC
19 20 21 22 23 24 25
0
100
200
300
400
500
600
4.2 K
Ramp Rate 1h/800oC 2h/800oC 4h/800oC 6h/800oC 10h/800oC
core
Jc
(A/m
m2 )
B (T)
0% RA800oCx10h
0 2 4 6 8 10 12 14 1617.3
17.4
17.5
17.6
17.7
17.8
0% RA
40% RA
T c (K
)
Ramp-Up Time to 800oC, t (h)
M9-4
M9-4 M9-4
DeformationJc enhancementLess sensitive to ramp rate
-10 -5 0 5 10 15 200
200
400
600
800
1000Transformation HT profilefor a W&R coil
Tem
pera
ture
(o C
)
Heat Treatment Time (h)
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TABLE I SPECIFICATIONS OF WIND & REACT NB3AL SOLENOID COILS
Previous M11-1
Present ME332
Present ME356
RHQT JR Nb3Al con-ductor
Stabilizer Cu-clad Cu-clad Cu-clad Piece length (m) 35 370 370
Cross section (mm2) 1.61x0.71 1.82x0.84 1.81x0.80 Filament diameter 70 74 75.5 Number of filaments 84 132 132 Cu/non-Cu ratio 0.45 0.38 0.39 Insulator Al2O3 fiber Al2O3 fiber Al2O3 fiber
Winding Inner diameter (mm) 19.7 90.2 64.6 Outer diameter (mm) 40.8 111.8 99.3 Height (mm) 49.7 200 132.4 Number of turns 311 949 988 Total length of wire 30 300.5 254
Coil Impregnation Beeswax Beeswax Beeswax Transformation RT? (5h) ? 800oC? (10h) ? 800oC? RT Coil constant (T/A) 0.00106 0.00562 0.00797
Coil specifications
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n-value (10-5 – 10-4 V/m)
Consistency of Icpoint, tail of 370 m
n-value25@21T,4.2K
0.3 mm(e)
CuNb
17 18 19 20 21 22 23 24 25 260
100
200
300
400
500
0
50
100
150
200
250
300
17 18 19 20 21 22 23 24 25 26
0
5
10
15
20
25
30
35
0
100
200
300
400
500
4.2 K
0.1 µV/cm criterion
370 m length of Cu-clad conductor
I c
(A)
B (T)
Ic_point Ic_tail
overall J
c (A/mm2)
voltage taps specing:25cmfitting range: 2.5µV-25µV
V = Const.In
n-in
dex
n value_point n value_tail
J c (A/mm2)
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Iq (coil) > 0.9 Ic (short samples)
Uniformity of a long-length of RHQ operation over 300 m
・Loading test
14 16 18 20 22 24 260
100
200
300
400
50014 16 18 20 22 24 26
0
100
200
300
400
500
0
50
100
150
200
250
300
0
50
100
150
200
250
300
3.2 T
1.8 K
4.2 K (b)
ME365 64.6I.D.x99.3O.D.x132H mm3
254 m, 988 turns
C
urre
nt, I
(A)
Magnetic Field, B (T)
Ic_point Ic_tail Quench Current load line
2.3 T
4.2 K (a)
90.2I.D.x111.8O.D.x200H mm3
300.5 m, 949 turnsME332
Cur
rent
, I (A
)
Ic_point Ic_tail Quench Current load line
Ove
rall
J (A
/mm
2 ) O
vera
ll J
(A/m
m2 )
NMR coil Jc
・RHQT Nb3Al is really reliable for practical coil application.
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0
500
1000
1500
2000
2500
6 8 10 12 14 16 18
M13-1-80.6(0.69)M13-2-79.3(0.69)M13-2-80.6(0.69)M13-3-79.3(0.69)M13-3-80.6(0.69)M13-4-79.3(0.69)M13-4-80.6(0.69)M13-5-81.8(0.69)
Jc n
on C
u (A
/mm
2 )
B (T)
KEK
• 1 kA Ic probe• Measurement of Jc of round wire
electroplated with Cu in fields from 8 to 17 T
• Optimizationwire diameter: 0.8 0.69 mmRA: 20% (< 40% for 21T)transformation HT: 775oC15h
• Highest Jc:1730 A/mm2 at 10 T
Sample length: 300 mmLarge cross section of Cu: 72 mm2
Heating at 1000 A: < 80 mW/lead(∆T < 10 mK)
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Internal Stabilization
0 10 20 30 40 500
20
40
60
80
100
120
140
160
180
200
RR
R
Stabilizer/Non-stabilizer Ratio
Cu Ag Ta/Cu (no stabilizer)
1. Less expensive2. Round cross section of wire3. Possible high current conductors (CICC,
Rutherford cables, etc)4. No contamination of Ag with Ga5. Large RRR (200)6. Applicability to high temperature
transformation (TRUQ, DRHQ)
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5mm
The 1st triplet: a Nb3Al, two Cu
0.8 mmΦAg/non-Ag:0.17
CableCable--inin--Conduit ConductorConduit Conductorfor Fusion Usesfor Fusion Uses
The third stage cable: 3 x 4 x 4
SUS conduit
CuNb3Al
SUS tape
Trial Manufactureof High-Current RHQT Nb3Al Conductors
12 14 16 18 20 22 240
1000
2000
3000
4000
5000
6000
Ic_point strand Ic_tail strand Ic_tail strand Ic_point x 16 Ic_tail x 16 Ic_tail x16 CIC conductor
4.2 K
Crit
ical
Cur
rent
, Ic (
A)
Magnetic Field, B (T)
Measure: 3.49 kADesign (Ic, strand x 16): 3.7 – 4.3 kA
Ic at 14 T
7% degradationInternally stabilized Nb3Al strand
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Measurement_1
V taps spacing: 100 mm, 375 mmCurrent ramp rate: 30A/sec, 60A/sec
0 500 1000 1500 2000 2500 3000 3500 4000-50
0
50
100
150
200
V taps spacing: 375 mm
V taps spacing: 100 mm
4.2 K
14T, 30A/sec,1st
Vol
tage
(µV
)Current (A)
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Table 1 Specifications of measured JR Nb3Al wires.
Sample #1 #2 #3
Diameter of wire (mm) 0.507 0.89 1.275
Number of filaments 36 84 84
Diameter of filament
(µm)
55 76 108
Average thickness
between filaments (µm)2.8 6 9.4
Nb/Non-Nb ratio 1.5 1.39 0.59
• bridging• proximity effect
AC Loss
Matrix: NbFlux jump
Not desirable for fusion and accelerator magnets
RHQT JR Nb3Al
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Manufacture of Ta matrix JR Nb3Al wire
Ta tube (sheath)Ta dummy
Ta barrier
Ta core
Nb/AlJerry-roll
2 other filament structures
Ta core-Nb barrier Nb core-Nb barrier(conventional)
Ta core-Ta barrier
by Tatsumi et al
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Workability
1.5φ65μm66Φ0.8mm
Matrix ratio(non JR / JR)
Filament diameter
No of filaments
Wire Diamete
r
Good (no breakage)
Good (no breakage)
Very Good(no breakage until
φ0.5mm)
Workability
Cross sectio
n
Nb core-Nb barrier(フィラメント間:Nb
JRコア:Nb)
Ta core-Nb barrier(フィラメント間:Nb
JRコア:Ta)
Ta core-Ta barrier(フィラメント間:Ta
JRコア:Ta)
Structure
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Magnetization curve
-10000 -5000 0 5000 10000
-0.1
0.0
0.1
Ta/Nb3Al ratio:1.53Fil. diam:64.7µm
Ta matrix 4.2K Ta matrix 10K
m (e
mu/
mm
3 )
H (Oe)-10000 -5000 0 5000 10000
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3 Nb matrix 4.2K Nb matrix 10K
m (e
mu/
mm
3 )H (Oe)
Nb/Nb3Al ratio:0.59Fil. diam:79.7µm
Ta matrix suppression of flux jump
Other advantages・high strength at high temperature・no formation of Ga-rich compound
on a surface・less induced-radioactivity
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Potential of RHQT Nb3Al
20 22 24 26 280
100
200
300
400
4.2 K
no
n C
u J c
(A/m
m2 )
B (T)
RHQT Nb3Al TRUQ Nb3Al DRHQ Nb3Al RRP Nb3Sn (OST) 16 % Sn Bronze Nb3Sn 14 % Sn Bronze Nb3Sn
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A15-typeNb3Al
bcc Nb(Al)ss
1 200
1 000
800
600
400
200
0
10 sec~10 min
trans
form
atio
nhe
at
free energyTe
mpe
ratu
re (°
C)
Time
10 h
TRUQ:time for 1 to 3 steps < 0.3 sec
(b)
(c)
propagation of heat
untransformedparttransformed
part
(a)sample
1
2
3
4
TRUQ (TRansformation-heat-based Up-Quenching)
1. ignition (nucleation of transformation)2. thermal explosion ·propagation of the transformation interface ·trasform to A15 via highly disordered bcc phase low long-range order free from stacking faults3. self-turn down to ambient temperature4. annealing for long-range order
similar to a combustion synthesis
TRUQ
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Microstructure
40 nm40 nm40 nm40 nm
TRUQ
RHQT
SF
SF
TEM像
SGB
SGB
0 20 40 60
Ave. 8.8 nm
Ave. 19.7 nm
Distance between Adjacent Stacking Faults
19.7 nm
8.8 nm
TRUQ
RHQT
0 20 40 60
Ave.34 nm
Ave. 52 nm
Subgrain Diameter (nm)
52 nm
34 nmTRUQ
RHQT
By N. Banno et al.
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Non-uniformity
10 12 14 16 18 20
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
norm
aliz
ed χ
', χ"
Temperature (K)
TRUQ χ' TRUQ χ" 700C-10h/800C-10h χ' 700C-10h/800C-10h χ" 800C-10h χ' 800C-10h χ"
16.0 16.5 17.0 17.5 18.0 18.50.00
0.05
0.10
0.15
0.37
0.350.24
χ"
Temp (K)
Microchemical homogeneity in filaments
↓Sharp transition
↓Enhancement in Jc
a) as-quenched wire at 1.27 mm and b) after Cu-cladding and forming into tape.
Microstructure by FESEM by P. Lee
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Optimization for Jc
• Wire diameter• Nb matrix ratio• No. of JR filaments• Filament diameter• Inter-filament spacing• Nb/Al ratio• layer thickness• Alloying
• Joule heating current density
• Heating distance• Wire speed at RHQ• R.A. after RHQ• Transformation HT
under the condition of ordinary transformationthat enables W&R coil (~800oC, ramp rate of 1-5 h/800oC)
Parameters
MicrochemistryCrystal imperfection
bcc grain, orderingA15 grainStacking faults
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Ongoing improvement of JR Nb3Al
by Iijima and Takeuchi20 22 24 26 28
0
100
200
300
400
230
1864.2 K
non
Cu
J c (A
/mm
2 )
B (T)
RHQT Nb3Al TRUQ Nb3Al DRHQ Nb3Al RRP Nb3Sn (OST) 16 % Sn Bronze Nb3Sn (Kobe) 14 % Sn Bronze Nb3Sn optimaization ongoing RHQT Nb3Al
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Development Schedule
• Long-length of precursor (>2km)large billet
• Long-length of RHQ processing (>2km)large-scale RHQ apparatus: under construction
• Reel-to-reel Cu ion platinginstallation, trial operation
Target: piece length of more than 2 km for 1.35 mmφ wire
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Multifilament billet (50kg)
Piece-length: 2.6 km for Φ 1.35 mm wire
Φ 2. 9 mm Φ 1. 75 mm
Φ 1. 50 mm
Φ 8. 4 mm Φ 5.9 mm
No breaking during drawing of wire
(corresponding to 9.7 km for Φ 0.7 mm wire)
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Prototype RHQ-apparatus
• >2 km length of 1.35mmΦ precursor-wire
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Prototype reel-to-reel ion plating apparatus
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Reel-to-reel Cu ion plating apparatus_2
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Summary• Large multifilament billet: 52 kg • Piece length of precursor (1.35 mm): 2.6 km• RHQ apparatus: just installed
300 m ? km• Non-Cu Jc improvement (21T): Ongoing• Stabilization of a round wire
internal stabilizationCu ion plating and electroplating