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B.A.Glowacki
Transport AC losses of a helix - Cable configuration
a)
tw
c
I
Transport AC losses of a helix: a) potential taps position and potential wires arrangement on the outer surface of the central turn, b) Measured transport ac losses. twcorr represent the tw voltage signal corrected by the c voltage to provide truly transversal voltage losses. (Majoros 1999c, 1999d)
10-5
10-4
10-3
10-2
10-1
100
101
102
103
0.1 1
40Hz-c40Hz-tw40Hz-tw cor90Hz-c90Hz-tw90Hz-tw cor
Qt
I/Ic
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B.A.Glowacki
Double helix configuration
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B.A.Glowacki
Cable -Conclusions
The distribution of AC currents dominated by the mutual inductances,
For two layer of equal pitch, the current divides very narly equly between the two helical layers
For higher number of layers of equal pitch the current flows preferentially in the outermost layers
For practical pitch angle of 30 degrees the hysteretic losses at low current applied are about 13% lower for two layers
Gap between the tapes would increase losses by the factor roughly equal to the width/ tape thickness
Tapes should be arranged edge to edge so radial magnetic fields are negligible, local fields have only longitudinal and asimutal components
Tapes can carry supercurrents only parallel to their length. These currents screen magnetic field component perpendicular to tapes.
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B.A.Glowacki
MgB2
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B.A.Glowacki
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B.A.Glowacki
H.L. Suo, C. Beneduce, X.D. Su and R. Flükiger
J c eng ??
MgB2/YSZ/Hastelloy
0.4m/1m/300m
J c eng =103 Acm-2 @4.2K
J c MgB2 =105 Acm-2
@4.2K
J c eng ˜104 Acm-2 @4.2K
J c MgB2 > 105 Acm-2
@4.2K
K. Komori, K. Kawagishi, Y. Takano, S. Arisawa, H. Kumakura, M. Fukutomi, K. Togano
MgB2 conductors
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B.A.Glowacki
103
104
105
106
0 2 4 6 8 10 12
MgB2-YSZ-Hastelloy(4.2K)MgB2-YSZ-Hastelloy(15K)Cu/MgB2 in-situ unirradiated Cu/MgB2 in-situ irradiated Bi-2212/Ag coated conductor
Transp
ort
cri
tica
l curr
ent
densi
ty, J
c
(A
cm-2
)
Magnetic field oH (T)
0 100
2 109
4 109
6 109
8 109
1 1010
0 2 4 6 8 10 12
ex-situ Nb/MgB2 as drawn wire ex-situ Fe/MgB2 - sinteredin-situ Cu/MgB2 - irradiated thin film MgB2/YSZ/Hastelloy
Pin
ning
For
ce F
p
(N
m -3 )
Magnetic field oH (T)
Fp
max thin film @9T = 5 x F
p
max wires @1T
IRRADIARION
Pinning force - MgB2 conductors
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B.A.Glowacki
Current vs Field Superconducting/magnetic structures
200
300
400
500
600
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Ic(A)(mono)Ic(A)(mono+Fe)Ic(A)(19 filam.)Ic(A)(19 filam.+magnetic)Ic(A)(19 filam.+Fe)
I c(A)
oH
ext(T)
r magnetic
=10
r max Fe
=9000
stainless steel core
Twisting may be a problem with hard Fe matrix.Twisting of Cu/MgB2 with the internal reinforcement can be viable solution.
Monocore: MgB2 OD=0.871mm, magnetic later 0.314 thick.
19 filaments: MgB2 OD=0.2mm, magnetic double layerm shielding 10m thick 10m separation around each filament as well as around whole composite (r=10 or r Fe).
1
10
100
1000
104
10-5 10-4 10-3 10-2 10-1 100 101
r
oH (T)
Laboratory Fe r max
=9000
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B.A.Glowacki
Cryomagnetic stability
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B.A.Glowacki
Critical Current distribution - MultifilamentMagnetic coating : critical current improvement Magnetic stability
a) a) Spatial distribution of the critical current density in a 19 filament Spatial distribution of the critical current density in a 19 filament MgBMgB22 wire cross section in self field, (no magnetic screens) wire cross section in self field, (no magnetic screens)
IIcc==442A442A
b) b) Spatial distribution of the critical current density in a 19 filament Spatial distribution of the critical current density in a 19 filament MgBMgB22 wire cross section in self field, for non-linear Fe wire cross section in self field, for non-linear Fe
rmaxrmax=9000, I=9000, Icc==628A.628A.
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B.A.Glowacki
MgB2 Cu in-situ wires stability ( coils)
Jc = 120000 Acm-2
4
4.5
5
5.5
6
6.5
7
7.5
0 0.2 0.4 0.6 0.8 1
1uV/cm8uV/cm13uV/cm
Tem
pe
ratu
re T
(K
)
Wire diameter , d (mm)
FeMgB2
LHe
MgB2
Fe
MgB2
Fe
MgB2
Fe
4.2 K
7.02 K
0
3*109 Acm-2 1Vcm-1
8Vcm-1
13Vcm-1
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B.A.Glowacki
Cryogenic stability defected MgB2-Fe-Cu Fe/MgB2 wire with
defect - applied electric field 1Vcm-1 and 13Vcm-1
MgB2 wire 0.6mm in diameter, Fe layer 0.2mm thick
4.2
4.22
4.24
4.26
4.28
4.3
4.32
0 0.2 0.4 0.6 0.8 1 1.2
Tem
pera
ture
, T (
K)
Wire diameter, r (mm)
CuFeMgB2
LH
e
Temperature
MgB2
Fe
Cu E=13Vcm-1
Current
4.2
4.4
4.6
4.8
5
5.2
0 0.2 0.4 0.6 0.8 1
Tem
pera
ture
, T (
K)
Wire radius r (mm)
FeMgB2
LHe
Fe
MgB2