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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

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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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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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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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