Passive magnetic field shielding by superconducting and … · 2016-06-30 · cryogenic Hall...
Transcript of Passive magnetic field shielding by superconducting and … · 2016-06-30 · cryogenic Hall...
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Passive magnetic field shielding by superconducting and
superconducting/ferromagnetic superimposed systems
Laura Gozzelino
Roberto Gerbaldo, Gianluca Ghigo, Francesco Laviano
Department of Applied Science and Technology, Politecnico di Torino and
INFN Sez. Torino, Torino, Italy
M. Truccato, V. Bonino
Department of Physics, University of Torino and INFN Sez. Torino, Torino, Italy
A. Agostino
Department of Chemistry, University of Torino and INFN Sez. Torino, Torino, Italy
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OutlineOutline
L. Gozzelino
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Magnetic shieldingMagnetic shielding
superconductors
ferromagnetsferromagnets
Ferromagnets + superconductorsFerromagnets + superconductors
low magnetic field low magnetic field
background background
electromagnetic noise electromagnetic noise --
stray field reductionstray field reduction
Why ?
Protection of magnetic field
sensitive detectors
• Equipment integration
• Worker protection
How ?Passive solutionsPassive solutions
Active solutionsActive solutions Magnets
improvement of the improvement of the
shielding efficiencyshielding efficiency
cloak effectcloak effect
F. Gomory et al., Science 335
(2012) 1466
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superconductors
ferromagnetsferromagnets
Ferromagnets + superconductorsFerromagnets + superconductorsPassive solutionsPassive solutions
Magnetic shieldingMagnetic shielding
LowLow--TcTc
HighHigh--Tc cupratesTc cuprates
MgBMgB22
• low cost of raw materials
• low density
• working temperature easily
achievable using cryogen free
cryocoolers
• randomly oriented grain boundaries
in MgB2 are not obstacles to current
flow
• easy to be jointed
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Magnetic shieldingMagnetic shielding
h
Rext
µ0Happl
Rext = 8.0 mm
Rint = 6.5 mm
Pb-doped BSCCO-2223 – 77 K
D. Denis et al.,
Supercond. Sci. Technol.
20 (2007) 418
Superconducting shields
G.P. Lousberg et al., IEEE
Trans. Appl. Supercond.
20 (2010) 33
Field mitigation requirement in situations where the
space occupied by the shield must be minimized:
•reduction of the shield height
•analysis of the edge effect
Open question:
A. Omura et al., Physica
C 386 (2003) 506
Ferromagnetic layer addition
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Fe cupFe cup� Made of a commercial
ARMCO-iron.
Outer radius: 14.0 mm
Inner radius: 11.5 mm
Ext. height: 12.5 mm
Inner depth: 10.5 mmOuter radius: 10.5 mm
Inner radius: 7.5 mm
Ext. height: 10.5 mm
Inner depth: 7.5 mm
Tc = 37.3 K
∆Tc = 0.5 K
MgBMgB 22 cupcup� Produced by a microwave-assisted Mg-RLI technique in
boron powder preforms:
� heating processes in Ar flow with liquid Mg infiltration in B cup-
shaped preform (650°C for 3 hours; 900° C for 20 hours)
� microwave heating (1600 W, 2.45 GHz for 30 min in Ar
atmosphere) to minimize the unreacted Mg amount
� production of manufacts of different shapes and
easily scalable sizes
L. Gozzelino et al., Supercond. Sci. Technol. 25, 115013
(2012) and refs. therein
Aspect ratio of height/radius ∼∼∼∼ 1
L. Gozzelino
Hybrid configuration:
Lateral air gap: 1.0 mm
Edge of both the cups at the same height
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Experimental setExperimental set --upup
� cryogenic Hall probe(s)
mounted on a custom-
designed stage moveable
along its axis with a spatial
resolution of 1 µm
(movement range: 10 cm)
� Cryomagnetics cryogen-free
magnet (0-6T)
� axial magnetic field
� samples cooled by means of a
cryogen-free Leybold RNK 10-
300 cryocooler
� zero field cooling
L. Gozzelino et al., IEEE Trans. Appl. Supercond. 21 (2011) 3146
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MgBMgB 22 /Fe hybrid shield: shielding vs. applied field /Fe hybrid shield: shielding vs. applied field
superconducting cup:
more efficient shield than
ferromagnetic cup
z
d
z
d
L. Gozzelino et al., Supercond. Sci. Technol. 25 (2012) 115013
L. Gozzelino
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Shielding factor = Bunsh,z/Bz
MgBMgB 22 /Fe hybrid shield: shielding vs. applied field /Fe hybrid shield: shielding vs. applied field
L. Gozzelino et al., Supercond. Sci. Technol. 25 (2012) 115013
z
d
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Shielding factor = Bunsh,z/Bz
MgBMgB 22 /Fe hybrid shield: shielding vs. applied field /Fe hybrid shield: shielding vs. applied field
L. Gozzelino et al., Supercond. Sci. Technol. 25 (2012) 115013
L. Gozzelino
hybrid shield:best shielding efficiency at
higher fields
enhancement of the shielding
factor in the hybrid configuration
higher than a factor of 3
at µµµµ0Happl = 0.9 T and T = 20 K
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MgBMgB 22 /Fe hybrid shield: shielding vs. applied field /Fe hybrid shield: shielding vs. applied field
superconductor shield:
best shielding efficiency at lower
fields
Fe cup induces a stronger curvature and a
greater accumulation of the magnetic flux
lines at the MgB2 cup edge
Shielding factor of the hybrid system: no straightforward composition of the
independent contributions of the two shields:
××××
G.P. Lousberg et al., IEEE Trans. Appl. Supercond. 20 (2010) 33
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Cup edgeaxial position (mm)
Cup edgeaxial position (mm)
µµµµ0Happl = 0.04
T
µµµµ0Happl = 1.0 T
shielding effects are present all along the cup axis, also close and
outside the cup opening
MgBMgB 22 /Fe hybrid shield: shielding vs. position/Fe hybrid shield: shielding vs. position
L. Gozzelino et al, IEEE Trans. Appl. Supercond.
23 (2013) 8201305
L. Gozzelino
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where
and An = 5×10-8 T/m.
At T = 20 K, k = 1.16⋅108 A/m2, γ = -0.4, δ = 2.0, Birr = 4.25 T.
ModelModel� To model the superconductor :
• A-formulation based procedure
• Starting from the virgin state, magnetic field penetrating monotonically from the
surface when Happl increases monotonically
• 2D axisymmetric configuration
� The ferromagnetic cup was modelled starting from the experimental BH curve.
� Boundary condition: at a large distance from the sample, the field was assumed
constant, equal to µ0Happl and parallel to the cup axis.
� Commercial finite-element software (COMSOL 4.3b)
A.M. Campbell, Supercond. Sci. Technol. 20 (2006) 292.
F. Gömöry et al., Supercond. Sci. Technol. 22 (2009) 034017.
K.Kitahara et al., Physica C 445-448 (2006) 471.
D. Dew-Hughes, Philos. Mag. 30 (1974) 293.
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Experimental vs. modellingExperimental vs. modellingµµµµµµµµ00HHapplappl = 0.04 T= 0.04 TB (T)MgB2 cup
Hybrid syst.
0 10 20 radial position (mm)
Very good agreement !
Cup edge
L. Gozzelino et al., Supercond. Sci. Technol. 29 (2016) 034004
L. Gozzelino
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
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Experimental vs. modellingExperimental vs. modellingµµµµµµµµ00HHapplappl = 0.2 T= 0.2 TB (T)MgB2 cup
Hybrid syst.
0 10 20 radial position (mm)
Very good agreement !
Cup edge
L. Gozzelino
L. Gozzelino et al., Supercond. Sci. Technol. 29 (2016) 034004
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
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Experimental vs. modellingExperimental vs. modellingµµµµµµµµ00HHapplappl = 1.0 T= 1.0 TB (T)
MgB2 cup
Hybrid syst.
0 10 20 radial position (mm)
Very good agreement !
Cup edge
L. Gozzelino
L. Gozzelino et al., Supercond. Sci. Technol. 29 (2016) 034004
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
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Cup edge
Towards new shield configurations:Towards new shield configurations:height difference between edge height difference between edge –– air gap modulation air gap modulation
System
characterized
experimentally
3 mm
2.5 mm
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Cup edge
Towards new shield configurations:Towards new shield configurations:height difference between edge height difference between edge –– air gap modulation air gap modulation
µµµµµµµµ00HHapplappl = 0.04 T= 0.04 T
System
characterized
experimentally
3 mm
2.5 mm
L. Gozzelino
L. Gozzelino et al., Supercond. Sci. Technol. 29 (2016) 034004
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Cup edge
Towards new shield configurations:Towards new shield configurations:height difference between edge height difference between edge –– air gap modulation air gap modulation
µµµµµµµµ00HHapplappl = 0.2 T= 0.2 T
System
characterized
experimentally
3 mm
2.5 mm
L. Gozzelino
L. Gozzelino et al., Supercond. Sci. Technol. 29 (2016) 034004
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Towards new shield configurations:Towards new shield configurations:height difference between edge height difference between edge –– air gap modulation air gap modulation
µµµµµµµµ00HHapplappl = 1.0 T= 1.0 T
System
characterized
experimentally
3 mm
2.5 mm
L. Gozzelino
L. Gozzelino et al., Supercond. Sci. Technol. 29 (2016) 034004
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Towards new shield configurations:Towards new shield configurations:multilayer configurationsmultilayer configurations
µµµµµµµµ00HHapplappl = 0.04 T= 0.04 TCup edge
System
characterized
experimentally
3 mm
2.5 mm
L. Gozzelino
M12 mm
M22 mm
2 mm
1.5 mm1.25 mm
2 mm
SC
SC
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Towards new shield configurations:Towards new shield configurations:multilayer configurationsmultilayer configurations
µµµµµµµµ00HHapplappl = 0.04 T= 0.04 TCup edge
L. Gozzelino
M12 mm
M22 mm
1.5 mm1.25 mm
2 mm
SC
SC
M33mm
M43 mm
3 mm
3 mm
System
characterized
experimentally
3 mm
2.5 mm
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Towards new shield configurations:Towards new shield configurations:multilayer configurationsmultilayer configurations
System
characterized
experimentally
3 mm
2.5 mm µµµµµµµµ00HHapplappl = 0.2 T= 0.2 TCup edge
L. Gozzelino
1.5 mm1.25 mm
2 mmM1M33 mm
M2M4
3 mm2 mm
M12 mm
M33mm
M43 mm
M22 mm
SC
SC
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Towards new shield configurations:Towards new shield configurations:multilayer configurationsmultilayer configurations
System
characterized
experimentally
3 mm
2.5 mm
L. Gozzelino
µµµµµµµµ00HHapplappl = 1.0 T= 1.0 T
1.5 mm1.25 mm
2 mmM1M33 mm
M2M4
3 mm2 mm
M12 mm
M33mm
M43 mm
M22 mm
SC
SC
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B (T)
Towards new shield configurations:Towards new shield configurations:out of axis shielding behaviourout of axis shielding behaviour
MgB2 cup
µµµµµµµµ00HHapplappl = 0.04 T= 0.04 T
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0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
3.5
mm
5.5
mm
2 mmM1M33 mm
M2M4
3 mm2 mm
Shielding factor:
|Bunsh|/|B|
SC SC
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ConclusionsConclusions
� The presence of the ferromagnetic layer can strongly affect the shielding
efficiency of the superconductor
�������� low field: low field: ☺☺☺☺☺☺☺☺ superconducting cupsuperconducting cup
�������� high field: high field: ☺☺☺☺☺☺☺☺ hybrid systemhybrid system
� Enhancements of the shielding capability of the hybrid system can be
achieved by a suitable shaping of the Fe cup with respect to the MgB2 one
☺☺☺☺☺☺☺☺ height difference between the edge of the SC/FM shieldsheight difference between the edge of the SC/FM shields
☺☺☺☺☺☺☺☺ multilayer systemsmultilayer systems
Comparison of the shielding properties of MgBComparison of the shielding properties of MgB22 and MgBand MgB22/Fe cups :/Fe cups :
Thanks to:Thanks to:- F. Gömöry
- M. Chiampi, A. Manzin, L. Zilberti
- SR2S-RD experiment
L. Gozzelino
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� The presence of the ferromagnetic layer can strongly affect the shielding
efficiency of the superconductor
�������� low field: low field: ☺☺☺☺☺☺☺☺ superconducting cupsuperconducting cup
�������� high field: high field: ☺☺☺☺☺☺☺☺ hybrid systemhybrid system
� Enhancements of the shielding capability of the hybrid system can be
achieved by a suitable shaping of the Fe cup with respect to the MgB2 one
☺☺☺☺☺☺☺☺ height difference between the edge of the SC/FM shieldsheight difference between the edge of the SC/FM shields
☺☺☺☺☺☺☺☺ multilayered systemsmultilayered systems
Comparison of the shielding properties of MgBComparison of the shielding properties of MgB22 and MgBand MgB22/Fe cups :/Fe cups :
ConclusionsConclusions
Thanks to:Thanks to:
THANK YOU !THANK YOU !
- F. Gömöry
- M. Chiampi, A. Manzin, L. Zilberti
- SR2S-RD experiment
L. Gozzelino