High T c Superconducting Applications in Geophysical Exploration and Telecommunications MANUFACTURING and DATA61 C.P. Foley CSIRO Team: Jia Du, Keith Leslie, Emma Mitchell, Shane Keenan, Kirsty Hannam, Jeina Lazar, Chris Lewis, Bill Vasilevski, Karl Wilson, Andrew Weily, Xiang Gao, Ting Zhang, Wendy Purches, Alex Gracea, Kyle Blay
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High Tc Superconducting Applications in Geophysical Exploration and Telecommunications
MANUFACTURING and DATA61
C.P. Foley
CSIRO Team: Jia Du, Keith Leslie, Emma Mitchell, Shane Keenan, Kirsty Hannam, Jeina Lazar, Chris Lewis, Bill Vasilevski, Karl Wilson, Andrew Weily, Xiang Gao, Ting Zhang, Wendy Purches, Alex Gracea, Kyle Blay
Relationship of Geophysical Exploration
and Communications
USA Population: 0.3B
Australian Population: 0.02B
Australia has the same
population as Shanghai
Presentation title | Presenter name | Page 4
Communication across vast distances to small populations
5 |
This talk
• Josephson junctions in HTS – recent emergence of step edges
• Geophysical applications• Magnetometers
• Gradiometers
• High frequency devices
• New concept antennas
7 |
YBCO is not an easy material
Nature Materials 6, 631 - 642 (2007) S. R. Foltyn, L. Civale, J. L. MacManus-Driscoll, Q. X. Jia, B. Maiorov, H. Wang & M. Maley
• Highly anisotropic
• a-b coherence length ≈ 2 nm
• One element is a gas
1 µm
1 µm
| Dimos et al Phys Rev B 1990 41 4038
1 nm
Making a Josephson junction in HTS
Enpuku and Minotani Simplistic Model IEICE Trans Electron E83-C (2000) 34
SuperconductorSuperconductor Insulator
Cooper Pair Direct tunnel (d-wave symmetry)
Direct tunnel
Resonant tunnel
Trap and escape (1/f noise)
Quasiparticles
| Fagaly Review of Scientific Instruments (2006) 77 101101
Bicrystal and ion beam damaged
Step edgeRamp
Important parameters:
- IcRn – aim for 1000 µV
- Critical current fluctuations with B
- Ic control <9% spread
Bicrystal Junctions
IcRn product of symmetric 20o bicrystal junctions ∼400 μV at 77.4 K
Ramp Junctions
|
Moeckly and Char APL 1997 71 2526
Wen et al Applied Physics Letters 75, 2470 (1999)
IcRn at 77 K 156 µV
Step edge grain boundary junctions
|
STO
MgO
c axis
c axis
Why MgO?
LAO
“Step-edge Josephson junctions and SQUIDs” F. Lombardi and A. Ya. Tzalenchuk
Step Edges on MgOJulich Group
M. Faley et al IEEE Transactions on Applied Superconductivity 23(3):1600705-1600705
CSIRO Group
30 papers eg C. P. Foley et al., IEEE Trans. Appl. Supercond. 9 (1999) 4281E.E. Mitchell and C.P. Foley, SUST. 23 (2010) 065007
S.Tanaka et al IEEE Trans. Appl. Supercond. 3 (1993) 2365
CSIRO HTS Step-edge Josephson Junction technology - many HTS electronic devices built upon
1m
Θ= 36.8±0.2o
YBCO film
C. P. Foley et al, IEEE Trans. Appl. Supercond. 9 1(999) 4281.E.E. Mitchell and C.P. Foley, Supercond. Sci. Technol. 23 (2010) 065007
Junction noise in a magnetic shield
0
1
2
3
0.4 0.6 0.8 1.0
cath1.ep
BC2 bi-xtal
ML384Pk.1Pk.2
ML789Pk.2 Pk.1
ML635
T/Tc
Sv (
nV
Hz
-1/2
)VOLTAGE NOISE vs. REDUCED TEMPERATURE FOR
3 STEP-EDGE JUNCTIONS (ML***) AND 1 BI-XTAL JUNCTION
0
0.5x10-6
1.0x10-6
1.5x10-6
0 0.4 0.8 1.2
(d) bc2b(d)
(c)
(c) ml635T70K
Step-edge Junctions ml789 A, ml635and Bi-crystal junction bc2b
c7&icib1.ep
(a) ml789, 1st Peak(b) ml789, 2nd Peak
(b)
(a)
B (mT)
Ic(B
) /I c(0
) (H
z-1/2
)
CRITICAL CURRENT FLUCTUATIONS vs. MAGNETIC FIELD
Critical Current fluctuations in applied magnetic fields
Bicrystal
Step edge
Lindfield Clean Room – HTS FoundaryDesign rules available
Geophysical ExplorationApplicationsMagnetometer – Active TEM
RF SQUID - 1 junction
|
X
conductorDecaying eddy current
Transient Electromagnetics (TEM)
1992-1993
First HTS Ground-based TEM system
BHPB
1994-1997
“Airborne System”
BHPB1999-2001
Prototype unit
Falconbridge/Crone2002-2004
LANDTEMTM
Outer-Rim Exploration Services
RF SQUID LANDTEMTM system
35 |
2 Junction: HTS DC SQUIDs
Field noise ~ 30 fT/root Hz (white)
Flux noise ~ 5 /root Hz
HTS Gradiometers
37 / 20
Gradiometers Systems using High Tc Junctions
Rotating axial gradiometersSensitivity – 10 pT/m/Hz at 10 Hz unshielded need 3
Static planar gradiometers (hexagonal-prism)Sensitivity – 2 pT/m/Hz at 10 Hz unshielded need 6
Rotating planar gradiometer-initial results; continuing improvement – need 1!Sensitivity ~ 50 pT /(m.√Hz) in rotation at 2nd harmonic (30 Hz) Stable operation in Earth’s field
1. 2. 3.
z
yx
Rotating the Axial Gradiometer.
• Fourier transform of signals from three rotating gradiometers provides information to derive all the components of the magnetic field gradient tensor and magnetic field vectors, providing information about the bearing and range to the target
• Common Mode Rejection of Earth’s field achieved by frequency separation.
- Gradient terms at 2x rotation frequency
- B field components at rotation frequency.
• Rotating system raises the vibration isolation requirements above ~15 Hz; advantageous for most airborne platforms
Rotating axial gradiometer
Fourier transform of the 2nd harmonic time series.Additional noise reduction using least squares fitting
Gradient noise density of a single rotating axialgradiometer
• Gradient signal modulated to second harmonic 2.
• Common mode response modulated to first 1
• Sensitivity – 10 pT/m/Hz at 10 Hz unshielded operation
1
2
Helicopter trial over a magnetic target
Slide Presentation Title
Two Drum System: Comparison of calculated and actual measured components
P-Drum Simulated
-100
-50
0
50
100
150
-15 -10 -5 0 5 10 15
distance (m)
gra
d (
nT
/m)
gxy
(gxx-gyy)
P-Drum Simulated
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-15 -10 -5 0 5 10 15
distance (m)
gra
d (
nT
/m)
gxy
(gxx-gyy)
0 100 200 300 400 500-150
-100
-50
0
50
100
1500 5 10 15 20 25 30
Gra
die
nt
(nT
/m)
FFT number
P Components
6 A-m, 2 m CPA
Bxx
minus Byy
Bxy
0 100 200 300 400 500-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.00 5 10 15 20 25 30
Gra
die
nt
(nT
/m)
FFT number
P Components
6 A-m, 2 m CPA
Bxx
minus Byy
Bxy
Measurement setup hexagonal system
Static planar tensor gradiometer
Presentation title | Presenter name44 |
• Six planar flip chip gradiometers
• 3 reference SQUID magnetometers
• Sensitivity – 2 pT/m/Hz at 10 Hz unshielded operation
Extracted tensor components from a 6 A.m2
dipole magnet pass
Gradient noise density of a single planar gradiometer
Calculated scaled moment vs the theoreticalmoment for a dipole magnet pass
Rotating Planar GradiometerR-Tensor –early development
R-Tensor is a magnetic tensor gradiometer that requires only a single rotating planar SQUID gradiometer to measure all the independent components of the magnetic gradient tensor.
45 |
• reduces system complexity (one sensor verses typically five minimum)
• significantly reduces size, weight and power (SWaP) requirements
• single rotating planar SQUID gradiometer + orthogonal referencing for field compensation (improves accuracy of some components)