high temperature superconductors for future fusion magnet systems
DESCRIPTION
High Temperature Superconductors for Future Fusion Magnet Systems Status, Prospects and Challenges. G. Janeschitz, R. Heller, W.H. Fietz, W. Goldacker, G. Kotzyba, R. Lietzow, R. Nast, B. Obst, S.I. Schlachter, C. Schmidt, K.-P. Weiss Forschungszentrum Karlsruhe, Karlsruhe, Germany. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/1.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 1
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
High Temperature Superconductors for Future Fusion Magnet Systems
Status, Prospects and Challenges
G. Janeschitz, R. Heller, W.H. Fietz, W. Goldacker, G. Kotzyba, R. Lietzow, R. Nast, B. Obst, S.I. Schlachter, C. Schmidt, K.-P. Weiss
Forschungszentrum Karlsruhe, Karlsruhe, Germany
![Page 2: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/2.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 2
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Use of High - Tc Superconductors (HTS) allows higher operating temperatures of 20 K to 77 K save investment
higher efficiencymuch lower effort for thermal shielding save investmentHigher thermal stability more reliable operation
ITER Demo / Proto CommercialFusion Power Plant
≈ 2016 ≈ 2035 ≈ 2050
Long Term Fusion Magnet R&D
Need for Efficiency and Reliability
![Page 3: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/3.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 3
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Efficiency optimization
For commercial power plants it is essential to reduce power consumption
ITP - refrigerator: 2 kW@ 4.4 K = 0.7 MW electric power
ITER: 64 kW@ 4.4 K = 22 MW electric power
DEMO: ??? MW electric power
With a magnet system at 20 K a fusion machine would be more efficient
with respect to electric power consumption for cryogenics.
Great would be a machine with a superconducting magnet system at 65 K to 77 K!
Cooling with liquid nitrogen would be possible!
Above 20 K operation will be more reliable due to higher enthalpy
![Page 4: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/4.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 4
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Critical Temperature of Superconductors
1900 1920 1940 1960 1980 20000
30
60
90
120
150
Nb3Ge
Nb3GaNb
3Sn
V3Si
NbNNbCNb
Hg Pb
Tem
pera
ture
[ °C
]
Tem
pera
ture
[K]
Year
-270
-240
-210
-180
-150
-120
BiSCCOYBCO
HgBaCaCuOTlBaCaCuO
BiSrCaCuO
YBaCuO
LaSrCuOLaBaCuO
LN2
![Page 5: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/5.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 5
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Magnets for a Fusion-reactor
HTS materials BSCCO and YBCO are promising
Boundaries indicate jc = 0 => ultimate boundary
![Page 6: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/6.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 7
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Problems of High - Tc Materials
For example: 90 K Superconductor YBa2Cu3O7
CuO2 - Layers (s.c.)Spacing LayerCuO2 - Layers (s.c.)
Charge Reservoir / Doping
•Layered structures •Correct orientation necessary!•S.C. properties depend on doping•Grain boundaries are detrimental•Brittle materials (ceramics)
Long time R&D was necessary on the road to High - Tc cables
Perfect crystal structure
Oxygen doped
Oxygen binds electrons => holes are forming Cooper pairs
![Page 7: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/7.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 8
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
BSCCO: c - axis orientation is necessary - > rolled tapes
c - axis c - axis c - axis
Application: HTS current lead demo for ITER (BSCCO) In the frame of the EU Fusion Development Program, a 70 kA HTS current lead with Bi - 2223/AgAu superconductor was developed and tested in FZK.
This material is industrially available in long lengths.
Current lead consists of three parts:Connection to low Tc S.C. HTS module (Bi - 2223/AgAu) Copper heat exchanger
4.5 K 4.5 K - 65 K 65 K - 300 K
![Page 8: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/8.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 9
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
YBCO offers higher B(T) but 3D orientation necessary
c - axisc - axisc
- axisc - axisc - axis
On top a protection layer is placed
An oriented buffer layer avoids chemical YBCO / tape reaction
The YBCO layer adopts the orientation of the buffer layer
A substrate tape is used for deposition
Composition of YBCO Coated Conductor (CC)
The protection layer serves also as a normal conducting shuntwhen YBCO looses superconductivity (quenches).
Deviation by > 6 degree would already reduce jc significantly
YBCO layer thickness ~ 1
![Page 9: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/9.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 10
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
However, progress has been achieved by industry:
up to 300 m high current coated conductor is available263 A for a 12 mm wide tape @ 77 K, self field (SuperPower)
Status of the YBCO Coated Conductor
Basic idea realized in 1996 for short length samples
anyhow major difficulties exist:• Homogeneity of long substrates• Buffer layer problem (complicated and time consuming)• Slow growth of YBCO film by sputtering or evaporation
![Page 10: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/10.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 11
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Potential of HTS for Fusion and Challenges
Potential of High Temperature Superconductors
• Much higher superconducting transition temperatures up to 105 K
• Very high upper critical fields of the order of 100 T
• High irreversible (operating) fields at higher temperatures
• Excellent critical current densities up to high temperatures & magnetic fields
Challenges
• Structural reinforcement is required
• High conductor (cable) current is necessary for technical application
• Hot spot temperature and quench are problematic (current extraction)
• Bundling & cabling development to limit AC losses is mandatory
![Page 11: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/11.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 12
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Structural Reinforcement
Conventional reinforcement is not possible,
• HTS conductors need heat treatment at high temperature in oxygen atmosphere
• Embedding of conductor in stainless steel is not possible before heat treatment
• React-and-wind technology has to be used which limits the conductor size and the bending radius by the stress-strain behavior
The necessary reinforcement technology including react & wind has to be developed.
HTS materials are brittle materials and thus strain sensitive.Therefore a structural reinforcement is necessary.
As a consequence the necessary reinforcement reduces the engineering current density.
![Page 12: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/12.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 13
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
High Conductor (Cable) Current
Starting with the parameter of ITER TF coils (N*I = 9.1 MA, L = 0.349 H)the discharge voltage and time constant were calculated for different conductor currents
As a compromise to limit both discharge voltage and time constant, 30 kA seems to be the minimum acceptable conductor current.
30 kA made of 40 A tapes (assuming Ic=50 A at 12 T & 50 K) would need 750 tapes!
Which minimum conductor current is reasonable?
Conductor current
Number of turns
Inductance ratio L/LITER
Discharge voltage (D = 12 s)
Discharge time constant
(UD = 10 kV)
68 kA 134 1 3.5 kV 4 s
30 kA 304 5 17.5 kV 21 s
10 kA 910 45 158 kV 190 s
![Page 13: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/13.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 14
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Hotspot Temperature and Quench
Cu
YBCO
Substrate
If the YBCO superconductor quenches the current has to be transferred to the protection layer which has to takes the current until the coil is discharged.
• For a 4 mm wide YBCO-CC with a critical current density of 2000 A/mm2, and a thickness of the copper stabilizer of 50 m, the hot spot temperature during a discharge ( = 21 s) will be about 120 K.
• For a critical current density of 10000 A/mm2, a copper thickness of 300 m is required to limit the hot spot temperature to 130 K.
The increase of the critical current density in the YBCO by a factor of five results in an increase of the overall engineering current density of only a factor of two. => This limits jc,eng!
The maximum temperature reached during quench is called hotspot temperature.The thickness of the Cu layer has to be adopted to limit the maximum temperature.=> Depends also on discharge time !!
![Page 14: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/14.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 15
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Bundling & cabling development to limit AC losses
AC - loss optimization is one of the most crucial points!
AC-loss optimized TFMC conductor:
Multi stage twisted cable-in-conduit with central cooling channel,
Rated current: 68 kA @ 11.8 T and 4.6 K
Nb3Sn strand (EM-LMI)
Cable-in-conduit conductor Roebel bar conductor conceptsalready used in NbTi-LCT and NET subsize
Applied in BSCCO-cable (SIEMENS)
![Page 15: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/15.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 16
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
• Mechanical precision punching• Tool optimized for material and
thickness• Sequential assembling to RACC
structure
Roebel-Assembled-Coated-Conductor (RACC)
Design and concept for low AC losses and high transport currents
Result of transport current measurements:
Ic = 1020 A @ 77 K, self field (1 μV/cm)
Result agrees well with expectations for a cable with 16 tapes.
12 mm
![Page 16: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/16.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 17
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Conclusions
HTS allows higher temperatures and fields compared to classical superconductors
However, today a high current HTS conductor for 30 kA is a real challenge
with following critical items:
• High current conductor layout
Conductor layout has to consider structure reinforcement and react&wind technology.
Main limitation is the large number of tapes which have to be used for cabling.
• Hotspot temperature and quench
The copper stabilizer has to be large to limit the hot spot temperature which limits the engineering current density.
• Bundling & cabling development to limit AC losses
Innovative cabling techniques have to be developed to limit AC losses.
A first 1 kA class Roebel type (RACC) cable was successfully fabricated by FZK from commercially YBCO coated conductor.
• The achieved critical current agreed well with expectations.
• The technique is reliable, suitable for long lengths & scalable for large currents.
![Page 17: High Temperature Superconductors for Future Fusion Magnet Systems](https://reader035.vdocument.in/reader035/viewer/2022062500/56815292550346895dc0b784/html5/thumbnails/17.jpg)
IAEA Conference Chengdu 20. October 2006 G. Janeschitz et.al. slide # 18
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
FZK - EURATOM ASSOCIATION
Outlook
HTS R&D has to be adopted to fusion needs.
The minimum Goal should be a ~ 30 kA cable at 50 K / 12 T for future Fusion reactors.
Main targets are:
•
•Improvement of bundling and cabling techniques
•
•Fusion conductor development in collaboration with industry
•
•Design, manufacturing and test of a HTS Model–Solenoid (around 2012)
•
•Design, manufacturing and test of a TF HTS Demonstration Coil in collaboration with industry (around 2015 to 2020)
Acknowledgment This work, partly supported by the European Communities under the contract of Association between EURATOM and Forschungszentrum Karlsruhe, was carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission.