Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 123rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

High Temperature Superconductors for the ITER Magnet System and Beyond

W.H. Fietz, S. Fink, R. Heller, P. Komarek, V.L. Tanna, G. Zahn

Forschungszentrum Karlsruhe, Institut für Technische Physik, Karlsruhe, Germany

G. Pasztor, R. Wesche

Centre de Recherches en Physique des Plasmas, Villigen, Switzerland

E. Salpietro, A. Vostner

European Fusion Development Agreement, Close Support Unit, Garching, Germany

• Motivation

• HTS Basics

• Fusion relevant application of HTS superconductor BiSCCO

• Prospects and Challenge for YBCO superconductor

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 223rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Use of High - Tc Superconductors allows • higher operating temperatures of 20 K to 77 K save investment

higher efficiency• much lower effort for thermal shielding save investment

ITER Demo / Proto CommercialFusion Power Plant

≈ 2012 ≈ 2030 ≈ 2045

Long Term Fusion Magnet R&D

Need for Efficiency

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 323rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

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 or Proto: ???

With a magnet system at 20 K a fusion machine would be much more efficient

by a factor of 5 - 10 on 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!

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 423rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Tc 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

in 2001:MgB2 (39K)

Pressure

HgBaCaCuOTlBaCaCuO

BiSrCaCuO

YBaCuO

LaSrCuOLaBaCuO

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 523rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Use of High - Tc Superconductors (HTS)allows higher operating temperatures

YBCO @ 20 K

BISCCO @ 20 KYBCO @ 65 K

but Carnot makes sure:even 20 K would ensure much higher efficiency

YBCO is most promising

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 623rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

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

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 723rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

c - axis orientation necessary for BiSCCO - > rolled tapes

Long length of BiSCCO superconductor are available on the market from several companies.

For example:

1200m BiSCCO tape from European Advanced Superconductor, Hanau, Germany

BiSCCO is available for technical use

c - axis c - axis c - axis

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 823rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

HTS current lead for ITER (BiSCCO)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.

The ITER requirements:

Safety: Withstand a loss of He mass flow for 3 min at nominal current (ITER TF - coil @ 68 kA).

Space: Horizontal installation in coil - terminal - boxes.

Solution: Current lead consisting 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

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 923rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

HTS module was fabricated by American Superconductor (AMSC)

• HTS tapes are sintered to stacks• Stacks are soldered on SS panels• 12 panels are arranged to form

the HTS module

Stainless Steel

Stacks

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 1023rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

70 kA HTS current lead

Bus bar III(for connection and in addition for current distribution measurements)

B300 Vacuum vessel

70 kA HTS Current Lead Test Arrangement in TOSKA

80 kA conventional current lead

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 1123rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Results from BiSCCO HTS current lead• Stable operation up to 80 kA World record for HTS !!• Temperature profiles agree with calculations• Contact resistances in HTS module okay but for Cu - Cu screw contact too high• Current sharing temperature 77 K at 68 kA (10 V criterion)• Refrigerator power consumption reduced by a factor of 5 compared to conventional lead

He mass flow stopped at a current of 68 kA !

The current lead carried the 68 kA without cooling for more than 6 (!) minutes

until a quench occurred

HTS current lead is very robust.

HTS material can be fabricated in industry with high and reproducible quality.

Quench performance of HTS module excellent.

HTS current leads can be used in ITER

0 1 2 3 4 5 6 7

60

80

100

120

140

Data Calculation

Te

mp

era

ture

at

95

%

[K]

Time [min]

Details: Poster P2T - E - 284

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 1623rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Option YBCO?

YBCO @ 20 K

BISCCO @ 20 KYBCO @ 65 K

what's about YBCO?

BISCCO @ 20K is ok but

Same problems as BiSCCO plus 3D orientation necessary!

But 65 K would be possible!

c - axisc - axisc

- axisc - axisc - axis

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 1723rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Methods to grow oriented layers of YBCOIon Beam Assisted Deposition + Pulsed Laser DepositionThese vacuum methods work well but growth rate is too low for large scale application

RABiTS (Rolling Assisted Biaxially Textured Substrates)Textured substrates are used for the growth of ideal oriented YBCO films.

Under ideal rolling and tempering conditions the {001} - plane is parallel to the rolling plane and the <100> - direction points to the rolling direction. Thus we have a textured substrate• A buffer layer avoids chemical YBCO / tape reaction• The YBCO layer adopts the orientation of the tape• On top a protection layer is placed

This is the "Coated Conductor"

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 1823rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Current Status:

10 - 50 m high current coated conductor ( 1 - 2 · 106 A/cm2 @ 77 K, self field)

Demonstration of 500 m coated conductor (vacuum methods) aimed for 2006 (Nexans) / 2007 (Japan) / 2008 (USA)

Status of the Coated ConductorBasic 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

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 1923rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Open challenges (1): Focus at present on cube textured Ni - alloy substrate tape

Challenge: Alternative tapes for fusion application

Focus at present on buffer layers / CeO2 on Ni

Challenge: New conductive buffer - or no buffer at all ? (increasing stabilization)

Best results with slow deposition techniques

Challenge: Speed up! - > chemical deposition

Industries active in chemical route:

- Nexans - Trithor (starting) - American Superconductor

G. Kotzyba R. NastB. ObstS. Schlachter W. GoldackerFZK/ITP

Chemically deposited buffer on Ni RABiTs tape and YBCO on SrTiO3

Already achieved in FZK:

New Virtual HGF Institute for chemical deposition of YBCO (FZK and Universities of Braunschweig, Tübingen, Dresden & Wuppertal

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 2023rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Open challenges (2):

1) From basic physics to technical solutions

- Adopt HTS R&D to fusion needs (e.g. Ni substrates are not ideal for fusion)

- Development of bundling and cabling techniques (ac loss optimization)

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 2123rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Development of bundling and cabling techniques

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: 70 kA @ 11.8 T and 4.6 K

Nb3Sn strand (=0.81mm)

(Europa Metalli - LMI)

Classic concepts

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 2223rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Open challenges (2):

1) From basic physics to technical solutions

- Adopt HTS R&D to fusion needs (e.g. Ni substrates are not ideal for fusion)

- Development of bundling and cabling techniques

- Strand and subcable tests

- Fusion conductor development in collaboration with industry

2) Design, Manufacturing and Test of a HTS - Model - Solenoid

3) Design Manufacturing and Test of a TF HTS - Demonstration Coil in Collaboration with Industry

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 2323rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

Conclusion:

The development, construction and demonstration of a High Temperature Superconductor coil system for Fusionis a scientific and technologic long term challengewhich has to be tackled already now for becoming ready in time.

This work should be done in close collaboration of European associations and industry.

The benefit from a HTS coil system will help Fusion - to be a commercial success - to secure worlds power generation during the next decades - to generate spin - offs (e.g. power engineering).

Forschungszentrum Karlsruhein der Helmholtz - Gemeinschaft FZK – EURATOM FUSION ASSOCIATION

# 2423rd SOFT, 20 - 24 Sept. 2004, Venice, Italy W.H. Fietz, 21.9.2004

END