MgB2 cables for space applicationsDr. Giovanni Grasso, Columbus Superconductors

SR2S Workshop - Turin, April 9th, 2014

High Tc for a binary compound

No evidence of “weak links”in polycrystalline MgB2

Large critical current densityLarge upper critical field

Why MgB2

Compound Mass density

Copper 8,96 g/cm3

NbTi 6 g/cm3

Nb3Sn 5,4 g/cm3

YBCO 6,35 g/cm3

BSCCO-2223 6,5 g/cm3

MgB2 2,6 g/cm3

Large critical current density

Simple crystal structure and common constituents

• Columbus is a world leader in the production of the new superconductor MgB2, that is distinguished for its workability in long lengths and high performances

• The actual plant is fully operational for MgB2 wire production and has recently completed its scaling up (plant area now is 4’400 m2 )

• MgB2 chemical synthesis is now also fully implemented

• Wire unit length today possible up to 20 Km in combination with a nominal plant full capacity exceeding 5’000 Km/ year

• Columbus MgB2 production is already implemented in commercial products and has a long record of fully tested and qualified wires

The Company

• Our new production plant is now fully operational

• June 2013 has been our record month so far

• A net wire production of 82,435 meters has been achieved in a single month

• 71,346 meters have fully passed QC and have been shipped to a number of customers

• 11,089 meters resulted of good quality but shorter than expected because of detected localized defects and were not shipped

• Virtually 100% of the produced wires in June exceeded 1’000 meters in unit piece length

• About 50% of the produced wires exceeded 3’000 meters in unit piece length

• The product mix has been very diversified in materials and shapes

• 40% of wires were sandwich-type wires, 30% were tapes, and 30% round wires

• All wire types were able to travel the entire production process in 9 (tapes) to 20 days (sandwich-type)

The Volumes The Product Mix

MgB2 wire industrial production started

•39 new machines•15 existing machines upgraded for use in new plant•10 main upgrades to the technical infrastructures•1 new 2 storey buildiing•2.280m2 of covered workshop area•20 direct production units – 40 employees

Columbus Superconductors Plant

• SEM with EDX• very fast XRD• Laser particle size analyzer• Eddy currents defect detector• Optical stereomicroscopes• Laser wire size and shape online monitor• Industrial video cameras for surface defect detection• Additional cryo-free critical current testing system under construction

Quality control techniques

surface visual inspection (appearance)

Eddy current (product integrity)

LINE TERMINALS

About 50% of our wires are passed through eddy currents / video cameras systemsGoal is to reach 100% and have enough flexibility to test all wire formats

Real time in-line sensors

+

B

Mg99%

pure

Mixing

Reaction700-1000°C in

Ar

MgB2Planetar

yBall

Milling

95-97 % pure

Drawing Cold rolling

Reaction900-1000°C

in Ar

Filling tube

1.3 g/cm3

Chemical Phase

Metallurgical Phase

Production Process

Optimizing the manufacturing process

There are 3 different wire formats: Round, Flat and SandwichFlat tape

• The flat tape architecture has been the work-horse for Columbus in the past years and it has been the preliminary choice of our end users to discover the potential of our material

• Flat tape conductor is mainly used in small bore magnets and low current devices

Sandwich conductor

• This architecture is our new solution for present and future magnet and winding applications

• It allows the maximum flexibility in the control of the wire absolute performance and in the amount of Cu stabilization

• Being the Cu stabilizer not subjected to the thermomechanical treatment of the MgB2 conductor, it’s soldered to it in its optimal mechanical and electrical condition

Round wire

• MgB2 is currently the only no low-Tc superconductor that can be easily produced in round wire shape with significant transport properties, multifilamentary structure and excellent reliability over long lengths

• Round wires present several advantages, particularly concerning easier solenoid and more complex magnet winding, and absence of anisotropy

Wire design: State-of-the-Art

Columbus cable for magnet applications

MgB2 superconducting cable for magnet applications:

•Flat tape (3x0,5mm) multifilamentary tape, nickel clad•Laminated with copper tape, various thicknesses, for thermal/electrical stabilization •Overall dimensions: 3x0,7mm

19 MgB2 filamentsNickel cladding

OFHC copper tape laminated (by tin soldering)

Columbus cable for magnet applications

Materials densities:nickel: ρ= 8.9 g/cm3

copper: ρ= 9 g/cm3

MgB2: ρ= 2.55 g/cm3

Materials percentages:nickel: 57%copper: 29%MgB2: 14%

Materials weight per component (per meter):nickel: 10.7gcopper: 5.4gMgB2: 0.77g Overall weight per 1m of MgB2 standard cable:

17 grams

Columbus cable for SPACE applications

Which way is it possible to reduce the averall weight for reducing the launching load?

1- REDUCE THE WEIGHT: -substitute nickel cladding with a lighter metal (as titanium)-substitute copper stabilizer with aluminum stabilizer2- IMPROVE CRITICAL CURRENT DENSITY: -If we are able to improve the current density, we can reduce the overall amount of conductor to be wound in the magnet

Is this realistic?

Columbus cable for SPACE applications

MgB2 superconducting cable for magnet applications:•Flat tape (3x0,5mm) multifilamentary tape, TITANIUM clad•Laminated with ALUMINIUM tape, various thicknesses, for thermal/electrical stabilization •Overall dimensions: 3x1mm

19 MgB2 filamentsTITANIUM cladding

ALUMINUM (few copper outside) tape laminated (by tin soldering)

Prototipe cable already developed in SR2S project:

Columbus cable for SPACE applications:

Materials densities:titanium: ρ= 4.5 g/cm3

alluminium: ρ= 2.7 g/cm3

MgB2: ρ= 2.55 g/cm3

Materials percentages:titanium: 40%alluminium: 50%MgB2: 10%

Materials weights per component (per meter):titanium: 5.4galluminium: 4.0gMgB2: 0.77g Global weight per 1m of MgB2 SPACE app. cable:

10.2 grams

Columbus cable for SPACE applications:

FROM 17 TO 10.2 grams, 40% weight reduction

FROM:3x0,5 nickel clad wire3x0,2 copper stabilization

TO:3x0,5 titanium clad wire3x0,5 alluminum stabilization

Transport properties

To further reduce the amount of cable to be wound (and thus the overall weight), much efforts have also been spent on transport properties enhancement

By an appropriate powder refinement study, the engineering critical current density has progressively been enhanced, almost doubling it

Ti tape, step 1

Ni strd tape

Ti tape, step 2 Ti tape, step 3

Transport properties

Already high transport properties, more than:- 450 Amps @ 4.2 Kelvin and - 250 Amps @ 10 Kelvin, 4 Tesla

Thanks to R. Musenich, INFN - Genoa

Thanks to B. Bordini, CERN - Geneva

Conclusions:

In the framework of the SR2S project, ways of reducing the weight load of the superconducting component have been explored and tangible results already witness significative progresses.In the upcoming future, a further technical enhancement can be expected…..