Superconducting Cable Joint R&D Proposal

Sandor Feher3rd of October, 2013

Outline• Introduction/motivation• Description of the Concept• R&D plan• Conclusions

What do we want from a Superconducting Cable Joint?

1) Mechanically and electrically sound• Stabilizer continuity – robust if it is possible welded joint• Low sub nΩ electrical resistance – superconducting transition is the best

2) Dismountable if necessary – multiple times3) Compact – space many times is an issue

• The splice itself to be short• Use “small” tooling

4) To be easily inspected and declared acceptable by QC5) Be of rapid installation and minimize the risk of error by design6) Use of tooling easy to multiply7) Possibly industrially based tooling

Superconducting cables• Too many different type of solutions are on the market

depending on the applications– LTS, HTS, MgB2

– Monolithic, Composite• Rutherford, CICC, Roebel, Transmission etc.

– How much stabilized material used– Core or cladding involved– Cooling issues

Cable targeted for this splice joint R&D• First phase: Heavily stabilized NbTi cable mainly used for Bus work and for

Detector magnets – large solenoids– LARP is developing Nb3Sn magnets but the bus work could be NbTi based– Detector solenoids R&D is still based on heavily stabilized Al cladded conductor

• Second phase: – Rutherford or round NbTi cable – external joints– MgB2 cable made from round wires

• Third phase: more exotic cable designs once the principle of the joint technique is proven

Splice Joint Concept

Welding together the composite superconducting cable

Make an angle cut

Place a thin sheet of Superconductor material

With or without making a sleeve

Use special welding technique to make the joint:• Rapid welding

• Explosive • Electromagnetic

• US welding

Potential advantages if it works1) Mechanically and electrically sound

• Stabilizer continuity – robust; welded joint• Low sub nΩ electrical resistance; likely to be a superconducting transition

2) Dismountable if necessary – multiple times• Require a shallow angle cut – only the cutting blade size will be lost• If double joint is used no length reduction

3) Compact • The splice itself is short – depending on the angle of the cut• In a case of utilizing the explosive welding technique the tooling is small

4) It is easy to inspect and declared acceptable by QC5) Rapid installation and minimize the risk of error by design6) The tooling is easy to multiply - good for large production7) Industrially based tooling – rapid welding and US welding

techniques are commonly used in industryIt could satisfy all the criteria for making excellent splice joints

Why would not work?

• Welding different flat or even shaped materials together is a common technique but it was not shown that could be made a welded joint for:– High complexity – possible voids in the material– Under angle– Sandwiched layers at the same time

• The joint resistance might be superconducting but may not achieve high Jc– Although the compression helps creating pinning centers – Melting the material reduces the number of pinning centers

• The question is how deep in the superconductor the dislocations will be affected

• Mechanically still could be fragile if the quality of the weld is not high enough

R&D PlanFirst phase• Working with a vendor to make joints using RQ bus cable;

vendor will utilize their experience to make a sound joints:– Need to determine the angle, speed, cleanliness, minimal thickness of

the Superconducting sheet– Making basic mechanical tests to make sure that the joint is a sound

welded joint

• Once the vendor has developed the technique they make samples for further tests:– CERN need to determine the geometry of the sample– We should start with nine samples

• 3 samples without any superconducting sheet in between• 3 samples with Nb sheet in between• 3 samples with NbTi sheet in between

R&D Plan

• CERN will analyze the samples:– Cold splice electrical measurements

• It is important to determine the Ic – sample should be tested under strong magnetic field to see the transition

– Mechanical tests• Determine the breaking force• Cut the bus at the joint location to check the quality of the weld

– Endurance tests• Bending the the bus at the joint location few times and repeat the Ic measurements

Vendor• S-MetallTech (Hungarian company) is interested in to work on this

project• In 2010 they proposed an alternative solution for CERN for the splice

consolidation using a special clamp-shunt design. They also made a demonstration clamp-shunt piece using explosive welding technique.

Copper-steel bimetal

Solder sheet

Copper rod, modeling the materials to be bonded

Steel sheet

Budget

• Phase one: samples procurement from S-MetallTech 2500 – 3000 Euro – CERN provide RQ cable and specify the sample geometry

• CERN involvement– Cold tests – 9 joints but 1 sample (if it is possible)

• Material cost: Sample holder ~ 2000 Euro • 1 week sample preparation – V-taps, soldering of the bottom joints

to the cable etc.• 1 week of testing – including all the overhead

– Mechanical tests????

Phase two• MgB2 Cable joint

– Basic research issues to solve• From MgB2 bulk making powder or flakes than re-compacting

them• Check how well the powder or flakes joined together – cold tests

to measure resistivity – Once it is proven that the re-compacted MgB2 is superconducting work

on utilizing round cable configuration for joints• Similar to phase one concept but using MgB2 for the

superconductor and the copper sleeve is essential– The copper sleeve will provide the required copper continuity –

welded joint and it will serve as a container for the MgB2 powder/flakes

Conclusions• A new concept of making superconducting cable joints were

presented for NbTi based heavily stabilized superconducting cables

• It was shown that there is a potential for utilizing this technique to MgB2 conductor based superconducting round cables

• With a moderate investment (time and money) superconducting cable joint R&D could be launched immediately

END

S-MetallTech

S-Metalltech 98 Ltd was founded in 1998 by Hungarian engineers.The aim of foundation was to create a flexible research-development- production base for

the special more components materials applied mainly in the field of the power engineering.

The strategy behind setting up of the S-METALLTECH 98 Ltd was to provide a link between the universities, research institutions and the industrial enterprises. The S-METALLTECH serves:

- on one hand as a technological RD workshop for universities and enterprises, - on the other hand as a small-scale production base for the special more components

materials used in the field of electrical engineering, vehicle production, nuclear technique, etc.

The small-scale production can be very economic because of the great value of the products and the applied special High Energy Rate Forming (HERF) techniques as electromagnetic and explosive tube- and sheetformings, claddings, powdercompactions, etc .

S-MetallTech

Participation in R & D projects in the last 15 years· „Development of HTSC Alternators Combining Rotating and Levitating Properties” (EU INCO R&D contract, 1998–2001, No. ERB IC15–CT98–0504,); consortium member· „Development and production of superconducting demonstration equipment” (Hungarian R&D project, 2000-2001, No.OM 00875/2000), project leader· „Development of production technology for thermobimetals …” (Hungarian R&D project, 2003-2004, No.OMFB 00552/2003), project leader· „Superconductivity in everyday life” (EU R&D project, 2004-2005, No.EU-ERA SAS6- CT-2003-509058 s 2004-2005) consortium member· „Development of electromagnetic metal processing equipment” (Hungarian R&D project, 2004-2005, No.OMFB 00266/2004) project leader· „Elaboration of the Hungarian research-development–production base for multi-component materials based on the HERF technologies” (Hungarian R&D project, 2006-2007, No. GVOP-3.3.2-05/1-2005-05-0004/3.0), project leader· „Development of nano-structural, multifunctional, intelligent materials and products …” (Hungarian R&D project, 2006-2009, No. NKFP5-00002/2005), consortium member· „Development of innovative products based on nano-powders of noble metals…” (Hungarian R&D project, 2008-2010, No. OM-225/2007), consortium member.