Lessons Learnt from LARP experience - PowerPoint Presentation

Slide1

Lessons Learnt from LARP experience

A. K. Ghosh

MQXF Conductor Review

November 5-6, 2014

CERNSlide2

Outline

IntroductionProduction History of 108/127 strandPerformance of 108/127Ta-Ternary

Ti-Ternary

Design Change to control RRR

Summary - Lessons LearnedSlide3

Introduction

108/127, 0.7 mm RRP® wire from Oxford Superconducting Technology first delivery of 90 kg in Feb-2008 under CDP

contract (

C

onductor

D

evelopment Program DOE-HEP)Used in TQS03 – a very successful 90 mm magnet2009-2012 substantial wire produced at 0.7 mm for LQ and 0.8 (0.778 mm) for HQTa-Ternary : (Nb – 7.5 wt.% Ta)3Sn 1300 Kg produced for LARP (316 km)108/127 Ti-Ternary : CDP development 2009First delivery of 3 billets at 0.8 mm (CDP) in Mar-2011 used for HQ-C18, C21 and a LHC-03 coilGood piece lengthRRR in the range of 60-70 for HT of 665°C/50h410 Kg of Ti-Ternary wire delivered Sep’12 through Jan’13Introduced design change: 5% lower Sn content in sub-elementSlide4

OST production of 108/127 for LARP

Production in parallel with ITER wire

Note: In this time frame the yield of 54/61 declined 10%

Ti-ternary piece-length better than Ta-TernarySlide5

OST qualified wires using the following HT schedule

210°C/48h + 400°C/48h + 665°C/50h

Overall, a very large fraction of the billets

surpassed

the

J

c minimum of 2650 A/mm2However, there was little manufacturing margin in meeting the RRR minimum of 60.To meet the specs. the HT temperature had to be lowered to 650 °C/48h or lower

with consequent loss in Ic

For the LQ coils (0.7 mm) the reaction temperature was further reduced to 640 °C/48h so that the RRR of extracted strands could be above 60 (deemed necessary for electro-magnetic stability), and for HQ (0.778 mm), 650 °C/48h was used to maintain RRR > 100.

Performance Highlights of Ta-108/127Slide6

Arup Ghosh

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OST data 0.8/0.778 mm 108/127 strand – 42 billets

210C/48h + 400C/48h + 665C/50h

Aug-23, 2012Slide7

Arup Ghosh

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OST data 0.8/0.778 mm 108/127 strand

210C/48h + 400C/48h + 665C/50h

Aug-23, 2012Slide8

Arup Ghosh

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OST data 0.8/0.778 mm 108/127 strand

Non-Cu Fraction

Aug-23, 2012Slide9

What do we learn from this experienceMuch like in NbTi (RHIC and SSC production), QA and SPC needs to be implemented in pre-production and in production phases.

Most of past production can be classified as development of new strand designsPerformance of the billets should be closely monitored with periodic meetings with vendor to evaluate production.

RRR is not well controlled in present design of RRP strand.

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Arup Ghosh

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OST Ti-Ternary Strand Production

410 Kg from 12 billets have been delivered

Production used to resolve RRR control

6 billets use

standard Tin content

(Nb/Sn ratio=

3.4)6 billets use 5%-Reduced Tin content (Nb/Sn ratio=3.6)Reduced Tin has significant impact

on the RRR

of the copper. Less Sn-diffusion through the Nb barrier and less barrier reaction into Nb

3

Sn.

Side-effect: Marginal decrease in J

c

.

Lower reaction temperatures needed for Ti-ternary than Ta-ternary wires for equivalent J

c

650°C instead of 665°C

Piece lengths

have been very

good

;

some

billets drew down in a single piece.Slide11

OST data For Ti-Ternary at 0.778 mm

210C/48h + 400C/48h + 650C/50hSlide12

OST data For Ti-Ternary at 0.778 mm

210C/48h + 400C/48h + 650C/50h

Reduced- Sn

5% reduction in Sn content has strong influence on RRRSlide13

OXF Cable StatusD.R. Dietderich – Hi-Lumi, Frascati, Nov. 14-16, 2012

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Lesson Learned fro LARP Cabling experience – cable for TQ

Cable 939R:

Reduced J

c

(12T,4.2K) by about ~5%Reduced stability current (Is) by ~50%All other cables: Reduced Jc(12T,4.2K) by about 0-3%Reduced stability current (Is) by ~10%

939RSlide14

Local Damage and Stability

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Stability compromised by low RRR at the cable edges due to sub-element shearing

Monitor in production

Facet measurement

Edge damage using microscopyLocal RRR measurementsSlide15

Summary – Lessons Learned (1)

108/127 strand procurement from three different labs and evolving specification from LQ to HQ to MQXF has made it hard to adequately oversee the various contracts and its production.

108/127 took several years to be a stable product.

So far

OST production for LARP

strand has been a mix of optimization of strand design, wire production that is not strictly a production, and has been a learning experience for OST.Going forward we need to apply production QA controls at OST and more oversight with vendor site visits on a regular basis.This might also require performing process audits at the vendor.Identifying a QA manager at OST that will be responsible for our product.11/5/2014Arup Ghosh

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Summary – Lessons Learned (2)

The “reduced-Sn” design change without making any other change in the processing has yielded high dividend in RRR control

and is being implemented for all billets going forward.

Monitor Cable Quality

Using microscopy of cable edges

Facet measurements

Local RRR measurements of Extracted Strands11/5/2014Arup Ghosh16Slide17

End of Presentation

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Arup Ghosh

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Ta-Ternary vs. Ti-Ternary

0.7 mm strand from CDP

Influence of Ta and Ti doping on the irreversible strain limit of ternary Nb3Sn superconducting wires made with restacked-rod process*

N. Cheggour, L. F. Goodrich, T. C. Stauffer , J. D. Splett , and X.F. Lu, A. K. Ghosh, G. Ambrosio

Supercond. Sci. and Tech

., 20, (2010)

Ti-doped Nb3Sn wire more strain tolerant than Ta-dopedeirr increases to 0.25 % from 0.04 %

This has been confirmed for 0.8 mm (Nb-1.5 at% Ti)

3

-Sn strand

e

irr

= 0.32-0.35 % as well as strands with 108 and192 filaments. Expect 169 design to be similar.

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