SC cavity design and manufacturing

Material studies for SPL cavities at CERNNiobium raw material procurement

SC cavity design and manufacturing

ARNAU IZQUIERDO, Gonzalo

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2 G. Arnau Izquierdo EN/MME

Intro Niobium for superconducting cavities Production of high RRR niobium

Niobium raw material procurement for SPL beta=1 cavities Shapes and Quantities Material specification Order follow up and QC Inspection and follow up at CERN Alternative suppliers

Material studies of assemblies see next presentation

SLHiPP-1, 8 December 2011

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Intro

3

Use of Nb for superconducting cavities High transition temperature Tc = 9,3 K and critical magnetic field Hc = 200 mT Available in industrial shapes Can be easily formed and machined, can be welded


G. Arnau Izquierdo EN/MME

K (

W/m

K)

F.Koechlin, and B.Bonin

Need of high purity ( high RRR) niobium Reduce defects and impurities acting as

normal conductive clusters High thermal conductivity to keep T< Tc

around normal conductive clusters and avoid propagation of normal conductive state (quench) thermal stability

Impurities and lattice defects act as scatter centres that reduce both thermal and electrical conductivity at low temperature.

Measuring the RRR is a practical way to evaluate purity and low temperature thermal conductivity of a material

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Intro


G. Arnau Izquierdo EN/MME4

Production of high RRR niobium Main impurity from the ore

is Ta Main impurities reducing

RRR are interstitial elements O, N, C and H.

Key points: Refining by several electron

beam remeltings under high vacuum.

Clean handling during forge, hot and cold rolling.

Final annealing 1-2 h at 700-800 °C in good vacuum.

R. Grill et al. Plansee-Heraeus

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Shapes and quantities

5SLHiPP-1, 8 December

2011G. Arnau Izquierdo EN/MME

t L W Quantity Qualitymm mm mm

Sheets

3.6 520 520 60RRR>300

3.2 240 180 12RRR>300

3 700 1000 1 RRR>40

t Ø Lmm mm mm

Sea

mless Tubes

3.2139.

8 1200 1RRR>300

3.2129.

8 910 1RRR>300

3.2 79.7 360 1RRR>300

3.2 99.7 840 1RRR>300

3.2 35.4 360 2RRR>300

3.2 16 300 1RRR>300

t L W Quantity QualityUnitary price

Total price

Weight

Specific price

mm mm mm €/piece € kg €/kg

Sheets

3.6 520 520 60RRR>300 3935

236100 500.0 472

3.2 240 180 12RRR>300 559 6708 14.2 472

3 700 1000 1 RRR>40 7766 7766 18.0 432Total Sheets:

250574 532.1

t Ø Lmm mm mm

Sea

mless Tubes

3.2139.

8 1200 1RRR>300 13886 13886 14.8 940

3.2129.

8 910 1RRR>300 10485 10485 10.4 1007

3.2 79.7 360 1RRR>300 9372 9372 2.6 3649

3.2 99.7 840 1RRR>300 8041 8041 7.4 1081

3.2 35.4 360 2RRR>300 3388 6776 2.4 2833

3.2 16 300 1RRR>300 5060 5060 0.5 10208

Total Tubes: 53620 38.1

Gross Total:

304194 570.2

Price Inquiry (restricted by FI to member states)

Plansee /AT with Heraeus /DE as supplier for ingots and subcontractor for smaller tubes

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Antecedents DESY (W. Singer, D. Proch)

Technical Specification for Niobium Applied for the Fabrication of 1.3 GHz Superconducting cavities RRR 300

FERMILAB (P. Bauer, C. Antoine) Technical Specification for High RRR Grade Niobium Sheet and Rod for use in

Superconducting Cavities

International standards No EN standards for niobium SAE AMS7850, Columbium Sheet, Strip, Plate and Foil ASTM, Standard Specification for Niobium and Niobium Alloy ...

B391-09 ... Ingots B392-09 ... Bar, Rod, and Wire B393-09 ... Strip, Shit, and Plate

Material Specification. Antecedents


The only standard dealing with a high RRR grade

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Material Specification. ASTM B393-09

ASTM B393-09 The only standard dealing with a high RRR grade UNS R04220, Type 5


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Material Specification. ASTM B393-09


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Material Specification. CERN Tech. Specs.

Two Material Technical Specifications for RRR>300 and RRR>40 issued for the Price Inquiry

General characteristics Chemical composition Microstructure Mechanical properties Electrical properties Surface defects Bulk defects

Manufacturing process Dimensions and tolerances Quality control Packing


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Order follow up and QC

10

Quality Control program defined in hte specification

A batch is defined as parts from the same melt, having followed the same forging and rolling and that have been annealed in the same charge



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Order placed to Plansee /AT (procurement of ingots and production of smaller tubes subcontracted to Heraeus /DE) Delivery schedule announced in the bid: 16–18 weeks (subject

to prior sales!) Order placed Aug 2010 Order confirmation Dec 2010 First sheets received Oct 2011 Last item received next week hopefully...

Five visits Discussion of CERN results on qualification samples Pushing up in view of continuous delays Ensuring strict respect of QC program and traceability

Various reasons given along the + 1 year for the cumulating delays



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Chemical composition Effect on electrical and

thermal conductivity. Most sensitive is RRR measurement

Specified: Analysis of interstitials on

final product because of risk of pick up during process

Obtained: OK

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Microstructure Homogeneous and fine, to

avoid heterogeneous behaviour on forming (ie. orange peel on deep drawing, not so critical for spinning)

Very high purity makes difficult to master the cast grain size because of few nucleation sites

Specified Completely recrystallized Homogeneous grain size G

6 (45 µm), locally G 4 (90 µm)

Obtained

Batch number Homogeneous Gmin Gmax Ømin [µm] Ømax [μm]

90722675 Yes 6 44.9 90689812 Yes 5.3 58.590755152 No 3 4.3 127 80.290755145 Yes 5 63.590755156 Yes 5.3 58.5

Cross-secton of qualification samples.

QC on sheets delivered. Worst cases found by the firm and by CERN:

Not fully recrystalized.

Regions of coarse grains

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Mechanical properties Annealed product is

required for forming. Specified

Max of hardness Band of yield strength

(Rp0,2) Min of ultimate strength (Rm) Min of ductility (A)

Obtained

Specif.QC on sheets

QC on tubes

Hardness HV <60 33-48 -Rp0,2 MPa 50-100 55-73 -Rm MPa >140 143-170 -A % >30 35-79 -

A

Rm

Rp0,2

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Electrical properties High RRR is (indirectly)

required for cavity performance

Specified RRR 300 @ 4.2 K

Obtained 297 – 396 @ 4.2 K (estimated

from measurements @ 9.3 K)

RRR check at CERN Cryostat four point setup of

TE/MCS. Measure just above Tc (9.3 to 10 K)

Samples 2x2x100 mm3, etched in a mixture of HF, HNO3 and H3PO4, kept below 15 °C to limit H2 pick up.

Sample holder of the RRR measurement setup at CERN/TE/MSC

Samples in the holder for chemical etching and etched

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Inspection and follow up at CERN



Square sheets Visual inspection, marking, cutting of

two corners for witness and sampling Tests in progress

Microstructure Hardness Tensile RRR Roughness

Anodising as a means of assisting visual inspection was tried and abandoned. Not easy, added handling is risky and no obvious enhancement of the surface inclusions.

Tubes Dimensional control deviations Roughness

Square sheet anodised

Anodising tests with different conditions on samples with metallic particlesembedded .

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Alternative suppliers

17

Alternative producers Wah Chang /US Tokyo Denkai /JP Ningxia Group /CN, represented in Europe by Elite Material

Solution /UK

Most propose only sheets Prices are similar A qualification sample from Ningxia has been tested

satisfactory RRR, microstructure, hardness, tensile test (on small specimen)



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Conclusions

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All shapes and quantities required will be procured with satisfactory quality

Most firms have made the effort of qualifying for previous and ongoing Nb SC projects and are now mature for sheet production

Seamless tubes required specific development not completely mastered for tight tolerances

Keeping the schedule is a concern, at least with a relatively small order, not standard dimensions and a producer for which Nb is a very minor share of activity

Grain size G 6 is tight for sheets of 3.6 mm

RRR measurement is not a widespread in house technique amongst Nb producers

Anodising for visual inspection do not seems to be advantageous for as received sheet



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SC cavity design and manufacturing

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