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Nb3Sn Magnet Development Breakthrough. Alexander Zlobin Technical Division, Fermilab. Introduction. Nb3Sn vs. NbTi Bc2~28T (NbTi: 14T) => higher operation fields Tc~18K (NbTi: 9K) => larger temperature margin Jc(12T)~3 kA/mm2 (=Jc(5T) NbTi) => efficient coils Issues - PowerPoint PPT Presentation
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SC Magnetsat Fermilab
Nb3Sn Magnet Development Breakthrough
Alexander ZlobinTechnical Division, Fermilab
SC Magnetsat Fermilab
Nb3Sn vs. NbTio Bc2~28T (NbTi: 14T) => higher operation fields o Tc~18K (NbTi: 9K) => larger temperature margino Jc(12T)~3 kA/mm2 (=Jc(5T) NbTi) => efficient coils
Issueso Nb3Sn is brittle material sensitive to stress and strain =>
special materials, fabrication technologies, handling, coil support during operation
o Nb3Sn strands are unstable wrt “flux jumps” due to large Jc and Deff => conductor optimization
Nb3Sn accelerator magnet development o started in 70’s (BNL, Saclay)o last 10 years centered in U.S. => magnets: LBNL, Fermilab,
BNL, TAMU; conductor: Labs, universities, industry)o Focused R&D + Adequate resources + Enthusiasm =>
breakthrough in Nb3Sn magnet development
Introduction
All Experimenters’ Meeting, September 21, 2009
2A. ZlobinNb3Sn Magnet Development Breakthrough
SC Magnetsat Fermilab
Process:o W&R approach (reaction at ~650C during ~50 hrs)o high-temperature insulation – ceramic, S2 or E-
glasso metallic coil components – water-jet methodo ceramic binder – critical invention o coil vacuum impregnation with epoxyo coil size control – field quality
Coil production:o 20 dipole and 34 quadrupole 1-m long coils
Good size reproducibility Short fabrication time
o 2 dipole and 11 quadrupole 4-m long coils Technology scale up
Handling and test:o Multiple reassembly without degradation with
different structureso Coil and magnet handling and transportation
across the country => Production quality Nb3Sn coil technology!
Nb3Sn coil technology
All Experimenters’ Meeting, September 21, 2009
3A. ZlobinNb3Sn Magnet Development Breakthrough
4m D coil
1m Q coils
SC Magnetsat Fermilab
YokeGap
PreloadShim
ControlSpacer
Skin
Collar
YokeCollaringKey
Stress Relief Slotin inner pole
Coil pre-load and support reduce turn motion Large Lorentz forces + Stress limit for Nb3Sn cable
(150 MPa) => possible degradation during assembly and operation of brittle Nb3Sn coils
Model magnets (D and Q) were assembled and successfully tested with three different structures!o good performance of collar-based structure => solid
base for accelerator quality Nb3Sn magnets!
Mechanical structures
All Experimenters’ Meeting, September 21, 2009
4A. ZlobinNb3Sn Magnet Development Breakthrough
SS shell w/o collar (FNAL-HFDA) Al shell w/o collar (LBNL-TQS) SS shell + SS collar (FNAL-TQC)
SC Magnetsat Fermilab
7000
8000
9000
10000
11000
12000
13000
14000
15000
0 5 10 15 20 25 30 35 40
Quench number
Qu
ench
cu
rren
t (A
)
TQM01
TQM02
TQM03
4.5K 1.9K
4.5K 1.9K
4.5K 1.9K
1.9K 4.5K
1.9K 4.5K
4.5K 1.9K
Conductor determines the SC magnet performance Stable, high Jc Nb3Sn strand (RRP-108/127 with increased
spacing) has been developed by Fermilab and OST RRP-108/127 TQ coil successfully tested in quadrupole mirror
o first time demonstration of stable operation at 4.5 and 1.9 Ko Bmax~12 T (4.5K) and ~13 T (1.9K)
=> RRP-108/127 is baseline conductor for 11T Nb3Sn magnets!
Nb3Sn strand optimization
All Experimenters’ Meeting, September 21, 2009
5A. ZlobinNb3Sn Magnet Development Breakthrough
SC Magnetsat Fermilab
Most important breakthroughs o Development of production-quality Nb3Sn coil technologyo Demonstration of collar-based mechanical structureso Development of high-performance Nb3Sn strand
=> accelerator-quality Nb3Sn magnets (D and Q)
Fermilab HFM program made key contributions to all these breakthroughs
10-11 T accelerator quality Nb3Sn magnets are real and can be considered now for practical applications
Solid base for higher field (~15 T) Nb3Sn accelerator magnets needed for Muon Collider and some other applications
Summary
All Experimenters’ Meeting, September 21, 2009
6A. ZlobinNb3Sn Magnet Development Breakthrough