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