Dr. Glen Crawford

Director, Research and Technology R&D

DOE Office of High Energy Physics

High Field Magnets Perspectives from High Energy Physics

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What is High Energy Physics?

The High Energy Physics (HEP) program mission is to understand how the universe works at its most fundamental level. We do this by: • Discovering the most elementary constituents of matter and energy, • Probing the interactions between them, • And exploring the basic nature of space and time.

To do this we typically build large particle accelerators and large

detectors. Both of these require advanced magnets. • To this end HEP maintains an infrastructure of equipment and people to

design and fabricate these magnets. • When necessary we support the development of state of the art

superconducting materials

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How Do We Want to Get There?

At the Energy Frontier, powerful accelerators are used to create new particles; At the Intensity Frontier,

intense particle beams and highly sensitive detectors study events that occur rarely in nature; and At the Cosmic Frontier,

ground and space-based experiments and telescopes offer new insight and information about the nature of dark matter and dark energy, and discover new phenomena.

Introduction

For the physical sciences, particularly High Energy Physics and Fusion science, the availability of advanced magnet systems has been an enabling technology.

– To manipulate and control charged particle beams

– To analyze reactions

We are presently operating at the state of the art in our accelerators, detectors and fusion reactors.

– Tevatron, RHIC, LHC, ITER

As a field of research and application we are one of the largest consumers of superconducting materials and magnets

– R&D to maximize the physics reach of the technology

– Production and operation at “industrial scale”

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NOvA (off-axis) NSF’s proposed

Underground Lab. DUSEL

MiniBooNE SciBooNE MINERvA

MINOS (on-axis)

1300 km

735 km

Current HEP Accelerator Facilities

Fermilab Tevatron Batavia, Illinois

Neutrino Program

Large Hadron Collider Geneva, Switzerland

Chicago

What do HEP magnet builders want?

The highest critical field and current density

Fabricability into wires with flexible architectures

High transport current to minimize inductance

Low cost/performance ratio

Small environmental footprint

High strength

Ability to wind as is

Long length

Low ramping losses and magnet protection

Industrial scalability

What do we have now…….? 6

LHC Magnet Statistics

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• 8000 Superconducting NbTi Magnets - 1232 Bending Dipoles (7 T) - 658 Focusing Quadrupoles - 6230 Correcting Magnets • HTS leads • 40,000 tons of material cooled to 2 K, operated in a “DC” fashion (magnets ramp a few times a week)

CMS Detector

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CMS Solenoid: 14 m diameter; 13 m long; 4 T central field

ATLAS Toroid at LHC. Diameter=20 meters. Length=25 meters.

ATLAS Detector

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HEP State-of-the-Art

All existing machines use Low Temperature Superconductors – NbTi

• Ductile alloy easy to work with

• Lowest cost practical superconducting material

• Commodity item used in MRI magnets (several thousand magnets per year)

• Relatively low critical temperature Tc and critical magnetic field Bc2 (9.8 K and 10.5 T @ 4.2 K)

– Nb3Sn • Brittle compound difficult to work with and must be formed by heat treatment

after magnet fabrication.

• Higher cost than NbTi (x 4-5)

• Small worldwide production relative to NbTi (NMR, Lab research magnets)

• Higher critical temperature Tc and critical magnetic field Bc2 (18.2 K and 24.5 T @ 4.2 K)

• React-and-Wind versus Wind-and-React

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Improvement in SC conductor

Improvement in Accelerator Dipole Magnets

Bi-2212

YBCO

NbTi

?

Nb3Sn

Tevatron

A combination of laboratory and industrial development.

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US LARP Long Nb3Sn Quadrupole

Main Features: Aperture = 90 mm Magnet length = 3.7 m Gradient = 200+ T/m

Objective:

-Demonstrate Nb3Sn magnet scale-up -Long shell-type coils -Long shell-based structure (bladder & keys) LQS01 SSL 4.3 K

Current 13.9 kA Gradient 242 T/meter

Peak Field 12.4 T Stored Energy 473 kJ/meter

First test

Future HEP Needs

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•Upgrade of the Large Hadron Collider (luminosity, energy) •Higher fields beyond NbTi (both quads and dipoles) •Radiation Resistance

•Performance Issues •Insulation •Cooling Issues

•Muon Accelerators (neutrino factory, high energy collider) • Very high fields, current densities

• e.g., cooling solenoids with B > 20-30T •Ramped ring magnets with highest possible fields •Harsh radiation environment (muons in beam decay!) •Large stored energy

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High Temperature Superconductors: New Enabling Technology?

We need to develop superconducting magnets which take advantage of this fantastic new operating space

Current HEP operating space

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10000

0 5 10 15 20 25 30 35 40 45

Applied Field (T)

JE

(A/m

m²)

YBCO Insert Tape (B|| Tape Plane)

YBCO Insert Tape (B⊥ Tape Plane)

MgB2 19Fil 24% Fill (HyperTech)

2212 OI-ST 28% Ceramic Filaments

NbTi LHC Production 38%SC (4.2 K)

Nb3Sn RRP Internal Sn (OI-ST)

Nb3Sn High Sn Bronze Cu:Non-Cu 0.3

YBCO B|| Tape Plane YBCO B⊥ Tape Plane

2212

RRP Nb3Sn

Bronze Nb3Sn

MgB2

Nb-Ti SuperPower tape used in record breaking NHMFL

insert coil 2007

18+1 MgB2/Nb/Cu/Monel Courtesy M. Tomsic, 2007

427 filament strand with Ag alloy outer sheath

tested at NHMFL

Maximal JE for entire LHC

Nb-Ti strand production

(CERN-T. Boutboul

'07)

Compiled from ASC'02 and

ICMC'03 papers (J. Parrell OI-ST)

4543 filament High Sn Bronze-16wt.%Sn-

0.3wt%Ti (Miyazaki-MT18-IEEE’04)

HTS greatly extends properties at 4K

Courtesy Peter Lee www.asc.magnet.fsu.edu

JE floor for practicality

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Preferred conductor features:

Multifilament

Round or lightly aspected shape with no Jc anisotropy

Capability to wind in unreacted form while conductor fragility is minimized

Nb47Ti (OST) Internal Sn Nb3Sn (OST)

Bi-2212 (OST)

Bi-2223 (AMSC)

MgB2 (Hypertech)

YBCO coated conductors next……………

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Very few HTS magnets so far – why?

High conductor cost – Complex structure – Challenging to work with

Low overall Jc (Je and Jwinding) – Bi-2223, but round wire Bi-

2212 is better Wires and tapes are still primitive

compared to Nb-Ti and Nb3Sn – Typical commercial batch lengths

for YBCO are currently 50 – 150 m – Stability and quench protection?

Mechanical stress at high fields a major concern

• What’s needed to make HTS more attractive?

Clear domain where LTS cannot compete

• Properties that are clearly superior to LTS

50µm substrate ~ 80nm alumina

~ 10nm IBAD MgO

~ 30nm LMO ~ 30nm Homo-epi MgO

~ 7nm yttria

~ 1µm YBCO 2µm Ag

40µm Cu

40µm Cu

Cartoon (not to scale!) of YBCO “sandwich”

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Recent MAP-related HTS Efforts

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Progress towards a demonstration of a final stage cooling solenoid: • Demonstrated 15+ T (16+ T on coil)

– ~25 mm insert HTS solenoid – BNL/PBL YBCO Design – Highest field ever in HTS-only solenoid (by ~1.5×)

• Preparing for a test with HTS insert in NC solenoid at NHFML >30 T

0 2 4 6 8 10 12 14 16-200

0

200

400

600

800

1000

1200

1400

1600

1800

I c (4.

2 K

) (A

)

B (T)

single-strand 6-around-1 cable

x6.3

BSCCO-2212 Cable - Transport measurements show that FNAL cable attains 105% Jc of that of the single-strand

Multi-strand cable utilizing chemically compatible alloy and oxide layer to minimize cracks

Rutherford and Roebel cables for large magnets

Predicted perp. field Ic of 15 strand, 5 mm wide Roebel YBCO cable – parallel 5-7 times higher

Arno Godeke, Magnet Group, LBNL

Bi-2212

YBCO – Nick Long (IRL) and Andrew Priest (General Cable

NZ)

Rutherford cable (flattened, fully transposed cable) works well for round wire 2212

– Major task of the HEP collaboration YBCO tape cannot be Rutherford cabled but

cabling by the Roebel method is possible – Under evaluation by Karlsruhe and General

Cable and IRL (NZ)

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Existing Facilities for High Field Magnet and Materials R&D

HTS conductors LTS HTS

NbTi HTS

Nb3Sn

LTS HTSHTS Nb3Sn

HTS

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Model HEP R&D Program for HTS Applications

“What would it take to…” – Demonstrate a relevant HTS conductor and magnet technology in five years?

Leveraging and continuing the program for the development of HTS conductor and magnet technology based on development of high Jc strands for HEP applications.

– A university materials program $600k/yr

– High strength materials development $500k/yr

– Industrial support $600k/yr

– Cable development $350k/yr

– Small coil development $600k/yr

– Total $2.5M/yr

Program provides significant orders for industry that has been an important component of development and also provides conductor for coil fabrication and development.

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Summary

DOE/HEP is an important stakeholder in high-field magnet research – “High-end” customer with particular needs (highest field, current density) but

generally pragmatic approach due to cost and scale.

– We contribute to the R&D effort in our part of parameter space

– We benefit from research infrastructure at NHFML, universities, industry

– Strong track record in developing LTS conductors and magnets (NbTi, Nb3Sn)

Current magnet technology may be near its limits for HEP applications – LARP Nb3Sn quads for LHC upgrades and then…?

– Future energy frontier machines will be driven by LHC results, but “buildable” options are limited

Future: “high-temperature” superconductors operated at low T? – Promise of very high field with good current density

– But: materials, technology development in early days. HTS production very labor-intensive high cost

– 5-10(+) year timescale to go from good conductor to accelerator magnets

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Backup Slides

The Tevatron

The confluence of leadership, skills and technology with industrial overtones in a pure research

environment

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Bi-2223 for HTS Current Leads

Bi-2223 CL conductors standard OPIT wire production industrial production process established AgAuMg matrix for

– superior mechanical properties – reduced thermal conductivity

Matrix content between 60 % and 70 % Je (77K, s.f.) up to > 150 A/mm² room temperature strength > 90 MPa Tape stacking for high current CL components Up to now > 20 km of HTS CL tape produced by Bruker HTS Up to now > 1000 HTS stacks produced by Bruker HTS

HTS CL for laboratory magnets and future MRI

HTS CL components

High current HTS CLs for CERN LHC and Fusion Courtesy Bruker EST

How about round wires?

YBCO stands above all – even though it is 1% of the cross-section, not the 30% of Bi-2212

But, Bi-2212 can be strongly overdoped to get its carrier density up

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1000

10000

0 5 10 15 20 25 30 35 40 45

Applied Field (T)

J E (A

/mm

²)

YBCO Insert Tape (B|| Tape Plane)

YBCO Insert Tape (Bperp TP)MgB2 19Fil 24% Fill HyperT

2212 OI-ST 28% SC (PMM030224)NbTi LHC 38%SC (4.2  K)

Nb3Sn RRP OI-STNb3Sn High Sn Bronze Cu:Non 0.3

YBCO B|| Tape Plane

YBCO B|_ Tape Plane

2212

RRP Nb3Sn

BronzeNb3Sn

MgB2

NbTi

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Bi-2212 is of particular interest to HEP: it can lead to a Rutherford cable

HTS has 3 times the critical field (<100T) of Nb3Sn (~28T)

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60

80

100

120

0 20 40 60 80Temperature (K)

Irrev

ersi

bilit

y Fi

eld

(T)

Nb-Ti

Nb3Sn

YBCO (⊥)

Bi-2223 (⊥)

MgB2 (⊥)

Bi-2212 RW

ARRA program started in June 2009

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