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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100
1000
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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100
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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20
40
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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