Transcript Superconducting Detector Magnets

Superconducting Detector Magnets
Evolution and Outlook
Roger Ruber and Akira Yamamoto
Uppsala University and KEK
Scope of this Presentation
• Chronological Evolution
– Identify Major Technology Steps
• Indirect cooling
• Conductor and Coil manufacturing
• Review Specific Issues
– Stability
• Materials and strength
• Protection
• Future Directions
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Technology Drivers
• Momentum resolution
– depends on sagitta term
s  qBL
2
8p
• Transparency
– reduction of material in the magnet structure
– use low radiation length materials
• Detector configuration
– determines magnet configuration
• Cost & reliability
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Solenoid Magnet
• Resolution
– inside solenoid: dp/p ~ {B·R2solenoid}-1
– outside solenoid: dp/p ~ {B·Rsolenoid}-1
• Transparency
– wall thickness: t ~ (R/σh) • B2/2µ0
• Field & Symmetry
– axial and uniform
– but field lines parallel to particle
path at small angles
• Installation
– self supporting structure
– iron yoke to contain stray field (improves bending power at small angles)
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Toroid Magnet
• Resolution
– inside toroid: dp/p ~ sinθ {Bφ·Rin·ln(Rin/Rout)}-1
q
• Field & Symmetry
– tangential field (1/r)
– field lines perpendicular to particle path
– closed field: centred on and circulating
around beam (no influence on beam)
• Installation
– support required to keep self balance
– no stray field: no iron yoke required
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ATLAS Toroids (2007) Largest Field Volume
• good resolution at small forward angles
• self contained 4 T field, volume 7000m3, no yoke
• open structure barrel, cryostats occupy ~2% volume
8 coils barrel toroid
2x 8 coils end cap toroid
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4.1
5 - 10
25
103
1550
T
m
m
Tm^2
MJ
8 degrees
Parameters
Field
Radius
Length
BR^2
Stored Energy
Mean Integral B.dl T.m
8
7
6
5
4
3
2
1
0
0
0.25 0.5 0.75
1
1.25 1.5 1.75
2
2.25 2.5 2.75
3
η = -ln tan(θ/2) Pseudorapidity
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Toroid Assembly with Barrel Calorimeter and Solenoid
Sag
28mm
End Cap Toroid
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Solenoid
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CELLO (CEA, 1978) First Generation
• monolithic NbTi/Cu conductor soldered to aluminium stabilizer
• indirect cooling
• BR2 ~ 1 Tm2
Indirect Cooling
Series Cooling Circuit
Support Banding
Aluminium
Stabilised
Conductor
Mandrel
H. Desportes, Adv.Cryo.Eng. 25 (1980) 175
Parameters
Field
Coil Radius
Length
BR^2
Stored Energy
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1.5
0.85
3.6
1.1
5.1
Tesla
m
m
Tm^2
MJ
Indirect cooling + Aluminium stabilsed conductor
Indirect
Bath
He Inventory in cryostat L
10-20
>1000
Radiation Length Xo
0.6
~3
Cold Mass wt tonnes
1
5
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Design Requirements
• Mechanical Safety
coil thickness  RB2/ (E/M)

RB2 γ/σh (γ=density)
– E/M (stored energy/cold mass) to be increased
scaling parameter that indicates peak temperature at homogeneous
energy dump (E = 0.5µ0∫B∙dV ; E/M=H= ∫CpdT)
– σh (hoop stress) to be decreased
superconductor to be stronger
• Thermal Safety
uniform energy absorption and
low peak temperature at quench to decrease thermal stress
– fast quench propagation
high RRR in stabilizer, or active/passive propagation techniques
– energy extraction by external dump
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CDF (Tsukuba Univ/FNAL, 1984) Second Generation
• co-extruded monolithic conductor
• aluminium alloy support cylinder, shrink-fit
• BR2 ~ 3 Tm2
Parameters
Field
Coil Radius
Length
BR^2
Stored Energy
Indirect Cooling
Circuit
1.5
1.5
4.8
3.4
30
Tesla
m
m
Tm^2
MJ
Welded to Al5083
Cylinder
H. Minemura et al., NIM A238 (1985) 18
• Mechanical: 30MPa > yield strength pure Al
• Electrical: allowed conductor joints formed
20mm
First full scale use of co-extruded conductor
• High quality bonding between
superconductor and pure aluminium
Shrink fit
of coil into
force
support
cylinder
by welding between aluminium sections
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TOPAZ, VENUS (KEK, 1984)
• direct internal winding, without mandrel
• kapton based insulation
VENUS: M. Wake et al.,
IEEE MAG-21 (1985) 494
TOPAZ: A. Yamamoto et al., JAPL 25 (1986) 1440
TOPAZ features:
Insulation and bonding
by B-stage epoxy on
conductor +
GFRP-Kapton
on support cylinder
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VENUS features:
• CFRP vacuum vessel
• Force support cylinder formed from
extrusion sections – welded in situ
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ALEPH (CEA, 1987) Third Generation
• parallel cooling circuits, thermo-siphon cooling
• BR2 ~ 10 Tm2
35mm
Parameters
Field
Coil Radius
Length
BR^2
Stored Energy
1.5
2.75
6.4
11.3
130
Tesla
m
m
Tm^2
MJ
J.M. Baze et al., IEEE MAG 24 (1988) 126.
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CMS (CEA/CERN/INFN, 2006): Fourth Generation
• EM Calorimeter inside solenoid → thin wall not a goal!
• 4 layers reinforced conductor
• hybrid conductor: pure-Al/A6082
• BR2 ~ 40 Tm2
Conductor
• Pure Al +
high strength alloy
• YS > 250MPa @ 4K
• RRR 1400
Parameters
Field
Coil Radius
Length
BR^2
Stored Energy
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4
3.15
12.5
40
2600
T
m
m
Tm^2
MJ
400 m3
D. Campi et al., IEEE TASC17-2 (2007) 1185
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ATLAS Central Solenoid (KEK, 2006)
• thin solenoid, fully integrated with LAr calorimeter cryostat
• high strength pure aluminium stabilizer
• Al-strip quench propagator
T
m
m
Tm^2
MJ
2/3
４５
A. Yamamoto at al., NIM A584 (2008) 53
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６７
2
1.25
6
3.1
40
<
<67
Parameters
Field
Coil Radius
Length
BR^2
Stored Energy
14
High Strength Conductor Development
• 0.1-2% Ni micro-alloying + 15-20% cold-work hardening
200
Al
Al
Al3Ni
1µm
Yield Strength at 4.2 K [MPa]
Ni 20000-ppm
(20%)
150
(20%)
100
( +)
Cu
ATLAS-CS
(20%)
50
Ni 1000-ppm
(0 %)
Zn 200-ppm
(0 %)
(0 %)
0
0
500
1000
1500
2000
Residual Resistivity Ratio
Al3Ni precipitated
contributes as
structural component
Pure-Al region
keeps low resistivity
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Peak temperature after a full
energy dump is less sensitive
to RRR for RRR > 100.
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BESS Polar (KEK, 2005)
• thinnest solenoid, no support cylinder!
• wall thickness 1gm/cm2 ~ 0.05X0
1
0.45
1
0.9
0.38
T
m
m
Tm^2
MJ
NbTi/Cu SC
Al-Ni alloy
3.4mm
Parameters
Field
Radius
Length
BR^2
Stored Energy
A. Yamamoto et al., IEEE TASC12-1 (2002) 438
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BESS Polar: How Thin is Thin?
thickness/diameter ~ 0.2%
coil thickness/diameter ~ 0.34%
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SiD Conceptual Design: Future ILC/CLIC Detectors
all proposals require
• large scale field & volume:
BR2 > 35 Tm2
• huge energy: 1.5 ~ 2 GJ
SiD proposal requires:
• 4~6 layer coil
• high strength conductor
• integrated dipole magnet
R. Smith et al., IEEE TASC 16-2 (2006) 489
4th
ILC Proposal:
• double solenoid with end disk!
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Parameters
Field
Coil Radius
Length
BR^2
Stored Energy
5
2.65
5.5
35
1500
T
m
m
Tm^2
MJ
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Future Technologies
Strong conductors
• for large field and thin-walled magnets
Magnet protection
• to prevent high peak temperatures during full energy dump
Field Tesla
10000
BR^2
good for physics
1000
Energy MJ
100
Cond MOI
E/M kJ/kg
10
C Mass
tonnes
1
CELLO
ALEPH
difficult winding process
MOI=moment of inertia
magnet safety
CMS
0.1
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E/M: A Scaling Factor for Coil Design
Stored energy increased ~300x from CELLO to CMS
• Large field volume + transparent coils
– leads to increased E/M ratio = enthalpy:
CMS 12kJ/kg = 85K mean temperature after homogeneous energy dump
• Design aim
– peak temperature <120K → differential stress < 30MPa
65, 80, 100
5,10,20
Thermal Expansion
H = E/M = ∫ Cp dt
80 120
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Temperature [K]
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Status Aluminium Stabilized Conductor
300
200
YS(MPa) @4.2K
200
RRR/100
150
Yield Strength [MPa]
250
150
100
50
BESS-Polar
(Al-Ni)
100
Ordinal Copper
LHC/ATLAS
(Al-Ni)
50
SSC/SDC
(Al-Zn/ Si)
ASTROMAG
(Al-Si)
(Pure-Al)
0
TOPAZ
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SDC
ATLAS-CS
CMS-overall
0
1975
1980
1985
1990
1995
2000
2005
Year
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Future Development of Stabilized Superconductor
Combine ATLAS and CMS technology
for high strength stabilizer:
• ATLAS high strength stabilizer
• CMS hybrid support
– A6058 → A7020
Yield strength (0.2%)
= 400 MPa
RRR ~ 400
Equivalent yield strength /MPa
– Ni-0.5 ~ 1 %
500
450
400
350
300
250
200
150
100
50
0
Improved
CMS
CMS
Bess P
ATLAS CS
0
400
800
1200
1600
RRR
S. Sgobba et al., IEEE TASC 16-2 (2006) 521
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Summary and Outlook
Indirect cooling + aluminium based conductor step made for
CELLO has seen huge developments in all aspects of the
technology:
• Scale
– Field volume ~700x for ATLAS
– Stored energy ~ 300x for CMS
8000
Performance of 0.8 mm dia wire
• Conductors
• Coil winding and assembly
– technology: materials
(impregnation – bonding)
– engineering: scale + accuracy
As of year 2000
Nb3Sn (4.2K)
6000
Jc(A/mm2)
– advances in scale and strength
7000
5000
NbTi (1.8K)
4000
3000
BSCCO2212 (4.2K)
2000
NbTi (4.2K)
1000
0
0
2
4
6
8
10
B(T)
12
14
16
18
20
Present state of the art can give 5 T.
R&D efforts ongoing for Al-stabilized Nb3Sn/Nb3Al cables and
solenoid beyond 10 T
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Acknowledgements
Many thanks for contribution of material and advice
Elwyn Baynham (RAL)
Yasuhiro Makida (KEK)
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