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Magnet designs for the ESRF-SR2 G. Le Bec, J. Chavanne
Compact and Low Consumption Magnet Designs for Future Linear and Circular Colliders
Geneva, November 26-28, 2014
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
OUTLINE
•Introduction: the ESRF-SR2
•Generalities about compact and efficient magnets
• Reducing the aperture• Minimum aperture magnets• Permanent magnets?
•Compactness and power efficiency for the ESRF-SR2
• PM dipole with longitudinal gradient• EM high gradient quadrupole• EM combined dipole-quadrupole
•Conclusion
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
OUTLINE
Introduction
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
INTRODUCTION
ESRF Upgrade Phase II
•Reduced horizontal emittance: 4000 147 pm.rad
•Same insertion devices source points
•New storage ring
•Increased number of magnets: 7-bend achromat
•Reduced longitudinal space
•Reduced power consumption
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
INTRODUCTION
ESRF Upgrade Phase II magnets: one cell
32 cells~1000 magnets (without correctors)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
INTRODUCTION
Design challenges
•High gradient quads (up to 85 T/m)
•High gradient combined magnets
•Dipoles with longitudinal gradient
•Longitudinal compactness required
•Integration of vacuum chambers and beam ports
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
OUTLINE
Compact and efficient magnets
Reducing the aperture
Compactness and power consumption
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
SMALL APERTURE MAGNETS
Power consumption and bore radius
If the magnets are not saturated:• Dipole power consumption g 2
• Quadrupole power consumption R 4
• Sextupoles power consumption R 6
Low power and compactness Reduced magnet apertures
Main limitations• Integration: vacuum chambers, beam ports, etc.• Sensitivity to mechanical errors
Compact magnetMinimum aperture reachedCompactness refers to the external dimensions
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
SMALL APERTURE MAGNETS
Assembly errors
Errors at the GFR boundary
,0
0
x yNB
Multipolar error at the bore radius
Mechanical error
Bore radius
1
00
N
N NB B
(GFR radius = r)
Error @ r =R/4 r0=R r0=R/2
Quadrupolar e2 4e2
Sextupolar e3 8e3
Octupolar e4 16e4
Compact & low consumption Tigh mechanical tolerances
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMPACT MAGNETS
Compactness… in which direction?
L
H 00
0 0
BLH H
ML BL
At constant integrated field(in first approximation: no saturation, no flux leakage, etc.)
Transverse size variation is much faster if the magnet is saturated
Longitudinal compactness
Transverse compactness
Compromise
(also true for EM magnets)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
TRANSVERSE COMPACTNESS VS. POWER CONSUMPTIONW
YO
KE
WPOLE
WCOIL
H COIL
Fixed parametersNIWPOLE & WYOKE
WCOIL (magnet length is fixed)
1mass and powerCOIL COILH H
Compact Low power
High J Low J
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
LENGTH, TRANSVERSE DIMENSIONS AND POWER CONSUMPTION
•Fixed integrated gradient: 50 T•Variable length•Variable NI and outer radius•Bore radius: 12.5 mm•Constant current density: 5 A/mm2
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
OUTLINE
Compact and efficient magnets
Normal conducting vs. permanent magnets
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
mm m
PM micro-motor PM DC motor Asynchronous motor Power plant generator
Short period undulator Lattice magnets
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
SCALE FACTOR
gg
0
23PMB M
gg
g
02JB g JCharacteristic aperture
(g0 is obviously design dependent, this is a very first approximation)
0 if 3PM JB B g M J g 2
0 06 cm if 1.1 T and 5 A/mmg M J
Gap < a few centimeters PM dipoles are more compact than EM dipoles
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
PERMANENT MAGNETS
PM systems advantages
•More compact for small aperture magnets
•No coil head: iron length = magnet length
•No power consumption
But…
•Risk of radiation damage? No if Sm2Co17 material is used
•Temperature variation? Can be compensated passively
•Mechanical complexity, tolerance stack-up
•Limited tunability
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
PERMANENT MAGNETS
Mechanical complexity
Yoke+pole: rigid assembly Yoke+pole: different partsNeed spacersTolerance stack-upNot compatible with laminated designs
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
PERMANENT MAGNETS TUNABILITY
Trimming coils
•Permanent magnets = air gaps for coils
•Field in the gap:
•Optimization of PM volume:
•Coil field at optimum PM dimensions:
x2 Amp turns needed!
wY
wP
Coils
Yoke
h
0P
Y
NI MhB
wg h
w
0 0
2 2 and P
Y
Bw Bgw h
M M
0 2NI
NIB
g
g
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
Rx1
x2
w h
PERMANENT MAGNETS TUNABILITY
Trimming coils
•Similar result for quad
(Tosin, NIMA 2012)
•Optimization of PM volume:
•Coil induced gradient at optimum PM dimensions:
22
1 2 20
1 2 1
1ln
2 2x h x xR
G NI Mhw x x x
221 2 2
0 0 2 1 1
2 and ln 1
G x x xR Gh w
M M x x x
0 02
12
NIG G
R where G0 is the gradient obtained without PM
Coil efficiency reduced by a factor 2
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
PERMANENT MAGNETS TUNABILITY
10% of these Amp turns 5% tuning range
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
PERMANENT MAGNETS TUNABILITY
Moving parts?
•Gap motions on insertion devices: 100% field tunability
But…
•Field quality and magnet centre may depends on the position of the moving parts
•Possible reliability issues (may be improved using stepper motors)
•Accuracy of mechanical assembly is not easy to reach, even without motion
•Complex mechanical system high cost
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
OUTLINE
Compactness and power efficiency for the ESRF-SR2
Dipoles with longitudinal gradient (DL)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
ESRF DIPOLE WITH LONGITUDINAL GRADIENT (DL)
• Field ranging from 0.17 T up to 0.55 T or 0.67 T • Total length: 1.85 m• Gap: 25 mm• Magnet mass: 400 kg
• PM Mass: 25 kg/Sm2Co17 and 25 kg Strontium ferrite per dipole
(Design and measurements of the DL magnet: J. Chavanne)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
ESRF DIPOLE WITH LONGITUDINAL GRADIENT (DL)
DL moduleNumber of PM blocks is module dependentTemperature compensation is not shown here
Complete DL magnet on its support
PM blocksIron pole and yoke Aluminium spacers
ESRF DIPOLE WITH LONGITUDINAL GRADIENT (DL)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
Homogeneity of central field
• Quality dominated by pole faces parallelism
• May need refinement of mechanical tolerances
• Easy and fast mechanical correction (shimming)
• Tolerance: DB/B < 10-3 @13 mm
Module 2 without shims (Hall probe meas.)Module 1 without shims (Hall probe meas.)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
Integrated field
• Preliminary study on straight integrals
• Stretched wire method
• Two modules with 0.62 T and 0.41 T
• Longitudinal gap 5 mm between poles
• End effect (sextupole) shims not installed
• Will improve with additional modules
ESRF DIPOLE WITH LONGITUDINAL GRADIENT (DL)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
ESRF DIPOLE WITH LONGITUDINAL GRADIENT (DL)
Longitudinal field
• Flat top field at longitudinal gap gs = 5 mm
•The optimum gs may change between the modules of the full magnet (field step dependence)
gs
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
OUTLINE
Compactness and power efficiency for the ESRF-SR2
High gradient quadrupoles
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
HIGH GRADIENT QUADRUPOLES
ESRF-SR2
•85 T/m nominal gradient
•12.8 mm bore radius, 0.5 m long
•Normal conducting
•Longitudinal compactness optimized
•90 A, 69 turns
•Low power consumption (1.6 kW)
•Total mass ~1 ton
•Fast pole shaping algorithm developed
•Prototype being manufactured
600
mm
600 mm500 mm
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
HIGH GRADIENT QUADRUPOLES
Magnetization m0M [T] of a moderate gradient (a) and high gradient (b) quadrupoles at nominal current.
Excitation curves
1.5 T
(a) (b)
1 T
0.5 T
2 T
1.5 T
1 T
0.5 T
Excitation curves and saturation
• Moderate gradient quads optimized at a linear working point
• High gradient quads optimized at a saturated working point
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
HIGH GRADIENT QUADRUPOLES
Energy savings and compactness
Low power quadrupole
Compact quadrupole
Current density 3.25 5 A/mm2
Power 1.65 2.50 kW
Height 605 535 mm
Mass 860 740 kg
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
OUTLINE
Compactness and power efficiency for the ESRF-SR2
Combined dipole-quadrupoles (DQ)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMBINED DIPOLE-QUADRUPOLES
Bz
x
Bz
x
Tapered dipoleHigh field, low gradient
Offset quadrupoleHigh field, high gradient
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMBINED DIPOLE-QUADRUPOLES
Bz
x
Offset quadrupoleHigh field, high gradient
DQ specificationsGFR radius 7 mmField 0.54 TGradient 34 T/mm
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMBINED DIPOLE-QUADRUPOLES
GFR
x
Bz
Region of interest
Additional power consumption, weight, etc.
Field of an offset quad
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMBINED DIPOLE-QUADRUPOLES
GFR
x
Bz
A new target for DQ field
Pro• Lower power consumption and weight• Easy access on one side (vacuum chamber, magnetic measurements)
Cons
• Design and construction are more complex
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMBINED DIPOLE-QUADRUPOLES
Single-sided dipole-quadrupole
• 2 poles + 2 “half” poles• 0.54 T field, 34 T/m gradient• Iron length: 1.1 m• Magnet mass ~ 1 ton• Power consumption: 1.5 kW
Main coil
Auxiliary coil(in series with main coil)
Trimming coil
Auxiliary poleMain pole
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMBINED DIPOLE-QUADRUPOLES
Magnetic design
GFR
Vertical field vs. position.Field is almost zero on one side.
DG/G expressed in 10-3. Specification: DG/G < 10-2.GFR: 7x5 mmField integration along an arc.
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
COMBINED DIPOLE-QUADRUPOLES
Energy savings and compactness
Single-side DQ vs. offset quadrupole
Single-sided DQ
Compact offset quadrupole
Low power offset quadrupole
Current density 3.25 5 3.25 A/mm2
Power 1.5 3.9 2.5 kW
Width x height 330 x 470 415 x 415 465 x 465 mm
Mass 900 940 1050 kg
CONCLUSIONS
Compactness and efficiency
•Small aperture magnets (tight tolerances)
•Trade off between compactness and power consumption
•Trade off between length and transverse dimensions
PM magnets?
•Good choice if reduced a tuning range is accepted (coil efficiency x1/2 for dipole and quadrupoles)
•Tight tolerances to be anticipated (more parts, tolerances stack-up)
ESRF-SR2 magnets: lower power and compact designs
•Dipole with longitudinal gradient: PM, compact, no power consumption
•Quadrupoles: low power, not so compact
•Combined dipole-quadrupoles: low power, single-sided design
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
MANY THANKS FOR YOUR ATTENTION
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014
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