1. Magnet designs for the ESRF-SR2
Compact and Low Consumption Magnet Designs for Future Linear and Circular Colliders
Geneva, November 26-28, 2014
Magnet designs for the ESRF-SR2
G. Le Bec, J. Chavanne

2. Introduction: the ESRF-SR2
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

3. OUTLINE
Introduction
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

4. Reduced horizontal emittance: 4000  147 pm.rad
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

5. ESRF Upgrade Phase II magnets: one cell
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

6. High gradient quads (up to 85 T/m) High gradient combined magnets
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

7. 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

8. 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 magnet Minimum aperture reached
Compactness refers to the external dimensions
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

9. Small aperture magnets
Mechanical error
Assembly errors
Errors at the GFR boundary
Multipolar error
at the bore radius
Bore radius
(GFR radius = r)
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

10. Compactness… in which direction?
Compact magnets
Compactness… in which direction?
At constant integrated field
(in first approximation: no saturation,
no flux leakage, etc.)
Transverse size variation is much faster
if the magnet is saturated H L
Compromise
Longitudinal compactness
Transverse compactness
(also true for EM magnets)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

11. Transverse Compactness vs. Power consumption
WYOKE
WPOLE
WCOIL
HCOIL
Fixed parameters NI
WPOLE & WYOKE
WCOIL (magnet length is fixed)
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

12. 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

13. Compact and efficient magnets Normal conducting vs. permanent magnets
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

14. Short period undulator Lattice magnets
PM micro-motor
PM DC motor
Asynchronous motor
Power plant generator mm m
Short period undulator
Lattice magnets
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

15. scale factor g g g g g
Characteristic aperture (g0 is obviously design dependent, this is a very first approximation)
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

16. More compact for small aperture magnets
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

17. Mechanical complexity
Permanent magnets
Mechanical complexity
Yoke+pole: rigid assembly
Yoke+pole: different parts
Need spacers
Tolerance stack-up
Not compatible with laminated designs
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

18. Permanent magnets Tunabilityh
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
Yoke wP g
Coils
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

19. Permanent magnets Tunabilityx1 x2 w h
Trimming coils
Similar result for quad
(Tosin, NIMA 2012)
Optimization of PM volume:
Coil induced gradient at optimum PM dimensions:
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

20. 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

21. 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

22. 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

23. 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

24. ESRF dipole with longitudinal gradient (DL)
Aluminium spacers
Iron pole and yoke
PM blocks
DL module
Number of PM blocks is module dependent
Temperature compensation is not shown here
Complete DL magnet on its support
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

25. ESRF dipole with longitudinal gradient (DL)
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 < mm
Module 1 without shims (Hall probe meas.)
Module 2 without shims (Hall probe meas.)
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

26. ESRF dipole with longitudinal gradient (DL)
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
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

27. 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

28. 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

29. 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 mm
500 mm
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

30. High gradient quadrupoles
Excitation curves and saturation
Moderate gradient quads optimized at a linear working point
High gradient quads optimized at a saturated working point
1.5 T
2 T
1.5 T
1 T
1 T
0.5 T
0.5 T
(a)
(b)
Magnetization m0M [T] of a moderate gradient (a) and high gradient (b) quadrupoles at nominal current.
Excitation curves
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

31. 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

32. 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

33. Combined Dipole-QuadrupolesBz Bz x x
Tapered dipole
High field, low gradient
Offset quadrupole
High field, high gradient
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

34. Combined Dipole-QuadrupolesBz x
DQ specifications
GFR radius 7 mm
Field 0.54 T
Gradient 34 T/mm
Offset quadrupole
High field, high gradient
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

35. Combined Dipole-Quadrupoles
Field of an offset quad
GFR x Bz
Region of interest
Additional power consumption, weight, etc.
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

36. Combined Dipole-Quadrupoles
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
GFR x Bz
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

37. 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 pole
Main coil
Auxiliary pole
Auxiliary coil
(in series with main coil)
Trimming coil
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

38. Combined Dipole-Quadrupoles
Magnetic design
GFR
Vertical field vs. position.
Field is almost zero on one side.
DG/G expressed in Specification: DG/G < 10-2.
GFR: 7x5 mm
Field integration along an arc.
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

39. 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
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
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014

40. Compactness and efficiency Small aperture magnets (tight tolerances)
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

41. Many thanks for your attention
G. Le Bec, Magnet designs for the ESRF-SR2, Compact and Low Consumption Magnets Workshop, Geneva, November 2014