1. Magnets for the ESRF upgrade phase II
G. Le Bec, J. Chavanne
on behalf of the ESRF upgrade project team
Low Emittance Rings workshop 2014, Frascati, Italy

2. Overview Context Where are we? Summary and conclusion
The ESRF phase II magnets
Design and prototyping challenges
Where are we?
Dipoles
Combined dipole-quadrupoles
Quadrupoles
Sextupoles, octupoles
Summary and conclusion
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

3. The ESRF phase II magnets
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

4. The ESRF phase II magnets
Reduced gradient
100 T/m 85 T/m
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

5. The ESRF phase II magnets
Reduced field and gradient
0.85 T  0.54 T
49 T/m  34 T/m
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

6. The ESRF phase II magnets
Challenges
High gradients
Combined magnets
Small bore radius
Tight tolerances
No space longitudinally
More than 1000 magnets
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

7. Design constraints Field quality
Integration and mechanical constraints
Magnet length
Vacuum chambers
Vibrations
Supports
Alignment
Tunability
Power consumption
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

8. Field quality and tunability
Magnet type
GFR radius
[mm]
Field quality
(systematic)
Tuning range [%] DL 13
DB/B < 10-3 DQ 7
DG/G < 10-2
Gradient: +/- 2
Q – 50 T/m
DB/B <
55 – 110
Q – 85 T/m
DB/B <
95 – 105 S
DH/H < 0.1
20 – 130 O
0 – 145
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

9. Prototyping Tolerances Magnet assembly Magnetic measurements
High gradients, small radius, field quality  Tight mechanical tolerances
Measurement accuracy: ~10 µm (magnet dimension dependent)
Poles are difficult to measure
Magnet assembly
Repeatability in case of disassembly
Magnetic measurements
Long magnets, small radius
A few bent magnets
Crosscheck magnetic simulations
Poor iron manufacturer data at high magnetization
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

10. Dipoles PM dipoles 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
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

11. Dipoles PM dipoles with longitudinal gradient (DL)
PM blocks
FeNi shims
Soft iron
yoke and poles
PM dipoles with longitudinal gradient (DL)
Sm2Co17 PM material (proven resistance to radiation damage)
Possible use of strontium ferrite for low field modules
25 kg of Sm2Co17 and 25 kg of strontium ferrite per dipole
“Thermoflux” FeNi shims for temperature compensation
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

12. High field (0.67 T) dipole module
Dipoles
Mechanical tolerances
Pole shape machining
Measured with a portable CMM (FARO Arm)
+/- 20 µm tolerances reached with both wire erosion and spherical end mill
Pole location
Yoke and poles are different parts
Tolerances stackup
Shims are helpful
Magnetic measurements
In progress
Good agreement with simulations
High field (0.67 T) dipole module
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

13. Dipole – quadrupoles (DQ)Bz Bz x x
Tapered dipole
High field
Low gradient
Offseted quadrupole
High field
High gradient
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

14. Dipole – quadrupoles (DQ)Bz x
DQ specifications
GFR radius 7 mm
Field 0.54 T
Gradient 34 T/mn
Offseted quadrupole
High field
High gradient
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

15. Dipole – quadrupoles (DQ)
Field of an offseted quadrupole
GFR Bz x
Additional power consumption, weight, etc.
Region of interest
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

16. Dipole – quadrupoles A new target for DQ field Pro Cons
Lower power consumption and weight
Easy access on one side (vacuum chamber, magnetic measurements)
Cons
Design is more complex
GFR Bz x
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

17. Dipole – quadrupoles (DQ)
Single sided dipole – quadrupole
A “3-pole” design (2 poles + 2 “half” poles)
0.54 T field, 34 T/m gradient
Iron length: 1.1 m
Magnet mass ~ 1 ton
Power consumption: 1.7 kW
Main coil
Main pole
Auxiliary pole
Auxiliary coil
(in series with main coil)
Trimming coil
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

18. Dipole – quadrupoles (DQ)
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 et al. -- Low Emittance Rings workshop, Frascati, 2014

19. Dipole – quadrupoles (DQ)
Pole shaping is mandatory
Simulation tools
Boundary integral method (Radia software)
Fast field integral computations for 3D geometries
Regularized descent method
Error function defined with elliptic multipoles (7x5 mm GFR)
Poles are described as a sum of smooth functions
Gauss-Newton algorithm:
Truncated SVD used for computation
(Le Bec et al., IPAC 14, applied to quad design)
Curved magnet
First optimization on a straight magnet (fast computations)
Final computations on a bent magnet (field integration over an arc)
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

20. Quadrupoles Two quadrupole families Moderate gratient 51 T/m
Bore radius: 15.5 mm
Iron length ranging from 160 up to 300 mm
Working point: 50 – 110 % of nominal gradient
Power: 1 kW for the largest quadrupole
High gratient 85 T/m
Bore radius: 12.5 mm
Iron length ranging from 390 up to 480 mm
Working point: 95 – 105 % of nominal gradient
Power: 1.6 kW for the largest quadrupole
Moderate gradient
High gradient
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

21. Quadrupoles Design criteria Field quality Overall dimensions
Fast pole shaping algorithm developed
Overall dimensions
Power consumption
Cooling and PS constraints
Sensitivity to background field
Decreased magnet’s power consumption
Decreased current density
Increased magnet’s transverse dimensions
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

22. Quadrupoles WPOLE & WYOKE constant WCOIL constant (magnet length)
RCOIL
WPOLE & WYOKE constant
WCOIL constant (magnet length)
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

23. Excitation curve of quadrupoles
Excitation curve and saturation
Moderate gradient quads optimized at a linear working point
High gradient quads optimized at a saturated working point T T
(a)
(b)
Magnetization m0M [T] of the moderate gradient (a) and high gradient (b) quadrupoles at nominal current.
Excitation curve of quadrupoles
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

24. Quadrupoles Magnet design properties Prototyping
DG/G = within the GFR
Solid iron yoke
Iron length 480 mm 540 mm total length
Magnet mass ~ 1 ton
90 A, 69 turns, 1.7 kW
Prototyping
Prototype being manufactured
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

25. Other magnets Sextupole Octupoles 900…1600 T/m2 nominal strength
Magnetic design stabilised
Engineering design almost completed
Opening/closure repeatability
Octupoles
Nominal strength 52 T/m3
Maximum strength 65 T/m3
Prototype delivered in the coming weeks
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014

26. Conclusion Magnet design Prototyping DL, DQ and quads are challenging
Magnetic design stabilized for all the magnets
Engineering design well advanced
Prototyping
DL prototype measurements in progress
Manufacturing of 85 T/m quadrupole prototype in progress
Octupole prototype delivered soon
G. Le Bec et al. -- Low Emittance Rings workshop, Frascati, 2014