1. BROOKHAVEN SCIENCE ASSOCIATES Abstract Magnet Design Workshop: Magnet Design and Analysis Charles Spataro, NSLS-II Project NSLS-II is a new 3Gev synchrotron light source designed to deliver state-of-the-art emittance with top-off operation for constant output. This presentation documents the magnet design challenges and choices as well as methodology and studies undertaken during the magnet design phase. Also described are a number of the problems encountered and solved from prototyping to full production of the almost one thousand magnets that comprise the storage ring. *Work performed under auspices of the United States Department of Energy, under contract DE-AC02- 98CH10886

2. BROOKHAVEN SCIENCE ASSOCIATES Charles Spataro Magnet Workshop Magnet Design/Analysis 2 NSLS-II Magnet Workshop, April 11-12, 2012

3. BROOKHAVEN SCIENCE ASSOCIATES Magnet Design/Analysis Outline Magnet Design Choices/Challenges Magnet Studies/Chamfering Problems Encountered and Solved. Quadrupole Fast CorrectorDC Corrector ID Corrector Sextupole Dipole 3 NSLS-II Magnet Workshop, April 11-12, 2012 3

4. BROOKHAVEN SCIENCE ASSOCIATES Magnet Design Challenges The Goal To design a magnet that can be built with current techniques, meets the harmonic specification, is reliable and reproducible, be manufactured for a low cost and fast as possible with minimal running costs and maintenance. 4 NSLS-II Magnet Workshop, April 11-12, 2012 4

5. BROOKHAVEN SCIENCE ASSOCIATES Design Considerations NSLS-II Magnet Workshop, April 11-12, 2012 5 Power Vacuum chamber Beam optics Cooling Manufacturability Field quality Physical space Capital costs Running Costs Survey Magnet Design First Article or Prototype 5

6. BROOKHAVEN SCIENCE ASSOCIATES Magnet Design Challenges What can be designed is different then what can be built-especially pole shape. Space limitations and tight harmonic specifications is what drove the need for very tight machining and assembly tolerances on the order of 10-20 microns. 6 NSLS-II Magnet Workshop, April 11-12, 2012 6

7. BROOKHAVEN SCIENCE ASSOCIATES Magnet Design -Choices Harmonic Specification Build to print vs harmonic specification Steel quality Physical size/Aperture size Ratio Good field radius/aperture radius Machining methods Magnet type-single vs combined function Magnet shape dipole- curved or straight Magnet type- C vs H Assembly choice- 2, 4, 6 lamination construction Power supply limits Mechanical constraints 2D/3D Design Software Material choices 7 NSLS-II Magnet Workshop, April 11-12, 2012 7

8. BROOKHAVEN SCIENCE ASSOCIATES Building to Harmonic Specification Pros: Allows innovative design from various manufacturers to be incorporated in final design. Do not have to accept magnets that do not meet harmonic spec resulting in a better performing machine. Cons: Manufacturers need ability to measure harmonics Differences between manufacturer and BNL measurements. More BNL design involvement from first article through production 8 NSLS-II Magnet Workshop, April 11-12, 2012 8

9. BROOKHAVEN SCIENCE ASSOCIATES Assembly Choice 2 Piece vs 4 Piece Lamination Smaller assembly errors Easier to align Harder for coil installation Limited shimming Larger assembly errors Harder to align Easier coil installation Shim broader range of harmonics 2 Piece lamination4 Piece lamination 9 NSLS-II Magnet Workshop, April 11-12, 2012 9

10. BROOKHAVEN SCIENCE ASSOCIATES Magnet Design Software Software choices dependent on cost, desired accuracy, and calculation time. 2D vs 3D Calculations. Finite Element vs Finite difference analysis. Examples: Tosca, Poisson,Mermaid, Radia, Roxie. Expensive software does not necessarily generate the best solution. User knowledge and experience is key. RadiaMermaid OperaPoissonRoxie 10 NSLS-II Magnet Workshop, April 11-12, 2012 10

11. BROOKHAVEN SCIENCE ASSOCIATES Magnet Design Choices: Linear vs Non-Linear Analysis Non-Linear modeling: Accurate modeling of magnetic models. Long meshing time and long solve time. Linear modeling: Inaccurate modeling of fields, saturation,etc. Short solve time. May be suitable in some cases for first pass/quesstimate. Key to robust, accurate design Should include key design concerns such as: Linear vs non-linear analysis, Packing factor, saturation,mesh size, material choices 11 NSLS-II Magnet Workshop, April 11-12, 2012 11

12. BROOKHAVEN SCIENCE ASSOCIATES Linear vs Non-Linear Analysis Linear analysis can lead to huge problems later on (saturation, incorrect fields, etc.) Non-Linear analysis helped determine that some quad magnets were undersized- additional iron thickness and length were added to create a more robust design. You can never have too much iron! 12 NSLS-II Magnet Workshop, April 11-12, 2012 12

13. BROOKHAVEN SCIENCE ASSOCIATES 66 mm Quadrupole – Linear Materials No saturation at poles and a field of 18.2 T !! 13 NSLS-II Magnet Workshop, April 11-12, 2012 13

14. BROOKHAVEN SCIENCE ASSOCIATES 66 mm Quadrupole – Non-Linear Materials Saturation at pole tip edges and a field of only 3.3T 14 NSLS-II Magnet Workshop, April 11-12, 2012 14

15. BROOKHAVEN SCIENCE ASSOCIATES Magnet Manufacturer Program Support Conclusion: BNL magnet design support critical to success of magnet production 15 NSLS-II Magnet Workshop, April 11-12, 2012 15

16. BROOKHAVEN SCIENCE ASSOCIATES Multipole Harmonic Specification- Choices Made Single function magnets (ie, no corrections coils). Magnets were built to Harmonic Specification. Aperture and good field region radius determined by ring location. R= 25mm for 66mm Quad and 68 mm sextupole. Low dispersion region. R=30mm for 90mm quadrupole and 76 mm sextupole high dispersion region. Two-piece lamination was chosen. 1006 steel was specified. 16 NSLS-II Magnet Workshop, April 11-12, 2012 16

17. BROOKHAVEN SCIENCE ASSOCIATES Magnet Chamfering/Shimming Sextupole-Shimming of center poles used to control b1 and b5 harmonic Quadrupole- Shimming of side blocks used to control b3,b4 Shim 17 NSLS-II Magnet Workshop, April 11-12, 2012 17

18. BROOKHAVEN SCIENCE ASSOCIATES Fine Tuning of Harmonics Through Chamfering Pole Chamfers Tip Chamfer There are two different types of chamfers: Pole and Tip for control of b6 in the quadrupole and and b9 in the sextupole. 18 NSLS-II Magnet Workshop, April 11-12, 2012 18 Tip chamfer Increases b6 in the quadrupole or b9 in the sextupole. Pole chamfer- Decreases b6 in the quadrupole or b9 in the sextupole

19. BROOKHAVEN SCIENCE ASSOCIATES Dipole Matching Chamfering Method A straight chamfer across the edge of the nose is used to tune the sextupole term. An angled chamfer across the edge of the nose is used to tune the quadrupole term. 19 NSLS-II Magnet Workshop, April 11-12, 2012 19

20. BROOKHAVEN SCIENCE ASSOCIATES Perturbation Study: Machining and Assembly Errors

21. BROOKHAVEN SCIENCE ASSOCIATES 68 mm Sextupole 2D Perturbation Study

22. BROOKHAVEN SCIENCE ASSOCIATES 35 mm Dipole Studies Nose & 50mm Solid Plate & 1mm Short Shim

23. BROOKHAVEN SCIENCE ASSOCIATES Dipole Studies

24. BROOKHAVEN SCIENCE ASSOCIATES Dipole Studies Best Option:75mm Solid Block + < 1mm Shim Solution: Leave the dipole nose as is Best Option

25. BROOKHAVEN SCIENCE ASSOCIATES Sextupole Chamfer: b9 Experimental vs Calculated

26. BROOKHAVEN SCIENCE ASSOCIATES Magnet Problems Encountered and Solved: Limited Axial Space Problem: ID Corrector with a 45 mm yoke length and 84mm overall length with only 90 mm of space available in lattice. Initial design used water cooled coils but current was too high and voltage too low. Solution: Use smaller conductor to increase coil length and use chill plates instead of water-cooled conductor. 90 mm 26 NSLS-II Magnet Workshop, April 11-12, 2012 26 Chill plates

27. BROOKHAVEN SCIENCE ASSOCIATES Magnet Problems Encountered and Solved: 66mm Quadrupole Saturation Problem: Saturation led to a large variation of the b6 harmonic with current.

28. BROOKHAVEN SCIENCE ASSOCIATES Quad Lengthening Study

29. BROOKHAVEN SCIENCE ASSOCIATES Magnet Problems Encountered and Solved 66mm Quadrupole Saturation Problem: Saturation led to a large variation of the b6 harmonic with current. Solution: Increased yoke length and backleg thickness created a more robust design. In one case, the baseplate was dug out so the backleg could be increased. 29 NSLS-II Magnet Workshop, April 11-12, 2012 29

30. BROOKHAVEN SCIENCE ASSOCIATES Magnet Problems Encountered and Solved: a3 Current Dependency Problem: a3 harmonic in the quadrupoles became current dependent due to a top-down asymmetry. Solution: Stainless steel or aluminum shim 3 mm thick was installed between baseplate and yoke. Shim 30 NSLS-II Magnet Workshop, April 11-12, 2012 30

31. BROOKHAVEN SCIENCE ASSOCIATES Magnet Problems Encountered and Solved: a3 Current Dependency

32. BROOKHAVEN SCIENCE ASSOCIATES Magnet Problems Encountered and Solved b6 Too large after tip Chamfering Problem: The tip chamfer on a quadrupole was machined incorrectly for a number of yokes which pushed the b6 harmonic out of specification. Solution: A 1.5 mm pole chamfer was added to the existing radial chamfer to drive b6 well into specification. Pole chamfer 32 NSLS-II Magnet Workshop, April 11-12, 2012 32

33. BROOKHAVEN SCIENCE ASSOCIATES Magnet Problems Encountered and Solved: Variation in 35mm Dipole Field Problem: A large periodic variation was found in the dipole field. Solution: Modeling led to the conclusion that it was caused by the gap between the top yoke plate and laminations and the bolt holes at 250 mm intervals in the top plate. The variation was deemed ok by the Physics group. Holes in top Plate 33 NSLS-II Magnet Workshop, April 11-12, 2012 33

34. BROOKHAVEN SCIENCE ASSOCIATES Problem: Higher fields in dipole laminations. Solution: Top, bottom and back plates changed from mild steel to 1006 steel to redistribute flux. Magnet Problems Encountered and Solved Too High fields in 35 mm Dipole Yoke Very little flux in the mild steel plate Note flux in 1006 plate Mild Steel Plates1006 Plates 34 NSLS-II Magnet Workshop, April 11-12, 2012 34

35. BROOKHAVEN SCIENCE ASSOCIATES Conclusion Magnet design support is not finished until all magnet manufacturing issues are resolved. And it still continues to this day...