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Abstract

Abstract. Magnet Design Workshop: Magnet Design and Analysis Charles Spataro, NSLS-II Project

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Abstract

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  1. 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. Magnet WorkshopMagnet Design/Analysis Charles Spataro NSLS-II Magnet Workshop, April 11-12, 2012

  3. Magnet Design/AnalysisOutline • Magnet Design Choices/Challenges • Magnet Studies/Chamfering • Problems Encountered and Solved. DC Corrector Fast Corrector Sextupole ID Corrector Quadrupole Dipole NSLS-II Magnet Workshop, April 11-12, 2012 3

  4. 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. NSLS-II Magnet Workshop, April 11-12, 2012 4

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

  6. 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. NSLS-II Magnet Workshop, April 11-12, 2012 6

  7. 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 NSLS-II Magnet Workshop, April 11-12, 2012 7

  8. 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 NSLS-II Magnet Workshop, April 11-12, 2012 8

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

  10. 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. Radia Mermaid Opera Poisson Roxie NSLS-II Magnet Workshop, April 11-12, 2012 10

  11. 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 NSLS-II Magnet Workshop, April 11-12, 2012 11

  12. 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! NSLS-II Magnet Workshop, April 11-12, 2012 12

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

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

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

  16. 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. NSLS-II Magnet Workshop, April 11-12, 2012 16

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

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

  19. 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. NSLS-II Magnet Workshop, April 11-12, 2012 19

  20. Perturbation Study:Machining and Assembly Errors

  21. 68 mm Sextupole 2D Perturbation Study

  22. 35 mm Dipole StudiesNose & 50mm Solid Plate & 1mm Short Shim

  23. Dipole Studies

  24. Dipole StudiesBest Option:75mm Solid Block + < 1mm ShimSolution: Leave the dipole nose as is Best Option

  25. Sextupole Chamfer: b9 Experimental vs Calculated

  26. Magnet Problems Encountered and Solved:Limited Axial Space Chill plates 90 mm 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. NSLS-II Magnet Workshop, April 11-12, 2012 26

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

  28. Quad Lengthening Study

  29. 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. NSLS-II Magnet Workshop, April 11-12, 2012 29

  30. 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 NSLS-II Magnet Workshop, April 11-12, 2012 30

  31. Magnet Problems Encountered and Solved: a3 Current Dependency

  32. Magnet Problems Encountered and Solvedb6 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 NSLS-II Magnet Workshop, April 11-12, 2012 32

  33. 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 NSLS-II Magnet Workshop, April 11-12, 2012 33

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

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

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