1. Design of the magnets for the MAX IV project Martin Johansson, Beam Dynamics meets Magnets-II workshop, Bad Zurzach, 01-04 Dec. 2014

2. MAX IV 3 GeV ring magnets key aspects: Relatively small magnet aperture of Ø25 mm. magnet block concept → integrated unit containing several consecutive magnet elements. Contents of this presentation: 1)The MAX IV facility and its 3 GeV ring magnet design. 2)magnet production U1 3d cad view with yoke bottom and top halves transparent. QFm1 SFm QFm2 x y SD1 SD2 DIP

3. The MAX IV Laboratory ● Currently in construction just outside Lund, Sweden. ● Facility dedicated to synchrotron radiation research. ● MAX I-III (old MAX-lab located in Lund University campus) remains in operation until end of 2015. full energy linac - commissioning in progress 1.5 GeV storage ring - manufacturing in progress 3 GeV storage ring - installation in progress Nov. 7 th, 2014 photo: Perry Nordeng

4. ● linac & transfer lines – various conventional magnet types ● 1.5 GeV ring – integrated magnet block ● 3 GeV ring – integrated magnet blocks MAX IV magnets overview May 13 th 2014 photo: Annika Nyberg

5. The MAX IV 3 GeV ring lattice ● 7 bend achromat consisting of five unit cells and two matching cells. ● 20 identical achromats ● 528 m circumference ● 0.33 nmrad bare lattice emittance ● 940 magnet elements (excl. correctors and trim coils).

6. 3 GeV ring achromat 3d cad assembly: ● Each lattice cell is realized as one mechanical unit containing all magnet elements. M1 U1 U2 U3 U4 U5 M2 ● Each unit consists of a bottom and a top yoke half, machined out of one solid iron block, 2.3-3.4 m long. U3 bottom half being assembled QF4 SFi1 QF3 y x SD2 DIP etc …

7. inside the 3 GeV ring tunnel Nov. 18 th, 2014 photo: Jonny Ahlbäck M1 U1 U2 U3 U4 U5 ● Achromat 14: magnet blocks on support stands awaiting vacuum chamber installation. concrete support stands magnet cabling ● Achromat 13 vacuum chamber installation ongoing.

8. 3 GeV ring magnet block layout Corresponding to the two lattice cell types, matching cell and unit cell, there are two basic magnet block layouts: U2, U3, U4, U5 and M2 are identical/mirror of U1 and M1. M1: U1:

9. Magnet element names, and lengths: Other magnet elements are QF (U2,3,4), SFo (U2,4) and SFi (U3). 100 3 GeV ring magnet block layout x y OXX OXY OYY QFend QDend DIPm SDend x M1: QFm1 QFm2 SFmyx SD1 SD2 DIP U1: 100 250 100 150 12 slices, total = 1.5° 12 slices, total = 3°

10. 2d simulations made from cross sections exported from the magnet block 3d cad models: + SFm, SD, SDend (Ø25 mm), OYY (Ø36 mm), x/y (g = 25 mm). 3 GeV ring magnet elements DIP: -0.524 T, 8.607 T/m DIPm: -0.524 T, 8.622 T/m g=28 mm at x=0 QF: -40.34 T/m QFm: -37.79 T/m QDend: 25.10 T/m QFend: -36.59 T/m Ø25 mm SFi: -2069 T/m 2 Sfo: -1742 T/m 2 Ø25 mm OXY: -65060 T/m 3 OXX: 32394 T/m 3 Ø25 mm

11. Why? Ø25 mm aperture: ● Lattice compactness. Enabled by NEG-coated Cu-vacuum chambers! Magnet block: ● Vibration stablility. ● Ease of installation. ● An alignment concept which is totally outsourced to industry.

12. 3 GeV ring magnet production Background: Production sourced as build to print-contracts for fully assembled and tested magnet blocks, with MAX-lab providing technical specifications and full sets of manufacturing drawings. Suppliers responsible for mechanical tolerances, ±20 µm for the yoke bottom and top blocks (2.3-3.4 m long), and for performing field measurements according to MAX-lab spec. MAX-lab responsible for magnetic field properties! Contracts signed Sept 2011: Danfysik A/S: M1, M2 and U3 = 60 magnet block units. Scanditronix Magnet AB: U1, U2, U4 and U5 = 80 magnet block units.

13. 3 GeV ring magnet production Yoke machining, The two magnet suppliers subcontracted the bottom/top yoke blocks machining to three different CNC machining companies. Mechanical tolerances verified by 3d CMM for all yoke parts.

14. 3 GeV ring magnet production Field measurement, Both suppliers chose to procure both new Hall mapping benches, and new rotating coil systems, Both suppliers chose rotating coil solution of long rotating shaft with several measurement coils longitudinally. Rotating axis

15. 3 GeV ring magnet production Timeline, 2011 Sept.Contracts signed 2012 springstart of yoke machining 2012 Sept.1 st yokes approved 2012 fall1 st magnets assembled 2012/2013 fall/winterfield measurement systems operational 2013 fallcoming into series production phase…

16. Production statistics from suppliers weekly status reports, Yoke machining pace = 1-2 yoke halves/week average Field meas pace = 1 Hall and 1 rot. coil /day possible 3 GeV ring magnet production Danfysik M1, M2 and U3:Scanditronix Magnet U1, U2, U4 and U5:

17. 3 GeV ring magnet production Status Dec. 2014 summarized, Production series was completed summer 2014 Of the 140 3 GeV ring magnet blocks, 137 are delivered. 3 approved magnet blocks remain at suppliers for extra field characterization beyond spec. (Cross talks etc). Installation is ongoing Subsystem tests (installed magnet + ps) will commence Jan. 2015. …

18. 3 GeV ring magnet field meas. results Standard specified field meas. performed for each magnet block, Hall probe: Dipole field map at nom. I Dipole field map at nom. I + pole face strips at max I Quadrupole single transverse lines at nom. I Rotating coil: Quads/6poles/8poles/corr at I = 0, 100, 0 % 6poles/8poles trim coils at max I for each connection mode + extended with more current levels and repeatability tests for a few magnet blocks. with the production the production series completed, we have above listed data for 1320 magnet elements. Some example results follows…

19. 3 GeV ring magnet field meas. results U1,2,4,5 quads spread in strength by rotating coil (160 magnets): max-min ≈ 0.7 % total or ≈ 0.5-0.6 % among inner/outer Expected from mech. tolerance ±25 µm at r = 12.5 mm: ± 0.4 %

20. 3 GeV ring magnet field meas. results U1,2,4,5 SD sextupoles spread in strength by rotating coil (160 magnets): max-min ≈ 1.4 % total or ≈ 1.2 % among inner/outer Expected from mech. tolerance ±25 µm at r = 12.5 mm: ± 0.6 %

21. Examples indicate that spread in strengths agree with expected. 3 GeV ring magnet field meas. results M1,2 OXX/OXY octupoles spread in strength by rotating coil (80 magnets): max-min ≈ 1.2 % total No difference in average strength between OXX and OXY. Expected from mech. tolerance ±25 µm at r = 12.5 mm: ± 0.8 %

22. 3 GeV ring magnet field meas. results U1,2,4,5 DIP spread in integrated gradient by Hall probe (80 magnets): max-min ≈ 0.5 %, similar to quads.

23. Field quality example, rotating coil measured higher order harmonic content for 10 quads: Expected from mech. tolerance ±25 µm at r = 12.5 mm: 10-15 1E-4 error terms in 2d simulations of different “worst case” displacements of poles. 3 GeV ring magnet field meas. results

24. Rotating coil meas, magnetic center offsets to rotating axis by harmonic content feed down: same, subtracting linear fits, shows relative alignment of 4 magnet elements over 675 mm:

25. elem ents length [mm] eval. [pcs] rel. align min [µm] max [µm] RMS [µm] M1,2 4675 39/40 dx-10123 dy-27209 U1,2,4,5 3400 79/80 dx-16124 dy-24306 U34928 20/20 dx-10135 dy-412918 3 GeV ring magnet field meas. results Relative alignment within magnet blocks, statistics for 39 pcs M1/M2, 79 pcs U1,2,4,5, and 20 pcs U3: dy includes rotating shaft sag. MAX IV DDR requirement = 25 µm RMS with 2σ cut-off. Our conclusion: rotating coil measurements indicate that MAX IV magnet block alignment concept works!

26. Thank you for your attention! photo: Annika Nyberg

27. Extra slides …

28. 3 GeV ring magnet block layout Ø25 mm aperture defines minimum distance between elements, Rule of thumb used for MAX IV: min. distance ≈ one pole gap If shorter, fringe fields overlap, destroying field quality. We are at this limit in M1 and M2: U1-5 are more relaxed, 75 mm between SF and adjacent QF. 100 x y OXX OXY OYY QFend QDend DIPm SDend x M1: 250 25 mm

29. … so, one pole gap distance between consecutive elements, does it work? Compare QFend and QDend harmonic content: These two elements see different iron surroundings, difference in n=4 could come from this … But for us this difference is negligible. Ie, our data indicates that in this case one pole gaps distance is enough. 3 GeV ring magnet block layout

30. 3 GeV ring magnet block features ● Dismountable at horizontal midplane. ● all yoke parts = Armco low carbon steel. ● Quad and corrector pole tips mounted over the coil ends. ● 6pole and 8pole magnet halves mounted into guiding slots in yoke block. ● Electrical and water connections located towards storage ringer inner side.

31. 3 GeV ring magnet block features ● 3d cad view from top of U1 magnet block bottom half with vacuum chamber in place: ● Vacuum chamber bolted to magnet block at bpm and two support brackets. ● Vacuum chamber cooling and signal connections located towards outer side.

32. 3 GeV ring magnet block features ● 3d cad view from outer side of M1 magnet block with vacuum chamber in place, on concrete support stand:

33. 3 GeV ring magnet block features ● U1 magnet block with plastic cover removed; view from inner side, where cooling and electrical connections are located: ● Water cooling circuits are separate for bottom and top halves. ● Electrical connections across the midplane has to be disconnected when dismounting top half – bus bars/external cables for main coils and plug in contacts for corr, trim and thermoswitches. top half cooling water inlet bottom half cooling water inlet top half cooling water outlet bottom half cooling water outlet QFm1 terminals QFm2 terminals SFm terminals DIP main coil & pfs terminals shunt board SD1 terminals SD2 terminals trim coils and corrector plug-in contacts Interlock D-sub contacts