1. Plans for Diamond-II ESLSXX Workshop, Bessy II, 19 November 2012 R. Bartolini Diamond Light Source and John Adams Institute for Accelerator Science University of Oxford

2. Brilliance improvement for Diamond reduced coupling 1%  0.3% 300 mA  500 mA reducing diamond emittance with present hardware 2.7 nm  2.1 nm lattice test – ongoing: issues with SCWs Initial studies for an ultra low emittance lattice for Diamond-II 5BA 7BA, and modified 4BA Thanks to T. Pulampong, R. Walker, J. Kay and N. Hammond Brilliance upgrade at Diamond ESLSXX Workshop, Bessy II, 19 November 2012

3. Emittance in 3 rd GLS, DR and B-factories Transverse coherence requires small emittance Diffraction limit at 0.1 nm requires 8 pm ~ 2012 ?

4. upgrade with Diamond-II (200pm): 300mA and 1%K Brilliance plot using U27 – 72 periods 2 m long with Kmax = 2.02 10 mm gap Tuning curves computed with Spectra 8.0 Assuming the operation with a 200pm lattice ESLSXX Workshop, Bessy II, 19 November 2012

5. Low emittance design for a Diamond-II upgrade (WIP) Wishlist for the upgrade of an existting medium size machine emittance lower than 200 pm in baseline (at least a factor 10 better than now) minimal changes to the machines Leave the straight section as they are reuse grider and/or magnets if possible beamline remains where they are (no offset or angle) avoid long interruptions. find options that can be phased... realistic engineering constraints (next…) ESLSXX Workshop, Bessy II, 19 November 2012

6. Engineering constraints on lattice design Magnet and geometric constraints quadruple gradient (100T/m) MAX IV has 40.4 T/m quadrupoles in dipoles (30 T/m)MAX IV has 8.68 T/m sextupoles (7000 T/m 2 )MAX IV has 2*2216 T/m 2 space between magnets (hard edge) 10 cm MAX IV has 7.5 cm Apertures = 20 mm diameter in arcsMAX IV inner diam. 22 mm ESLSXX Workshop, Bessy II, 19 November 2012

7. 5BA – 140 pm

8. 5BA cell 14 quads per cell 14 sextupoles 10 cm distance Straight section length slightly reduced 11 m  9.5 m 8.3 m  6.5 m Optics matched and optimised with MOGA (quads vs emittance) ESLSXX Workshop, Bessy II, 19 November 2012

9. Parameters Total length Natural emittance Natural chromaticity : hor./ver. Straight length : long/short 561.6 m 142.5 pm-rad -152/-53 9.5 m/ 6.5 Chrom(0,0) S7X:SEXT,L=0.1,K2=786.45 S7Y:SEXT,L=0.2,K2=-703.26 Gradient in bend < 15 T/m Quads gradient < 55 T/m

10. 5BA sextupoles compensation 5 pi horizontal phase advance each cell, 5 pi vertical phase advance every two cells 5π5π 5π5π ESLSXX Workshop, Bessy II, 19 November 2012

11. Some 5BA solutions from MOGA (WIP) 2 mm DA Optimisation just started Large tuneshift with amplitude to be compensated ESLSXX Workshop, Bessy II, 19 November 2012

12. Driving terms analysis (WIP) Chormatic sextupoles only – no harmonic sextupoles with harmonic sextupoles

13. Issue with path length and alignment of straights Keeping the same circumference (same RF and harmonic number) generates an offset in the position of the straight sections. This will require offsetting the beamlines – 1 cm is deemed acceptable ESLSXX Workshop, Bessy II, 19 November 2012

14. M. Borland quoting B. Hettel @ USR WS “if you can inject off-axis you have not pushed your lattice hard enough” 7BA – 45 pm

15. 7BA - giving up more straight section length V and H sextupoles in dispersion bump only 14 quads per cell 8 Sextupoles per cell 10 cm distance Straight section length slightly reduced 11 m  8.0 m 8.3 m  5.0 m ESLSXX Workshop, Bessy II, 19 November 2012

16. 7BA – 45 pm emittance Parameters Total length Natural emittance Natural chromaticity : hor./ver. Straight length : long/short 561.6 m 45.7 pm-rad -348/-118.7 8.0 m/ 5.0 m S7X: SEXT,L=0.3,K2=248.9 S7Y: SEXT,L=0.3,K2=-325.6 Chromatic Sextupoles (0,0) Gradient in bend < 30 T/m Quads gradient <100 T/m

17. doubling the number of beamlines while still pushing the emittance down Modified 4BA - 320 pm 4BA with an additional short straight section between the dipole pairs emittance not pushed as for a pure 4BA but can double the number of straight sections Length of additional straight sections forced to be at least 3 m while keeping the remaining 6.7 m and 9 m straight sections

18. Modified 4BA cell Broken the 4 BA cell to leave 3 m space 12 quads per cell 10 Sextupoles per cell 10 cm distance Straight section length slightly reduced 11 m  9.7 m 8.3 m  6.7 m ESLSXX Workshop, Bessy II, 19 November 2012

19. Modfied 4BA – one superperiod Ring circumference shrinks from 561.6 to 561.0 -> loss 1 harmonic of RF Parameters Total length Natural emittance Natural chromaticity : hor./ver. Straight length : long/short/middle 561.0 m 314.7pm-rad -146.7/-85.6 9.7/6.7/3 Gradient in bend < 15 T/m Quads gradient < 70 T/m

20. 4BA 561m footprint comparison with the existing ring Δ: 12.07 cm Δ: 0.19 cm Δ: 0.39 cm Current Diamond Modified 4BA

21. MOGA optimisation for DA just started Revising also tune point 12 quadrupoles per cell 10 sextuples per cell 1 mm DA insufficient (WIP) ESLSXX Workshop, Bessy II, 19 November 2012

22. 5BA c oupling 10% rms bunch length @ 0mA 1.8 mm Emittance blow up with IBS ESLSXX Workshop, Bessy II, 19 November 2012 7BA coupling 10% rms bunch length @ 0mA 1 mm Emittance blow up for the modified 4BA (280 pm) less important (300pm 500 mA) coupling 10% rms bunch length @ 0mA 1.8 mm

23. 4 wires pulsed kicker magnet for Diamond Cross section of 4 wires pulsed kicker with the generated B field Provide Flat field for both injected and stored beam Long straight septum Injected beam Matching cell PM A pulsed kicker magnet can be used for beam injection instead of conventional 4 kicker magnets 15mm 14mm Injected beam stored beam Copper wire More simple for operation and maintenance. Much smaller perturbation kick on the stored beam (good for top-up mode). Require smaller space of just one kicker magnet of ~ 40 mm long. Horizontal magnetic field Thanks to P. Kuske and O. Dressler

24. Multi-turn tracking shows a beam injection efficiency >98% if the kicker is located at the end of straigth 2 1 st turn 2 nd turn 3 rd turn 4 th turn 5 th turn Acceptance Tracking studies of injection with a pulsed kicker Tracking with kicker magnet turned only on the first turn The injected beam can be kicked inside the machine’s acceptance Injection position Injected beam after 5turns Injected beam ESLSXX Workshop, Bessy II, 19 November 2012

25. Effect on the stored beam Pusled quadrupole kicker4wires pusled multipole kicker The stored beam at the position of pulsed multipole kicker 4wires pulsed multipole provides flat field at the position of the stored beam Tracking results show no perturbation on the stored beam.

26. ESLSXX Workshop, Bessy II, 19 November 2012 Conclusion and (some) open issues Leaving straight sections as they are looks very complicated. No space: the straight section must be slightly shortened 5BA, 6BA, 7BA and a less aggressive design with more beamlines (4BA – modified) are under investigation DA and lifetime studies crucial for all such designs Alternative injection schemes are under study Collective effects, Harmonic Cavity for bunch lengthening, round beams to be studied phase out installation strategy to avoid long interruptions still to be found.. However the subject is now seriously tackled by a large community, some rings are already solved (PEP-X at 10 pm) and new solutions will likely appear. Benefits from this worldwide effort are foreseeable.