1. A DDBA lattice upgrade of the Diamond ring R. Bartolini, C. Bailey*, M. Cox*, N. Hammond*, R. Holdsworth*, J. Kay*, J. Jones**, E. Longhi*, S. Mhaskar*, T. Pulampong, G. Rehm*, R. Walker* John Adams Insititute and *Diamond Light Source ** ASTeC/Cockcroft Institute 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

2. Outline Diamond upgrade plans MBAs options considered Tools used for optimisation DDBA lattice and its evolution Cell2 modification for VMX beamline AP and ID performance Design issues targeting VMX Technical subsystems (requirements, challenges and WIP) magnets (see C. Bailey’s talk on Tuesday) engineering integration (see N. Hammond’s talk on Wednesday) vacuum, RF, diagnostics, … Future work 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

3. Emittance in 3 rd GLS, DR and B-factories Transverse coherence requires small emittance Diffraction limit at 0.1 nm requires 8 pm ~ 2013 ?

4. MAX IV7BA3 GeV320 pm500 mASS length 5mDA 7mm w/errors Sirius5BA w/superbend 32805005m & 6m5 mm w/errors Spring-86BA667.53004.5m & 27m3 mm w/errors APS7BA6147100 Pep-X7BA4.5112005 m10 mm w/errors ESRF Phase II 7BA61302005m10 mm SOLEILQBA w/longit.. gradient dipole 2.75980 (220) 500Robins. Wiggler + beam adapter Diamondmod. 4BA, 5BA, 7BA 345-3003005m & 7 m2 mm ALS5BA - 7BA250-1005005 m2-3 mm BAPS7BA-15BA55015010m & 7m10 mm w/errors tUSR7BA93100TEV tunnel0.8 mm Survey of low emittance lattices (Beijing Nov. 2012)

5. Lattice design at Diamond Initial criteria Reuse tunnel and beamlines Reuse as much hardware as possible Phased installation (avoid long shutdown) Evolution of MBA design Initial low emittance lattice design used standard MBA cells M = 7, 6, 5 and 4 It transpired that a 4BA cell can be modified to introduce an additional straight in the middle of an arc (a generalisation of SOLEIL’s approach * ) while keeping the dispersion small and the emittance small 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

6. Lattice design at Diamond Early studies with MBAs 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

7. Original DBA 5BA 5BA and 7BA fitting Diamond cell length Original DBA 7BA

8. 5BA optimisation Driving term compensation after 4 cells Fourth order and detuning terms much harder to compensate

9. MOGA sumDiff + sumRDTs using harmonic sextupoles; chromaticity (2,2) DA optimisation 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013 The optimisation of the DA and lifetime is an iterative process that involves Linear optic matching and working point selection RDT analysis, FM and detuning curve check MOGA DA achieved (WIP) 4BA DA  5 mm 5BA DA  3.5 mm 7BA DA  1 mm

10. IBS emittance blow-up as a function of stored current coupling 10% 900 bunches – computed with elegant 4BA H emittance IBS emittance increase 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013 5BA H emittance 7BA H emittance 4BA lattice265 pm  280 pm @ 300 mArelative increase 6% 5BA lattice140 pm  180 pm @ 300 mArelative increase 29% 7BA lattice45 pm  90 pm @ 300 mArelative increase 100% 300 mA

11. Lattice design at Diamond 4BA 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

12. Increase dispersion at chromatic sextupoles Optimize magnets positions and length leaving more distance between dipoles (no coil clash) removed sextupoles in the new straight Longer mid-cell straight section from 3m to 3.4 m – longer is unmanageable A 4BA lattice for Diamond-II original DBA cell 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

13. This lattice combines the ideas of doubling the capacity of the ring with the low emittance ParametersModified 4BA Circumference [m]561.0 Emittance [pm.rad]275 Tune Point [Q x / Q y ]50.76/18.36 Chromaticity(ξ x / ξ y )-128/ -94 straight sections [m]9.1 / 6.7 / 3.2 Momentum compaction1.02e-04 Bunch length [mm]1.77 Energy spread (rms)7.94e-4 Damping time h/v/s [ms]14.78/19.60/11.70 Energy loss/turn [MeV]0.573 A 4BA lattice for Diamond-II 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

14. Optimisation (I): driving terms Qx: 4.5 /cell Qy: 0.775*2 /cell 1 superperiod i.e. 4 cells give (2n)pi All first terms cancellation within 1 super period Cell phase advance adjusted to compensate 1 st order RDTs Chromaticity set to (2,2): detuning terms still large; higher order resonances still large 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

15. DA still below 5 mm – under optimisation Optimisation (II): Multi-objective GA for DA 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

16. Lattice design at Diamond One (or more) modified 4BA cells in the present lattice (to be called DDBA) 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

17. One DDBA cell in the existing lattice DDBA cell Replacing the existing cell2 with a DDBA cell  Introduces an additional straight section (bending magnet beamline upgraded to ID beamline)  Serves as a prototype for low emittance lattice upgrade  In line with phased upgrade  Lots of R&D required (magnet design challenging, vacuum with small apertures, engineering integration, etc) Additional straight 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

18. Cell 2 upgrade for VMXi-VMXm VMXm VMXi 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

19. ID performance (courtesy EL) VMXi moved from the side branch to the middle of the straight 2 2 m U21 in-vac 0.7 m U30 ex-vac 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

20. Ring optics with and without the DDBA cell in cell2 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

21. Parameters Emittance [ m-rad] Tune x Tune y Chromaticity Lifetime [h] 2.5e-9 28.18 13.29 2,2 27 (29) One DDBA: dynamic aperture and lifetime with MOGA 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

22. Fight for space A constant priority in the AP design has been the safeguard of the maximum length in the new mid-cell straight section Mid-cell length increased from 3m to 3.2m to 3.4m – 3.5m proved unworkable pushing magnets apart, merging quads corrector magnets with special design coil overhang of magnets Shortening of ID vessel to maximise ID length: e.g. flexible taper length 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

23. Saving space: merging quads 3m 3.35m 4BA_1 Original DBA 3.35m 3 m 3.35m 4BA_2 4BA_3 3.2m 3.4m 3.35m 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

24. Fight for space: Fight for space: 9cm H/V embedded correctors 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

25. Saving space: reducing flexible taper length 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

26. (half) DDBA cell 3.4m mid-cell straight 55 T/m 15 cm 65 T/m 20 cm -14 T/m 66cm -15 T/m 96cm 55 T/m 15 cm 50 T/m 2 20 cm Challenging magnets which require a small bore radius (15mm) but no showstoppers ! Other projects have much more agressive requirements Even if the minimisation of the emittance is not a primary target, the tight control of dispersion and beta functions requires very strong quads 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

27. Magnets for USR (Beijing November 2012) Diffraction limited emittance requires magnets with unprecedented strength in storage ring. High gradient and high precision required quadrupole gradient MAX IV has 40.0 T/m ESRF 100 T/m Spring8-II 80 T/m BAPS50 T/m  USR90 T/m quadrupoles in dipoles MAX IV has 9 T/m ESRF 30 T/m sextupoles MAX IV has 4000 T/m2 ESRF-  USR7000 T/m 2 Spring-8 II 13000 T/m 2) BAPS7500 T/m 2 space between magnets (hard edge) 10 cm MAX IV has 2.5 cm Apertures = 20-26 mm diameter in arcsMAX IV inner diam. 22 mm 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

28. Ring optics with and without two DDBA cells 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

29. Parameters Emittance [ m-rad] Tune x Tune y Chromaticity Lifetime [h] 2.55e-9 29.18 13.30 2,2 8.2 (23.h) Two DDBAs: dynamic aperture and lifetime with MOGA 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

30. Conclusions Diamond is investigating a full ring upgrade for Diamond – II Various MBA options are under analysis. We concentrated on a modified 4BA (DDBA) that doubles the capacity and reduces the emittance by a factor 10. Feasibility studies for the cell2 upgrade to a DDBA cell are promising AP-wise the design is feasible Many technical subsystems prove challenging but no showstoppers have been identified (magnets, vacuum, engineering integration, diagnostics,. …) Benefit for ID performance are noticeable Underpins R&D for the full upgrade. Significant further detailed design is needed, as well as R&D for vacuum vessel fabrication and NEG coating Costing exercise is underway but the project has been fully supported from a technical point of view. 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013