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A DDBA lattice upgrade of the Diamond ring

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.

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A DDBA lattice upgrade of the Diamond ring

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  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 3rd 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 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

  4. 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 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

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

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

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

  10. IBS emittance increase IBS emittance blow-up as a function of stored current coupling 10% 900 bunches – computed with elegant 4BA H emittance 5BA H emittance 7BA H emittance 300 mA 300 mA 300 mA 4BA lattice 265 pm  280 pm @ 300 mA relative increase 6% 5BA lattice 140 pm  180 pm @ 300 mA relative increase 29% 7BA lattice 45 pm  90 pm @ 300 mA relative increase 100% 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

  12. A 4BA lattice for Diamond-II original DBA cell • 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 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

  13. A 4BA lattice for Diamond-II This lattice combines the ideas of doubling the capacity of the ring with the low emittance 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

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

  17. One DDBA cell in the existing lattice 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) DDBA cell Additional straight 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

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

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

  21. One DDBA: dynamic aperture and lifetime with MOGA 3rd 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 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

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

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

  26. (half) DDBA cell Even if the minimisation of the emittance is not a primary target, the tight control of dispersion and beta functions requires very strong quads 55 T/m 15 cm 65 T/m 20 cm 55 T/m 15 cm 50 T/m2 20 cm -14 T/m 66cm -15 T/m 96cm 3.4m mid-cell straight Challenging magnets which require a small bore radius (15mm) but no showstoppers ! Other projects have much more agressive requirements 3rd 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 BAPS 50 T/m  USR 90 T/m quadrupoles in dipoles MAX IV has 9 T/m ESRF 30 T/m sextupoles MAX IV has 4000 T/m2 ESRF- USR 7000 T/m2 Spring-8 II 13000 T/m2) BAPS 7500 T/m2 space between magnets (hard edge) 10 cm MAX IV has 2.5 cm Apertures = 20-26 mm diameter in arcs MAX IV inner diam. 22 mm 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

  29. Two DDBAs: dynamic aperture and lifetime with MOGA 3rd 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. 3rd Low Emittance Ring Workshop Oxford, 8 July 2013

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