Diamond upgrade R Bartolini Diamond Light Source and
Diamond upgrade R. Bartolini Diamond Light Source and John Adams Institute for Accelerator Science University of Oxford Advanced Optics Workshop CERN, 5 February 2015
Outline • Motivation and 10 -years vision • low emittance options MBA DDBA • Optics challenges • Conclusions Advanced Optics Workshop CERN, 5 February 2015
Motivations Diamond operates since 2007 with nominal parameters • 2. 7 nm H emittance (top of the league in 2007) • 300 m. A • 8 pm V emittance (since 2010) However: – 2010 Petra-III was commissioned 1 nm H emittance – 2011 -12 SLS and ASP ~1 pm V emittance (best achieved) – 2012 ESRF et al. operate with 8 pm V emittance or less – 2013 ALS upgraded to a 2 nm H emittance lattice – 2014 NSLS-II started operation 0. 5 nm H emittance – 2014 Petra III has tested a 160 pm lattice at 3 Ge. V – 2016 MAX IV 300 pm H emittance lattice – 2019 ESRF II 140 pm H emittance lattice Advanced Optics Workshop CERN, 5 February 2015
10 years vision @ Diamond ü Stability improvements over 1 -1 k. Hz ü IDs development (CPMU, Superconducting undulators) ü Higher current and collective effects ü Short pulses ü Tailored straight sections – broken symmetry ü Lower emittance for diffraction limited rings Advanced Optics Workshop CERN, 5 February 2015
Survey of low emittance lattices Advanced Optics Workshop CERN, 5 February 2015
Lattice design at Diamond Original DBA 7 BA Nonlinear dynamics 7 BA lattice 5 BA lattice 45 pm 140 pm 270 pm DA achieved (WIP) 7 BA DA 1 mm 5 BA DA 3. 5 mm 4 BA DA 5 mm Fourth order and detuning terms very harder to compensate Not enough freedom to set the cell phase advance as needed IBS emittance 7 BA 5 BA 45 pm 90 pm @ 300 m. A relative increase 100% 140 pm 180 pm @ 300 m. A relative increase 30% 270 pm 280 pm @ 300 m. A relative increase 5%
IBS emittance increase IBS emittance blow-up as a function of stored current coupling 10% 900 bunches – computed with elegant 4 BA H emittance 5 BA H emittance 300 m. A 7 BA H emittance 300 m. A 4 BA lattice 265 pm 280 pm @ 300 m. A relative increase 5% 5 BA lattice 140 pm 180 pm @ 300 m. A relative increase 30% 7 BA lattice 45 pm 90 pm @ 300 m. A Advanced Optics Workshop CERN, 5 February 2015 relative increase 100%
A 5 BA lattice for Diamond-II upgrade A 140 pm lattice for a ~20 -fold decrease in emittance Energy [Ge. V] Circumference [m] Tune: h/v Beam current [A] Coupling, % Emittance: x, y [pm·rad] Bunch length [mm] Energy spread (rms) Momentum compaction Damping time: x/y/s [ms] Natural chromaticity: x/y Energy loss per turn [Me. V] RF voltage [MV] RF frequency[MHz] Length of ID straight [m] @ ID centre (long, short): x/y [m] 3. 0 561. 6 55. 32/26. 62 300 10% 141. 8 0. 731× 10 -3 0. 000122 17. 23/26. 16/17. 65 -152/-53 0. 42964 2. 5 500 4× 9. 5, 18× 6. 5 8. 76/5. 62 , 4. 33/1. 92 DA 3. 5 mm preliminary studies – not bad for the amount of work done on 5 BA Advanced Optics Workshop CERN, 5 February 2015
A modified 4 BA (DDBA) lattice for Diamond-II This lattice combines low emittance with doubling the capacity of the ring DLS will produce a Conceptual Design report for Diamond II ~2016 The modified 4 BA is a strong candidate Advanced Optics Workshop CERN, 5 February 2015
One superperiod for Diamond-II Parameters Modified 4 BA Circumference [m] 561. 0 Emittance [pm. rad] 275 Tune Point [Qx / Qy] 50. 76/18. 36 Chromaticity(ξx / ξy) -128/ -94 straight sections [m] 9. 1 / 6. 7 / 3. 2 Momentum compaction Bunch length [mm] Energy spread (rms) Damping time h/v/s [ms] Energy loss/turn [Me. V] Advanced Optics Workshop CERN, 5 February 2015 1. 02 e-04 1. 77 7. 94 e-4 14. 78/19. 60/11. 70 0. 573
Issues with cell design Original DBA 3. 35 m 3. 35 m • • • 3 m 4 BA_1 3 m 4 BA_2 3. 2 m 4 BA_3 3. 4 m 3. 35 m H phase advance is ~2 *0. 8 3. 35 m Longer mid-cell straight section from 3 m to 3. 4 m for IDs – longer is unfeasible Hard to control phase advance between the chromatic sextupoles Increases dispersion at chromatic sextupoles removed sextupoles in the new straight Optimized magnets positions and length avoiding coil/support clashes
Maintain customised optics (I 09 – I 13) (WIP) • introduced quadrupole doublet + additional quads in long straight sections • reduced vertical beta functions to allow two independent lines with in-vac IDs • additional horizontal focussing allows photon focus down the beamline • no other machine implemented two such customised optics Advanced Optics Workshop CERN, 5 February 2015
Optimisation of beam dynamics Advanced Optics Workshop CERN, 5 February 2015
Optimisation of beam dynamics Advanced Optics Workshop CERN, 5 February 2015
MOGA optimisation for DA and lifetime (4 BA) Nonlinear beam dynamics optimised mostly with MOGA and resonance driving terms compensation DA still under optimisation - ~5 mm (WIP) Touschek lifetime ~ 7 h without harmonic cavities Advanced Optics Workshop CERN, 5 February 2015
upgrade with Diamond-II (200 pm): 300 m. A and 1%K Brilliance plot using U 27 – 72 periods 2 m long with Kmax = 2. 02 Tuning curves computed with Spectra 8. 0 Advanced Optics Workshop CERN, 5 February 2015
Lattice design at Diamond One (or more) modified 4 BA cells in the present lattice (called DDBA) Advanced Optics Workshop CERN, 5 February 2015
One DDBA cell in the existing lattice Replacing the existing cell 2 with a DDBA cell Ø Introduces an additional straight section (beamline upgrade bending magnet to ID beamline) Ø Serves as a prototype for low emittance lattice upgrade Ø Lots of R&D required (magnet design challenging, vacuum with small apertures, engineering integration, etc) DDBA cell Additional straight Advanced Optics Workshop CERN, 5 February 2015
One DDBA cell in the existing lattice One more beamline (no significant gain in emittance) existing DBA cell modified DDBA cell BM beamline Insertion Device LER 2014 Workshop Frascati, 17 September 2014 ID beamline
Ring optics with and without the DDBA cell in cell 2 red = present lattice black = new lattice with modified cell 2 Optics optimised with very modest perturbation to adjacent straight sections Advanced Optics Workshop CERN, 5 February 2015
One DDBA: dynamic aperture and lifetime with MOGA Parameters Emittance [m-rad] Tune x Tune y Chromaticity Lifetime [h] Advanced Optics Workshop CERN, 5 February 2015 2. 5 e-9 28. 18 13. 29 2, 2 27 (29)
DDBA DA with engineering apertures DA slightly reduced +8 mm -12 mm one DDBA cell +12 mm – 15 mm for the existing machine Injection efficiency ~93% with injection point at -6. 8 mm Touschek lifetime (300 m. A, 686 bunches, 1 % coupling), 16. 5 h one DDBA cell 19. 6 h for the existing machine
Ring optics with three DDBA cells A bid for capital funds for more DDBA cells will be put forward. This will include a 3 HC for bunch lengthening to be located in the third cell Advanced Optics Workshop CERN, 5 February 2015
Main engineering issues • small bore quadrupoles (30 mm diameter to reach 70 T/m) and a rather complex gradient dipole (0. 8 T with 14 T/m) All quads and all sextupoles with the same length and design • much reduced vacuum chamber in the arc now elliptical 29 mm * 20 mm; it was octagonal 84 mm * 38 mm • initial investigation of NEG coating chamber was abandoned too complex geometry for coating no antechamber – systems of localised bumps to absorb radiation and cast downstream shadow • Engineering integration standardisation of magnet lengths (one type of quads and sexts) clashes between elements (space for coils overhang, flanges, …) • Orbit feedback based on a reduce number of fast correctors sitting on SS vessel (avoid eddy current in copper vessel)
Conclusion and open issues Many light source operate with low emittance lattices. Vertical emittance in the 1 -2 pm range are no longer uncommon. New projects aim at reaching diffraction limited rings in Horizontal plane as well. These are based on MBA lattices A modified 4 BA for diamond is under investigation DA and Touschek lifetime studies are crucial. Magnets and apertures design will be at the cutting edge of present R&D. Collective effects (IBS) will limit the stored current to 100 -200 m. A. They might be mitigated by Harmonic Cavity for bunch lengthening. Round beams could help and more R&D is needed. However the subject is now seriously tackled by a large community, some rings are already solved (e. g. PEP-X at 10 pm) and new solutions will likely appear for upcoming projects
Low emittance ring community • ICFA Low Emittance Rings Workshops (Low. ERing) • XDL 2011 Workshops for ERLs and DLSRs, Cornell, June 2011 • Beijing USR Workshop, Huairou, October 2012 • DLSR Workshop, SPring-8, December 2012 • Low Emittance Ring Workshop, Oxford, July 2013 • SLAC DLSR Workshop, SLAC, December 2013 • Workshop on Low Emittance Rings Technology (ALERT 2014), Valencia, 2014 • Low Emittance Rings Workshop (LER 2014), Frascati, September 2014 • DLSR Workshop, Argonne, November 2014 EUCARD 2 – WP 6 workshop on beam dynamics for low emittance ring ALBA , Barcelona, 23 -24 April Advanced Optics Workshop CERN, 5 February 2015
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