A DDBA lattice upgrade of the Diamond ring R. Bartolini, C. Bailey*, - PowerPoint PPT Presentation

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

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

Emittance in 3 rd GLS, DR and B-factories ~ 2013 ? flux            2 2 2 ( D )     brilliance x x x x x x , e ph L u         ph  ' 2 4 ph x x ' y y '  L       2      2 2 4 ( D ' ) u '  x ' x x x x ' x ' , e ph  Transverse coherence requires small emittance    4 Diffraction limit at 0.1 nm requires 8 pm

Survey of low emittance lattices (Beijing Nov. 2012) MAX IV 7BA 3 GeV 320 pm 500 mA SS length 5m DA 7mm w/errors Sirius 5BA 3 280 500 5m & 6m 5 mm w/errors w/superbend Spring-8 6BA 6 67.5 300 4.5m & 27m 3 mm w/errors APS 7BA 6 147 100 Pep-X 7BA 4.5 11 200 5 m 10 mm w/errors ESRF 7BA 6 130 200 5m 10 mm Phase II SOLEIL QBA w/longit.. 2.75 980 500 Robins. Wiggler + gradient dipole (220) beam adapter Diamond mod. 4BA, 3 45-300 300 5m & 7 m 2 mm 5BA, 7BA ALS 5BA - 7BA 2 50-100 500 5 m 2-3 mm BAPS 7BA-15BA 5 50 150 10m & 7m 10 mm w/errors tUSR 7BA 9 3 100 TEV tunnel 0.8 mm

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

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

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

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

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 ) Linear optic matching and working point selection 4BA DA  5 mm RDT analysis, FM and detuning curve check 5BA DA  3.5 mm MOGA 7BA DA  1 mm 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

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 265 pm  280 pm @ 300 mA relative increase 6% 4BA lattice 140 pm  180 pm @ 300 mA relative increase 29% 5BA lattice 45 pm  90 pm @ 300 mA 7BA lattice relative increase 100% 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

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 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

A 4BA lattice for Diamond-II Parameters Modified 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 compaction 1.02e-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 This lattice combines the ideas of doubling the capacity of the ring with the low emittance 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

Optimisation (I): driving terms Cell phase advance adjusted to compensate 1 st 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 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

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

One DDBA cell in the existing lattice Replacing the existing cell2 with a DDBA cell  Introduces an additional straight section DDBA cell (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

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

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

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

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

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

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

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

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

(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 65 T/m 55 T/m 55 T/m 50 T/m 2 15 cm 20 cm 15 cm 20 cm -14 T/m -15 T/m 66cm 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 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

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/m 2 13000 T/m 2) Spring-8 II 7500 T/m 2 BAPS 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 3 rd Low Emittance Ring Workshop Oxford, 8 July 2013

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

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

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