A DDBA lattice upgrade of the Diamond ring

A DDBA lattice upgrade of the Diamond ringA 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 Insitituteand

*Diamond Light Source** ASTeC/Cockcroft Institute

3rd Low Emittance Ring WorkshopOxford, 8 July 2013

OutlineOutline

• Diamond upgrade plansMBAs options consideredTools used for optimisationDDBA lattice and its evolution

• Cell2 modification for VMX beamlineAP and ID performanceDesign 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


Emittance in 3Emittance in 3rdrd GLS, DR and B-factories GLS, DR and B-factories

Transverse coherence requires small emittanceDiffraction limit at 0.1 nm requires 8 pm

4

~ 2013

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fluxbrilliance

2ph

2exx ,

2ph

2exx ',''

2xxxx )D(

2xxxx D )'('

4

Luph

uph L

'

?

MAX IV 7BA 3 GeV 320 pm 500 mA SS length 5m DA 7mm w/errors

Sirius 5BA w/superbend

3 280 500 5m & 6m 5 mm w/errors

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 Phase II

7BA 6 130 200 5m 10 mm

SOLEIL QBA w/longit.. gradient dipole

2.75 980 (220)

500 Robins. Wiggler + beam adapter

Diamond mod. 4BA, 5BA, 7BA

3 45-300 300 5m & 7 m 2 mm

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

Survey of low emittance lattices (Beijing Nov. 2012)

Lattice design at DiamondLattice design at Diamond

• Initial criteria

Reuse tunnel and beamlinesReuse as much hardware as possiblePhased 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



Early studies with MBAs


Original DBA

0 5 10 15 20X[m]

-8

-6

-4

-2

0

2

4

6

8

10

Y[m]

5BA

5BA and 7BA fitting Diamond cell length5BA and 7BA fitting Diamond cell length

Original DBA

0 5 10 15 20X[m]

-8

-6

-4

-2

0

2

4

6

8

10

Y[m]

7BA

5BA optimisation5BA optimisation

Driving term compensation after 4 cells

Fourth order and detuning terms much harder to compensate

MOGA sumDiff + sumRDTs using harmonic sextupoles; chromaticity (2,2)

DA optimisationDA optimisation


The optimisation of the DA and lifetime is an iterative process that involves

Linear optic matching and working point selectionRDT analysis, FM and detuning curve checkMOGA

DA achieved (WIP) 4BA DA 5 mm5BA DA 3.5 mm7BA DA 1 mm

IBS emittance blow-up as a function of stored current coupling 10% 900 bunches – computed with elegant

4BA H emittance

IBS emittance increaseIBS emittance increase


5BA H emittance 7BA H emittance

4BA lattice 265 pm 280 pm @ 300 mA relative increase 6%



300 mA 300 mA 300 mA


4BA


• 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-IIA 4BA lattice for Diamond-II

0 5 10 15 20X[m]

-8

-6

-4

-2

0

2

4

6

8

10

Y[m]

original DBA cell


This lattice combines the ideas of doubling the capacity of the ring with the low emittance

Parameters Modified 4BA

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 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

A 4BA lattice for Diamond-IIA 4BA lattice for Diamond-II


Optimisation (I): driving termsOptimisation (I): driving terms

Qx: 4.5 /cellQy: 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 1st order RDTsChromaticity set to (2,2): detuning terms still large; higher order resonances still large


DA still below 5 mm – under optimisation

Optimisation (II): Multi-objective GA for DAOptimisation (II): Multi-objective GA for DA



One (or more) modified 4BA cells in the present lattice

(to be called DDBA)


One DDBA cell in the existing latticeOne 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


Cell 2 upgrade for VMXi-VMXmCell 2 upgrade for VMXi-VMXm

VMXm VMXi


ID performanceID performance

(courtesy EL)

VMXi moved from the side branch to the middle of the straight 2

2 m U21 in-vac0.7 m U30 ex-vac


Ring optics with and without the DDBA cell in cell2Ring optics with and without the DDBA cell in cell2


Parameters

Emittance [m-rad]

Tune x Tune y ChromaticityLifetime [h]

2.5e-9 28.18 13.29

2,227 (29)

One DDBA: dynamic aperture and lifetime with MOGAOne DDBA: dynamic aperture and lifetime with MOGA


Fight for space 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


Saving space: merging quads Saving space: merging quads

0 5 10 15 20X[m]

-6

-4

-2

0

2

4

Y[m]

3m3.35m3.35m

4BA_1

OriginalDBA

0 5 10 15 20X[m]

-8

-6

-4

-2

0

2

4

6

8

10

Y[m]

3.35m3 m

3.35m4BA_2

4BA_33.2m

3.4m 3.35m3.35m


Fight for space: Fight for space: 9cm H/V embedded correctors


Saving space: reducing flexible taper length Saving space: reducing flexible taper length


(half) DDBA cell(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 cm50 T/m2

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


Magnets for USR (Beijing November 2012)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/mESRF 100 T/mSpring8-II 80 T/mBAPS 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/m2ESRF- 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 cmApertures = 20-26 mm diameter in arcs MAX IV inner diam. 22 mm


Ring optics with and without two DDBA cellsRing optics with and without two DDBA cells


Parameters

Emittance [m-rad]

Tune x Tune y ChromaticityLifetime [h]

2.55e-9 29.1813.30

2,28.2 (23.h)

Two DDBAs: dynamic aperture and lifetime with Two DDBAs: dynamic aperture and lifetime with MOGAMOGA


ConclusionsConclusions

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.


Documents

A DDBA lattice upgrade of the Diamond ring