1. Update on Diamond II and DDBA upgrade
R. Bartolini
Diamond Light Source
and
John Adams Institute, University of Oxford
LER 2014 Workshop Frascati,
17 September 2014

2. Outline Diamond “10-years plan” Options for Diamond II (DDBA – 5BA)
Challenges in design and technology
The DDBA single cell programme
Other requests and conclusions
LER 2014 Workshop Frascati,
17 September 2014

3. Diamond perspective
Diamond operates since 2007 with nominal parameters
2.7 nm H emittance (second best behind APS)
300 mA reached in 2008
8pm V emittance in 2012 (2 pm world record in fall 2009)
However:
2010 Petra-III was commissioned  1 nm H emittance
SLS and ASP ~1 pm V emittance (best achieved)
2012 ESRF et al. operate with 8pm V emittance
2013 ALS upgraded to a 2 nm H emittance lattice
2014 NSLS-II started operation  0.5 nm H emittance
2014 ASP claimed the quantum limit V emittance 0.35 pm
2014 Petra III has tested a 160 pm lattice at 3GeV
2016 MAX IV 300 pm H emittance lattice
2019 ESRF II 140 pm H emittance lattice
LER 2014 Workshop Frascati,
17 September 2014

4. Survey of low emittance lattices
Diamond (561.6 m)
Present emittance 2.75 nm
Target emittance < nm
LER 2014 Workshop Frascati,
17 September 2014

5. 10 years plan – (WIP)
Priorities identified to remain competitive in the next 10 years
Diamond II
develop the science case and the technical design study
DDBA upgrade of one cell (possibly two)
Reliability
RF improvement: SS amplifiers (options for NC cavities)
Photon beam stability (> 100 Hz ~1kHz)
electron beam stability and photon stability at the sample
Higher current (> 300 mA) with Harmonic Cavity
Development of SCU (with ASTeC and STFC TD)
LER 2014 Workshop Frascati,
17 September 2014

6. Lattice design at Diamond
Original DBA
7BA
DA achieved (WIP)
7BA DA 1 mm
5BA DA 3.5 mm
4BA DA 5 mm
7BA lattice 45 pm
5BA lattice 140 pm
4BA lattice 270 pm
Nonlinear dynamics
Fourth order and detuning terms very harder to compensate
Not enough freedom to set the cell phase advance as needed
7BA 45 pm  mA relative increase 100%
5BA 140 pm  mA relative increase 30%
4BA 270 pm  mA relative increase 5%
IBS emittance 6

7. A 5BA lattice for Diamond-II upgrade
A 140pm lattice for a ~20-fold decrease in emittance
Energy [GeV]
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 [MeV]
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
1.8
0.731×10-3
17.23/26.16/17.65
-152/-53
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 5BA
LER 2014 Workshop Frascati,
17 September 2014

8. A modified 4BA (DDBA) lattice for Diamond-II
Longer mid-cell straight section from 3 m to 3.4 m – longer is unmanageable
Increase dispersion at chromatic sextupoles
Optimize magnets positions and length leaving more distance between dipoles (no coil clash, space for flanges, bellows, tapers, …)
removed sextupoles in the new straight
LER 2014 Workshop Frascati,
17 September 2014

9. Issues with cell design
H phase advance is ~ 2*0.8
Optic function tailored to add one more in-vacuum ID in the mid straight
Hard control of phase advance between chromatic sextupoles
LER 2014 Workshop Frascati,
17 September 2014

10. One superperiod for Diamond-II
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
This lattice combines the ideas of doubling the capacity of the ring
with the low emittance
LER 2014 Workshop Frascati,
17 September 2014

11. MOGA optimisation for DA and lifetime (4BA)
Nonlinear beam dynamics optimised mostly with MOGA and resonance driving terms compensation
DA still under optimisation - ~5 mm (WIP)
Touschek lifetime ~ 7h without harmonic cavities
LER 2014 Workshop Frascati,
17 September 2014

12. upgrade with Diamond-II (200pm): 300mA and 1%K
Brilliance plot using U27 – 72 periods 2 m long with Kmax = 2.02
Tuning curves computed with Spectra 8.0
LER 2014 Workshop Frascati,
17 September 2014

13. Lattice design at Diamond
One (or more) modified 4BA cells in the present lattice
(called DDBA)
LER 2014 Workshop Frascati,
17 September 2014 13

14. One DDBA cell in the existing lattice
Replacing the existing cell2 with a DDBA cell
DDBA cell
Introduces an additional straight section (beamline upgrade bending magnet to ID beamline)
Serves as a prototype for low emittance lattice upgrade
Lots of R&D required (magnet design challenging, vacuum with small apertures, engineering integration, etc)
Additional straight
LER 2014 Workshop Frascati,
17 September 2014

15. One DDBA cell in the existing lattice
One more beamline (no significant gain in emittance)
Insertion Device
existing DBA cell
modified DDBA cell
BM beamline
ID beamline
LER 2014 Workshop Frascati,
17 September 2014

16. Ring optics with and without the DDBA cell in cell2
red = present lattice
black = new lattice with modified cell2
Optics optimised with very modest perturbation to adjacent straight sections
LER 2014 Workshop Frascati,
17 September 2014

17. Ring optics with one DDBA cell in cell2
DA slightly reduced
+8mm -12mm one DDBA cell
+12mm – 15mm for the existing machine
Injection efficiency ~93%
with injection point at -6.8 mm
Touschek lifetime
(300 mA, 686 bunches, 1 % coupling),
16.5 h one DDBA cell
19.6 h for the existing machine
LER 2014 Workshop Frascati,
17 September 2014

18. Low alpha
Low alpha operation will be preserved for time resolved Users and THz users
DA in low alpha is reduced and injection efficiency lowered 30%  ~20%
maintaining the same injection efficiency required moving in the
septum and injecting to -6.8 mm (from the original -8.3 mm)
A shorted bunch from the booster will help (2.6 cm now)
LER 2014 Workshop Frascati,
17 September 2014

19. 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)

20. Orbit correction and ray tracing…
Copper pipe used wherever possible to take the heat load
Stainless steel pipe required at the location of fast corrects
In some location heat load proved excessive and the copper vessel was extended and these correctors excluded form the FOFB

21. Status (magnets – see talk by C. Bailey tomorrow)
Even if the minimisation of the emittance is not the primary target, the tight control of dispersion and beta functions requires very strong quads
60 T/m 25 cm
55 T/m 25 cm
55 T/m 25 cm
<2000 T/m cm
-14.4 T/m 67 cm
-14.4 T/m 97 cm
3.4m
mid-cell straight
Challenging designs but no showstoppers !
Other projects (e.g. ESRF) have more aggressive requirements

22. Project status Magnets contract awarded to Danfysik
Vacuum pipe contract awarded to FMB
Preparatory cabling work started
VMX optics frozen by end July 2014
Magnet delivery Nov 2015
Installation complete August 2016
Commissioning October 2016
Further work
Second DDBA cell (DIAD) design Autumn 2014 (possible installation 2018)
Third DDBA (for a HHC) is considered (low effort and priority so far)
Proceed with the technical design of Diamond II
LER 2014 Workshop Frascati,
17 September 2014

23. Conclusions
Diamond is investigating a full ring upgrade for Diamond – II. Various MBA options are under analysis. We have so far concentrated on a modified 4BA (DDBA) that doubles the capacity and reduces the emittance by a factor 10.
The upgrade for cell2 is ongoing and underpins the R&D for the full upgrade.
The design of Diamond II will resume in the next weeks. Still lots of flexibility in the technical choices
Need input from PBSs and Users
what emittance?
are round beams needed?
alternate high beta – low beta straight sections?
operating modes (e.g. low alpha, …)?
how to convince users that do not need brightness?
maintain oversubscription
Consultation exercise with SAC planned for end September
LER 2014 Workshop Frascati,
17 September 2014