Overview of optics corrections at Diamond and plans for Diamond-II R. Bartolini Diamond Light Source and John Adams Institute for Accelerator Science University of Oxford USR Workshop, Beijing, 31 October 2012

Outline Review of optics correction techniques at Diamond LOCO turn-by-turn data analysis old techniques experimental results Initial studies for an ultra low emittance lattice for Diamond-II MBA with M = 4.5.6.7 and modified 4BA Thanks to T. Pulampong, R. Walker, J. Kay and N. Hammond USR Workshop, Beijing, 31 October 2012

Optics Correction ORM based – LOCO J. Safranek very successful for linear optics (beta-beating and coupling) Turn by turn data post processing linear optics LOCO outperform the analysis with tbt data Nonlinear optics FMA (now used everywhere!) driving terms (diamond, ESRF, SOLEIL, …) Old techniques Closest tune approach Quads variation for beta functions measurements USR Workshop, Beijing, 30 October 2012

Linear optics modelling with LOCO Linear Optics from Closed Orbit response matrix – J. Safranek et al. Hor.  - beating Ver.  - beating Modified version of LOCO with constraints on gradient variations (see ICFA Newsl, Dec’07)  - beating reduced to 0.4% rms Quadrupole variation reduced to 2% Results compatible with mag. meas. Quadrupole gradient variation FLS2010, SLAC, 02 March 2010 LOCO has solved the problem of the correct implementation of the linear optics

Measured emittances and reduced coupling With beta-beating < 1%  agreement on measured emittance and energy spread Emittance [2.78 - 2.74] (2.75) nm Energy spread [1.1e-3 - 1.0-e3] (1.0e-3) betatron coupling corrected to ~ 0 using skew-quadrupoles emittance coupling ~0.08% achieved → vertical emittance ~ 2.0 pm 6 mm rms vertical closest tune approach  0 Pinhole camera images before/after coupling correction C. Thomas, R. Bartolini et al. PRSTAB 13, 022805, (2010) Diamond is currently running at reduced coupling 0.3% (8pm V) for users

Comparison machine/model and Lowest vertical emittance Model emittance Measured emittance -beating (rms) Coupling* (y/ x) Vertical emittance ALS 6.7 nm 0.5 % 0.1% 4-7 pm APS 2.5 nm 1 % 0.8% 20 pm ASP 10 nm 0.01% 1-2 pm CLS 18 nm 17-19 nm 4.2% 0.2% 36 pm Diamond 2.74 nm 2.7-2.8 nm 0.4 % 0.08% 2.0 pm ESRF 4 nm 1% 3.7 pm SLS 5.6 nm 5.4-7 nm 4.5% H; 1.3% V 0.02% 0.9 pm SOLEIL 3.73 nm 3.70-3.75 nm 0.3 % 4 pm SPEAR3 9.8 nm < 1% 0.05% 5 pm SPring8 3.4 nm 3.2-3.6 nm 1.9% H; 1.5% V 6.4 pm SSRF 3.9 nm 3.8-4.0 nm <1% 0.13% * best achieved

Frequency map and detuning with momentum comparison machine vs model (II) detuning with momentum model and measured FM measured FM model Sextupole strengths variation less than 3% multipolar errors to dipoles, quadrupoles and sextupoles (up to b10/a9) correct magnetic lengths of magnetic elements fringe fields to dipoles and quadrupoles Substantial progress after correcting the frequency response of the Libera BPMs FM and detuning used as a fit DA is a result 7

Spectral line (-1,1) from tracking data observed at all BPMs Spectral line (-1, 1) in V associated with the sextupole resonance (-1,2) Comparison spectral line (-1,1) from tracking data and measured (-1,1) observed at all BPMs Spectral line (-1,1) from tracking data observed at all BPMs model model; measured BPM number BPM number USR Workshop, Beijing, 31 October 2012 8

Frequency map and detuning with momentum comparison machine vs model (III) Synchrotron tune vs RF frequency DA measured DA model FM and detuning used as a fit; borders limited by the knowledge of the enginnering apertures DA is a result The fit procedure based on the reconstruction of the measured FM and detunng with momentum describes well the dynamic aperture, the resonances excited and the dependence of the synchrotron tune vs RF frequency R. Bartolini et al. PRSTAB 14, 054003 (2011) USR Workshop, Beijing, 31 October 2012 9

Brilliance upgrade at Diamond Brilliance improvement reduce coupling 1%  0.3% 300 mA  500 mA reducing diamond emittance with present hardware 2.7 nm  2.1 nm lattice test – ongoing: issues with SCWs An ultra low emittance lattice for Diamond-II 5BA 7BA, and modified 4BA USR Workshop, Beijing, 31 October 2012

Emittance in 3rd GLS, DR and colliders ~ 2012 ? Transverse coherence requires small emittance Diffraction limit at 0.1 nm requires 8 pm

upgrade with Diamond-II (200pm): 300mA and 1%K Assuming the operation with a 200pm lattice Brilliance plot using U27 – 72 periods 2 m long with Kmax = 2.02 10 mm gap Tuning curves computed with Spectra 8.0 USR Workshop, Beijing, 31 October 2012

Low emittance design for a Diamond-II upgrade (WIP) Wishlist for the upgrade of an existsting medium size mahcine emittance lower than 200 pm in baseline (a factor at least 10 better than now) minimal changes to the machines Leave the straight section as they are ! reuse grider and/or magnets if possible beamline remains where they are (no offset or angle) Avoid long interruptions. Find options that can be phased... Realistic engineering constraints (next…) USR Workshop, Beijing, 31 October 2012

Engineering constraints on lattice design Magnet and geometric constraints quadruple gradient (100T/m) MAX IV has 40.4 T/m quadrupoles in dipoles (30 T/m) MAX IV has 8.68 T/m sextupoles (7000 T/m2) MAX IV has 2*2216 T/m2 space between magnets (hard edge) 10 cm MAX IV has 2.5 cm Apertures = 20 mm diameter in arcs MAX IV inner diam. 22 mm USR Workshop, Beijing, 31 October 2012

5BA – 140 pm

5BA cell Optics matched and optimised with MOGA (quads vs emittance) 14 quads per cell 14 sextupoles 10 cm distance Straight section length slightly reduced 11 m  9.5 m 8.3 m  6.5 m USR Workshop, Beijing, 31 October 2012

Gradient in bend < 15 T/m Quads gradient < 55 T/m Parameters Total length Natural emittance Natural chromaticity : hor./ver. Straight length : long/short 561.6 m 142.5 pm-rad -152/-53 9.5 m/ 6.5 Chrom(0,0) S7X:SEXT,L=0.1,K2=786.45 S7Y:SEXT,L=0.2,K2=-703.26

5BA sextupoles compensation 5π 5 pi horizontal phase advance each cell, 5 pi vertical phase advance every two cells USR Workshop, Beijing, 31 October 2012

Some 5BA solutions from MOGA 2 mm DA Optimisation just started Large tuneshift with amplitude to be compensated USR Workshop, Beijing, 31 October 2012

Issue with path length and alignment of straights Keeping the same circumference (same RF and harmonic number) generates an offset in the position of the straight sections. This will require offsetting the beamlines – 1 cm is deemed acceptable USR Workshop, Beijing, 31 October 2012

M. Borland quoting B. Hettel “if you can inject off-axis you have not pushed your lattice hard enough” 7BA – 45 pm

7BA - giving up more straight section length 14 quads per cell 8 Sextupoles per cell 10 cm distance Straight section length slightly reduced 11 m  8.0 m 8.3 m  5.0 m V and H sextupoles in dispersion bump only USR Workshop, Beijing, 31 October 2012

7BA – 45 pm emittance Chromatic Sextupoles (0,0) Parameters Total length Natural emittance Natural chromaticity : hor./ver. Straight length : long/short 561.6 m 45.7 pm-rad -348/-118.7 8.0 m/ 5.0 m Gradient in bend < 30 T/m Quads gradient <100 T/m Chromatic Sextupoles (0,0) S7X: SEXT,L=0.3,K2=248.9 S7Y: SEXT,L=0.3,K2=-325.6

doubling the number of beamlines while still pushing the emittance down Modified 4BA - 320 pm 4BA with an additional short straight section between the dipole pairs emittance not pushed as for a pure 4BA but can double the number of straight sections Length of additional straight sections forced to be at least 3 m while keeping the remaining 6.7 m and 9 m straight sections

Broken the 4 BA cell to leave 3 m space Modified 4BA cell Broken the 4 BA cell to leave 3 m space 12 quads per cell 10 Sextupoles per cell 10 cm distance Straight section length slightly reduced 11 m  9.7 m 8.3 m  6.7 m USR Workshop, Beijing, 31 October 2012

Modfied 4BA – one superperiod Ring circumference shrinks from 561.6 to 561.0 -> loss 1 harmonic of RF Parameters Total length Natural emittance Natural chromaticity : hor./ver. Straight length : long/short/middle 561.0 m 314.7pm-rad -146.7/-85.6 9.7/6.7/3 Gradient in bend < 15 T/m Quads gradient < 70 T/m

4BA 561m footprint comparison with the existing ring Δ: 12.07 cm Δ: 0.19 cm Δ: 0.39 cm Current Diamond Modified 4BA

MOGA optimisation for DA just started Revising also tune point 12 quadrupoles per cell 10 sextuples per cell 1 mm DA insufficient (WIP) USR Workshop, Beijing, 31 October 2012

Conclusion and (some) open issues Leaving straight sections as they are looks very complicated. No space: the straight section must be slightly shortened 5BA, 6BA, 7BA and a less aggressive design with more beamlines (4BA – modified) are under investigation DA and lifetime studies crucial for all such designs Alternative injection schemes are under study Collective effects, Harmonic Cavity for bunch lengthening, round beams to be studied phase out installation strategy to avoid long interruptions still to be found.. However the subject is now seriously tackled by a large community, many rings already solved (PEP-X at 10 pm) and solutions will likely appear USR Workshop, Beijing, 31 October 2012

3rd LOWERING workshop in Oxford 8-10 July 2013 USR Workshop, Beijing, 31 October 2012