Design considerations and operation of state-of-the-art light sources R. Bartolini Diamond Light Source Ltd and John Adams Institute, University of Oxford XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Outline Introduction to 3 rd generation light sources Users’ requirements and AP challenges Beam optics studies linear and nonlinear optics Beam stability slow timescale fast timescale Recent trends in 3 rd generation light sources Compatibility of a modern light sources with a collider XVII SuperB and kick-off Meeting, Elba 29 th May 2011

1992ESRF, France (EU) 6 GeV ALS, US GeV 1993TLS, Taiwan1.5 GeV 1994ELETTRA, Italy2.4 GeV PLS, Korea 2 GeV MAX II, Sweden1.5 GeV 1996APS, US7 GeV LNLS, Brazil1.35 GeV 1997Spring-8, Japan8 GeV 1998BESSY II, Germany1.9 GeV 2000ANKA, Germany2.5 GeV SLS, Switzerland2.4 GeV 2004SPEAR3, US 3 GeV CLS, Canada2.9 GeV 2006:SOLEIL, France2.8 GeV DIAMOND, UK 3 GeV ASP, Australia3 GeV MAX III, Sweden700 MeV Indus-II, India2.5 GeV 2008SSRF, China 3.4 GeV 2009PETRA-III, D6 GeV 2011ALBA, E3 GeV 3 rd generation storage ring light sources ESRF SSRF

> 2011NSLS-II, US 3 GeV SESAME, Jordan 2.5 GeV MAX-IV, Sweden1.5-3 GeV TPS, Taiwan 3 GeV CANDLE, Armenia3 GeV 3 rd generation storage ring light sources under construction or planned NLSL-II Max-IV XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Photon energy Flux Brilliance Stability Polarisation Time structure Ring energy Small Emittance Insertion Devices High Current; Feedbacks Vibrations; Orbit Feedbacks; Top-Up Short bunches; Short pulses Users’ requirements and AP and technology challenges XVII SuperB and kick-off Meeting, Elba 29 th May 2011

The brilliance of the photon beam is determined (mostly) by the electron beam emittance that defines the source size and divergence Brilliance and low emittance

Brilliance with IDs Medium energy storage rings with in-vacuum undulators operated at low gaps (e.g. 5-7 mm) can reach 10 keV with a brilliance of ph/s/0.1%BW/mm 2 /mrad 2 Thanks to the progress with IDs technology storage ring light sources can cover a photon range from few tens of eV to tens 10 keV or more with high brilliance XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Low emittance lattices Lattice design has to provide low emittance and adequate space in straight sections to accommodate long Insertion Devices Zero dispersion in the straight section was used especially in early machines avoid increasing the beam size due to energy spread hide energy fluctuation to the users allow straight section with zero dispersion to place RF and injection decouple chromatic and harmonic sextupoles DBA and TBA lattices provide low emittance with large ratio between Minimise  and D and be close to a waist in the dipole Flexibility for optic control for apertures (injection and lifetime)

DBA used at: ESRF, ELETTRA, APS, SPring8, Bessy-II, Diamond, SOLEIL, SPEAR3... TBA used at ALS, SLS, PLS, TLS … DBA and TBA APS ALS Double Bend Achromat (DBA) Triple Bend Achromat (TBA)

ASP APS Leaking dispersion in straight sections reduces the emittance ESRF 7 nm  3.8 nm APS7.5 nm  2.5 nm SPring84.8 nm  3.0 nm SPEAR318.0 nm  9.8 nm ALS (SB)10.5 nm  6.7 nm The emittance is reduced but the dispersion in the straight section increases the beam size Breaking the achromatic condition Need to make sure the effective emittance and ID effects are not made worse

New designs envisaged to achieve sub-nm emittance involve Damping Wigglers Petra-III: 1 nm NSLS-II: 0.5 nm MBA MAX-IV (7-BA): 0.5 nm Spring-8 (10-BA):160 pm 10-DBA abandoned because no DA, reverted to a QBA Low emittance lattices MAX-IV Spring-8 upgrade

Diamond aerial view Diamond is a third generation light source open for users since January MeV LINAC;3 GeV Booster; 3 GeV storage ring 2.7 nm emittance – 300 mA – 18 beamlines in operation (10 in-vacuum small gap IDs) Oxford 15 miles Frascati 1200 miles

Diamond storage ring main parameters non-zero dispersion lattice Energy3 GeV Circumference561.6 m No. cells24 Symmetry6 Straight sections6 x 8m, 18 x 5m Insertion devices4 x 8m, 18 x 5m Beam current300 mA (500 mA) Emittance (h, v)2.7, 0.03 nm rad Lifetime> 10 h Min. ID gap7 mm (5 mm) Beam size (h, v)123, 6.4  m Beam divergence (h, v)24, 4.2  rad (at centre of 5 m ID) Beam size (h, v)178, 12.6  m Beam divergence (h, v)16, 2.2  rad (at centre of 8 m ID) 48 Dipoles; 240 Quadrupoles; 168 Sextupoles (+ H and V orbit correctors + 96 Skew Quadrupoles) 3 SC RF cavities; 168 BPMs Quads + Sexts have independent power supplies

Linear optics modelling and correction Hor.  - beating < 1% ptp Ver.  - beating < 1 % ptp Very good control of the linear optics with LOCO Emittance [ ] (2.75) nm Energy spread [1.1e e3] (1.0e-3) Coupling correction to below 0.1% V beam size at source point 6 μm V emittance 2.2 pm

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 1 %0.01%1-2 pm CLS 18 nm17-19 nm4.2%0.2%36 pm Diamond 2.74 nm nm0.4 %0.08%2.2 pm ESRF 4 nm 1%0.1%4.7 pm SLS 5.6 nm5.4-7 nm4.5% H; 1.3% V0.05%2.0 pm SOLEIL 3.73 nm nm0.3 %0.1%4 pm SPEAR3 9.8 nm < 1%0.05%5 pm SPring8 3.4 nm nm1.9% H; 1.5% V0.2%6.4 pm SSRF 3.9 nm nm<1%0.13%5 pm * best achieved

Non-linear optics control Low emittance  Large Nat. Chromaticity with Strong quads and Small Dispersion  Strong SX  Small Apertures (Dynamic and Momentum apertures) Usually the phase advance per cell is such that low resonance driving terms are automatically compensated (to first order) Numerical optimisation is however unavoidable need 6D tracking (watch out alpha_2) use DA and FM plots use MOGA ! MOGA in elegant to optimise 8 sextupole families at Diamond improved the Touschek lifetime by 20 % XVII SuperB and kick-off Meeting, Elba 29 th May 2011

FM measuredFM model Sextupole strengths variation less than 3% The most complete description of the nonlinear model is mandatory ! Measured 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 detuning with momentum model and measured Frequency map and detuning with momentum comparison machine vs model (I)

DA measuredDA model Synchrotron tune vs RF frequency Frequency map and detuning with momentum comparison machine vs model (II) 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. Phys. Rev. ST Accel. Beams 14, XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Orbit stability: disturbances and requirements Beam stability should be better than 10% of the beam size 10% of the beam divergence up to 100 Hz but IR beamlines will have tighter requirements Ground settling, thermal driftsGround vibrations, cooling systems Insertion Device Errors Power Supply Ripple Hertz for 3 rd generation light sources this implies sub-  m stability identification of sources of orbit movement passive damping measures orbit feedback systems

Beam stability should be better than 10% of the beam size For Diamond nominal optics (at short straight sections) IR beamlines might have tighter requirements Orbit stability requirements for Diamond XVII SuperB Meeting, Elba 29 th May 2011

Seismometer mounted on top of a quadrupole XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Ground vibrations to beam vibrations: Diamond Amplification factor girders to beam: H 31 (theory 35); V 12 (theory 8); Hz HorizontalVertical Long Straight Standard Straight Long Straight Standard Straight Position (μm) Target Measured3.95 (2.2%)2.53 (2.1%)0.70 (5.5%)0.37 (5.8%) Angle (μrad) Target measured0.38 (2.3%)0.53 (2.2%)0.14 (6.3%)0.26 (6.2%)

Significant reduction of the rms beam motion up to 100 Hz; Higher frequencies performance limited mainly by the correctors power supply bandwidth Global fast orbit feedback: Diamond Hz Standard Straight H Standard Straight V Position (μm) Target No FOFB2.53 (2.1%)0.37 (5.8%) FOFB On0.86 (0.7%)0.15 (2.3%) Angle (μrad) Target No FOFB0.53 (2.2%)0.26 (6.2%) FOFB On0.16 (0.7%)0.09 (2.1%)

Higher average brightness Higher average current Constant flux on sample Improved stability Constant heat load Beam current dependence of BPMs Flexible operation Lifetime less important Smaller ID gaps Lower coupling Top-Up motivation BPMs block stability without Top-Up  10  m with Top-Up < 1  m Crucial for long term sub-  m stability XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Top-Up operation consists in the continuous (very frequent) injection to keep the stored current constant – with beamline shutters open. Trends and improvements (I) Top-Up Operation Already in operation at APS, SLS, SPring8, TLS New machines such as Diamond, SOLEIL are also operating Top-Up Retrofitted in ALS, SPEAR3, ELETTRA, BESSY-II, ESRF (few bunches mode) Operating modes are machine specific (frequency of injection, # of shots, charge)  I/I  10 –3 Standard decay modeTop-Up mode

Top-Up Longest period with no trip 147h XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Improvement of orbit stability in Top-Up mode - measured using one of the photon BPMs (fixed ID gap) - in both cases, Fast Orbit Feedback (electron BPMs) ON horizontal angle vertical angle  x ’/10  y ’/10

Kicker transient at diagnostic BPM: +/- 250 μm horizontal p.t.p +/- 75 μm vertical Septum produces no observable effect Gating signals supplied to beamlines No complaints so far from transient at injection, users seem happy, but IR (and others..) beamlines have yet to come. Injection transient during Top-Up XVII SuperB Meeting, Elba 29 th May 2011

Trends and improvements Customised optics for special beamlines Many storage ring light source have implemented two canted undulators in the same straight to increase the number of beamlines. Many of these have also speical optics in the straight sections, e.g. APS, ESRF, Bessy, SLS; Diamond, Soleil, 2 mini-  z (8 m  2 m) to host two low-gap IDs and a chicane (quadrupole triplet tested. Further Commissioned + breaking of the 4-fold symmetry) Courtesy L: Nadolski (SOLEIL)

I13: “Double mini-beta” and Horizontally Focusing Optics I13 Nov I09 March new quadrupoles new mid-straight girder existing girders modified future in-vacuum undulators

Customised optics in straight 9 and 13 Residual Beta-beating INFN, LNF, 15 th April 2011 Customised optics in I09 and I13 None of the long straight sections (8 m) has been used in full for a single beamline with a single ID yet. Two of them were split and reoptmised to serve two separate beamlines. However long straight section are good for injection and RF. Many of the short straight sections (5m) are also serving two beamlines each. Design non optimised, they are just using canted undulators

Comments on the compatibility of light source / collider Light source operation can be parasitic to collider operation but to compete with other state of the art light sources it needs: Orbit and optics control: the orbit and optics must be controlled at all the source points not just at the interaction points The beamlines do not want to re-align their optics. The orbit should be back to the beamline within few hundreds of microns after a shut down so that only minor adjustments are made. >10% beat-beating is considered unacceptable There is no freedom to use the orbit to correct the optics at least at the source point. XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Comments on the compatibility of light source / collider Stability: Orbit variation up to 100 Hz or more must be compensated. This requires a FOFB. Additional variation when moving the IDs gap Thermal load variation generate BPM block movement of the order of um in decay mode at 150 mA at Diamond. The variation heat load of a 6 GeV 0.7 A beam will be huge. Top up required for stability Lifetime – Touschek lifetime requires large momentum aperture. (3-4%). True even in Top-Up. Watch alpha_2. High current operation: Collective effects stronger in B factories, but will be made more acute if in-vacuum Id and narrow gap vessels are to be introduced. IBS does not seem to be a problem even for most recent light sources (e.g NLSL-II) XVII SuperB and kick-off Meeting, Elba 29 th May 2011

Third generation light sources provide a very reliable source of high brightness, very stable X-rays No evidence of under subscription: user’s community and the number of beamlines per facility is increasing; Future developments in light sources are targeting higher brightness even lower emittance < 1 nm, lower coupling higher stability Top-Up, sub-  m over few hundreds Hz short pulses < 1 ps higher current  500 mA larger capacitymore undulator per straights (canted undulators) Technological progress is expected to further improve brightness and stability (IDs, RF, BPMs, DPS, …) Conclusions Thank you for your attention XVII SuperB and kick-off Meeting, Elba 29 th May 2011