Ultimate Storage Rings and the Low Emittance Rings

Ultimate Storage Rings and the Low Emittance Rings Collaboration R. Bartolini Diamond Light Source and John Adams Institute for Accelerator Science University of Oxford CLIC Workshop 2013 CERN, 31 January 2013

Motivations: the low emittance community Light sources diffraction limited operation at 0. 1 nm requires ~10 pm Colliders (e. g B-factories) 1036 cm-2 s-1 requires 2 nm (5 nm for super. KEKB) as present state-of-the-art light sources Damping rings 500 pm H and 2 pm V (specs for ILC-DR) <100 pm H and 5 pm V (specs for CLIC-DR) CLIC Workshop 2013 CERN, 31 January 2013

Outline • Present scenario • Low emittance light sources MAX-IV large rings projects medium size rings projects • R&D challenges (reviewed at the USR workshop in Beijing Nov 2012) AP, magnets, RF, vacuum, Diagnostics, … • The Lowering network CLIC Workshop 2013 CERN, 31 January 2013

Emittance in 3 rd GLS, DR and B-factories ~ 2013 Transverse coherence requires small emittance Diffraction limit at 0. 1 nm requires 8 pm

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. 1 e-3 - 1. 0 -e 3] (1. 0 e-3) • betatron coupling corrected to ~ 0 using skew-quadrupoles • emittance coupling ~0. 08% achieved → vertical emittance ~ 2. 0 pm closest tune approach 0 6 mm rms vertical 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% (8 pm V) for users

SLS world record for smallest vertical emittance Courtesy L. Rivkin PSI and EPFL CLIC Workshop 2013 CERN, 31 January 2013

Max-IV 20 -fold 7 -BA achromat Max-IV studies proved that a 7 -BA (330 pm, and 260 pm with DW) can deliver suffcient DA and MA to operate with standard off-axis injection schemes Tools used FM – driving terms Additional octupoles were found to be effective Courtesy S. Leemans

PEP-X 7 bend achromat cell Natural emittance = 29 pm-rad at 4. 5 Ge. V 5 TME units Cell phase advances: mx=(2+1/8) x 3600, my=(1+1/8) x 3600. CLIC Workshop 2013 CERN, 31 January 2013 Courtesy B. Hettel, Y. Cai

Reduced emittance with damping wigglers Emittance = 11 pm-rad at 4. 5 Ge. V with parameters lw=5 cm, Bw=1. 5 T Wiggler Field Optimization Wiggler Length Optimization Average beta function at the wiggler section is 12. 4 meter. Courtesy Min-Huey Wang, B. Hettel, Y. Cai CLIC Workshop 2013 CERN, 31 January 2013

Additional sextupoles for tuneshift and 2 Qx-2 Qy Without Harmonic Sextupoles With Harmonic Sextupoles Optimized with OPA (Accelerator Design Program from SLS PSI) 10 mm DA achieved Courtesy Min-Huey Wang, B. Hettel, Y. Cai CLIC Workshop 2013 CERN, 31 January 2013

Multi-bend achromats ( x ~ 1/ND 3) t. USR – M. Borland A Tevatron-size USR based on a 7 BA lattice Courtesy M. Borland DA small (~ mm) requires new injection concepts (e. g. low emittance injector for swap out injection)

A 5 BA lattice for Diamond-II upgrade A 150 pm lattice for a ~20 -fold decrease in emittance Energy [Ge. V] 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 [Me. V] 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% 148. 1 1. 8 0. 731× 10 -3 0. 000122 17. 23/26. 16/17. 65 -152/-53 0. 42964 2. 5 500 4× 9. 5, 18× 6. 5 8. 76/5. 62 , 4. 33/1. 92 14 quads per cell 14 sextupoles 10 cm distance between magnetic elements CLIC Workshop 2013 CERN, 31 January 2013

Some 5 BA solutions from MOGA 2 mm DA Optimisation just started Large tuneshift with amplitude to be compensated Spring 8 -II, and t. USR have similar DA It is likely that we have to learn to cope with these small DA New injection schemes need to be developed nonlinear pulsed kicker or swap out injection schemes are under investigation CLIC Workshop 2013 CERN, 31 January 2013

Survey of ultra-low emittance lattices MAX IV 7 BA 3 Ge. V 320 pm 500 m. A SS length 5 m DA 7 mm w/errors 5 BA w/superbend 3 280 500 5 m & 6 m 5 mm w/errors Spring-8 6 BA 6 67. 5 300 4. 5 m & 27 m 3 mm w/errors APS 7 BA 6 147 100 Pep-X 7 BA 4. 5 11 200 5 m 10 mm w/errors ESRF Phase II 7 BA 6 130 200 5 m 10 mm SOLEIL QBA w/longit. . gradient dipole 2. 75 980 (220) 500 Diamond mod. 4 BA, 5 BA, 7 BA 3 45 -300 5 m & 7 m 2 mm ALS 5 BA - 7 BA 2 50 -100 5 m 2 -3 mm BAPS 7 BA-15 BA 5 50 10 m & 7 m 10 mm w/errors t. USR 7 BA 9 3 100 TEV tunnel 0. 8 mm Sirius Robins. Wiggler + beam adapter

Some open issues on low emittance lattice design What is the optimal energy for a DLSR? tens ke. V high brilliance (and some at 300 ke. V) requires > 3 Ge. V What M is optimal in MBA? longer cells (larger M) produce smaller emittances trade off between small emittances and straight section length What is the optimal length for straight sections? not much interest for very long undulators (SS 5 – 7 m) Ratio circumference vs lengths of IDs straight section still a valid figure of merit Dynamic aperture and lifetime minimise sextupoles strength as much as possible use octupoles for correction detuning with amplitude Optimisation techniques FMA (used everywhere), driving term cancellation (MAX IV, Pep-X, …), MOGA (Diamond, …)

Accelerator Physics: current and instabilities (I) Small emittance short bunches low instability thresholds Small apertures everywhere arcs & straight sections is worrying for large stored current IBS; Touschek lifetime Coherent Synchrotron Radiation; Resistive Wall Current limited by IBS, especially for very low emittance lattices Effect of CSR also potentially catastrophic especially for those lattices with short natural bunch length Heat load on beamlines optics can be an issue at large current high beam energies (1. 5 A Pep-X old design) but IBS is the limiting factor. Unlikely that ultra low emittance will work with current above few 100 s m. A. CLIC Workshop 2013 CERN, 31 January 2013

Accelerator Physics: current and instabilities (II) Countermeasures for CSR: vacuum pipe shielding with small apertures was discussed. Relative impact of RW to be worked out Countermeasures for RW and FII: feedback and fill pattern gaps can help Countermeasures: long bunches Choice Ideal RF frequency HHC factor 5 lengthening for MAX IV 70 mm rms bunches Leave out time resolved studies (to the Linac injector) one ring cannot fit everything ! CLIC Workshop 2013 CERN, 31 January 2013

Accelerator engineering: magnets R&D Diffraction limited emittance requires magnets with unprecedented strength in storage ring. High gradient and high precision required New designs under consideration foresee magnets whose strength exceed even the most aggressive existing designs and distance is of the order of the gap quadruple gradient ESRF – Diamond-II Spring 8 -II BAPS USR quadrupoles in dipoles ESRF – Diamond-II sextupoles ESRF-Diamond - USR Spring-8 II BAPS MAX IV has 40. 0 T/m 100 T/m 80 T/m 50 T/m 90 T/m MAX IV has 9 T/m 30 T/m MAX IV has 2*2200 T/m 2 7000 T/m 2 13000 T/m 2 7500 T/m 2 space between magnets (hard edge) 10 cm Apertures = 20 -26 mm diameter in arcs MAX IV has 7. 5 cm MAX IV inner diam. 22 mm

Quadrupole magnet design with g > 100 T/m (ESRF) EM quadrupole PM are also envisaged for dipoles due to power consumption and stability

Accelerator Engineering (III) Components Integration: separate magnets on girders or common blocks a la MAX IV ? blocks integration: alignment left to machining not adjustments and pushes the structure eigenfrequencies up above 50 Hz but complicated vacuum pumping requires NEG e. g. vacuum leak requires opening the whole cell CLIC Workshop 2013 CERN, 31 January 2013

Accelerator Engineering: Vacuum Small magnets bore (20 -26 mm diameter) required to achieve high gradients creates problem with the vacuum system pumping cross section limited insufficient space for pumps, absorbers, antechambers, … MAX IV solution distributed NEG coating Neg coating Cu chamber with external cooling channel Time consuming for NEG coating (~ 10 days for a vacuum chamber) process Limited coating production capability in the world long procurement time (costs). Activation system to be considered during the vessel design stage. CLIC Workshop 2013 CERN, 31 January 2013

Injection Crucial aspect for this studies when the low emittance is achieved compromising the DA Traditional 3 or 4 Kicker bump: require 10 mm DA required Top-Up is crucial for sub-um stability Injection transient seems unavoidable; gating needed New scheme emerging are multipole pulsed injection and swap out injection CLIC Workshop 2013 CERN, 31 January 2013

Injection: new schemes Multipole kicker schemes still off-axis: it requires ~5 mm DA (MAX IV data) some R&D still needed but excellent perspective at BESSY-II (BESSY-II data) Swap out injection kick in - on axis - a new bunch and kick out the depleted bunch requires a small emittance injector – can work with 2 mm DA no top up – but fractional replacement of current the injector and the achievable fill pattern limit the total stored current (0. 5 n. C/bunch) - with a booster or linac CLIC Workshop 2013 CERN, 31 January 2013

Stability and feedback system Stability requirements 10% rules still valid (up to 200 Hz): J. C. Denard’s talk implies no longer submicron stability but 100 -200 nm already achieved (or very close) in the V plane in some machines H plane issues – Amplification factor is higher than in V Top-Up mandatory R&D: civil engineering: common slab for ring and experimental hall tunnel temperature control (within 0. 1 C) girders’ eigenfrequencies above 50 Hz BPM accuracy: new designs for round pipes; decoupling by bellows; invar supports; better resolution (esp. turn by turn) No revolution is needed but steady improvement on what already achieved

SOLEIL’s orbit feedback perfomance Vertical plane FOFB ON FOFB OFF FOFB ON J. C. Denard SOLEIL Vertical beam motion averaged on all e-BPMs ~300 nm (0. 1 -500 Hz ) It means 200 nm RMS in the middle of the straight sections

IDs from J. Chavanne’s talk: ID impact with new low emittance lattice Beam dynamics: will need FF tables correction Photon quality: rms phase errors 2 -3 degree is adequate Energy spread will become the dominant effect to higher harmonics Heat load: no major changes as the size of the photon beam is weakly dependent on emittance (mostly depends on K) from J. Bardth’s talk: comparison CMPUs vs SCUs CPMU mature design; SCU higher field for periods above 10 mm SCU have big potential; CMPU still compatible with users application in the next 5 -10 years due to flexibility, fast tuning, reproduclbility

R&D IDs: SCU at APS § § SCU has been built at the APS Beff = 0. 64 T at 500 A 21 periods of 16 mm Installation is scheduled for December 2012 Completed magnet assembly M. Jaski APS: Ivanyushenkov et al. . IPAC 12, CLIC Workshop 2013 CERN, 31 January 2013 Fit test of cold mass and current lead assemblies in cryostat

Conclusion and open issues Lots of issues – long to-do list but no show stopper Many light source operate with low emittance lattices. Vertical emittance in the 1 -2 pm range are no longer uncommon. New projects aim at reaching diffraction limited rings in Horizontal plane as well. These are based on MBA lattices. DA and Touschek lifetime studies are crucial. Magnets and apertures design will be at the cutting edge of present R&D. Alternative injection schemes are under study Collective effects (IBS) will limit the stored current to 100 -200 m. A. They might be mitigated by Harmonic Cavity for bunch lengthening. Round beams could help and more R&D is needed. However the subject is now seriously tackled by a large community, some rings are already solved (e. g. PEP-X at 10 pm) and new solutions will likely appear for upcoming projects

All presentations in http: //indico. ihep. ac. cn/conference. Other. Views. py? view=standard&conf. Id=2825

Low emittance rings’ collaboration Initiated by the ILC-CLIC working group on damping rings Acknowledging common interests and fostering collaboration among different communities facing very similar problems (both R & D) Two workshop organised: January 2010 – CERN October 2011 – Crete Collaboration now within the Eu. CARD 2 received support for networking activities workshops + reports visits and exchanges on common R & D programmes Approved with 330 k. Euros for 4 years – staring May 2013 CLIC Workshop 2013 CERN, 31 January 2013

Work packages and objectives Cooridinators Y. Papahilippou CERN), R. Bartolini (JAI-Diamond), S. Guiducci (INFN) represent the communities of Damping rings, e+/e- colliders, X-ray storage rings. CERN, INFN-LNF and UOXF will coordinate and communicate the network’s activities and results. annual Low Emittance Rings workshop follow up the topical workshops’ outcome. Participation of non-EU members in the board is essential (Accelerator Test Facility - ATF) and USA (Cornell Electron Storage Ring Test Accelerator-CESRTA) Task 6. 1. Coordination and Communication Task 6. 2. Low Emittance Ring Design (LERD) Task 6. 3. Instabilities, Impedances and Collective Effects (IICE) Task 6. 4. Low Emittance Rings Technology (LERT) CLIC Workshop 2013 CERN, 31 January 2013

Work packages tasks and organisation – subtask 1 Sub-Task 6. 2. 1. Optics Design of Low Emittance Rings (ODLER): methods, approaches and numerical tools for designing ultra-low emittance optics in damping rings, storage rings and circular colliders. multi-bend achromats, damping wigglers, dipole magnets with longitudinally variable bending field, or Robinson wigglers Sub-Task 6. 2. 2. MInimization of Vertical Emittance (MIVE) Hurdles to achieving ultra low emittacne (quantum limit) magnetic error tolerances and alignment of the magnets diagnostics for precise beam size, position and emittance measurement Beam-based correction techniques Experimental work carried out in light sources such as SLS, DIAMOND, Australian Syncrotron, ESRF and test facilities such as ATF and CESRTA. CLIC Workshop 2013 CERN, 31 January 2013

Work packages tasks and organisation – subtask 2 Task 6. 3. Instabilities, Impedances and Collective Effects (IICE) This task will be led by SOLEIL. Sub-Task 6. 3. 1 Impedances and Instabilities in Low Emittance Rings (IILER) low gap chambers, coatings, kickers, RF, etc with shot bunches Sub-Task 6. 3. 2. Two-Stream Instabilities in Low Emittance Rings (2 -SILER) electron cloud and Fast Ion instabilties – vacuum technology Sub-Task 6. 3. 3. Particle Scattering in Low Emittance Rings (PASLER): IBS, Touschek scattering Sub-Task 6. 3. 4. Coherent Synchrotron Radiation Instabilities (CSRI): microbunhing dynamics and countermeasures (shileding) CLIC Workshop 2013 CERN, 31 January 2013

Work packages tasks and organisation – subtask 3 Task 6. 4. Low Emittance Ring Technology (LERT) This task will be led by CERN Sub-Task 6. 4. 1. Insertion Device, Magnet design and Alignment (IDEMA) high gradient, small filed errors, alignment superconducting magnet for high field- high gradients Sub-Task 6. 4. 2. Instrumentation for Low Emittance (ILE): high resolution BPM (including turn by turn) + orbit feedback ultra small beam sizes Sub-Task 6. 4. 3 Design of Fast Kicker Systems (DEFKIS): fast kickers – 50 Hz stable to 10– 4; long flat top 100 ns – of faster for ILC Sub-Task 6. 4. 4 RF Design (RFDE) RF desing, HOM damping, efficiency, and RF power sources CLIC Workshop 2013 CERN, 31 January 2013

Work packages deliverable Organisation of annual general workshop Organisation of subgroup workshop Interim reports (month 18) D 6. 1 Low Emittance Ring Design interim report - month 18 D 6. 2 Instabilities, Impedances and Collective Effects interim report – month 18 D 6. 3 Low Emittance Ring Technology interim report – month 18 Final reports (month 46) D 6. 4 Low Emittance Ring Design final report – month 46 D 6. 5 Instabilities, Impedances and Collective Effects final Report – month 46 D 6. 6 Low Emittance Ring Technology final report – month 46 CLIC Workshop 2013 CERN, 31 January 2013

Storage ring as damping ring test beds Ring achieving lowest possible emittances in all three dimensions, in the range of few Gev. Vertical and longitudinal easier than horizontal Short bunch train structure similar to damping rings Bunch spacing of 0. 67 ns (1. 5 GHz RF system) should be a good compromise Space for installing wigglers, kickers (and extraction line), vacuum test areas, RF, instrumentation Beam conditions for studying IBS, space-charge, low emittance tuning, e-cloud (positrons), fast ion instability, CSR… High brightness single bunches/trains, small bunch length Available beam time for experimental tests (Diamond, SLS, …, ANKA soon) CLIC Workshop 2013 CERN, 31 January 2013

3 rd LOWERING workshop in Oxford 8 -10 July 2013 Oxford 8 -10 th July third Lowering meeting CLIC Workshop 2013 CERN, 31 January 2013