Ultimate Storage Rings and Ultimate Storage Rings and the Low Emittance Rings Collaboration the Low Emittance Rings Collaboration
R. Bartolini
Diamond Light Source
and
John Adams Institute for Accelerator ScienceUniversity of Oxford
CLIC Workshop 2013 CERN, 31 January 2013
Motivations: the low emittance communityMotivations: the low emittance community
Light sources
diffraction limited operation at 0.1nm requires ~10 pm
4
Colliders (e.g B-factories)
1036 cm-2 s-1 requires 2nm (5nm for superKEKB)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
OutlineOutline
• Present scenario
• Low emittance light sources
MAX-IVlarge rings projectsmedium size rings projects
• R&D challenges (reviewed at the USR workshop in Beijing Nov 2012)
AP, magnets, RF, vacuum, Diagnostics, …
• The Lowring network
CLIC Workshop 2013 CERN, 31 January 2013
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
'yy'xx24
fluxbrilliance
2ph
2exx ,
2ph
2exx ',''
2xxxx )D(
2xxxx D )'('
4
Luph
uph L
'
Measured emittances and reduced couplingMeasured 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
closest tune approach 0
Pinhole camera images before/after coupling correction
C. Thomas, R. Bartolini et al. PRSTAB 13, 022805, (2010)
6 m rms vertical
Diamond is currently running at reduced coupling 0.3% (8pm V) for users
SLS world record for smallest vertical emittanceSLS world record for smallest vertical emittance
Courtesy L. RivkinPSI and EPFL
CLIC Workshop 2013 CERN, 31 January 2013
Max-IV 20-fold 7-BA achromatMax-IV 20-fold 7-BA achromat
Courtesy S. Leemans
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
PEP-X 7 bend achromat cellPEP-X 7 bend achromat cell
Cell phase advances: x=(2+1/8) x 3600, y=(1+1/8) x 3600.
Natural emittance = 29 pm-rad at 4.5 GeV
5 TME units
Courtesy B. Hettel, Y. Cai
CLIC Workshop 2013 CERN, 31 January 2013
Reduced emittance with damping wigglersReduced emittance with damping wigglers
Emittance = 11 pm-rad at 4.5 GeVwith parameters lw=5 cm, Bw=1.5 T
Courtesy Min-Huey Wang, B. Hettel, Y. Cai
Average beta function at the wiggler section is 12.4 meter.
Wiggler Field Optimization Wiggler Length Optimization
CLIC Workshop 2013 CERN, 31 January 2013
Additional sextupoles for tuneshift and Additional sextupoles for tuneshift and 2Q2Qxx-2Q-2Qyy
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
USR – M. BorlandA Tevatron-size USR based on a 7BA lattice
Multi-bend achromats (Multi-bend achromats (xx ~ 1/N ~ 1/NDD33))
Courtesy M. Borland
DA small (~ mm) requires new injection concepts (e.g. low emittance injector for swap out injection)
A 5BA lattice for Diamond-II upgradeA 5BA lattice for Diamond-II upgrade
14 quads per cell 14 sextupoles 10 cm distance between magnetic elements
A 150pm lattice for a ~20-fold decrease in emittance
Energy [GeV]Circumference [m]Tune: h/vBeam current [A]Coupling,%Emittance: x,y [pm·rad]Bunch length [mm]Energy spread (rms)Momentum compactionDamping time: x/y/s [ms]Natural chromaticity: x/yEnergy loss per turn [MeV]RF voltage [MV]RF frequency[MHz]Length of ID straight [m] @ ID centre (long, short): x/y [m]
3.0561.655.32/26.6230010%148.11.80.731×10-3
0.00012217.23/26.16/17.65-152/-530.429642.55004×9.5,18×6.58.76/5.62 , 4.33/1.92
CLIC Workshop 2013 CERN, 31 January 2013
Some 5BA solutions from MOGA Some 5BA solutions from MOGA
2 mm DA
Optimisation just started
Large tuneshift with amplitude to be compensated
Spring8-II, and tUSR 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 latticesSurvey of ultra-low emittance lattices
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
Some open issues on low emittance lattice designSome open issues on low emittance lattice design
What is the optimal energy for a DLSR?
tens keV high brilliance (and some at 300 keV) requires > 3 GeV
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)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 100s mA.
CLIC Workshop 2013 CERN, 31 January 2013
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 Physics: current and instabilities (II)Accelerator Physics: current and instabilities (II)
Accelerator engineering: magnets R&DAccelerator 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 MAX IV has 40.0 T/mESRF – Diamond-II 100 T/mSpring8-II 80 T/mBAPS 50 T/m USR 90 T/m
quadrupoles in dipoles MAX IV has 9 T/m ESRF – Diamond-II 30 T/m
sextupoles MAX IV has 2*2200 T/m2ESRF-Diamond -USR 7000 T/m2
Spring-8 II 13000 T/m2
BAPS 7500 T/m2
space between magnets (hard edge) 10 cm MAX IV has 7.5 cmApertures = 20-26 mm diameter in arcs MAX IV inner diam. 22 mm
Quadrupole magnet design with g > 100 T/m (ESRF)Quadrupole magnet design with g > 100 T/m (ESRF)
PM quadrupole
PM are also envisaged for dipoles due to power consumption and stability
EM quadrupole
Accelerator Engineering (III)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: VacuumAccelerator 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
InjectionInjection
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 schemesInjection: 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 nC/bunch) - with a booster or linac
CLIC Workshop 2013 CERN, 31 January 2013
Stability and feedback systemStability 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 perfomanceSOLEIL’s orbit feedback perfomance
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
Vertical plane
FOFB ON
FOFB OFF
FOFB ON
FOFB OFF
J. C. Denard SOLEIL
IDsIDs
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 APSR&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
Fit test of cold mass and current lead assemblies in cryostat
M. Jaski APS: Ivanyushenkov et al.. IPAC12,
CLIC Workshop 2013 CERN, 31 January 2013
Conclusion and open issuesConclusion 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 mA. 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/conferenceOtherViews.py?view=standard&confId=2825
Low emittance rings’ collaborationLow 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 EuCARD2 received support for networking activities
workshops + reports
visits and exchanges on common R & D programmes
Approved with 330 kEuros for 4 years – staring May 2013
CLIC Workshop 2013 CERN, 31 January 2013
Work packages and objectivesWork 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 workshopfollow 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 CommunicationTask 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 1Work 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 measurementBeam-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 2Work 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 3Work 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, alignmentsuperconducting magnet for high field- high gradients
Sub-Task 6.4.2. Instrumentation for Low Emittance (ILE):high resolution BPM (including turn by turn) + orbit feedbackultra 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 deliverableWork packages deliverable
Organisation of annual general workshopOrganisation of subgroup workshop
Interim reports (month 18)
D6.1 Low Emittance Ring Design interim report - month 18D6.2 Instabilities, Impedances and Collective Effects interim report – month 18D6.3 Low Emittance Ring Technology interim report – month 18
Final reports (month 46)
D6.4 Low Emittance Ring Design final report – month 46D6.5 Instabilities, Impedances and Collective Effects final Report – month 46D6.6 Low Emittance Ring Technology final report – month 46
CLIC Workshop 2013 CERN, 31 January 2013
Storage ring as damping ring test bedsStorage ring as damping ring test beds
CLIC Workshop 2013 CERN, 31 January 2013
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 0.67ns (1.5GHz 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)
33rdrd LOWERING workshop in Oxford 8-10 July 2013 LOWERING workshop in Oxford 8-10 July 2013
Oxford 8-10th July third Lowering meeting
CLIC Workshop 2013 CERN, 31 January 2013