Ultimate Storage Rings and the Low Emittance Rings Collaboration

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)


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


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

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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


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


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


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


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


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


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.


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 !


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


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.


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


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


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,


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


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)


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.



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)



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


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


Storage ring as damping ring test bedsStorage 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 0.67ns (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


Ultimate Storage Rings and the Low Emittance Rings Collaboration

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