C L I CC L I C

Low emittance generation in

Damping rings: Optics, DR layout, SC wigglers vs NC

wigglers

February 3rd, 2010

Yannis PAPAPHILIPPOU

CLIC Advisory ComittEe,

C L I CC L I C

DR parameters and challenges High-bunch density

Emittance dominated by Intrabeam Scattering, driving energy, lattice, wiggler technology choice and alignment tolerances

Electron cloud in e+ ring imposes chamber coatings and efficient photon absorption

Fast Ion Instability in the e- ring necessitates low vacuum pressure Space charge sets energy, circumference limits

Repetition rate and bunch structure Fast damping achieved with wigglers RF frequency reduction considered due to many challenges @ 2GHz (power

source, high peak and average current) Output emittance stability

Tight jitter tolerance driving kicker technology Positron beam dimensions from source

Pre-damping ring challenges (energy acceptance, dynamic aperture) solved with lattice design

Target Parameters NLC CLIC

bunch population (109) 7.5 4.1

bunch spacing [ns] 1.4 0.5

number of bunches/train 192 312

number of trains 3 1

Repetition rate [Hz] 120 50

Ext. hor. norm. emittance [nm] 2370 <500

Ext. ver. norm. emittance [nm] <30 <5

Ext. long. norm. emittance [keV.m] 10.9 <4

Inj. hor. norm. emittance [μm] 150 63

Inj. ver. norm. emittance [μm] 150 1.5

Inj. long. norm. emittance [keV.m] 13.18 1240Design Parameters CLIC

Energy [GeV] 2.86

Circumference [m] 493.2

Energy loss/turn [Me] 5.8

RF voltage [MV] 7.4

Compaction factor 6e-5

Damping time x / s [ms] 1.6 / 0.8

Number of arc cells / wigglers 100/76

Dipole/ wiggler field [T] 1.4/2.5

C L I CC L I C

Schematic layout

ee++ Damping Ring Damping Ring

ee-- Damping Ring Damping Ring

ee-- Pre-damping Ring Pre-damping Ringee++ Pre-damping Ring Pre-damping Ring

Y.P., 03/02/2010 3ACE 2010

C L I CC L I C Scaling of emittances

with energy obtained with analytical arguments and including IBS effect (constant longitudinal emittance)

Broad minimum for horizontal emittance ~2-3GeV

Higher energy reduces ratio between zero current and IBS dominated emittance

Vertical emittance increases linearly with energy

Similar results obtained for other machines (e.g. CESRTA)

Choice of 2.86GeV in order to relax collective effects while achieving target emittances

Damping ring energy

C L I CC L I CPDR design

Main challenge: Large input emittances especially for positrons to be damped by several orders of magnitude

Design optimization following analytical parameterization of TME cells

Detuning factor (achieved emittance/TME)> 2 needed for minimum chromaticity

Target emittance reached with the help of conventional high-field wigglers (PETRA3)

Non linear optimization based on phase advance scan (minimization of resonance driving terms and tune-shift with amplitude)

F. Antoniou, CLIC09Injected

Parameterse- e+

Bunch population [109] 4.4 6.4

Bunch length [mm] 1 10

Energy Spread [%] 0.1 8

Hor.,Ver Norm. emittance [nm]

100 x 103

7 x 106

C L I CC L I C

6

DR layout

Y.P., 03/02/2010 ACE 2010

Racetrack shape with 96 TME arc cells (4 half cells for dispersion

suppression) 38 Damping wiggler FODO cells in the long straight

sections (LSS) Space reserved upstream the LSS for

injection/extraction elements and RF cavities

S. Sinyatkin, et al., LER 2010

C L I CC L I CS. Sinyatkin, et al.,

LER 2010Arc cell

2.36m-long TME cell with bends including small gradient (as in NLC DR and ATF)

Phase advances of 0.452/0.056 and chromaticities of -1.5/-0.5

IBS growth rates reduced due to optics function inversion

Y.P., 03/02/2010 7ACE 2010

C L I CC L I C

Wiggler cell and LSS

LSS filed with wiggler FODO cells of around ~6m

Horizontal phase advance optimised for minimizing emittance with IBS, vertical phase advance optimised for aperture

Drifts of 0.6m downstream of the wigglers, long enough for absorbers, vacuum equipment and instrumentation

S. Sinyatkin, et al., EPAC 2009

8Y.P., 03/02/2010 ACE 2010

C L I CC L I C

Dynamic aperture

Arc cell phase advance scan to optimize horizontal and vertical DA

Very large in both planes especially in vertical

Further optimisation DA needed (including misalignments, magnetic errors and wiggler effects)

New

ACE 2010Y.P., 03/02/2010

Horizontal Vertical

C L I CC L I C

New DR parametersParameters Value

Energy [GeV] 2.86

Circumference [m] 493.2

Coupling 0.0013

Energy loss/turn [MeV] 5.8

RF voltage [MV] 7.4

Natural chromaticity x / y -172 / -64

Momentum compaction factor 6e-5

Damping time x / s [ms] 1.6 / 0.8

Dynamic aperture x / y [σinj] 30 / 120

Number of dipoles/wigglers 76/100

Cell /dipole length [m] 2.36 / 0.43

Dipole/Wiggler field [T] 1.4/2.5

Bend gradient [1/m2] -1.10

Max. Quad. gradient [T/m] 73.4

Max. Sext. strength [kT/m2] 6.6

Phase advance x / z0.452/0.05

6

Bunch population, [109] 4.1

IBS growth factor 1.7

Hor./ Ver Norm. Emittance [nm.rad] 410 / 4.7

Bunch length [mm] 1.2

Longitudinal emittance [keVm] 3.8

Reasonable magnet strengths (magnet models already studied) and space constraints

DA significantly increased

TME optics with gradient in the bend and energy increase reduces IBS growth factor to 1.7 (as compared to 5.4 in original DR design)

Further optics optimization with respect to IBS (F. Antoniou PhD thesis) and tracking code for comparaison with analytical theory

Y.P., 03/02/2010 ACE 2010

C L I CC L I C

IBS tracking code A. Vivoli, LER2010

Developed Monte-Carlo tracking code for IBS including synchrotron radiation damping and quantum excitation (SIRE, based on MOCAC)

Differences between analytical growth rates and the mean values obtained by 50 SIRE runs (under investigation)

Final emittances obtained by SIRE are just within the CLIC DR budget

1/Tx (s-1) 1/Ty (s-1) 1/Tz (s-1)

MADX (B-M) 2007.29 1485.97 1096.57

SIRE (compressed) 1207.96 240.69 802.08

SIRE (not compressed) 1188.98 252.99 811.21

Mod. Piwinski 546.54 354.13 383.50

x (m)

y (m)

z (eV m)

Injection 74e-6 1.8e-6 130589

Extraction 498e-9

4.3e-9 3730

Equilibrium (NO IBS)

254e-9

3.7e-9 2914

Y.P., 03/02/2010 11ACE 2010

C L I CC L I C

Nb3Sn SCwiggler

NbTi SCwiggler

BINP PMwiggler

Wigglers’ effect with IBS Stronger wiggler fields and shorter

wavelengths necessary to reach target emittance due to strong IBS effect

Current density can be increased by different conductor type

Nb3Sn can sustain higher heat load (potentially 10 times higher than NbTi)

Two wiggler prototypes 2.5T, 5cm period, built and currently tested

by BINP 2.8T, 4cm period, designed by CERN/Un.

Karlsruhe Mock-ups built and magnetically tested Prototypes to be installed in a storage

ring (ANKA, CESR-TA, ATF) for beam measurements

ParametersBINP

CERN

Bpeak [T] 2.5 2.8

λW [mm] 50 40

Beam aperture full gap [mm]

13

Conductor type NbTi Nb3Sn

Operating temperature [K]

4.2

12

C L I CC L I C

Permanent magnet performance

Pure permanent magnet not able to reach very high field (i.e. 1.2T for Sm2Co17)

Pole concentrators used (e.g. vanadium permendur) to enhance pole field to a max value of 2.3T

Not more than 1.1T reached for 40mm period and 14mm gap

Higher field of 1.8T reached for 100mm period

Max field of 2.3T can be reached for a gap/period ratio of ~0.1, (140mm period for 14mm gap)

In that case, output emittance gets more than doubled (>800nm)

In order to reach target DR performance, number of wigglers has to be increased by more than a factor of 2, i.e. ~40% of ring circumference increase

Only way to reach high field for high gap/period ratio is by using super-conducting wigglers

Simulations by P. Vobly

Scaling by Halbach

C L I CC L I CWiggler short prototypes

CERN

BINP

Iron yokeRegular coil

End coils to compensate the first

and the second integral

Corrector coils with

individual PS

Y.P., 03/02/2010 14ACE 2010

C L I CC L I C

Present design uses NbTi wet wire in separate poles clamped together

Wire wound and impregnated with resin and prototype assembled including corrector coil and quench protection system by spring 2009

Field measurements in June showing poor performance (reaching 420 instead of 660A) due to mechanical stability problems (GFP separators)

Magnet delivered at CERN for further measurements and verification

New design under evaluation by BINP and CERN magnet experts

BINP NbTi Wiggler

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420 I, A

Number of the quench

"B " ha lf of the w iggler

"A " ha lf of the w iggler

C L I CC L I CMid plane peak field vs Current

0

0.5

1

1.5

2

2.5

3

0 200 400 600 800 1000

[ A ]

[ T ]

50 mm period

40 mm period

CERN prototype with NbTi wire

Crash test program at CERN with 40mm mock-up using NbTi wire

Reached peak field of 2.5T at 1.9K (2T at 4.2K) Current density extrapolated to 50mm, provides more

than 2.5T field Currently continuing with Nb3Sn winding tests

Y.P., 03/02/2010 16ACE 2010

C L I CC L I CSynchrotron radiation

Synchrotron radiation power from bending magnets and wigglers

Critical energy for dipoles and wigglers

Radiation opening angle

DR radiation parameters

PDR

DR

Power per dipole [kW] 3.3 1.2

Power per wiggler [kW] 15.2

16.1

Total power [MW] 0.7 1.3

Critical energy for dipole [keV]

16.0

19.0

Critical energy for wiggler [keV]

9.3 13.6

Radiation opening angle [mrad]

0.11

€

Pbend =2c 2re

3m03

E 2lbB2I

€

Pw =2c 2re

3m03

E 2lwBw2 I

€

Ec =3hc

2m03

E 3

ρ

€

θy =0.608

γ

€

Ecw =3hc 2

2m03

Bw E 2

90% of radiation power coming from the 76 SC wigglers

Design of an absorption system is necessary and critical to protect machine components and wigglers against quench

Radiation absorption equally important for PDR (but less critical, i.e. similar to light sources)

Y.P., 03/02/2010 17ACE 2010

C L I CC L I C

4 5 6 7 8 9 100

5

10

15

20

25

30

35

40

Vertial colimaor gap size, mm

Load

for

W4

cham

ber,

W

gap 10 mm

gap 11 mmgap 12 mm

gap 13 mm

A 4-wigglers scheme

Gap of 13mm (10W/m) Combination of collimators and absorbers Terminal absorber at the end of the straight section

(10kW)

Radiation absorption scheme

K. Zolotarev, CLIC09

0 5 10 15 20 25 30 350

2

4

6

8

10

12

Absorber #

Pow

er lo

ad,

kW

C L I CC L I C

ρwig = 5x1012 m-3, ρdip = 3x1011 m-3

Electron cloud in the e+ DR imposes limits in PEY (99.9% of synchrotron radiation absorbed in the wigglers) and SEY (below 1.3) Cured with special chamber coatings

Fast ion instability in e- DR, molecules with A>13 will be trapped (constrains vacuum pressure to around 0.1nTorr)

Other collective effects in DR Space charge (large vertical tune spread

of 0.19 and 10% emittance growth) Single bunch instabilities avoided with

smooth impedance design (a few Ohms in longitudinal and MOhms in transverse are acceptable for stability)

Resistive wall coupled bunch controlled with feedback (100s of turns rise time)

Chambers PEY SEYρ

[1012 e-/m3]

Dipole

0.0005761.3 0.04

1.8 2

0.05761.3 7

1.8 40

Wiggler

0.00109 1.3 0.6

0.109

1.3 45

1.5 70

1.8 80

Collective effects in the DR

Y.P., 03/02/2010 19ACE 2010

G. Rumolo

C L I CC L I CCoatings for e- Cloud Mitigation Bakeable system

NEG gives SEY<1.3 for baking @ > 180C

Evolution after many venting cycles should be studied

NEG provides pumping Conceivable to develop a

coating with lower activation T Non-bakeable system

a-C coating provides SEY< 1 (2h air exposure), SEY<1.3 (1week air exposure)

After 2 months exposure in the SPS vacuum or 15 days air exposure no increase of e-cloud activity

Pump-down curves are as good as for stainless steel

No particles and peel-off Very good results obtained at

CESR-TA (although contaminated by silicon from kapton adhesive tape)

M. Taborelli LER2010

CESRTA e+

bare Al

TiNTiN new

a-C CERN

C L I CC L I CA. Grudiev, CLIC08

RF system RF frequency of 2GHz

R&D needed for power source

High peak and average power of 6.6 and 0.6MW

Strong beam loading transient effects Beam power of 6.6MW

during 156 ns, no beam during other 1488 ns

Small stored energy at 2 GHz

Wake-fields and HOM damping should be considered

1GHz frequency considered (2 trains with 1ns bunch spacing) Easier extrapolation from

existing designs (e.g. NLC) Lowering peak current and

thus transient beam loading Delay line for train

recombination

CLIC DR parameters

Circumference [m] 493.2

Energy [GeV] 2.86

Momentum compaction 0.6x10-4

Energy loss per turn[MeV]

5.9

Maximum RF voltage [MV]

7.4

RF frequency [GHz] 2.0

C L I CC L I CKicker stability

Kicker jitter translated in beam jitter in IP, withσjit ≤0.1σx

Tolerance typically ~10-4

Double kicker system relaxes requirement, i.e. ~3.3 reduction achieved @ATF

Striplines required for achieving low longitudinal coupling impedance

Significant R&D needed for PFL (or alternative), switch, transmission cable, feedthroughs, stripline, terminator (PhD thesis student at CERN)

Should profit from collaborator with ILC and light source community

Y.P., 03/02/2010 22ACE 2010

M. Barnes CLIC09

C L I CC L I C

Low emittance tuning

Present tolerances not far away from ones achieved in actual storage rings

SLS achieved 2.8pm emittance

DIAMOND claim 2.2pm and ASP quoting 1-2pm (pending direct beam size measurements)

Participate in low emittance tuning measurements in light sources (SLS) and CESR-TA

Y.P., 03/02/2010 23ACE 2010

M. Boege,, LER2010

C L I CC L I CEmittances @ 500GeV

Light sources (SLS, DIAMOND and ASP) achieve ~2pm geometrical vertical emittance, at 3GeV,

corresponding to ~12nm of normalised emittance

Below 2pm, necessitates challenging alignment tolerances and low emittance tuning

Seems a “safe” target vertical emittance for CLIC damping rings @ 500GeV

Horizontal emittance of 2.4µm is scaled from NSLSII parameters, a future light source ring with wiggler dominated emittance and 10% increase due to IBS

NSLSII PARAMETERS Values

energy [GeV] 3

circumference [m] 791.5

bunch population [109] 11.8

bunch spacing [ns] 1.9

number of bunches 700

rms bunch length [mm] 2.9

rms momentum spread [%] 0.1

hor. normalized emittance [µm] 2.9

ver. normalized emittance [nm] 47

lon. normalized emittance [eV.m] 8700

coupling [%] 0.64

wiggler field [T] 1.8

wiggler period [cm] 10

RF frequency [GHz] 0.5

C L I CC L I CRoute to 3TeV

The 3TeV design can be relaxed by including only a few super-conducting wigglers and relaxing the arc cell optics (reduce horizontal phase advance)

Another option may be operating a larger number of super-conducting wigglers at lower field of around 2T.

The same route can be followed from conservative to nominal design, considering that some time will be needed for low-emittance tuning (reducing the vertical emittance)

Considering the same performance in the pre-damping rings, the 500GeV design relaxes the kicker stability requirements by more than a factor of 2

The dynamic aperture of the DR should be also more comfortable due to the relaxed arc cell optics

Energy loss/turn is significantly reduced and thereby the total RF voltage needed

C L I CC L I C

CLIC/ILC DR collaboration

ILC and CLIC DR differ substantially as they are driven by quite different main RF parameters

Intense interaction between ILC/CLIC in the community working on the DR crucial issues: ultra low emittance and e--cloud mitigation.

Common working group initiated at the end of 2008

Short term working plan includes Chamber coatings and e--cloud measurements

at CESRTA, e-cloud and instability simulations with

HEADTAIL (CERN) and CMAD (SLAC) IBS measurements at CESRTA Low Emittance Rings workshop organization

(12-15/01/2010 @CERN)

Parameters ILC CLIC

Energy (GeV) 5 2.86

Circumference (m) 3238 493.2

Bunch number 1305 - 2632 312

N particles/bunch 2x1010 4.1x109

Damping time x (ms) 21 1.6

Emittance x (nm) 4200 410

Emittance x (nm) 20 4.7Momentum compaction (1.3 - 2.8)x10-4 0.6x10-4

Energy loss/turn (MeV) 8.7 5.4

Energy spread 1.3x10-3 1.2x10-3

Bunch length (mm) 9.0 - 6.0 1.1

RF Voltage (MV) 17 - 32 7.4

RF frequency (MHz) 650 2000

Y.P., 03/02/2010 26ACE 2010

C L I CC L I CLER2010 scope

Bring together experts from the scientific communities working on low emittance lepton rings (including damping rings, test facilities for linear colliders, B-factories and electron storage rings) in order to discuss common beam dynamics and technical issues.

Targets strengthening the collaboration within the two damping ring design teams and with the rest of the community.

Profit from the experience of colleagues who have designed, commissioned and operated lepton ring colliders and synchrotron light sources.

Y.P., 03/02/2010 27ACE 2010

C L I CC L I C

Beyond LER2010 Low emittance rings working groups

Any other subjects? Coordinators to be confirmed (others to be added?) Task: Identify collaboration items as discussed in the workshop Collect “expressions of interest” from community (LER2010

participants and beyond) Start collaboration work to be reported to the next workshop!

Subject Coordinators1Low emittance cells design M. Borland (APS), Y. Cai (SLAC), A. Nadgi (Soleil)2Non-linear optimization R. Bartolini (DIAMOND/JAI), C. Steier (LBNL)3Minimization of vertical emittance A. Streun (PSI), R. Dowd (Australian Synchrotron)

4Integration of collective effects in lattice design

R. Nagaoka (SOLEIL), Y. Papaphilippou (CERN)

5Insertion device, magnet design and alignment

S. Prestemon (LBNL), E. Wallen (MAXlab)

6Instrumentation for low emittance M. Palmer (Cornell), G. Decker (APS)7Fast Kicker design P. Lebasque (Soleil), C. Burkhardt (SLAC)

8Feedback systems (slow and fast)A. Drago (INFN/LNF), B. Podobedov (BNL), T. Nakamura (JASRI/SPring8)

9Beam instabilities G. Rumolo (CERN), R. Nagaoka (SOLEIL)

10Impedance and vacuum designK. Bane (SLAC), S. Krinsky (BNL), E. Karantzoulis (Elettra), Y. Suetsugu (KEK)Y.P., 03/02/2010 28ACE 2010

C L I CC L I CSummary

PDR optics design achieves comfortable DA and energy acceptance DR lattice design rationalised for space and magnet requirements,

achieving large DA Some refinement in non-linear dynamics needed for the CDR

IBS effect significantly reduced (energy increase, lattice design) Monte-Carlo tracking simulations give encouraging results

DR performance based on super-conducting wigglers Short prototype on “conventional” wire technology achieved required

field More challenging wire technologies and wiggler designs are under

study Robust absorption scheme

Collective effects (e-cloud, FII) remain major performance challenge Novel coatings very promising as measurements in CESR-TA confirm

low SEY RF system present difficulties with respect to transients and power

source at 2GHz 1GHz frequency under consideration, including design of delay loop for

train recombination

Stability of kickers challenging Collaboration with ILC and light sources for technical design

Vertical emittance close to the ones achieved in modern light source Participation in low emittance tuning measurement campaigns in SLS

and CESR-TA Working group on CLIC/ILC common issues for DR

Low Emittance Rings task groups established for expanding the collaboration

Established conservative and nominal DR parameters for CLIC @ 500GeV Scaled design not far from existing design of existing or future light

sources

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

Brilliance and low emittanceBrilliance and low emittance

''24 yyxx

fluxbrilliance

2,

2, ephexx

2,

2,'' ' ephexx

2)( xxxx D

2' )'( xxxx D

R. Bartolini, LER2010

Comparison model/machine for linear opticsComparison model/machine for linear optics

Model emittance

Measured emittance

-beating (rms) Coupling*

(y/ x)

Vertical emittance

ALS 6.7 nm 6.7 nm 0.5 % 0.1% 4-7 pm

APS 2.5 nm 2.5 nm 1 % 0.8% 20 pm

ASP 10 nm 10 nm 1 % 0.01% 1 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% 2.2 pm

ESRF 4 nm 4 nm 1% 0.25% 10 pm

SLS 5.6 nm 5.4-7 nm 4.5% H; 1.3% V 0.05% 2.8 pm

SOLEIL 3.73 nm 3.70-3.75 nm 0.3 % 0.1% 4 pm

SPEAR3 9.8 nm 9.8 nm < 1% 0.05% 5 pm

SPring8 3.4 nm 3.2-3.6 nm 1.9% H; 1.5% V 0.2% 6.4 pm

* best achieved

R. Bartolini, LER2010

Vertical Emittance in 3Vertical Emittance in 3rdrd generation light sources generation light sources

Best achieved values – not operational valuesAssuming 10–3 coupling correction , the V emittance of the new projects can

reach the fundamental limit given by the radiation opening angle;Measurements of such small beam size is challenging !

R. Bartolini, LER2010