C L I C C L I C Low emittance generation in Damping rings: Optics, DR layout, SC wigglers vs NC wigglers February 3 rd , 2010 Yannis PAPAPHILIPPOU CLIC Advisory ComittEe,
Jan 07, 2016
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