LER2011
Lattice Team
K. Soutome, Y. Shimosaki, T. Nakamura, M. Takao,
T. Tanaka
K. Soutome (JASRI / SPring-8)on behalf of
SPring-8 Upgrade Working Group
SPring-8 Upgrade: Lattice Design of a Very Low-Emittance Storage Ring
Talk based on the work by
Y. Shimosaki, IPAC2011,"Lattice Design of a Very Low-emittance Storage Ring for SPring-8-II"
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Ultimate Target of Machine Upgrading
"Diffraction Limited" Light Source
in Both H. and V. Directions for ~ 10keV Photons e ~ 10pmrad
E = 6 GeVI = 100 mAk = 0.02sd = 0.12%bx = 1 mby = 1 m10 keV Photon byHybrid Undulator
by T.Watanabe
SPECTRA
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Present Lattice Structure of the SPring-8 SR
4 ´ [ 9 ´ (Normal Cell, DB) + (Matching Cell) + (Long Straight) + (Matching Cell) ]
Matching LS MatchingNormal
C = 1436 mE = 8 GeVe = 3.4 nmrad( eeff = 3.7 nmrad ) 3
Way of Upgrading
Convert present DB cell to Multi-Bend cell.
Reuse the present machine tunnel.
Keep the number and position of present ID-BLs.
Lower the energy: 8GeV 6GeV (or lower)
Hard X-ray is covered by undulator upgrading (short period).
Reduce the emittance with damping wigglers.
Control the coupling (if necessary).
2B: 1.9nmrad (Non-Achomat, 6GeV)
3B: 0.43nmrad
4B: 0.16 nmrad
6B: 0.07 nmrad (Achomat)
:
:
Strong Q Large Nat. Chrom.Small DispersionStrong SXSmall DA
"Chromaticity Wall"
(J.Bengtsson, EPAC08)We set 6B lattice as a
candidate of a new ring.
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Multi-Bend Lattice
〜 3 × Theoretical Minimum Emittance (TME)
×M
Half-Length B at Both Ends of Unit Cell (Achromat)
D.Einfeld and M.Plesko, NIMA335 (1993) 402
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Multi-Bend Lattice2B (eeff = 2.09nmrad)
3B (eeff = 0.54nmrad)
4B (eeff = 0.19nmrad)
6B (e = 0.07nmrad)
2009 6
Multi-Bend Lattice6B Lattice
LB LB LB LBLB/2LB/2
bx〜1mby〜1mhx = 0
matching
unit
matching
unit
unit
unit
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Multi-Bend LatticeDA @ Inj. Point
Normalizedby b1/2
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Multi-Bend Lattice
e (N∝ B-1)-3
NB: LB/2 at both ends → (NB-1)
8B 10B 12B
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Multi-Bend Lattice
Number of B ↓Quad. Tune Chrom.(abs) Dispersion ↓ Chromaticity Cor.Sextupoles ↓ Dynamic Apt.
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too small DA for M > 6
6B Lattice Design (typical)
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2B (Double-Bend)Dispersion Leaked
6B (Sextuple-Bend) Achromat
Unit Cell Length 29.9156 m
Ring Circumference 1435.9488 m
Beam Energy 8 GeV 6 GeV
Emittance 3.4 nmrad (3.7 nmrad) 0.068 nmrad
Energy Spread 0.109 % 0.096 %
Betatron Tune (H/V) 40.135 / 18.345 141.865 / 36.650
Natural Chromaticity (H/V) -88 / -42 -477 / -191
Momentum Compaction 1.68e-4 1.55e-5
Beta at Normal Straight 22.6 m / 5.6 m 1.0 m / 1.4 m
Bending Field 0.68 T 0.70 T
No. of Quadrupoles / Cell 10 26 (9 Family)
Max. Quad. Str. B'L/(Br) 0.40 m-1 1.49 m-1 (B' = 79 T/m)
No. of Sextupoles / Cell 7 23 (12 Family)
Max. Sext. Str. B''L/(Br) 6.2 m-2 110 m-2 (B''=13000 T/m2)
Radiation Loss 9 MeV/turn 4 MeV/turn12
v. 110921
Bending Field Dependence of Chromaticity
Use 6B lattice with 0.7 T / 0.9 T / 1.4 T bending field, vary QF and QD and find optics having the emittance of less than 90pmrad.
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Nat. Chrom. & Rad. Power & Emit. Reduction by DW 0.7 T
SF/2 SF/2SF SF SF SF SF
SD SD SD SD SDSD
Interleaved SX Configuration within a Cell
Basic Idea: Cancellation of SX Kicks within a Cell (Hor.)
small but non-zero DA
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- I transformation
SF/2 SF/2SF SF SF SF SF
SD SD SD SD SDSD
Interleaved SX Configuration within a Cell
Actual Consraints we put in SX Optimization
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- I transformation
To increase SX degree of freedom, we relaxed the constraints and added harmonic SXs outside the arc.
12-family (mirror sym.)
close but not the same strength
Betatron phase advance Dyx ~ 25p
Dyx ~p
Interleaved SX Configuration between Cells
Cell 1 Cell 3 Cell 5
Cell 1 Cell 3
Dyy ~ 3p
Cell 5
Horizontal
Vertical
- I transformation
cf.) "sextupole symmetrization" in SLS 16
We found the vertical constraint is effective.DA becomes double in vertical direction.
Linear Optics“as low natural-chromaticity as possible” (so that SX becomes weak)
Tune Selection (1) avoidance of strong resonances (2) phase adjustment for interleaved sextupole configuration
Design of Nonlinear Opticsharmonic method with interleaved SX for correcting (1) linear chromaticity (2) nonlinear resonances independent of Dp/p (on- and off-mom.) (3) nonlinear resonances by Q and SX for off-mom. (4) higher order resonances for on-mom. (5) amplitude-depence of tune
Iteration (tune survey, etc)
Strategy of Lattice Design
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+ “(On-momentum) Higher Order Resonant Potentials by Sx”
+Δpp
U 2Qx ~ int .( )Sx+ U 2Qy ~ int .( )
Sx{ }
+Δpp
U 2Qx ~ int .( )QQ+ U 2Qy ~ int .( )
QQ{ }
Resonant Potential Induced by SX without Dp/p
(Qx, Qy): Tune
(Off-momentum) Resonant Potential by Q
(Off-momentum) Resonant Potential by Sx
Cancel
Set to~ 0
Suppress
Isolated Resonance Hamiltonian
H ∝ U Qx ~int.( )Sx+ U 3Qx ~int.( )
Sx+ U Qx ±2Qy ~int.( )
Sx
Design of Nonlinear Optics
Sextupole Optimization (latest)
Amplitude- and Energy-Dependence of Tune
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Sextupole Optimization (latest)
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Sextupole Optimization (latest)
21Frequency Map (d = 0%)
Dynamic Aperture w/o Error
@ Inj. Point (LSS) bx = 24.2 m, by = 7.8 m sx = 40 mm
DA Boundary x: integer resonance y: sextupole resonance
Sextupole Optimization (latest)
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DA w/ SX Alignment Error (s = 10mm, cutoff 2 )s
Sextupole Optimization (latest)
Momentum Acceptance
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Damping by Insertion Devices
Residual dispersion must be suppressed: Dhx < 1mm
Planar ID (lU = 14.4mm, L = 3m) ×28 ( the same number as present @ normal straights )
At user-time: 67pmrad → around 30 pmrad
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Damping WigglersAt user-time : 67pmrad → around 30pmrad
DWs are used to realize an extremely small emittance less than 20pmrad.
They can also be used to keep the emittance at some value during user-time (compensation of ID gap change).
Add DWs (lDW = 50mm, LDW = 4m) at LSSs.
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Intrabeam Scattering & Touschek Lifetime
Emittance and Energy Spread
Ref.) K.Bane, PRST-AB 5 (2002) 084403. K.Kubo, PRST-AB 8 (2005) 081001.
Touschek Lifetime
cf.) 1nC/bunch 0.2mA/bunch
Bunch Length (rms): 7.7 – 10 ps
Control of bunch length is under consideration.
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w/o ID
Brilliance
About 103 times higher brilliance than that of the present storage ring (0.5 ~ 100 keV).
by T.Tanaka
New (6GeV, 300mA)
Present (8GeV, 100mA)
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1023
ID Parameters (tentative)
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30m-LSS for Beam Injection
One example of LSS Optics (to be optimized)No Sextupoles (Linear)Low Natural ChromaticityBetatron-Phase MatchedHigh b for Beam Injectionalso for Damping Wigglers / RF
p Dyx, Dyy2p
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Injector
A high-quality injection beam is needed.
At SPring-8 we have XFEL Linac, which will be used as a full-energy injector to the storage ring.
Energy: 8 GeV (max.)Emittance: 40 pm.radEnergy Spread: 0.01 %Bunch Length: 30 fs (rms)Electron Charge: 300 pC – 1 nC
XFEL(SACLA)
SRBooster
Design Parameters(typical)
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Summary
SPring-8 upgrade plan is under discussion.
6B lattice is a current tagret : e 〜 70 pmrad (natural, at 6GeV) → < 20 pmrad (w/ damping) Brilliance > 1023
Studies are ongoing including further optimization of lattice.
DAY-3K.Fukami, "Strong Magnets for Ultimate Storage Rings"T.Nakamura, "A Fast Kicker System for Beam Injection"
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IPAC2011 Papers
T. Watanabe, et al.Current Status of SPring-8 Upgrade Plan
Y. Shimosaki, et al.Lattice Design of a Very Low-emittance Storage Ring for SPring-8-II
T. NakamuraBucket-by-bucket On/Off-axis Injection with Variable Field Fast Kicker
M. Masaki, et al.A Proposal of Short X-ray Pulse Generation from Compressed Bunches by mm-wave iFEL in the SPring-8 Upgrade Plan
K. Fukami, et al.Beam-based Alignment for Injection Bump Magnets of the Storage Ring using Remote Tilt-control System
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