SuperKEKB Lattice and Dynamic Aperture H. Koiso Apr. 20, 2005 Super B Factory Workshop in Hawaii
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Transcript of SuperKEKB Lattice and Dynamic Aperture H. Koiso Apr. 20, 2005 Super B Factory Workshop in Hawaii
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SuperKEKB Lattice and Dynamic Aperture
H. KoisoApr. 20, 2005
Super B Factory Workshop in Hawaii
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Lattice ParametersLER HER
Horizontal emittance 24 24 nm
Beta function @ IP 200/3 200/3 mm
Bunch length 3 3 mm
RF voltage 15 20
Momentum compaction
2.7×10-4 1.8×10-4 MV
Synchrotron tune -.031 -.019
•No major change in arcs.•Only the interaction region in Tsukuba straight section (~200m) will be fully reconstructed.
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2.5π cell structure
x and α are independently adjustable.
x 10 ~ 36 nm , α -4 ~ 4×10-4
Noninterleaved sextupoles (52HER/54LER pairs)
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Geometrical Conditions • Both rings are geometrically adjusted in the a
ccuracy of 1> mm.– The position of IP is same as that of KEKB.
• Crossing angle at IP is satisfied the requirements.e-e+ now, Belle solenoide+ SuperKEKB22mrad8mradSuperKEKB
beam pipe axis
7mrad
e+/e-:before charge switch)
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Unit Cell x =24 nm LER (left), HER(right)
Both rings reserve sufficient tuning range of x and α.
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LER ring
RF RF IP wiggler RF
The horizontal emittance is adjusted as xarc ~ xwig
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HER ring
RF IP RF (ARES) (Super)
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IR Lattice• x-y coupling components and H/V dispersions are all
corrected to zero at IP, and are localized on each side of IP with 6(LER)/6(HER) skew quadrupoles and H/V dipoles.
• SuperBelle solenoid field is compensated on each side of IP.
• Field distributions of solenoids, QCS are given by 2-cm slices with constant strengths.
• Conditions for Crab cavities are not satisfied.– Crab cavities can be placed in Nikko straight section if the te
st at KEKB is successful.
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Solenoid Field
QCS field gradient (T/m) (top)
Solenoid field (T) (bottom)
QC2RP (QC1RE) QCSR IP QCSL (QC1LE) QC2LP
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QCS Multipole Fields
QCS field gradient (T/m) (top)
K5(12-pole), K9(20-pole), K13(28-pole)
QC2RP (QC1RE) QCSR IP QCSL (QC1LE) QC2LP
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LER IR (x*/y* = 20/0.3 cm)
LER IR with local chromaticity correction.
(crab) SL SL IP SL SL (crab)beam→
x/y
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Coupling Components (LER IR)
x/y
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HER IR (x*/y* = 20/0.3 cm)
(crab) IP (crab)
x/y
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LER dynamic aperture bare lattice BXBY=20/.3 cm (4cm-thick slices)
injection beam
Required: H/V 7.5/1.2 ×10-6m
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HER dynamic aperture bare lattice BXBY=20/.3 cm (4cm-thick slices)
injection beam
Required: H/V 4.5/0.52 ×10-6m
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Dynamic Aperture with Beam-Beam Effect
• Case y = 0.14, dynamic aperture shrinks in large momentum deviation for LER.
• Transverse aperture decreases in HER due to beam-beam effect.
• Touschek lifetime with beam-beam(xy= 0.14): 50 min in LER / 180 min in HER
Stored beam Jy/Jx = 2 %
x/y = 45.510/43.545
No beam-beam
y = 0.07
y = 0.14
* no machine errorStored beam Jy/Jx = 2 %
x/y = 45.510/43.570
y = 0.14
y = 0.07
No beam-beam
by Y.Onishi
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LER dynamic aperture bare lattice BXBY=20/.3 cm (2 cm-thick slices)
injection beam
Required: H/V 7.5/1.2 ×10-6m
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LER dynamic aperture lattice with QCS multipoles BXBY=20/.3 cm (2 cm-thick slices)
injection beam
Required: H/V 7.5/1.2 ×10-6m
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HER Sextupole Magnet
• Strengths of 9 SD pairs K2 ~ -14. (the present limit is -12)• New sextupole magnets are needed to improved the dynamic apertures. • Local chromaticity correction in HER may be needed.
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Interactive procedure ofmeasurement + analysis + correction
Knobs:■ Local bumps at sextupoles■ Fudge factors for quads/skews
dispersion
XY-coupling
beta function
Works very well !
Optics measurement and correction
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Chromaticity Measurement
There are differences from the model in off-momentum optics.
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Summary• LER dynamic aperture satisfies the requirements for transverse a
cceptances at injection. • Modeling method of QCS and solenoid fields (for example, the thi
ckness of slices) affects the dynamic aperture.– Effect of the edge of quadrupole field? Need to check.
• QCS multipoles do not change the dynamic aperture significantly. • HER aperture still needs improvement.
– Local chromaticity correction may be necessary.• Dynamic apertures are decreased by the beam-beam effect. • Dynamic apertures of both rings will be improved by further optimi
zation of sextupole strengths. – should be estimated at a working point ~(.503 ,530) .
• Correction methods for off-momentum optics should be developed.
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Synchro-betatron ResonanceHER(KEKB)
by K. Oide, et.al.
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LER dynamic aperture bare lattice BXBY=20/.3 cm
injection beam
Required: H/V 7.5/1.2 ×10-6m
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Bumps at sextupoles
scan
• Horizontal/Vertical bumps at sextupoles are used for optics correction.• 8 vertical bumps at SD sextupoles in each side of IP.• Vertical dispersion and its angle, x-y coupling components are independently adjustab
le. R1,R2,R3,R4,EY, and EPY• Sextupole movers will be used instead of vertical bumps.
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Merit of Local Chromaticity Correction
by A. Morita
LER dynamic aperture with a crab cavity (KEKB)
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Solenoid Field
QCS field gradient (T/m) (top)
Solenoid field (T) (bottom)
QC2RP (QC1RE) QCSR IP QCSL (QC1LE) QC2LP