1 optics and ir design for superkekb y.ohnishi 1/19-22, 2004 super b factory workshop in hawaii
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![Page 1: 1 Optics and IR design for SuperKEKB Y.Ohnishi 1/19-22, 2004 Super B Factory Workshop in Hawaii](https://reader035.vdocuments.net/reader035/viewer/2022062407/56649d7d5503460f94a5ff1f/html5/thumbnails/1.jpg)
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Optics and IR design for SuperKEKB
Y.Ohnishi1/19-22, 2004
Super B Factory Workshop in Hawaii
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Machine parameters for SuperKEKB
• Flexibility of lattice :– 10 nm < x < 36 nm
– -4x10-4 < p < 4x10-4 (Negative p → advantage for short bunch length)
LER HER Unit
Beam currrent I 9.4 4.1 A
Horizontal beta at IP βx cm
Vertical beta at IP βy mm
Bunch length σz mm
Emittance x nm
Coupling κ % Crossing angle θx mrad
Momentum compaction αp 2.7x10 -4 1.8x10 -4
RF voltage Vc 15 20 MV
Synchrotron tune νs 0.031 0.019
1-6
30
Parameter
20
3
3
24 (18-30)
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Items considered for IR design
• IR magnets closer to IP– Lower beta at IP
• Physical aperture– Beam injection
• Dynamic aperture– Beam injection / Lifetime
• Crossing angle– Beam separation / Magnet design
• Synchrotron radiation from IR magnets– Heating of components / Detector background
Magnet aperture (bore)Good magnetic field qualitySmall leakage field
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Layout of beam axis and SuperBelle• No change of HER axis (already has 22 mrad)• LER axis is rotated by 8 mrad (θx=22 -> 30 mrad).
– minimize rearrangement of magnets
• No rotation of Belle solenoid (translation is allowed)• Beam pipe and SVD have 7 mrad w.r.t Belle
solenoid. (middle of LER and HER)e-
e+ KEKB / Belle solenoid / Belle beam pipe axis
e+ SuperKEKB22mrad
8mradSuperBelle beam pipe axis
7mrad IP
30 mrad
SuperKEKB and SuperBelle
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IR magnet layout
QC2LP
QC2RPQCSL QCSRQC1LE
QC2LE
QC1RE
QC2RE
← LER
HER →
IP s (m)
x (m)
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Relationship between SuperBelle and SuperKEKB
• Spatial constraints for IR components :
• We assume the same condition as the present Belle and KEKB.
• Except for EFC (extremely forward calorimeter) replaced with a part of compensation solenoid magnets (ES).
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QCS for SuperKEKB and KEKB
Move QCS closer to IP and compensation solenoid isdivided into two parts, one is overlaid with QCS.
SuperKEKB
KEKB
θ=17°θ=150°
EFC
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IR aperture requirements
• Required acceptance depends on linac beam emittance
• Positron damping ring (DR) will be constructed prior to IR upgrade.
ws nsσinjnrσring
septum
2Jx,inj
2Jx,ring
Injectionbeam
Acceptanceof ring
x
Px
€
x 2
β ring+ β ring px
2 = 2Jx,ring
(x − x i)2
β inj+ β inj px
2 = 2Jx,inj
x i = nrσ ring + ws + nsσ inj
2Jx,inj = ni2ε inj
(ni,ns,nr)=(2,2,3)
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Injector linac for SuperKEKB
1. Positron dumping ring (1 GeV)2. Positron energy upgrade with C-band
for energy exchange (e- LER / e+ HER)
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IR aperture requirements (cont'd)
LER HER
Energy (GeV)
3.5 8
Inj. beam
e+ with DR
e-
x/y (m) 1.4x10-8 2x10-8
LER HER
Energy (GeV)
3.5 8
Inj. beam e-
e+ with DR
x/y (m) 4.6x10-8 6.3x10-9
Energy Exchange(adiabatic construction)
Required acceptance depends on linac beam emittance
HER transverse aperture :Ax=1.9x10-6 m(1.5x10-6 m due to inj. error)Ay=8x10-8 m
LER transverse aperture :Ax=2.6x10-6 m(1.8x10-6 m due to inj. error)Ay=1.8x10-7 m
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Beam envelope and IR magnets
LER
HER
QCSRI
QCSRC
QCSRAQCSLA
QCSLC
QCSLI
IP
BELLE AXIS
0 5-5
0
-200
-400
200
400
m
QC1R
QC1LQCSL QCSR
QC2L-LER
QC2L-HER
QC2R-LER
QC2R-HER
ESL-1ESR-1
ESL-2 ESR-2
Pos. from the IP KEKB Super-KEKBQCS-R 1920 mm 1163.3 mmQCS-L 1600 mm 969.4 mm
← LERHER →
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Design of IR magnets
• QCSL and QCSR with ES• QC1LE and QC1RE
– Choice of superconducting or normal magnet
• QC2LP, QC2LE, QC2RP, QC2RE– normal magnets
• Synchrotron lights from QCS– Effects of dynamic beta and dynamic emittance– Orbit displacement from design orbit (estimated
from KEKB experience)
– PSR=65 kW from QCSL / 179 kW from QCSR
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Dynamic beta and dynamic emittance
x
βx
If x=0.1, x becomes 58 nm.
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QCS and QC1(superconducting magnet)
Crossing angle=30mrad, βx=20cm beam envelope & synchrotron radiation(SR)
Left side Right side
pink : SR (design orbit)green : SR (inc. dynamic effects and orbit displacement)
QC1LEQC1RE
QCSL QCSR
Synchrotron light passes through cryostat-bore
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QC1(superconducting magnet)
G=42.86 T/mLeff=0.232 mIop=1319A, Bmax=1.62 TIop/Ic=59%
QC1LE
Leakage field<1.5 Gauss
QC1RE
Leakage field<20 Gauss
G=34 T/mLeff=0.266 mIop=1319 A, Bmax=3.28 TIop/Ic=73%
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QC1 (normal magnet)
g=15.54 T/m, L=0.64 m R0=25mm3turn-8x8-φ5 3920ATi=30A/mm2
QC1LE
g=12T/mL=0.75m R0=48mm 3turn-9x9-φ6 11050AT i=70A/mm2
QC1RE
SR
SR
Leakage field<0.65 Gauss
Leakage field<1.1 Gauss
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QC2 magnets
QC2LP
QC2LE
QC2RP
QC2RE
SR SR
SR SR
Leakage field<0.85 Gauss
Leakage field<0.4 Gauss
Leakage field<0.35 Gauss
Leakage field<0.25 Gauss
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IR magnets and Belle detector
QC1RE
QC2RP
QC2RE
QC2LE
QC2LP
QC1RE
No interference between QC1 and end yoke.
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IR optics
LER IR optics with localchromaticity correction
HER IR optics
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LER and HER optics (ring)LER optics
HER optics
wigglersRFRF
RF RF
IP
IP
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2.5 cell and non-interleaved chromaticity correction
LER arc section
Two sextupole magnets in a pair are connected with -I' transformer.Nonlinearities from sextupoles are cancelled. → Large dynamic aperture
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Optics correctionLocal sextupole bumps are utilized to correct optics. It works very well at KEKB.
Sextupole movers(±2.5mm) are necessary instead of bump orbit.Large SR may hit beam channel of ante-chamber due to bumps. (SR channel : height ~ 7 mm)
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Dynamic aperture
Injectionbeam
Coupling Lifetime
1% 51 min
2% 72 min
4% 102 min
6% 145 min
Dynamic aperture in LER Machine errors are not included. Transverse aperture is acceptable.
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Summary• Strategy of IR design• Positron DR prior to IR upgrade• Design of IR magnets• Two options for QC1 :
– superconducting / normal
• IR magnets is designed so that SR from QCS does not hit QC1 and QC2 as possible.
• Vacuum chamber in IR is under study.• Optics for SuperKEKB is designed.
– Dynamic aperture in LER ( p/p0 ~ 1.5 %)– Injection aperture can be kept.