Y. Funakoshi, N. Ohuchi, F. Tawada, S. Kanazawa, H. Koiso ... · Y. Funakoshi, N. Ohuchi, F....
Transcript of Y. Funakoshi, N. Ohuchi, F. Tawada, S. Kanazawa, H. Koiso ... · Y. Funakoshi, N. Ohuchi, F....
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Y. Funakoshi, N. Ohuchi, F. Tawada, S. Kanazawa, H. Koiso, K. Oide, Y. Ohnishi and O. Tajima (KEK)
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Design strategy!• Natural extension of present KEKB
– the same physical boundary between KEKB and Belle
– conventional flat beam scheme • round beam
• A baseline design of SuperKEKB IR was completed. – Details are described in LoI (2004). – New issues on IR physical aperture
• Under redesigning the IR magnets
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Machine parameters!Present KEKB
LER/HER KEKB Design
LER/HER Super KEKB
LER/HER
βx* [m] 0.59/0.56 0.33 0.2 (0.4)
βy* [mm] 6.5/5.9 10 3
εx [nm] 18/24 18 12
σz [mm] ~8/~7 5 3
φc [mrad] ±11 ±11 ±15 (Crab)
Ibeam [A] 1.66/1.34 2.6/1.1 9.4/4.1
L [1034/cm2/s] 1.71 1 55
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Issues of IR Design!Issues Causes Measures
Dynamic aperture Lower beta’s at IP. Place QCS magnets. closer to IP. Damping ring.
Physical aperture Lower beta’s at IP. Dynamic beam-beam effects
Damping ring. Larger crossing angle. (22mrad -> 30mrad)
Heating of IR components
Higher beam currents. Higher power of SR from QCS magnets. Shorter bunch length (HOM).
Careful design.
Detector beam background
Higher beam currents. Higher power and critical energy of SR from QCS magnets. QCS closer to the IP. Higher Luminosity.
Shield. Detector upgrade.
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General remarks�
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Place QCS magnets closer to IP!SuperKEKB
KEKB
The boundary between KEKB and Belle is the same.ESL and ESR will be divided into two parts (to reduce E.M. force).QCSL (QCSR) will be overlaid with (the one part of ) ESL(ESR).
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QCS-related parameters !QCSR QCSL
Distance from IP [m] 1.16 (1.92) 0.969 (1.60)
Effective length [m] 0.333 (0.385) 0.398 (0.483)
Δx [mm] 34.5 29.1
G [T/m] 37.2 (21.73) 35.4 (21.66)
B [T] 1.28 (0.918) 1.03 (0.762)
Eb [GeV] 8.0 3.5
I [A] 4.1 (1.1) 9.4 (2.6)
P [kW] 179 (27) 64.6 (10)
Critical Energy [keV] 54.7 (39.1) 8.40 (6.2)
( ): present KEKB Design
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Relationship between SuperBelle and SuperKEKB!
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e+ now, Belle solenoid
e+ SuperKEKB22mrad
8mrad
SuperKEKB
beam pipe axis
7mrad
Belle Solenoid will not rotate.The HER axis will not change.The LER axis will rotate by 8mrad.The beam pipe (and SVD) have a finite angle of 7mrad with respect to Belle Solenoid.QCS magnets will be set parallel to Belle Solenoid.
±11mrad → ±15mrad
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IR magnet layout!
QCSRQCSLQC2RP
QC2LP
QC2LE
QC2RE
QC1RE
QC1LELERbeam
HERbeam
LoI
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LER IR Optics
HER IR Optics
LoI
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Dynamic beam-beam effect�
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The dynamic effects are very strong with tunes near to (half) integer.
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HER IR βx
*= 1.5cm, εx = 82nm (red) with dynamic beam-beam βx
*= 20cm, εx = 24nm (blue) no beam-beam
σx in IR with dynamic effects!νx = .503
σx@QC2RE ~ 40mm Aperture of QC2RE ~ 90mm (LoI): ~2.5σx
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no b-b
nominal higher emittance higher βx* even higher βx*
νx0 .503 .505 .510 .503 .505 .510 .503 .505 .510 .503 .505 .510
εx0 [nm] 12 12 12 12 24 24 24 12 12 12 12 12 12
βx0* [cm]
20 20 20 20 20 20 20 40 40 40 100 100 100
ξx0 0 .270 .270 .270 .135 .135 .135 .272 .272 .272 .273 .273 .273
εx [nm] 81.9 64.1 46.6 117 91.5 66.8 82.1 64.3 46.7 82.3 64.4 46.8
βx* [cm] 1.50 1.93 2.77 2.1 2.7 3.8 2.99 3.87 5.53 7.40 9.65 13.4
σx@ QC2RE
[mm] 4.0 39.5 30.9 22.3 38.7 30.1 21.7 28.6 22.7 16.9 20.6 17.3 14.5
Nσ1) 12.5 1.26 1.62 2.24 1.29 1.66 2.30 1.75 2.20 2.96 2.43 2.89 3.45
Parameter search for smaller beam size
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New IR magnet layout!
QCSRQCSLQC2RP
QC2LP
QC2LE
QC2RE
QC1RE
QC1LELERbeam
HERbeam
QC2RE, QC2LE -> moved to the position of QC2RP, QC2LP {QC2RE, QC2RP} and {QC2LE, QC2LP} :two-in-one SC-Quad QC1RE, QC1LE -> SC-Quad
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HER QC2 New Layout
QCS QC1 QC2
QCS QC1 QC2 (QC2)
New
1180.3 m
590.5 m670.0 m
1353.8 m
H. Koiso
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Modified Lattice Higher magnetic field with shorter distance between QC1 and QC2
QC2LE • IP-Magnet 5.7 → 5.0 m • K1 +0.24370 → 0.37175
QC1LE • K1 -0.40688 → -0.50831
QC2RE • IP-Magnet 6.8 → 5.1 m • K1 +0.24179 → 0.39439
QC1RE • K1 -0.34984 → -0.47530
H. Koiso
SC-Quad
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Countermeasure for the physical aperture issue�
• Move QC2R(L)E closer to IP – QC1 -> SC-Quad
• More moderate tune – .503 -> .505
• Relax βx* – 20cm ->40cm
• Keep 5σx aperture
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Beam size @ IR Q-magnets�
QC1LE� QC2LE� QC1RE� QC2RE� QC2LP� QC2RP �βx*=20cm QC2RE: origina�
8.2 (41) �
26.9 (134.5) �
11.6 (58) �
28.8 (144) �
14.7 (73.5) �
18.6 (93) �
βx*=20cm QC2RE->IP �
8.4 (42) �
19.0 (95) �
12.0 (60) �
20.7 (103.5) �
βx*=40cm QC2RE->IP �
5.9 (29.5) �
13.4 (67) �
8.5 (42.5) �
14.6 (73) �
9.8 (49) �
12.3 (61.5) �
νx =.505 (): 5 σx
{9.7761,.9536,.3712,4.2204,3.4765,12.3323}
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Other issues �
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Ring acceptance for beam injection!
• Assume α=0 at injection point • Required acceptance is determined
by the following parameters. – Ring emittance: εxr – nr – ws – ns – ni – Ring β: βxr – Linac beam emittance : εxi – Injection line β: βxi
• βxi is determined so that required acceptance is minimum with each parameter set.
• We do not utilize so-called “kicker jump”.
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Ring acceptance vs. Linac beam emittance!
• Required acceptance depends largely on Linac beam emittance. – Damping ring is very effective to
reduce the requirement.( εxi 1.5e-7m (@8GeV) – Electron:2.0e-8m (@8GeV)
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Strategy of IR aperture for beam injection!
• We will take the “adiabatic construction” scenario into consideration. – The Linac energy switch will be realized some
time later after the IR reconstruction is completed.
– This means that the both rings will have to accept the position beam.
– Required acceptance becomes large with this strategy.
– If we can construct the damping ring before the IR reconstruction, required acceptance will be drastically reduced.
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Ring acceptance!Requirement for Beam Injection!
w/o e+ damping ring�
w/ e+ damping ring�
Linace beam
εx (m) [LER] 3.5 x 10-7
positron �4.6 x 10-8
electron �
Linace beam
εx (m) [HER] 1.5 x 10-7
positron �2.0 x 10-8
electron
Ring Ax (m) [LER] 7.5 x 10
-6 2.6 x 10-6
Ring Ax (m) [HER] 4.5 x 10
-6 1.9 x 10-6
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Required aperture for beam injection (w/o beam-beam)�
Required Acceptance �
βx�Required Aperture�
QC1LE � 4.5 x 10-6 m� 115 m� 22.7 mm �
QC1RE � 235 m� 32.5 mm �
QC2LE � 591m � 51.6 mm �
QC2RE � 692 m� 55.8 mm �
QC2LP � 7.5 x 10-6 m� 194 m� 38.1 mm �
QC2RP � 301 m� 47.5 mm �
The required physical aperture for beam injection is smaller than that for beam lifetime with dynamic beam-beam effect.
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HER dynamic aperture bare lattice BX/BY=20/.3 cm
injection beam
Required: H/V 4.5/0.52 ×10-6m
H. Koiso
Estimated dynamic aperture of HER is marginal. Do we need a local chromaticity correction also In HER?
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Local chroma2city correc2on
KEKB Design Report Local correction (LER)
Effects of local correction - widen dynamic aperture - weaken synchro-betatron resonance
KEKB: local correction only in LER
KEKB upgrade : local correction also in downstream of HER
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Another constraint for IR physical aperture: Fan of SR!
• On the downstream side of QCS magnets, high power SR is emitted.
• We need to prevent SR from hitting the IR magnets.
• Procedure of estimation – Consideration of the particle distribution in
the phase space – Effects of dynamic-β and dynamic-emittance
• These effects are very large with the horizontal tune very close to the half integer.
– We took 9εx (3 σx, 3σx’) into consideration.
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Fan of SR from QCS magnets with dynamic effects!
ξx0 = 0.1, νx = .510
νx = .510 -> σx’~1.4mradνx = .503 -> σx’~2.5mrad
9εx (3 σx, 3σx’) is taken into account.
Old layout (LoI) We need to upgrade the estimation with the new IR layout.
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Super-KEKB QCS Magnets !Cross Section of Magnet Cryostat and Parameters!
• 6 layer coils (3-double pane cake coils) • Inner coil radius : 90.0 mm • Outer coil radius : 116.8 mm • Cable size : 1.1 mm × 4.1 mm
1.1 mm × 7.0 mm (KEKB) • Number of turns : 271 in one pole
1st layer = 38, 2nd layer = 39 3rd layer = 46, 4th layer = 47 5th layer = 50, 6th layer = 51
• Field gradient : 40.124 T/m • Magnet current : 1186.7 A • Magnetic length : 0.299 m • Inductance : 69.98 mH • Stored energy : 49.3 kJ Magnet cryostat cross section
in the right side
Design parameters of final focus quadrupole in the right side
(QCS-R:R&D Magnet)
2007/3/20 KEKB Review 2007 31
N. Ohuchi
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Detector beam background issues (Tajima)!
Mechanism Reason of severeness
Particle loss
Radiative Bhabha High Luminosity, QCS’s closer to IP
Collision with residual gas
High currents
Touschek effect Short bunch length, High current, smaller dynamic aperture
SR Emitted in QCS’s High current, larger φc, Higher field of QCS’s
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SVD
3.5 GeV (LER)
8.0 GeV (HER)
CDC
KLM
PIDECL
Detector will be upgrade to work under BGx20 SVD will work under BGx30 (rbp: 1.5 1.0 cm) Almost same structure
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FWD EndCap
BWD EndCap
Barrel
L=1034 /cm2/s
~4 % of total BG
L=25x1034 /cm2/s
Expected BG from other
sources with heavy metal total ~ 1.5 ton
Realistic design based on discussion with QCS group
O. Tajima
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Suppressed by Neutron shield
Beampipe radius 1.51cm
BGx33 (several MRad/yr)!? (sim. for particle shower)
1st layer
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• Backscattering of QCS-SR is not serious, but strongly depends on IR chamber configuration
• Vacuum level is very important Original design (5x10-7 Pa) is serious BGx25 w/ further effort (2.5x10-7 Pa) BGx18
• Increasing of Touschek origin BG Smaller bunch size & higher bunch currents are reason Might be reduced by further study
• Radiative Bhabha origin BG can be suppressed • Beampipe radius 1.5cm 1cm
Further simulation study of shower particles into SVD is important
-30%
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Summary and prospects�• We have made a big change in the layout of IR
magnets. – Dynamic beam-beam effects impose a very tight
restriction. Agreement with Belle on the space boundary is too severe in case of SuperKEKB?
• QCS magnet R&D in progress • Future works
– Re-calculation of SR fan with latest IR layout (very soon) – Design of vacuum system
• How to avoid the HOM heating? – Design of SC Quad-magnets – Other engineering design – Re-estimate detector beam background with the latest
IR design
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Spare slides!
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3台 -> 6台:+2.5億円?- > 12.95億円 (SC-mag関連合計) 真空機器その他:3億円? -> IR合計 16億円?
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Cost estimation!Old estimation
Full Spec SuperKEKB Construction (for 3 years)
Upgrade after operation restart
Vacuum 116.86 139.36 0 RF 115.873 16.45 84.25 Infrastructure 84.3 3 75.2 + α Injector 58 10 53.7 Magnet 16.7008 31.9 0 Crab 17 5 10 Beam monitor 17.4684 17.7 4.5 Damping Ring (other than RF, monitor)
16.8 0 21.26
Control 9.4 2 7.4 IR 8 14.7 -> 16 0 Beam transport 2.5 2.5 0 Sum 462.9022 242.61 -> 243.91 256.31
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Summary and Schedule !
• The QCS-R R&D was built and successfully tested at 4.2 K. – The magnet quench started from the magnet current of 1437 A, which is
higher than the design operating current. – After 21 times of quenches, the magnet current reached 95% of the S.C.
cable limitation. – The quench location concentrated on the first built coils (2nd quadrant). It is
considered that the cause came from the immature control of the coil size. – The integral field gradient of the quadrupole was roughly measured, and the
measured value is 0.23 % different from the design. – The precise field measurement will be performed with the harmonic coil
system and the signal integrators until this summer.
• The corrector and the compensation solenoid R&D magnets are being built now, and they will be completed in March. – The corrector R&D coils will be cooled by thermal conduction from the
helium vessel, and for transporting the current, the HTS current leads will be used in the system in order to reduce heat load. The system will be tested until this summer.
– The solenoid R&D magnet will be tested separately at first. After this test, the QCS R&D magnet will be assembled in the solenoid bore, and the excitation test of both magnets will be performed in this year.
2007/3/20 42 KEKB Review 2007
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M. Kikuchi