Y. Funakoshi, N. Ohuchi, F. Tawada, S. Kanazawa, H. Koiso, K. Oide, Y. Ohnishi and O. Tajima  (KEK) 

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

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

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.

General remarks�

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).

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

Relationship between SuperBelle and SuperKEKB!

e-

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

IR magnet layout!

QCSRQCSLQC2RP

QC2LP

QC2LE

QC2RE

QC1RE

QC1LELERbeam

HERbeam

LoI

LER IR Optics

HER IR Optics

LoI

Dynamic beam-beam effect�

The dynamic effects are very strong with tunes near to (half) integer.

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

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

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

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

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

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

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}

Other issues �

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”.

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)

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.

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

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.

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?

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

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.

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.

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

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

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

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

Suppressed by Neutron shield

Beampipe radius 1.51cm

BGx33 (several MRad/yr)!? (sim. for particle shower)

1st layer

•  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%

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

Spare slides!

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？

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

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

M. Kikuchi