1 SuperKEKB Upgrade project of KEKB KEK Yukiyoshi Ohnishi.

1

SuperKEKBSuperKEKB

Upgrade project of KEKB

KEKYukiyoshi Ohnishi

　 Y.　Ohnishi　(KEK)

2

Target of SuperKEKBTarget of SuperKEKB

Extremely high luminosity B factory– Luminosity = 1035 ~ 1036 cm-2s-1

– Int. L > 1000 /fb/year at SuperKEKB

(Int. L = 100 /fb/year at present machine)

Strategy :1. Unique

– Asymmetric energy, double ring collider, finite x-angle, high beam current, extremely low beta & short bunch, crab crossing

2. Upgrade– Scrap & Build

– Application of existing components

Major upgrade in 2006-2007


3

History of peak luminosity in last 25 yearsHistory of peak luminosity in last 25 years

SuperKEKB1035 cm-2s-1

2007 year ~ ?

1035 is good prediction for the future !


4

MotivationMotivation

KEKB will loose its competitiveness in 2005-2007. Competitors in 5 years

– LHC-B, BTeV, (SuperPEP-II)– Luminosity of LHC-B/BTeV corresponds to 1036 cm-2s-1 e+e-

collider.

Physics motivation1. PRECISION TEST of Kobayashi-Maskawa scheme

2. Search for NEW SOURCE of Flavor Mixing and CP Violation

3. Study of the FLAVOR STRUCTURE of SUSY, identification of SUSY breaking mechanism

KEKB is R&D machine for SuperKEKB.


5

Machine parameters of SuperKEKBMachine parameters of SuperKEKB

Luminosity formula :

Beam-beam tune shift parameters :

Assumed that the "transparency" conditions :

Alternative expression of luminosity :

L =NeN e f4πσ x

*σ y* RL

ξx,ye =re

2πγe

Ne βx,ye*

σ x,y* σ x

* +σ y*

( )Rξx,y

γeIe =γe Ie , εe =εe , etc.

L =γe

2ere1+r( )

Ieξyβy

*

⎛

⎝ ⎜

⎞

⎠ ⎟ RLRξy

r =βy

*

βx* =

εyεx

=σ y

*

σ x* “Optimal coupling”


6

Machine parameters of SuperKEKB (cont'd)Machine parameters of SuperKEKB (cont'd)

Luminosity is proportional to :

Brute Force Concept :– Higher beam current– Smaller beta function at I.P

(as well as short bunch length) – Larger beam-beam parameters

€

Ibeam ⋅ξ y

β y*

€

RL

Rξ y

xLuminosityreductions


7

Luminosity reductionsLuminosity reductions

Half crossing angle: x = 15 mrad Horizontal beta at I.P: x* = 30 cm Vertical beta at I.P: y* = 3 mm Emittance : 33 nm (6.4 % coupling)

RL : Luminosity reduction due to geometrical R : Tune shift reduction RL/Ry is a function of crossing angle, beta, emittance, bunch length.

RL/Ry = 0.8(KEKB : ~1)

x* = 15 cm

x* = 30 cm

x = 15 mrad


8

Strategy of SuperKEKBStrategy of SuperKEKB

Primary target of luminosity is 1035 cm-2s-1.– Beam-beam parameter : ~ 0.05 (experience at KEKB)– Vertical beta at I.P : 3 mm (bunch length : 3 mm)– Beam current : 9.4 A (LER) x 4.1 A (HER)– Half crossing angle : 15 mrad

Brute force concept

1036 cm-2s-1 is also considered.– Extensibility in the future is important.

Political issue should NOT KILL 1035 cm-2s-1 machine.


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Machine parameters of SuperKEKB (detail)Machine parameters of SuperKEKB (detail)

Head-on collision(effective)Need crab cavityS-S, S-W simulation

Energy : 3.1/9 GeVOptions April 2002from SBF Luminosity

LER HER LER HER LER HER

Horizontal emittance 33 33 33 33 92 92 nm

Vertical emittance 2.1 2.1 0.33 0.33 0.92 0.92 nm

x-y coupling 6.4 6.4 1 1 1 1 %

Beam current 9.4 4.1 17.2 7.8 27 9.3 A

Number of bunches 3400 3400

Bunch current 1.87 0.817 3.43 1.55 7.94 2.74 mA

Bunch spacing m

Half crossing angle mrad

Luminosity reduction RL

x reduction R ξx

ξy reduction R ξy

Bunch length 3 3 3.5 3.5 1.8 1.75 mm

Radiation loss U 0 1.23 3.48 MeV/turn

Betatron tunes νx/ νy 45.515/43.57 44.515/41.57

Beta at IP βx*/ βy* 30/0.3 30/0.3 15/0.3 15/0.3 15/0.15 15/0.15 cm

Beam-beam parameters ξx/ξy 0.068/0.05 0.068/0.05

Beam lifetime ~150 ~150 min

Luminosity 10 35 /cm 2 /sec

unit

10

0.83

0.65

0.1

0.6

0

0.1~0.2

4~10

SuperKEKB HyperKEKB SuperPEP-II

5018 5018

1

0.6

15

0.748

0.691

0.916


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High beam currentHigh beam current

RF systemVacuum systemPhotoelectron cloud effectFast ion instability (FII)Bunch by bunch feedback systemHigher order mode (HOM) Injector linac


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RF systemRF systemRequirements :

– Large amount of RF power– Very large HOM loss at cavities– Heavy beam-loading

Strategy : Existing RF system is used as much as possible.

RF frequency : 509 MHz (same as KEKB)Cavity : ARES (LER) / ARES+SCC (HER)

– Improvements and modifications are needed.– ARES (NC cavity) / SCC (SC cavity)

K. Akai et al.


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The ARES cavity

Storage Cavity

Coupling Cavity

Accelerating CavityCoupling Cavity DamperHOM damperEight SiC tiles per Groove

Two SiC bullets per WaveguideTuner Port

Tuner Port

Input CouplerPortPumping Port

Mode ShiftingGroove

Two SiC bullets per WaveguideRF Parametersof the π/2 Accelerating Mode

0.00010.0010.010.1

495500505510515520

π/2 mode0 modeQL≈100π modeQL≈100frequency /MHz

S21 responseHigh-Power PerformanceUa : Us = 1 : 9R / Q = 15 ΩQ = 1.1 x 105

Ua / Us = ks / ka22π / 2 - mode basics

Pc = 150 kW / ARES Cavitygenerating Vc = 0.5 MV (KEKB Design)Maximum ContinuousPc = 380 kWMaximum for 20 minutuesPc = 450 kW

HOM damperAccelerator Resonant coupled with Energy Storage


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0 0.5 1m

LHe

GATE　VALVE

GATE　VALVEFREQUENCY　　　　　　　TUNER

HOM　DAMPER　　　　(LBP)

HOM　DAMPER　　　　(SBP)

N2 　SHIELD ION　PUMP

DOOR　KNOB　TRANSFORMER

INPUT　COUPLER

Nb　　CAVITY

Superconducting　Damped　Cavity　for　　KEKBSuperconducting　Damped　Cavity　for　　KEKBT. Furuya


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Modification of RF systemModification of RF system

Total beam power is higher than KEKB by factor 4. Need high power fed to each cavity. Increase number of RF stations. ~ Double RF.

– Half of wigglers in LER is replaced to RF cavities.


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RF system parametersRing LER HERBeam current (A) 9.4 4.1Wiggler magnets yes (half) noEnergy loss/turn (MeV) 1.2 3.5Loss factor (V/pC) 40 50Radiation loss power (MW) 11.3 14.3Parasitic loss power (MW) 7.1 1.7Total beam power (MW) 18.4 16.0Total RF voltage (MV) 14 23

(Total)Cavity type ARES ARES SCC ARES / SCCNo. of cavities 28 16 12 44 / 12Voltage /cav. (MV) 0.5 0.5 1.3Input coupling 5.4 5.4 -Loaded-Q value (x10E4) 1.7 1.7 4.0Beam power /cav. (kW) 660 660 460Wall loss /cav. (kW) 150 150 -Detuning frequency (kHz) 71 31 74

Klystron power (kW) 850 850 480No. of klystrons 28 16 12 56Total AC plug power (MW) 40 23 10 73

30/8

2345

KEKB


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(Each building for 4〜 6 RF units.)

D8 D7

D4

D10

D11

new new

new

newnew

D1 D2

D5LER-RF

(ARES)

HER-RF(ARES)HER-RF

(SCC)

5 buildings should be added.

Layout of RF stations


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Heavy beam-loading on the accelerating modeHeavy beam-loading on the accelerating mode

Longitudinal instabilityGrowth rate of the -1 mode caused by large detuning is very

high (~104), even with ARES and / or SCC.

– Strong damping by feedback with comb filter is inevitable.

– Zero-mode stabilization should also be improved.

Beam phase modulation due to abort gapAbort gap of KEKB has been reduced (1 s → 0.5 s).

– Further reduction to 0.2 s is required.Δφ = 5.2° (LER 9.4A @0.2 s gap)


18

R&D issues for RFR&D issues for RF

HOM dampers– as well as Input couplers and Damper at C-cavity

Impedance estimation RF control

– Feedback for zero mode and -1, -2 modes

Klystron and high-power system – Reduce crowbar trips

– Improve reliability of dummy loads

Beam test of improved system


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Vacuum systemVacuum system Ante-chamber

– Reduce power density of synchrotron radiation at Wall.– Reduce effect of photoelectron cloud.– Low impedance / no pumping port in beam chamber– High linear pumping speed (Target : 100 l/s/m)– Solenoid winding before installation (e+ ring)

Bellows– No heating or discharge problem due to HOM– Need low impedance

Movable masks– No damage of mask head due to beam hitting– No HOM heating– Need low impedance

HOM absorber chamber

Y. Suetsugu et al.


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Design of Ante-chamberDesign of Ante-chamber

Ante-chamberBeam

SR Cooling water

Pump

LER arc section

LER

[Ion pump section]

IP, NEG feed through

Cooling water

NEGstrip


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Design of Ante-chamber (cont'd)Design of Ante-chamber (cont'd)

Very large SR power

No photon stop

Ante-chamber for LER– Max. SR power line density : 29 kW/m (14.8 kW/m)– Power density : 40 W/mm2 (37 W/mm2)

Ante-chamber for HER– Max. SR power line density : 25 kW/m (5.8 kW/m)– Power density : 40 W/mm2 (14.5 W/mm2)

(KEKB)


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Ante-chamber R&D Ante-chamber R&D Ante-chamber with photon stop (Prototype 2001)

Bending　[B2P.73]

Quadrupole　[QF2P.33]

positron beam

PhotoelectronMonitor

Photon Stop


23

Ante-chamber R&D (cont'd)Ante-chamber R&D (cont'd)

Prototype has been tested in LER at KEKB. Photoelectrons in beam chamber are measured.

Number of electrons measured by a photoelectron monitor reduced to about 1/7 compared to the usual single chamber.

Solenoid is still effective to reduce number of electrons by 1/2.


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Ante-chamber R&D (cont'd)Ante-chamber R&D (cont'd)

R&D for production procedure (BINP, Russia) No photon stops (special material : GlidCop etc.) New prototype will be installed during this summer. Confirm reduction of photoelectrons in beam chamber.

Prototype 2003


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New Bellows with RF-shieldNew Bellows with RF-shield (Comb structure)(Comb structure)

Low HOM leakage High thermal strength Loss factor : 1/4 of present

bellows No multipactering Less flexibility :

– expansion < ± 3 mm– offset < ~ 0.2 mm – bending angle < ± 2 deg.

RF-shield

2 mm 1 mm

10 mm

Reduction of impedance sources


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New Bellows with RF-shield (cont'd)New Bellows with RF-shield (cont'd)

Machining is available.

Application to ante-chamber


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Movable mask R&DMovable mask R&D Heating of components near mask:

– Chamber type (Version 4) as KEKB is better. But, • Heating of bellows is a problem.

– Beam steering scheme solves the troubles of bellows.

– Long tapers will reduce TE mode HOM power.

• How does the mask head harmonize the ante-chamber structure ?

Version 4 HOM absorbers near the mask

head is needed. Plunger type (Version 5) is

another option.


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HOM absorber chamber (slot type)HOM absorber chamber (slot type)

SiC rod

Effective for TE mode HOM that causes heating of bellows. Tested at KEKB


29

Small beta function at I.PSmall beta function at I.P

Optics – flat beam

– beta functions : x* / y* = 30 cm / 3 mm

Interaction region (IR) design– QCS, special magnets (QC1, QC2)

Dynamic aperture


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Optics at IROptics at IR

beta function at I.P : x* / y* = 30 cm / 3 mm

LER HER

H. Koiso et al.


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Layout of beam lines at IR

Half crossing angle : 15 mrad

Final focusing quadrupoles (QCS) locate at the position as close to the IP as possible.Pos. from the IP Super-KEKB KEKB

QCS-R 1163.3 mm 1920 mmQCS-L 969.4 mm 1600 mm

The QCS magnets are overlaid with the compensation solenoids (ES).compact & short in z

N. Ohuchi et al.


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200

HER50

-50

LER

100-100200 250

ø100

-100 100

QCS (Left) QCS (Right)

QC1 (Left) QC1 (Right)

Option 1: Superconductingmagnet

Option 2: Normal-conductingmagnet

ESR

QCS

QCSL

100-100

50

-50

LERHER

ESL

50

-50

-100 100

QCSR

LER

HER

ESR


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Bz (central field), TL (coil length), m

ESR ESL3.00 2.771.20 0.752

Super-KEKB KEKBESR: 42288 N (4.3 tons) ESR: 7050.5 N (0.7 tons)ESL: -134820 N (13.8 tons) ESL: -23505 N (2.4 tons)

Electro-magnetic force acting on ESR and ESL from the Belle (in z-direction)

Field distortion in Belle detector


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Dynamic apertureDynamic aperture Field distributions of the

detector, compensation solenoids, QCSs along longitudinal direction are given by slices of 4 cm thickness with const. field.

Multipole components not included.

Natural chromaticity :– -87.9 (horizontal)– -132.2 (vertical)

LER

6-D tracking simulation with SADNo lattice errors

Dynamic aperture of LER lattice satisfies the requirement for theinjection and lifetime (Touschek ~230 min).

injection


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Short bunch lengthShort bunch length

Higher order mode (HOM)– Impedance estimation

Coherent synchrotron radiation (CSR)Optics design

– Momentum compaction factor () : -2 ~ +4x10-4

– Negative lattice may help to reduce bunch length.


36

Beam lifetime at 10Beam lifetime at 103535 cm cm-2-2ss-1-1

Luminosity lifetime– dN/dt = -σL– Cross section of radiative Bhabha: 2.14x10-25 cm2

– Loss rate : 0.34 mA/s– LER/HER : 460/200 min

Vacuum lifetime– ~10 hours (? depends on vacuum system)

Touschek lifetime– LER/HER : 230/1650 min (estimated from dynamic aperture)

Overall lifetime of LER/HER : > ~150 min (inc. beam-beam)– Loss rate : 1 mA/s (LER)/ 0.46 mA/s (HER)

Continuous injection– Need 5Hz ~ 10 Hz repetition (70% injection efficiency)


37

Requirements to linac injector at SuperKEKB

1. e+ beam energy 3.5 → 8.0 GeV

Energy switch :

8.0 GeV e- / 3.5 GeV e+ → 8.0 GeV e+ / 3.5 GeV e-

(a) This helps to reduce beam blowup due to photoelectron effects.

(b) e- charge > e+ charge

2. Injection charge 1.0 → 5.0 nC (e-)

0.6 → 1.2 nC (e+)

For larger stored current :

1.1A e- / 2.6 A e+ → 9.4 A e- / 4.1 A e+

3. Simultaneous Injection (both e+/e-)

4. Smaller e+ emittance

T. Kamitani et al.


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Higher acceleration field scheme for 8 GeV e+

(Beam recirculation scheme is also under consideration, but skipped here.)

ABHER12345Ce- GunDampingRing1.7-GeVJ-arc for e–LERe+ targetE(e–)=3.5 GeV, Q(e–)=10 nC to targetQ(e–)=5 nC for Injection

E(e+)=1.0 GeVE(e–)=3.5GeV, Q(e–)=5 nCE(e+)=8.0 GeV, Q(e+)=1.2 nCQ(e+)=1.2nC New C-band units

2-Bunches for Simultaneous Injection 1-st bunch -> e- Injection 2-nd bunch -> e+ production

S-band accl. units are replacedwith C-band units.Accl. Field 21 -> 41 MV/m

e+ Damping Ring for loweremittance


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KEKB injector linac accelerator unit

New C-band accelerator unitPresent S-band accelerator unit

Wave guide

C-bandSLED

PulseModul-ator

C-bandKly-stron

Wave guide

C-bandSLED

PulseModul-ator

C-bandKly-stron

Wave guide

S-bandSLED

PulseModulator

S-bandKly-stron

C-band accelerating structuresS-band accelerating structures

S-Band to C-Band


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C-band components R&D status

Klystron (Toshiba 50 MW C-band Klystron ) Pulse Modulator (Compact type) Sub-booster klystron (satellite 40 kW Klystron is modified to 5712 MHz)

Already Fabricated Accelerating structure #1 (2pi/3-mode, scaled down from S-band)

Under Engineering design (parameter tuning) Wave guides, RF Window, Flange

Under fabrication 3-dB Hybrid, Dummy load

Under Engineering design (parameter tuning)

• Toward 2003 Summer beam test at KEKB Linac(1 Pulse Modulator + 1 Klystron + 1 Accel. structure 1m-long)

• Toward 2004 Spring beam test at KEKB Linac(1 Pulse Modulator + 1 Klystron + 1 RF compressor

+ 2 Accel. structures 1m-long) Accelerating structure #2 (New power coupler design)

Under basic design RF pulse compressor (LIPS-type TE038-mode)

Under basic design


41

C-band Klystron

Compact pulse modulator

Test accel. cavity RF measurement


42

Toward higher luminosityToward higher luminosity

Crab crossing– Beam-beam simulations– Design of crab cavity for 1-2 A (KEKB)– Design of crab cavity for 10 A

Four beams (neutralization)– Analytic calculation– Beam-beam simulations

Round beam– Not considered yet.


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Beam-beam simulation Beam-beam simulation Target luminosity : 1035 ~ 1036 cm-2s-1

Number of bunches : 5000 Energy : 3.5 GeV (LER) / 8 GeV (HER) Beam current : I(HER) = (3.5/8) x I(LER) Weak-strong simulation

x = 0 mradx = 15 mrad

x = 0.5156x = 0.5256x = 0.5356x = 0.549

x = 0.5156

K. Ohmi et al.


44

Crab cavityCrab cavity

Squashed cell operating in TM2-1-0 (x-y-z)

Coaxial beam pipe + HOM dampers

Designed for 1〜 2A beam

Squashed cell operating in TM2-1-0 HOM damping using wave guides

without coaxial beam pipe damper– Heavy damping of all HOM’s except TM1-1-0.– Smaller loss factor– More power to damper is allowed than the

present scheme.

Cure high-Q TM1-1-0– Frequency control, Feedback w/ parallel comb

filter

K. Hosoyama and K. Akai et al.

Absorbing materialNotch　filter

Absorbing material

Squashed　Crab　cavity　for　B-factories

Coaxial　beam　pipeCooling for inner conductor

(axial view)

inner conductor

"Squashed　cell"

(K. Akai et al., Proc. B-factories, SLAC-400 p.181 (1992).)

New design for SuperKEKB

Present design for KEKB


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Crab crossingCrab crossing

Crab crossing is powerful scheme to achieve high luminosity. It is hard to develop crab cavity for extremely high beam current. Test of crab crossing at KEKB in 2005

– 1 crab : 11 mrad / HER x= 200 m

Crab cavity

Nikko straight section

Need magnetreconfiguration

A. Morita et al.

KEKB HER

KEKB HER


46

Crab crossing (cont’d)Crab crossing (cont’d)

Dynamic aperture can be kept as same as the case w/o crab

cavity at KEKB.

w/o crab cavity

w/ crab cavity

KEKB(operation)


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SummarySummary

R&D of SuperKEKB is going on. Long-term plan of KEKB includes SuperKEKB.

– KEKB has already achieved L = 9.5 x 1033 cm-2s-1. (design:1034)

New components and schemes to achieve higher luminosity have been or will be tested at KEKB.

Expression of Interest was written in Jan. 2002. Workshops on higher luminosity B-Factory were held.

– Aug. 2001, Jan. 2002, Aug. 2002, Feb. 2003

Letter of Intent will be written this year. Thanks to a lot of efforts of volunteers working on

KEKB.

1 SuperKEKB Upgrade project of KEKB KEK Yukiyoshi Ohnishi.

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