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BINP Tau-Charm Project

3 February 2010, KEK, Tsukuba

E.Levichev

For the BINP C-Tau team

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Outline

1. Introduction of Crab Waist collision approach2. Scientific program and specifications3. Optics4. FF and QD05. Polarization insertions6. Energy calibration

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Crabbed waist is realized with a sextupole inphase with the I P in X and at / 2 in Y

2z

2x

z

x

2x/

2z*

e-e+Y

1. Large Piwinski’s angle = tg(z/x

2. Vertical beta comparable with overlap area y x/

3. Crab waist transformation y = xy’/(2)

Crab Waist in 3 Steps

1. P.Raimondi, 2° SuperB Workshop, March 2006

2. P.Raimondi, D.Shatilov, M.Zobov, physics/0702033

M.Zobov, Tau08, Novosibirsk

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x

y 2

x

y 2

Crabbed Waist Scheme

x

x

yy

K

*

*

1

2

1

Sextupole (Anti)sextupole

20 2

1yxpHH

Sextupole strength Equivalent Hamiltonian

IPyx , yx ,** ,

yx

*

2* /

yyy

xs

M.Zobov, Tau08, Novosibirsk

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Collisions with and without Crab Sextupoles

1. Bigger blowup

2. Sharp lifetime reduction for bunch currents > 8 -10 mA

February

2009

Courtesy G. Mazzitelli

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Frequency Map Analysis for CW

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Scientific case for the BINP C-tau project

► D-Dbar mixing► CP violation searches in charm decays► Rare and forbidden charm decays► Standard Model tests in leptons decays► Searches for lepton flavor violation →► CP/T violation searches in leptons decays► Production of the polarized anti-nucleons E = 1 GeV (may be with reduced luminosity)

Requirements: L > 1034 cm-2 s-1, longitudinal polarization, beam energy range from 1 GeV to 2.5 GeV

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Specifications

► Variable energy Ecm= 2 – 5 GeV

► Luminosity L = 1÷2×1035 cm-2s-1

► Electrons are polarized longitudinally at IP

► No energy asymmetry

► No beam monochromatization

► Energy calibration with medium accuracy

is sufficient (Compton backscattering)

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Facility key features and principles

► Two rings with a single interaction point► Crab waist collision► SC wigglers to keep the same damping and emittance in the whole energy range (optimal luminosity)► Polarized e- injector and spin control to get the longitudinally polarized electron beam at IP► Wide re-using of the existing structures and facilities tosave the cost

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Layout

Injection facility exists

Tunnel for the linac and the technical straight section of the factory is ready

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Main ring

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Main ring: tunnelReady-built tunnel FF region

Technical reg. (RF and injection)

Damping wiggler sections

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Main accelerator parameters

6 m of the SC wigglers with 20-cm-period are used to control the beam parameters at different energies

Energy 1.0 GeV 1.5 GeV 2.0 GeV 2.5 GeV

Circumference 783 m

Emittance hor/ver 10 nm/0.05 nm @ 0.5% coupling

Damping time hor/ver/long 30/30/15 ms

Bunch length 20 mm 13 mm 10 mm 10 mm

Energy spread 10.5·10-4 10.4·10-4 8.8·10-4 7.6·10-4

Energy loss/turn 174 keV 261 keV 349 keV 430 keV

Momentum compaction 1.00·10-3 1.06·10-3 1.06·10-3 1.06·10-3

Synchrotron tune 0.013 0.014 0.012 0.010

Wiggler field 5.4 T 4.0 T 2.8 T 0

RF frequency 500 MHz

Harmonic number 1260

Particles/bunch 7·1010

Number of bunches 294

Bunch current 4.3 mA

Total beam current 1.3 A

Beam-beam parameter 0.15 0.15 0.15 0.12

Luminosity 0.55·1035 0.81·1035 1.08·1035 1.08·1035

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Main ring: arc cellFODO but close to the theoretical minimum emittance

x, y

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Main ring: injection section

x, y

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IR optics

L1/2 = 75 m

x, y

IP

FF telescope

Y Section of chroms correction

X Section of chroms correction

Crab Sext

End of the telescope

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Luminosity D.Shatilov

0.5 0.55 0.6 0.65 0.7 0.75

0.5

0.55

0.6

0.65

0.7

0.75

0.5 0.55 0.6 0.65 0.7 0.75

0.5

0.55

0.6

0.65

0.7

0.75

Crab ON: ξy=0.13

Lbeam=2.76·1032 @ Np=7·1010

Lmax=1.05·1035 @ Nb=380

Crab OFF: ξy=0.06

Lbeam=4.94·1031 @ Np=3·1010

Lmax=0.44·1035 @ Nb=890

y=750 um, Θ=50, mrad, σz=1cm, x=10 nm·rad, 0.5% coupling

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Polarization scheme

IP

snake1

snake2 snake3

dampingwiggler1

dampingwiggler2

Polarization scheme with 3 snakes (arc=1200

+2 damping wigglers in the arc’s middle )

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Polarization vs energy

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.60

0.2

0.4

0.6

0.8

1

Beam Energy, GeV

Po

lari

zati

on

Deg

ree

5 snakes

1 snake

3 snakes

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QD0

SC iron yoke twin aperture magnet Excitation current 1150 ASingle aperture 2 cmGradient 150 T/m

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Damping wigglers

Field amplitude at 1.0 GeV 5.4 T

Period length 0.2 m

Total length 8 m

Damping integral i2 at 1.0 GeV 12.4 m-1

Excitation integral i5 at 1.0 GeV 0.08 m-1

The damping wigglers keep the damping time x =30 ms and thehorizontal emittance (εx=10 nm) in the energy range 1.0 – 2.5 GeV

Wiggler field amplitude vs energy

Wiggler with similar parameters produced by BINP

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Energy calibration

Compton backscattering Ecalibration (~10-410-5)

Spectrum edge 5105 E

E

Na24 (1)=1368.625 keV Na24 (2)=2754.008 keV

Na24 (1+2)=4122.633 keV

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Injection facility

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Injection facility upgrade

• Today:• 21010 e-/pulse (1.5% conversion) 3 108

e+/pulse 50 Hz = 1.51010 e+/s

• Upgrade:• e- current increase ( 3)• Better focusing in positron linac ( 1.5)• Debuncher usage ( 2)• = 1.351011 e+/s

• Reserve: electron energy can be increased by 100 MeV ( 1.3)

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Summary

► Crab Waist collision seems a very promising idea to enhance a circular colliders luminosity beyond the present value by factor of 10-100 without current increase.

► CW approach was successfully proved experimentally at DAFNE in the end of 2008

► Novosibirsk SuperCT project is under way. The key issues like IR design, DA optimization, polarization scheme, QD0 design, etc. seem solved successfully

► In 2010 we hope to finish a CDR and in parallel apply for funding to Russian Government.