Transcript Document

BINP Tau-Charm Project
E.Levichev
For the BINP C-Tau team
3 February 2010, KEK, Tsukuba
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Outline
1. Introduction of Crab Waist collision approach
2. Scientific program and specifications
3. Optics
4. FF and QD0
5. Polarization insertions
6. Energy calibration
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Crab Waist in 3 Steps
1. Large Piwinski’s angle F = tg()z/x
2. Vertical beta comparable with overlap area y x/
3. Crab waist transformation y = xy’/(2)
x
Y
e+
e-
2x/

2z*
z
1. P.Raimondi, 2° SuperB Workshop,
March 2006
2. P.Raimondi, D.Shatilov, M.Zobov,
physics/0702033
2z
2x
Crabbed waist is realized with a sextupole in
phase with the IP in X and at /2 in Y
M.Zobov, Tau08, Novosibirsk
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Crabbed Waist Scheme
Sextupole
IP
x, y
x, y
 *x ,  *y
 y 

 y 
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Sextupole strength
M.Zobov, Tau08, Novosibirsk
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Equivalent Hamiltonian
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H  H0 
xp 2y
2
 x*
x
y 

 x  
 x  
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1
K
2  *y  y
(Anti)sextupole
 *y

s  x /  )2

 *y
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Collisions with and without Crab Sextupoles
1. Bigger blowup
2. Sharp lifetime reduction for
bunch currents > 8 -10 mA
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Courtesy G. Mazzitelli
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 →g
► 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 to
save 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: tunnel
Ready-built tunnel
FF region
Technical reg. (RF and injection)
Damping wiggler sections
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Main accelerator parameters
Energy
1.0 GeV
1.5 GeV
2.0 GeV
Circumference
783 m
Emittance hor/ver
10 nm/0.05 nm @ 0.5% coupling
Damping time hor/ver/long
Bunch length
2.5 GeV
30/30/15 ms
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
Beam-beam parameter
Luminosity
1.3 A
0.15
0.15
0.15
0.12
0.55·1035
0.81·1035
1.08·1035
1.08·1035
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6 m of the SC wigglers with 20-cm-period are used to control the beam parameters at different energies
Main ring: arc cell
FODO but close to the theoretical minimum emittance

x , y
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Main ring: injection section
x , y
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x , y
IR optics
IP
Y Section
FF
telescope of chroms
correction
L1/2 = 75 m
X Section
of chroms
correction
Crab
Sext
End of
the telescope
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Luminosity
D.Shatilov
y=750 um, Θ=50, mrad, σz=1cm, x=10 nm·rad, 0.5% coupling
Crab ON: ξy=0.13
Crab OFF: ξy=0.06
Lbeam=2.76·1032 @ Np=7·1010
Lbeam=4.94·1031 @ Np=3·1010
Lmax=1.05·1035 @ Nb=380
Lmax=0.44·1035 @ Nb=890
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Polarization scheme
Polarization scheme with 3 snakes (arc=1200
+2 damping wigglers in the arc’s middle )
IP
snake2
snake3
damping
wiggler2
damping
wiggler1
snake1
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Polarization vs energy
1
5 snakes
Polarization Degree
0.8
0.6
3 snakes
0.4
1 snake
0.2
0
1
1.2
1.4
1.6
1.8
2
Beam Energy, GeV
2.2
2.4
2.6
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QD0
SC iron yoke twin aperture magnet
Excitation current 1150 A
Single aperture 2 cm
Gradient 150 T/m
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Damping wigglers
The damping wigglers keep the damping time x =30 ms and the
horizontal emittance (εx=10 nm) in the energy range 1.0 – 2.5 GeV
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Field amplitude at 1.0 GeV
5.4 T
Period length
0.2 m
Total length
8m
Damping integral i2 at 1.0 GeV
12.4 m-1
Excitation integral i5 at 1.0 GeV
0.08 m-1
Wiggler field amplitude vs energy
Wiggler with similar parameters
produced by BINP
Energy calibration
Compton backscattering E
calibration (~10-410-5)
Na24 (1)=1368.625 keV
Na24 (2)=2754.008 keV
Na24 (1+2)=4122.633 keV
Spectrum edge
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E
E
 5  10 5
Injection facility
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Injection facility upgrade
• Today:
• 21010 e-/pulse  (1.5% conversion)  3 108 e+/pulse
•  50 Hz = 1.51010 e+/s
•
•
•
•
•
Upgrade:
e- current increase ( 3)
Better focusing in positron linac ( 1.5)
Debuncher usage ( 2)
= 1.351011 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 10100 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.
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