Round Beams

New electron-positron collider VEPP-2000
( ISTC project 1928)
Yuri Shatunov for VEPP-2000 team
BINP SB RAS, 630090, Novosibirsk
CERN-ISTC SAC seminar
Novosibirsk, 2010
OUTLINE
VEPP-2M
VEPP-2000
Round beams and luminosity
VEPP-2000 systems
Beam-beam study
Round beam test
First experimental run 2009-2010
Energy calibration
Conclusion
Overview of VEPP-2M results
−1
Ldt
≥
100
(
pbarn
)
∫
?
VEPP-2M
VEPP-2000
(2001-2007)
ILU
ILU
MeV
33 MeV
Linac
Linac
CMD-3
RF cavity
CMD-2
–+
e,e
B-3M
-3M
B
200 MeV
MeV
200
synchrosynchrobetatron
betatron
VEPP-2000
VEPP-2M
BEP
BEP
–+
–+
e,e
e,e
booster
booster
900 MeV
MeV
900
SC
wiggler
e
–
SND
SND
2m
e
180–700 MeV
+
––
→
→
ee
ee
++
convertor
convertor
♦
♦
E ≈ 1 GeV
(per beam)
L ≈ 1×1032 cm-2 sec-1 (1×1 bunch)
Physics at VEPP-2000 at beam
energy 0.2 – 1 GeV
1. Precise measurement of the quantity
R=σ(e+e-- > hadrons)/ σ(e+e-->μ+μ--)
2. Study of hadronic channels:
e+e-- > 2h, 3h, 4h …, h= π,K,η
3. Study of ‘excited’ vector mesons: ρ’, ρ’’, ω’, ϕ’,..
4. CVC tests: comparison of e+e-- > hadr. (T=1)
cross section with τ-decay spectra
5. Study of nucleon-antinucleon pair production –
nucleon electromagnetic form factors,
search for NNbar resonances, ..
6. Hadron production in ‘radiative return’
(ISR) processes
7. Two photon physics
8. Test of the QED high order processes 2-> 4,5
Luminosity approach
‰ Number of bunches (collision frequency)
‰ Bunch-by-bunch luminosity
πγ ξxξ yε x f
L=
2 *
re β y
2
⎛ σy ⎞
⎜⎜1+ ⎟⎟
⎝ σx ⎠
2
Round Beams:
2 2
4πγ ξ ε f
L=
re2 β ∗
9Geometric factor (gain=2)
9Beam-beam limit enhancement
9IBS for low energy? worth life time!
N − re
ξ=
≥ 0.1
4π ⋅ ε ⋅ γ
“Strong-strong” beam-beam simulations
VEPP-2000 scheme
CMD
RF 172 MHz
V=120 kV
SND
Bbend = 2.4 T
Bsol. = 13 T
Solenoid 13.0 T
15
10
B,T
5
0
5
10
100
0
100
200
300
400
S,mm
500
600
700
800
900
Quads, skew quads, sextupoles,
steering coils
Beam diagnostics
CCD
CCD
CCD
CCD
RF
CT
pick-up
Luminosity: e+e- → e+e-
CCD
CCD
CCD
pick-up
CCD
TV
IBS counter
IBS counter
pick-up
CCD
CCD
CCD
CCD
PhM
PhM
pick-up
Luminosity: e+e- → e+e-
CCD
CCD
CCD
CCD
TV
VEPP-2000 (first beam - Sept. 2007)
CCD pictures
injection
VEPP-2000 lattice and beam sizes
ν1 = 2.1; ν 2 = 4.1
Betatron tunes measurement
(FFT)
“Weak-strong” beam-beam study
I+=3 mA; I-=45 mA; ξ+ =0.1
Test «flat» - «round»
«round beams»
Specific luminosity versus electron beam current
L, cm-2s-1
VEPP-2000 Luminosity
1 . 10
33
1 . 10
32
1 . 10
31
1 . 10
30
1 . 10
29
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Centrum mass energy, GeV
Run 2009-2010 (SND + CMD)
ΔL (pb-1)
−1
Ldt
10
(
pb
)
∫
Beam energy (MeV)
Beam energy calibration
Requirement ΔE E ≤10−4
Magnetic field measurements
16 NMR probes in dipoles
Phi meson mass
Radiative polarization
IBS polarimeter
Resonant depolarization by RF- field
Back Compton scatering
Beam energy calibration
e+e- -> 3pi visible cross section
80
SND
(2009)
70
MФ=1019.455 ± 0.020 (MeV)
(PDG)
nb
60
50
40
30
20
10
0
1010
1015
1020
1025 1030
2Ebeam, MeV
1035
1040
1045
Radiative polarization at VEPP-2000
1.0
ζ
1.0 ζ
0.8
ΔBs Bs = 10−3
ζ
0.8
-
+
0.6
0.6
0.4
0.2
0
1.0
0.4
0.6
0.8
-
+
GeV
0.4
0.4
0.6
0.2
0
1.0
0.8
τpp 104
102
102
1
1
ζ
+
10-2
1.0 ζ
-
sec
ΔBs Bs = 10−3
0.8
+
0.6
0.6
0.8
0.6
-
1.0
0.8
τp
ΔBs Bs = 10−2
0.6
0.4
-
GeV
0.4
0.4
10-2
1.0 ζζ
ζ
0.8
0.4
0.2
0
1.0
GeV
GeV
τp 104
sec
ΔBs Bs = 10−2
0.4
0.6
+
GeV
0.8
1.0
0.2
0
GeV
0.4
0.6
0.8
1.0
Resonant depolarization
⎛ E ( MeV )
⎞
fd = ⎜
− 1⎟ f 0
⎝ 440.6484 ⎠
E = 750.67 ± 0.03 MeV
f&d = −10 ( Hz sec)
f&d = − 10 ( Hz sec)
f&d = 1( Hz sec)
E (MeV)
750.0
750.5
751.0
751.5
Conclusion
VEPP-2000 started-up for data taking.
«Round beams» give luminosity enhancement.
Luminosity 1×1031 cm-2s-1 achieved at phi - meson
energy.
Potentially 2×1031 cm-2s-1 is possible at φ
and 1.6×1032 cm-2s-1 at 2 GeV.
To reach the target luminosity, more positrons are
required duster BEP upgrade is needed.
Beam energy calibration in progress.
Thanks for attention!