SuperB Positron source
SuperB Positron source
SuperB project
• Super-B aims at the construction of a very high luminosity (1x 1036 cm-2 s−1 ) asymmetric e+e− flavor factory with a possible location on or near the campuses of the University of Rome at Tor Vergata or the INFN Frascati National Laboratory LNF.
• Aims: – Very high luminosity (~1036) target luminosity of 1036 cm-2 s-1 at the U(4S) – possibility to run at t/charm threshold with L = 1035 cm-2 s-1
– Flexible parameter choices.
– High reliability.
– Longitudinally polarized beam (e-) at the IP (>80%).
– Ability to collide at the Charm threshold.
Parameter Table
Baseline + other 2 options: •Lower y-emittance •Higher currents (twice bunches)
Baseline: •Higher emittance due to IBS •Asymmetric beam currents
RF power includes SR and HOM
Tor Vergata Campus
SuperB site @ Tor Vergata
Possible beamlines
Crab waist and test
Large Piwinski angle : -Very small beam sizes at IP (hourglass and D) -Crab Waist kill the resonances
0 0.2 0.4 0.6 0.8 1
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
0
0.2
0.4
0.6
0.8
1
Tune scan with and wo crab waist
Injector requirements e- e+
Energy (GeV) 4.18 6.70
Number of bunches 978 978
Particles/bunch 6.6x1010 5.1x1010
Charge/bunch (nC) 10.6 8.2
Charge/bunch (nC) required for injection (1 bunch/pulse, 50 pps)
0.79 0.65
Horizontal emittance (nm) 2.5 2.0
Vertical emittance (pm) 6.2 5.0
Relative energy spread 7.3x10-4 6.4x10-4
Lifetime (s) 269 254
Polarization ~80% 0
Section L-band C-band Energy (GeV) 1.0 6
Repetition rate (pps) 50 100
Length (m) 100 170 Number of klystrons 20 50 Klystron peak power (MW) 40 50 Number of sections 40 100 Gradient (MV/m) 12.5 40
Section 1 2 3 Energy (GeV) 0.6 0.2 6.0
Repetition rate (pps) 50 50 100
Length (m) 30 10 270 Number of klystrons 3 1 40 Klystron peak power (MW) 50 50 60 Number of sections 9 3 80 Gradient (MV/m) 23 25
Energy (GeV) 1.0 Circumference (m) 51.1
horizontal emittance e0x(nm) 23
vertical emittance e0y, k=.01 (nm) 0.2
Betatron damping time (ms) 7.3
Equilibrium energy spread 6.2x10-4
Momentum compaction 5.7x10-3
RF frequency 475 RF voltage (MV) 0.5
Bunch length (mm) 4.8
Sband, positron drive, electron injector and main linac Damping Ring L and C band
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani
SLAC Gun Thermoionic Gun SHB
0.6 GeV PC 0.7 GeV
BUNCH COMPRESSOR
5.7 GeV e+ 4.0 GeV e-
POLARIZED GUN (80%) SHB
b graded S band Sections 50 MeV
e+
e-
combiner DC dipole
0.2 GeV
300 MeV CAPTURE SECTION
SuperB injector
6.7 GeV e+ 0.6nC
4.2 GeV e- 0.8nC
1.0 GeV Damping Ring circ. 51 m
50 Hz (e+) + 50 Hz (e-)
L-band linac
S-band (TM020)+L-band
0.6 GeV 10nC
S or C band
Positron source - Concepts • All the scheme’s target is to minimize the drive beam energy (at
present 600 MeV) • At the exit of the target the positron occupies an ‘infinite’
phase space • Need to reduce the angles : AMD transforms angles in positions • Need to reduce the energy spread and the bunch length (DR
acceptance) • L Band is necessary to reduce the energy spread and to increase
transverse acceptance. • If we go for full S band we need either a higher energy drive
beam (~1.5 -1.8 GeV) or increase of other parameters • L band Linac length can be reduced by reducing the Iris radius
(emittance matching). • We can profit from KEKB studies • L Band Klystrons and RF components available
9
Production
For a 600 MeV e- beam, the optimum yield is 1.7 e+/e- with a W-target thickness of 1.04 cm
Target Geant 4 simulation
(O. Dadoun – LAL): 1.7
If we increase the energy of the drive beam, the positron yield goes up linearly.
Thermal stress and PEDD checked : Ok
Positron sources : CAPTURE SCHEMES Reduce the bunch length and so the asymptotic energy spread to match
the damping ring acceptance.
S band 600 MeV
LBAND 1291, 1GeV
LBAND 1428, 1 GeV
S band 600 MeV
S band 600 MeV LBAND 1428/1291, 1 GeV TM020
S band = SLAC type , 0.9 cm iris L Band 1.428/1.291=> possible up to 1.3-1.5 cm iris. What gradient?
2.856, iris 2 cm
Target & AMD
Target & AMD
S band 1.8 GeV S band 1 GeV Target & AMD
Target & AMD LAL and KEK approach to increase the transverse acceptance. KEK => Hybrid
Classic
LAL new proposal
F. Poirier
Results after the capture section @ 300 MeV
S band acceleration L band deceleration L band deceleration TM020
12
At end of 4th tank – 3000MHz • Average Energy = ~333 MeV
~21.9 m long beam line
Total Yield = ~31.9%
Energy (MeV)
Ener
gy (
MeV
) Z (m)
Z (m)
Scenario 4 => Asymptotic behavior
Realisations: Design Study of Travelling wave Section (1)
Design of RF structure (using Superfish)
- Structure with 6 cylindrical cavities
- Using TM020-2/3
- Operating at 3 GHz
- Design Parameters: - Cell dimensions: Rcell ~ 9 cm Lcell ~ 3.331cm
- Irises dimensions: Riris=1.5 cm Liris= 0.8 cm
E-field TM020-2/3
Ez along z-axis
Design Study of Travelling wave Section (2)
3D Structure (Under study)
Structure will include reduced height waveguides for matching
The goal is to realize a low power demonstrator in aluminum material
HFSS Simulation
Mode 2/3
Mode
Simulations show the good separation of the TM020 -2/3
Mode 0
S11 (dB)
Conclusions
• SuperB is an exciting lepton collider project. It explore the luminosity frontier. It is financed by the italian gouvernment and at present is THE european project as far as the lepton colliders are concerned
• It is based on a new (tested) innovative collision scheme • The injector System has to guarantee the top up injection with a rate
defined by the luminosity losses !!!
• Positron source : We have studied 4 cases • 1) Classic S band • 2) Deceleration S band • 3) Deceleration L band • 4) New idea => Deceleration TM 020 • The last case assure a very high yield in the longitudinal acceptance of
the damping ring. It is at present the SuperB baseline. Future upgrades and studies towards a hybrid scheme are possible
• Prototyping is ongoing