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