1. Accelerator Overview M
Accelerator Overview M. Biagini for the SuperB Accelerator Group XII SuperB Project Workshop, LAPP-Annecy March 2010

2. Goals of this WS Get approved ! Keep momentum of collaboration
Define lattice & parameters for TDR
Discuss on site issues
Discuss new topics not yet addressed (synchotron light beamlines, effects of detector solenoid and its fringe field, ...)
Complete CDR2
Plan work in view of TDR

3. What’s new since December?
Green: talks
Updated ring lattices (V12) (Nosochkov)
Updated beam parameters (not far from V10) (Raimondi)
Updated RF studies (Novokhatski, Bertsche)
Updated IR design (Sullivan)
Simulations of bunch-by-bunch feedback (Drago)
Spin tracking (Wienands, Monseu, Chao)
Beam-beam depolarization and diffusion studies (Rimbault, Monseu)
New Intra Beam Scattering code being developed (Demma, Chao)
Low emittance tuning tools (Liuzzo)
Dynamic aperture & beam-beam (Levichev, Shatilov)
Injector design also progressing:
Positron production (Poirier)
Bunch compressor & Transfer lines design (Chancé)
Measurement of polarization at injection by Mott technique (Baylac)
CDR2 is 70% done

4. Layout & geometry LER SR IP 66 mrad LER SR LER arc LER arc HER arc HER
HER and LER arcs are parallel to each other in the H-plane while separated by 2.1 m.
Each ring has one inner and one outer arc.
Both inner and outer arcs provide the same bending angle but outer arc is made longer (increased drift space around the dipoles) in order to provide the same azimuth location as the inner arc
LER
arc
LER
arc
HER
arc
HER
arc
Rings
crossing e- e+ RF

5. Parameters Tau/charm threshold running at 1035 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

6. V12 Lattice Final Focus optimized: ARCs optimized:
Shortened CCSx to decrease emittance growth and intrinsic chromaticity
Y-CCS Bends rescaled to make +/- 33mrad Left-Right for both rings
Distance between lines = 2.13 m
ARCs optimized:
Levichev: ARC sextupoles, although all –I paired, generate higher order aberrations due to X-Y interleaving. Last SD sextupole in the Dispersion Suppressor (DS) was not properly paired with its “ARC” twin. Fixed by changing DS dipole length and its position  less chromaticity (1 unit) but 1% ex increase
LER Arc cell length readjusted to take into account different sagitta due to shorter bends
Left-Right Arcs lengths readjusted
Doglegs removed  secondary crossing (“parasitic) now in the first 3p cell in HER, lengthened by about 25 m

7. Arcs
HER and LER arcs have conceptually the same lattice. LER arc dipoles are shorter (bend radius about 3 times smaller) than in the HER in order to match the ring emittances at the asymmetric beam energies.
LER
HER
mx = 3p, my = p
Cell in HER
mx = 3p, my = p
Cell in LER

8. “Parasitic” crossing
Doglegs have been removed and the secondary crossing (“parasitic) is made by lengthening the first 3p cell in HER by about 25 meters
This makes the two beam lines cross with and angle of about 165mrad (was about 150 with the dogleg) and there should be no interference between the two beam lines (some readjustment still needed for LER  in progress)
This longer HER cell is suitable for the injection
Lot of space remaining for utilities (RF, feedbacks, wigglers,...)

9. LER Spin Rotators 2 SR just before and after the FF
4 solenoids and 5 quadrupoles each
Lower chromaticity

10. Injection arc cells
Injection into rings is performed in one modified arc cell (very compact design)
High horizontal beta for higher efficiency
Kick needed is very small
Having dispersion at injection septum actually helps

11. Full rings optical functions

12. MAD tracking LER b vs Dp/p x-px plane (Dp/p=0) y-py plane (Dp/p=0) HER
Each contour is a 10 s particle. Energy acceptance from tracking: 1%

13. IBS in SuperB LER (lattice V12)
v=5.812 pm
@N=6.5e10
h=2.412 nm
@N=6.5e10
Effect is reasonably small. Nonetheless, there are some interesting questions to answer:
What will be the impact of IBS during the damping process?
Could IBS affect the beam distribution, perhaps generating tails?
More sophisticated simulation in progress (Chao, Demma)
z=4.97 mm
@N=6.5e10
T. Demma

14. IR Design
The white paper design uses the “Italian design” for QD0 and QF1 – self-compensating air core super-conducting quads next to each other
We are taking a close look at the “Siberian design” of Panofsky style quads for QD0 and QF1
This design option is showing some promise
More details in the IR talk
M. Sullivan

15. The Present Baseline Design
M. Sullivan

16. Energy change
The baseline design has been studied to see how we change center of-mass energy while maintaining the same magnetic field strength ratio for QD0 and QF1
The result is we can get to all of the Upsilon resonances and are able to scan the center-of-mass energy above the 4S while maintaining a constant field ratio in both QD0 and QF1 without removing or changing any of the permanent magnets
We have to remove most if not all of the permanent magnets to go down to the Tau-charm region
M. Sullivan

17. Energy table M. Sullivan Resonance Upsilon 4S Upsilon 3S Upsilon 2S
Ecm (GeV)
9.4609
HER
E (GeV)
6.694
6.553
6.343
5.988
QD0 (T/cm)
QF1 (T/cm)
LER
4.18
4.091
3.96
3.737
QD0 ratio
QF1 ratio 
Boost ()

18. Bunch-by-bunch feedback simulation
Feedback kick
Phase of a bunch
vs # turns
Longitudinal invariant of motion vs # turns

19. RF
RF system complies with SR losses and beam currents requirements also for high current option
Number of cavities ok for phase transient
A. Novokhatski, K. Bertsche

20. Spin dynamics studies Carried out with different codes:
SLICTRACK  Wienands (SLAC), Barber DESY)
ZGOUBI  Meot, Monseu (Grenoble)
GiuneaPig++  beam-beam depolarization effects  Rimbault (LAL)

21. Beam tilt in x-z and y-z planes due to lattice distortions
A. Chao (SLAC) is speding a 3 months sabbatical at LNF
Will study with 6D SLIM code the effect of solenoids, skew quads and sextupoles errors on the beam tilt at the IP, possibly affecting luminosity
These effects may be small but need to be evaluated
Will also work on new IBS code
A. Chao

22. Beam dynamics “to do list”
Spin rotator matching studies and spin dynamics
Benchmark different tracking codes
Evaluate the solenoid fringe field effect
Evaluate beam-beam depolarization and diffusion
Dynamic aperture & beam-beam
...

23. Polarimeter at injector
M. Baylac

24. Bunch compressor after DR
Due to the acceleration in the Linac, the longitudinal distribution of the beam will be changed and the energy spread may increase.
Compression of the beam is performed after the DR and before the Linac in order to minimize the rms momentum spread
A magnetic C-chicane (achromatic) will change the beam path according to its energy
Used PEP-II LER dipoles
A. Chancé

25. Status of CDR2 (White Paper)
About 70% of text already received and assembled
Need some more effort in order to finish soon
Most of technical issues solved, some will be addressed here (ex. synchrotron radiation beamlines option)

26. Conclusions
Lattice and parameters optimization continued for better and better performances and flexibility
New beam dynamics issues studied (IBS, spin, beam-beam effects)
Accelerator design is converging
All aspects are starting to look feasible
Need more manpower for TDR
Hope to hear good news soon!