1. Summary of Accelerator Sessions
M. Biagini
for the Accelerator Team
SuperB XIV Workshop
LNF, Oct. 1st 2010

2. Accelerator Talks Working Groups: IR Lattice
RF, feedbacks, collective effects
Injection system
bb depolarization

3. Workshop Topics (except IR, MDI)
Dynamic aperture comparison (MADX, Acceleraticum) (Chancé, Piminov)
Intra Beam Scattering studies (Boscolo)
RF & HOM absorbers studies (Novokhatski)
Estimation of synchrotron light properties (Wittmer)
Feedback interface (Drago)
Low level RF (Bourrion)
Low Emittance Tuning for LER (Liuzzo)
Optics improvements ARC&FF (Raimondi, Syniatkin)
Injection system status (Boni)
Linac lattice design (Poirier/Variola)
BB depolarization (Rimbault)
Site and utilities (Tomassini)
Crab waist scheme variations (Bogomyagkov)

4. CDR2 Accelerator Status
Accelerator part of CDR2 is completed !
160 pp., 27 chapters
Need some update in beam-beam, Low Level RF and synchrotron light beamlines sections (next weeks)
Just published on arXiv:
Thanks to all contributors!

5. BB tune scan with CDR2 parameters (Shatilov, prior to WS)
CDR, xy = 0.17
CDR2, xy = 0.097
L_Max = 1.04∙1036

6. Lattice studies Work continued on lattice optimization
Modified V12 (CDR2) 3p ARC cell lattice with alternating long and short arc cells
Modified Final Focus design for better performances
Near-IP lattice with detector solenoids and compensation of coupling (in Mike’s summary)
Dynamic aperture checks and improvements of tools
Some studies also performed for a Ring that fits entirely in the LNF site

7. Layout of HER arcs (Syniatkin)
V12
V14
V13
new

8. Parameters comparison
Circumference of short ring is less by 100 m than the 12 versions.
Parameters
of the cell
V12 old
V12 mod
New short lat.
L, m
1258.4
1263.5
1159.5 Qx
40.575
43.575 Qy
17.595
18.595
19.595
Cx0 (sext. Off)
-134.7
-125.1
-112.8
Cy0 (sext. Off)
-449.3
-448.5
-443.2
I2, m-1
7.4360E-02
7.3489E-02
7.8903E-02
I5, m-1
2.2350E-06
2.3308E-06
2.3161E-06
Em, nm*rad
2.0
2.1
1.9
Betatron tunes of short version are higher but chromaticity is smaller than in 12 version.
Emittances of the rings are the same.

9. Dynamic Aperture studies (Piminov, Chancé)
Work on MADX (Chancé) to be able to benchmark DA results with Acceleraticum code (Piminov)
Found few discrepancies  corrected and agreed
Will be able now to work in parallel at LNF and BINP
Found that, as expected, crab-waist sextupoles reduce dynamic aperture

10. Example of DA studies
Acceleraticum
MADX
HER
LER

11. Intra Beam Scattering (Boscolo, Chao, Demma)
3 methods used, all in good agreement:
Bane (theoretical), allows for emittance growth rates estimate
Chao (theoretical), allows for emittance time evolution estimate
6D MonteCarlo  more accurate, all of above, will include non-gaussian tails, soon to be translated from Mathematica to Fortran for speed and precision reasons
ex,z vs bunch current

12. Low Emittance Tuning for LER (Liuzzo)
LER ARC's tolerances evaluated using a Response Matrix technique that optimizes orbit, in order to recover the design values for Dispersion, Coupling and Beta-beating, and obtain the lowest possible vertical emittance
Different sets of correctors tested, may be reduced to 109.
Final Focus introduces
stringent restrictions on alignment of both FF and
ARCS (even for no errors in FF)

13. Feedback Operator Interface (Drago)
R&D in progress
Tests at DAFNE

14. RF & Power (Novokhatski)
Need
collimators

15. HOMs Absorbers (Novokhatski)
PEP-II absorbers
suitable
and
available

16. Low Level RF (Bourrion)
Problem: high intensity beams perturbate RF cavity voltage
Instability growth rates due to the cavities are proportional to the sum of cavity impedances and beam current for each eigenmode
With no feedback system growth rates would exceed by ~700 times the damping ratio
Implement feedbacks to maintain constant gap voltage, and thus decrease impedance « seen by the beam »
Loop efficiency strongly depends on the group delay (distance between klystron and cavity + electronics latency)
Use PEP-II gained experience with modernized electronics (purely digital solution)
Work to do: try to consolidate understanding of LLRF and implement better simulation tools...

18. Synchrotron light from SuperB (Wittmer)
SuperB LER and HER compared with dedicated synchrotron light sources
Synchrotron light properties from dipoles are competitive
Assumed undulators characteristics as NSLS-II
Light properties from undulators still better than most LS, slightly worst than PEP-X (last generation project)

19. Flux & Brilliance comparison
SuperB LER
SuperB HER
From dipoles
From undulators

20. Possible beamlines location
Beamlines from dipoles
Beamlines from undulators

21. Injection System (Boni)
Pros:
Main Rings injection rate: 50 Hz instead of 25
Damping Ring operates just for positrons
Only 2 TL’s between Linacs and D.R., instead of 4; no special dipoles; no by-pass of the PC
No long flat top kickers in the damping ring and transfer lines
The gun for the positron line can be thermionic, thus delivering larger current
Cons:
Main Linac Klystron rep. rate: 100 Hz
The e- beam emittance is higher (round beam), can be reduced with scrapers/collimators
Total length about 350 m

22. Proposed scheme (new wrt CDR2) positron linac combiner DC dipole
R. Boni, S Guiducci, M. Preger, P. Raimondi (LNF)
O. Dadoun,P. Hermes, F. Poirier, A. Variola (IN2P3)
A. Chancé, CEA Saclay e+
THERMIONIC
GUN
SHB
0.6 GeV PC
CAPTURE
SECTION
positron linac
BUNCH
COMPRESSOR
5.7 GeV e GeV e- e-
combiner
DC dipole
0.25 GeV
POL.
SLAC
50 MeV
Wien
filter
Mott
polarim
collimators
1 GeV
Parameter
Units
SLC
Electron charge per bunch nC 16
Bunches per pulse 2
Pulse rep rate Hz
120
Cathode area
cm2 3
Cathode bias kV
-120
Bunch length ns
Gun to SHB1 drift cm
150
en,rms,gun (fm EGUN)
10-6 m 15
from A. Brachmann - SuperB Workshop SLAC, October 2009
Round beam
Emittance @ 4.16 GeV = 1.8 nm
Required bunch charge for electrons ≈ 0.3 nC
… scrapers .. collimators needed
R. Boni, XiV SuperB meeting, Frascati 22

23. Conclusion & Perspective
Linac design & diagnostics (Hermes, Poirier, Variola)
Conclusion & Perspective
Conclusion:
Linac:
Found a suitable design to carry both positrons and electrons beams up to main ring energy
Matching section designed
Missing combiner
Diagnostics for linacs:
Design and Dimension done for Emittance and Energy dispersion measurements
Perspective:
Every calculation is done to the first order. Second order should be the next step
More realistics beams should also be used for the linac to check energy/phase distribution. Simulation of the complete linac simulation, probably with ASTRA
Alignment errors impact on emittance should also be checked

24. Site (Tomassini)
The rings footprint is the same as presented at Elba. Injection and transfer lines are also unchanged
A preliminary design of the civil infrastructure should be done soon, probably by outsourcing
Few studies are still ongoing about the positioning of the tunnel, buildings and access pits
A second campaign of geological prospections has been done (four additional holes) and results will be available in the coming weeks
A new campaign of ground motion measurements is scheduled for October 4th with the collaboration of the LAPP group

25. Road map for site and utilities
In order to not waste time, the day after the SuperB funding we must have civil infrastructure preliminary design done
DAY AFTER FUNDING
RADIOLOGICAL AUTHORIZATION FOR THE SUPERB OPERATION
CONFERENZA DEI SERVIZI
About 8-12 months to set it up
About 5÷6 years to get it

26. Summary for working group “Lattice”
Participants: Biagini, Okunev, Piminov, Raimondi, Syniatkin
Lattice choice:
V13 present choice
Action Items:
Build LER lattice
Adjust IR angles to comply with Spin Rotation requests
Insert near-IP solenoids & skew quads (detector, coupling compensation)
Optimize sextupoles arrangements
Verify possibility to vertically move HER wrt LER (by 30 cm or so) without increasing ey (would ease beamlines installation)
Beamlines from dipoles layout (HER/LER)
Insert undulators in both rings:
straigth sections
Spin rotator sections (to verify)
Dynamic aperture optimization w/out undulators

27. HER IBS (Demma) (MAD params used for this estimate)
V13 vs V12
R=2.1%
R=2.5%
R=2.1%
R=2.5%

28. Summary for working group “RF, Feedback and Collective effects”
Participants: Sasha Novokhatski, Alessandro Drago, Olivier Bourrion, Christophe Vescovi, Makoto Tobiyma, Kirk Bertsche, Manuela Boscolo, Theo Demma
Discussions and suggestions
Lattice V12 and V13
There are no problems with RF, feedback and collective effects
Low Level RF
To write a more detailed chapter in CDR-2 as a step to TDR. Olivier Bourrion agrees to do this.
Makoto Tobiyma suggested that if the length of a waveguide has to be longer (SuperB rings are at the level -25m) then additional time delay (2X100 ns) will decrees the efficiency of the feedback. Olivier did quick simulation and found that efficiency decrease more than 2 times.
We suggest to place klystrons not very far from the cavities.

29. Summary for working group “Injection System”
Participants: Seeman, Boni, Guiducci, Preger
Action Items:
Adopt two gun solution
Wien filter to rotate spin from longitudinal to vertical at low energy (~100 keV)
Study the reduction of the length of L band linac using more S-band length by putting a longitudinal bunch compressor at about 100 MeV for positrons
Investigate lowering the DR energy to save linac costs
Keep the capability to inject at 100 Hz (to have 50 Hz each beam)
Investigate whether two sets of klystrons+modulators fit in first half of the linac gallery.
Recheck that the polarized e- gun can produce low emittance bunches at low charge.
Design e- gun scraper system to reduce vertical emittance

30. Summary for working group “BB depolarization ”
Participants: A. Bogomyagkov, C. Rimbault, U. Wienands
Discussed results of Cecile which indicate a 10-7 effect of the bb interaction on spin in single-turn simulation. In order to assess the significance of her results, it may be interesting to run the parameters of the HERA electron ring through her model as measurements of polarization at HERA in collision exist (and they show a significant but not totally destructive effect of the beam-beam interaction).
The possibility of combining her model with the ZGOUBI code is also being explored
Budker INP has developed a formula for VEPP (2000?) to estimate the effect of beam-beam interaction on polarization. They find it to be significant
The DESY code SLICKTRACK can also in principle simulate the effect of the beam-beam interaction on spin motion. This work has not been done up to now infavour of gaining understanding of the single-ring spin motion in the SuperB LER and the effect of the spin rotators first

31. Action Items
Run Guinea Pig model with HERA parameters to allow comparison with measurements
Run the SuperB parameters through the BINP formula
Continue investigation into combining Guinea Pig model with ZGOUBI
Run SuperB LER with beam-beam through SLICKTRACK (which can simulate beam-beam)

32. Accelerator TDR Effort
TDR work has been organized and some of the responsabilities decided. Still some question marks
11 subsystems have been identified, 60 FTE needed
We need an injection of manpower to be able to complete it in a reasonable time (end of next year?)

34. Conclusions
CDR2 is completed and published on ArXiv. Will be updated soon with the latest bb, beamlines and RF results
Good progresses have been made during the working-group sessions
We have a “stable” lattice to work with (not far from the CDR2 one)
We planned short-term work on finalizing lattice, geometry, RF and beam dynamics issues for this particular lattice
We have strenghten the collaboration with BINP, LPSC (Grenoble), KEKB
We have estimated the flux and brilliance from SuperB dipoles and possible undulators; we are working on the layout of the beamlines to be discussed with IIT
In order to proceed to the SuperB TDR phase smoothly we need to increase manpower, mostly engineers and technical designers (some are coming from CNRS recruitment)

35. We need to stay
focused,
motivated
and...
KEEP GOING !
Thank you