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

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

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)

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: http://arxiv.org/abs/1009.6178 Thanks to all contributors!

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

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

Layout of HER arcs (Syniatkin) V12 V14 V13 new

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.

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

Example of DA studies Acceleraticum MADX HER LER

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

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)

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

RF & Power (Novokhatski) Need collimators

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

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...

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)

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

Possible beamlines location Beamlines from dipoles Beamlines from undulators

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

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+ 3.9 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 29-09-2010 22

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

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

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

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

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

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.

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

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

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)

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?)

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)

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