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The SuperB Accelerator

The SuperB Accelerator. M. Biagini for the SuperB Accelerator Team Epiphany 2012 Conference Krakow, January 9-11, 2012. SuperB Accelerator. SuperB is a 2 rings, asymmetric energies (e - @ 4.18, e + @ 6.7 GeV) collider with:

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The SuperB Accelerator

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  1. The SuperB Accelerator M. Biagini for the SuperB Accelerator Team Epiphany 2012 Conference Krakow, January 9-11, 2012

  2. SuperB Accelerator • SuperB is a 2 rings, asymmetric energies (e- @ 4.18, e+ @ 6.7 GeV) collider with: • large Piwinski angle and “crab waist” (LPA & CW) collision scheme • ultra low emittance lattices • longitudinally polarized electron beam • 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 • Criterias used for the design: • Minimize building costs • Minimize running costs • Minimize wall-plug power and water consumption • Reuse of some PEP-II B-Factory hardware (magnets, RF) • SuperB can be also a good “light source”: there will be some Sinchrotron Radiation beamlines (collaboration with Italian Institute of Technology)

  3. World e+e- colliders luminosity SuperB Super Factories Linear colliders Factories SuperB: highest world luminosity collider ever B-Factories F-Factories Future Colliders

  4. Ultra-low emittance Very small b*at IP Large crossing angle “Crab Waist” transformation Small collision area Lower b*ispossible NO parasitic crossings NO x-y-betatron resonances Large Piwinski Angle & Crab Waist:a novel idea for Luminosity increase P.Raimondi, 2° SuperB Workshop, March 2006 P.Raimondi, D.Shatilov, M.Zobov, physics/0702033 Principle: beams more focused at IP + “large” crossing angle (LPA) + 2 sextupoles/ring to “twist” the beam waist at the IP (CW) Proved to work at upgraded DAFNE F-Factory 2008-2009

  5. DANE Peak Luminosity Design Goal NEW COLLISION SCHEME

  6. SuperB main features • Goal: maximize luminosity while keeping wall power low • 2 rings (~4 GeV and~7 GeV) with flexible design • Ultra low emittance optics: 7x4 pm vertical emittance • Beam currents: comparable to present Factories • LPA & CW scheme used to maximize luminosity and minimize beam size blow-up • No “emittance”wigglers used (save power) • Design based on recycling PEP-II hardware (save costs) • Longitudinal polarizationfor electrons in the LER (unique feature) • Possibility to push the cm energy down to thet-charmthreshold with a luminosity of 1035 cm-2 s-1

  7. Parameter Table 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

  8. SuperB layout • Site chosen @ Tor Vergata University (Rome II) campus • Sinchrotron Light (SL) beamlines are becoming part of the layout (HER preferredat the moment) • One tunnel willhostbothrings, whichwillprobablyhave a tilt onerespect to the other, to allow for easiercrossing and SL beamlines from both HER and LER (ifneeded) • The position of the Linaccomplexhasstill to be finalized, depending on the injectionrequirements • The rings layout hasbeenrecentlyimproved to accomodate InsertionDevices (ID) needed for SL users

  9. Tor Vergata University campus Site About 5 Km LNF

  10. Ground measurements • Ground motion measurements performed on site in April show very «solid» grounds in spite of the vicinity of the highway, just 100 m away • The highway is at higher level with respect to the site, and the traffic vibrations («cultural noise») are very well damped Ground x-section Volcanic soil

  11. SuperB @ Tor Vergata Tomassini SR Beamlines SR Beamlines Injection complex

  12. Rings Lattice • The two rings have similar geometry and layout, except for the length of dipoles • The arcs cells have a design similar to that of Synchrotron Light Sources and Damping Rings in order to achieve the very low emittances • In the latest version of the lattice some cells for Insertion Devices have been inserted • Rings are separated about 2m in horizontal and 1m in vertical

  13. Collider Layout IP • Circumference 1195 m • Horizontal separation of arc ~2 m • Vertical separation of RF section 0.9 m • Dimension sizes of rings 416 m x 342 m FF Spin Rotator 3 ID cells 3 ID cells Injection section RF section

  14. Vertical rings separation αtilt=2.6 mrad Vertical separation 0.9 m Rings tilt at IP (by small solenoids not vertical bends) provides ~1 m vertical separation at the opposite point: (a) e+e- beams separation, (b) SR beamlines from both rings, (c) better equipment adjustment

  15. Polarization in SuperB S.r. dipoles(270° spin) S.R. solenoids (90° spin) IP HER LER LER HER • 90°spin rotation about x axis • 90°about z followed by 90°about y • “flat” geometry  no vertical emittance growth • Solenoid scales with energy  LER more economical • Solenoids are split & decoupling optics added • The SR optics design has been matched to the Arcs and a similar (void) insertion added to HER • This design poses severe constraints on the FF bending angles of LER and HER in order to achieve the “right” spin dynamics • A polarimeter has been designed to measure polarization

  16. Polarization resonances • Beam polarization resonances do constraint the beam Energy choice • Plot shows the resonances in the energy range of LER • Beam polarization computed assuming • 90% beam polarization at injection • 3.5 minutes of beam lifetime (bb limited) • From this plot is clear that the best energy for LER should be 4.18 GeV  HER must be 6.7 GeV ELER

  17. Interaction Region • The Interaction Region must satisfy both machine and detector requirements: • Final Focus elements as close as possible to the IP • Small detector beam pipe • Enough beam stay clear  small emittance helps • Control Synchrotron Radiation backgrounds • Have an adequate detector solid angle • Magnet vibrations need to be damped (at the level of 10nm) • A state-of-the-art luminosity feedback is needed • With the large crossing angle the beam is off-axis in the first quadrupoles, hence it is not only focused but also bent, producing unwanted SR backgrounds and emittance growth • For SuperB a new design of the first doublet with «twins» quadrupoles was developed

  18. Final Focus sections • “Spin rotator” optics is replaced with a simpler matching section b* = 26 / 0.25 mm IP IP Y-sext Y-sext Crab Match & Spin Rotator HER X-sext Crab Match X-sext • Matching section is shorter than HER to provide space for spin rotator optics. • ±33 mrad bending asymmetry with respect to IP causes a slight spin mismatch between SR and IP resulting in ~5% polarization reduction. b* = 32 / 0.21 mm LER

  19. QD0 Design: 2 possible choices Vanadium Permendur “Russian” Design Air core “Italian” QD0, QF1 Design

  20. Field generated by 2 double helix windings in a grooved Al support Air-core QD0 is a SC iron free septum double quad

  21. Construction of a model coil for addressing quench issues The coil has been constructed at ASG Superconductors and now is at INFN Genova for testing at 4.2K. The results of this test are crucial for the design. Test this month

  22. Collettive effects • Stored beams are subject to effects that can produce instabilities or degrade the beam quality, such as: • Intra-Beam-Scattering (IBS) inside the bunch produces emittance and energy spread growth (not important in Damping Ring) • Electron-cloud instability limits the current threshold of the positron beam  needs mitigation methods (ex. solenoids, beam pipe coating, clearing electrodes...) • Fast Ions Instability is critical for the electron beam • CSR (Coherent Synchrotron Radiation) degrades beam quality (not important in Damping Ring) • These effects have been studied and remediation techniques chosen

  23. E-cloud build-up in Free Field Regions Snapshot of the electron (x,y) distribution 50G solenoids on Snapshot of the electron (x,y) distribution Solenoids reduce to 0 the e-cloud density at center of beam pipe Density at center of the beam pipe is larger then the average value.

  24. e-cloud buildup in HER Dipoles Demma By=0.3 T; =95%SEY=1.1 e- density averaged over the beam chamber e- density at center of the beam pipe 10 X beam sizes th= 1012 [e-/m3] Snapshot of the electron (x,y) distribution “just before” the passage of the last bunch

  25. e-cloud clearing electrodes in DAFNE Drago Very positive results: vertical beam dimension, tune shift and growth rates clearly indicate the good behaviour of these devices, which are complementary to solenoidal windings in field free regions Beam loss above this current if no feedbacks

  26. Low emittance tuning • The extremelylow design beamemittanceneeds to be tuned and minimizedcarefulcorrection of the magnetalignment and fielderrors • Theseerrors produce emittancecoupling with transfer of some horizontalemittance to the verticalplane thisneeds to be minimized • Beta-beating (ring b-functions are notas in the model machine, but are perturbed by the magneterrors) alsoneedsminimization • Vertical dispersionat IP needs to be corrected to the lowestpossiblevaluenot to compromise luminosity

  27. LET Tool This tool has been successfully tested at Diamond (RAL) and SLS (PSI) synchrotron light sources, which have similar emittances as SuperB. This work allows to set tolerances on magnet alignment and once the machine is running is able to detect such errors for correction

  28. First tolerance tests for HER V16 50 random sets, correcting with LET for 2 iterations after 3 orbit pre-correction iterations 4.4 pmrad before

  29. Injection System • Injection in top-up requires a very stable, reliable injection complex • Latest design: • Only e+ beam is stored in Damping Ring (DR) while e- beam is directly accelerated andinjected  e+ stored in DR for the time between two injection pulses, achieving same emittance damping factor at twice the repetition frequency  possible with a 100 Hz Linacto inject at 50 Hz in each ring using a single bunch per pulse to make the current per bunch very uniform along the bunch trains • Proposal: use SLAC gun (high charge, 10 nC) for the e+ line and have a custom made polarized, lowcharge, lowemittancegun for the e- line • R&D in progress at LAL/Orsay for the positron source • Contacts with SPARC group in Frascati for the lowemittancegun • R&D at SPARC on C-band Linacmaybeusefulalso (shorter) Boni, Guiducci, Preger, Variola et al)

  30. Injection system layout Positron Source positron linac e+ Damping Ring 1 GeV e+ CAPTURE SECTION THERMIONIC GUN SHB L-band PC 0.6 GeV ≈ 350 m Main Linac e+ BUNCH COMPRESSOR 5.7 GeV e+ 3.9 GeV e- 50 MeV CAPTURE SECTION 0.2 GeV POLARIZED SLAC GUN SHB e- combiner DC dipole Polarized Electron Source Transfer lines Positron Source to Damping Ring Damping Ring to Main Linac Electron Source to Main Linac Main Linac to HER Main Linac to LER Details: “SuperB Progress Reports – Accelerator”, (Dec. 2010) – Chapter 15 http://arxiv.org/abs/1009.6178v3. “Updated Design of the Italian SuperB Factory Injection System”, IPAC’11

  31. Injection Complex • Present status • Parameters and site layout selected • Layout and parameters of the system components defined • Beam dynamics evaluation started • Remaining work: • Baseline decision on electron source: direct injection or damping ring • Baseline decision on positron source: conversion at low energy (.6 GeV), L-band linac for capture and acceleration up to 1 GeV (or a combination of S and L band) • Transfer lines layout and composition follows • Systems ready for TDR • Damping ring • Main linac

  32. Injection tracking with bb Average over (1 ÷ 100) turns No beam-beam Crab = 1 Crab = 0.5 Crab = 0 Average over (4001 ÷ 4100) turns Average over (30001 ÷ 30100) turns No beam-beam Crab = 1 Crab = 0.5 Crab = 0 No beam-beam Crab = 1 Crab = 0.5 Crab = 0

  33. SuperKEKB

  34. Feedbacks Drago

  35. R&D on Controls (!CHAOS) Bisegni • Thisactivityattractedinterest from severalother INFN structuresand Universities

  36. SuperB not «just a collider»

  37. Brilliance SuperB vs ESRF (and ESRF upgrade) Bartolini Used U23 of ESRF ID27 ESRF parameters (4nm) 200 mA 0.7% coupling 2 m undulator ESRF upgrade (4nm) 300 mA 0.3% coupling 4 m undulator SuperB (2nm) 500 mA 0.7% coupling 2m undulator SuperB ESRF upgrade ESRF Compatibility with collider operation (current, orbit stability, heat load management,… ) needs to be studied

  38. Quintieri MC simulations of different targets for different particles production

  39. Summary on Accelerator work • Lattice «close» to be frozen, some more work needed on beam dynamics issues • We do have some systems «close» to TDR phase • Some strategical design choices still to be taken (ex. in injection system) • Most important issues to solve in the next months have been identified • R&D on control system started • R&D on new bunch-by-bunch feedback very positive (test at DAFNE) • Tests on e-cloud suppression electrodes at DAFNE successfull

  40. Organization • The CabibboLaboratory, in charge of building and operating the SuperB Accelerator and Detector, hasbeenfounded on October 7th 2011 as a Consortiumbetween INFN and University of Tor Vergata • Systems (almost) ready for technical design: • Magnets, vacuum chamber, support structure of the main rings • Beam diagnostic and control • Power supplies • Damping ring • Linear accelerator • Polarized electron source and positron source

  41. List of present partners

  42. Conclusions I • Organization of the accelerator structure is progressing • We have a draft organization of the accelerator work structure in Work Packages, with milestones and deliverables, needs refinement • We plan to commission to other laboratories/Institutions parts of the accelerator, taking into account their expertise in the field • Some examples at present: • France for the positron source, FF vibration control, ground measurements,… • England for the Final Focus, IP feedback, SL beamlines,… • BINP for DR, special magnets, vacuum pipe,… • SLAC for PEP-II components (RF, magnets,…) • Poland contribution to be discussed

  43. Conclusions II • An MOU with SLAC for procurement of PEP-II equipmentisbeingprepared • Synchrotron Light Italian community started to considerSuperBproperties for SL usersneeds more thoughts on maximum current, operation mode, experiments • MC simulations on the possibility to have a «SuperBeamTestFacility» started interest from users • With the CabibboLaboratorynow in placewewill be ready soon to hirepersonnel and reinforce the collaboration in order to finish TDR and start digging the tunnel before the end of thisyear Thankyou for yourattention !

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