The SuperB Accelerator

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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: - PowerPoint PPT Presentation

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  • The SuperB AcceleratorM. Biagini for the SuperB Accelerator TeamEpiphany 2012 ConferenceKrakow, January 9-11, 2012

  • SuperB AcceleratorSuperB is a 2 rings, asymmetric energies (e- @ 4.18, e+ @ 6.7 GeV) collider with:large Piwinski angle and crab waist (LPA & CW) collision schemeultra low emittance latticeslongitudinally polarized electron beamtarget 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 costsMinimize running costsMinimize wall-plug power and water consumptionReuse 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) *

  • *World e+e- colliders luminosityB-FactoriesF-FactoriesFuture CollidersSuperB: highest world luminosity collider ever

  • Ultra-low emittanceVery small b* at IPLarge crossing angleCrab Waist transformationSmall collision areaLower b* is possibleNO parasitic crossingsNO x-y-betatron resonancesPrinciple: beams more focused at IP + large crossing angle (LPA) + 2 sextupoles/ring to twist the beam waist at the IP (CW)Large Piwinski Angle & Crab Waist:a novel idea for Luminosity increaseProved to work at upgraded DAFNE F-Factory2008-2009P.Raimondi, 2 SuperB Workshop, March 2006P.Raimondi, D.Shatilov, M.Zobov, physics/0702033*

  • NEW COLLISION SCHEMEDANE Peak LuminosityDesign Goal*

  • *SuperB main featuresGoal: maximize luminosity while keeping wall power low

    2 rings (~4 GeV and ~7 GeV) with flexible designUltra low emittance optics: 7x4 pm vertical emittanceBeam currents: comparable to present Factories LPA & CW scheme used to maximize luminosity and minimize beam size blow-upNo emittance wigglers used (save power)Design based on recycling PEP-II hardware (save costs)Longitudinal polarization for electrons in the LER (unique feature)Possibility to push the cm energy down to the t-charm threshold with a luminosity of 1035 cm-2 s-1

  • Parameter TableBaseline + other 2 options:Lower y-emittanceHigher currents (twice bunches)Tau/charmthreshold runningat 1035Baseline: Higher emittance due to IBSAsymmetric beam currents RF power includes SR and HOM*

  • SuperB layoutSite chosen @ Tor Vergata University (Rome II) campusSinchrotron Light (SL) beamlines are becoming part of the layout (HER preferred at the moment)One tunnel will host both rings, which will probably have a tilt one respect to the other, to allow for easier crossing and SL beamlines from both HER and LER (if needed)The position of the Linac complex has still to be finalized, depending on the injection requirementsThe rings layout has been recently improved to accomodate Insertion Devices (ID) needed for SL users

    *

  • Tor Vergata University campus*

  • Ground measurementsGround motion measurements performed on site in April show very solid grounds in spite of the vicinity of the highway, just 100 m awayThe highway is at higher level with respect to the site, and the traffic vibrations (cultural noise) are very well damped Ground x-sectionVolcanic soil*

  • SuperB @ Tor VergataSR BeamlinesInjection complex*SR BeamlinesTomassini

  • *Rings LatticeThe two rings have similar geometry and layout, except for the length of dipolesThe arcs cells have a design similar to that of Synchrotron Light Sources and Damping Rings in order to achieve the very low emittancesIn the latest version of the lattice some cells for Insertion Devices have been insertedRings are separated about 2m in horizontal and 1m in vertical

  • Spin RotatorFF3 ID cells3 ID cellsInjection sectionRF sectionIPCircumference 1195 mHorizontal separation of arc ~2 mVertical separation of RF section 0.9 mDimension sizes of rings 416 m x 342 m

    SiniatkynCollider Layout

  • *tilt=2.6 mradVertical separation 0.9 mVertical rings separationRings 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

  • Polarization in SuperB 90spin rotation about x axis90about z followed by 90about yflat geometry no vertical emittance growthSolenoid scales with energy LER more economicalSolenoids are split & decoupling optics addedThe SR optics design has been matched to the Arcs and a similar (void) insertion added to HERThis 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*

  • Polarization resonancesBeam polarization resonances do constraint the beam Energy choicePlot shows the resonances in the energy range of LERBeam polarization computed assuming90% beam polarization at injection3.5 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*

  • Interaction RegionThe Interaction Region must satisfy both machine and detector requirements: Final Focus elements as close as possible to the IPSmall detector beam pipe Enough beam stay clear small emittance helpsControl Synchrotron Radiation backgroundsHave an adequate detector solid angle Magnet vibrations need to be damped (at the level of 10nm)A state-of-the-art luminosity feedback is neededWith 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 growthFor SuperB a new design of the first doublet with twins quadrupoles was developed*

  • Final Focus sectionsSpin rotator optics is replaced with a simpler matching section 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* = 26 / 0.25 mm b* = 32 / 0.21 mm *

  • QD0 Design: 2 possible choicesVanadium Permendur Russian DesignAir core Italian QD0, QF1 Design*

  • Air-core QD0 is a SC iron free septum double quad *Field generated by 2 double helix windingsin a grooved Al support

  • Construction of a model coil for addressing quench issuesThe 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

  • Collettive effectsStored 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

    *

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

  • *e-cloud buildup in HER DipolesBy=0.3 T; =95% SEY=1.1th= 1012 [e-/m3]e- density at center of the beam pipee- density averaged over the beam chamber10 X beam sizesSnapshot of the electron (x,y) distribution just before the passage of the last bunch Demma

  • e-cloud clearing electrodes in DAFNEVery positive results: vertical beam dimension, tune shift and growth ratesclearly indicate the good behaviour of these devices,which are complementary to solenoidal windings in field free regionsDragoBeam loss above this current if no feedbacks*

  • Low emittance tuningThe extremely low design beam emittance needs to be tuned and minimized careful correction of the magnet alignment and field errorsThese errors produce emittance coupling with transfer of some horizontal emittance to the vertical plane this needs to be minimizedBeta-beating (ring b-functions are not as in the model machine, but are perturbed by the magnet errors) also needs minimizationVertical dispersion at IP needs to be corrected to the lowest possible value not to compromise luminosity*

  • LET ToolThis 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*

  • First tolerance tests for HER V1650 random sets, correcting with LET for 2 iterations after 3 orbit pre-correction iterationsbefore4.4 pmrad

    misalignmentsARCSFFQUAD SEXT DX,DY50 m30 mQUAD SEXT DPHI100 rad50 radMonitor resolution1 m1 mMonitors OFFSETs50 m50 mDIPOLE DPHI and DTHETA50 rad50 rad

  • Injection SystemInjection in top-up requires a very stable, reliable injection complexLatest design:Only e+ beam is stored in Damping Ring (DR) while e- beam is directly accelerated and injected 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 Linac to inject at 50 Hz in each ring using a single bunch per pulse to make the current per bunch very uniform along the bunch trainsProposal: use SLAC gun (high charge, 10 nC) for the e+ line and have a custom made polarized, low charge, low emittance gun for the e- line R&D in progress at LAL/Orsay for the positron sour