Status and perspectives of high luminosity flavour factories
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Status and Perspectives of High Luminosity Flavour Factories. M. E. Biagini, INFN/LNF EPS-HEP, Stockholm July 20 th 2013. Flavour Factories. Past: PEP - II @ SLAC, USA KEKB @ KEK, Japan Present: DA F NE @ INFN-LNF, Italy Vepp2000 @ BINP, Russia BEPCII @ IHEP, China Future :

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Status and Perspectives of High Luminosity Flavour Factories

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Status and Perspectives of High Luminosity FlavourFactories

M. E. Biagini, INFN/LNF

EPS-HEP, Stockholm July 20th 2013


Flavour Factories

  • Past:

    • PEP-II @ SLAC, USA

    • KEKB @ KEK, Japan

  • Present:

    • DAFNE @ INFN-LNF, Italy

    • Vepp2000 @ BINP, Russia

    • BEPCII @ IHEP, China

  • Future:

    • SuperKEKB @ KEK

  • Proposals:

    • Tau-Charm @ BINP, INFN, IHEP, TAC (Turkey)


  • e+e- colliders Luminosity vsEnergy

    Super BF

    Linear

    CircularXbeam

    Super TC


    The past…


    PEP-II B-Factory 1999-2008


    KEKB B-Factory 1999-2010


    Integrated Luminosity


    KEKB tried “crab cavities”

    • Crab cavities installed in Feb. 2007 at KEKB and worked very well until the end of the KEKB operation

    • Highest luminosity with the crab cavities was about 23% higher than that before crab (prediction by bb simulation: ~100% increase)

    • Tuning with skew-sextupole magnets was effective to increase the luminosity with the crab cavity (~15% gain)

    • Found that skew-sextupoles are also effective to increase the luminosity when the crab cavities were switched off


    Recipes for success

    • Efficient injection system  Trickle injection

    • Tuning knobs  beam control

    • Strenuous instabilities fight  e-cloud mitigation, bunch-by-bunch feedbacks

    • Higher currents than design  see a)

    • New ideas (crab cavities, skew sextupoles)

    • Stable RF system

    • Powerful diagnostics  see b)

    • Skilled and expert staff


    Standard CollisionSchemeLimitations

    1. Hourglass effect limits minimum IP b:by* ≤ sz

    2. Bunch length reduction not advisable

    bunch lengthening, microwave instability, CSR

    3. Further multibunch current increase would result in

    coupled bunch instabilities, HOM heating, higher wall-plug power

    4. Higher emittances conflict with

    beamstay-clear and dynamics aperture limitations

    5. Tune shifts saturate, beam lifetime drops due to

    beam-beam interactions


    Changing the approach…

    • Less than 10 years ago the “brute force” (increasing currents) was the only approach to higher luminosity

    • P. Raimondi (LNF) studied a new collision scheme with larger crossing angle and lower IP beam sizes (Large Piwinski Angle) PLUS a couple of sextupoles to twist the IP waist and cure x-y and synchro-betatron resonances raising from the angle (Crab Waist). Test at DAFNE

    • Adopted by all Factory projects after 2008

    Oide, Progress of Theoretical Physics, Vol. 122, No. 1, July 2009


    CrabWaistAdvantages

    • Luminosity gain with N

    • Verylowhorizontaltuneshift

    • Vertical tuneshiftdecreases with oscillationamplitude

    • Large Piwinski’s angle

    • F = tg(q/2)sz/sx

    • 2. Vertical beta comparable

    • with overlap area

    • by 2sx/q

      3. Crabwaisttransformation

    • y = xy’/q

    • Geometricluminosity gain

    • Lower verticaltuneshift

    • Suppression of verticalsynchro-betatronresonances

    • Geometricluminosity gain

    • Suppression of X-Y betatron and synchro-betatronresonances


    ....and besides…

    • No need to increaseexcessivelybeamcurrent and to decrease the bunchlength:

      • Beaminstabilities are less severe

      • Manageable HOM heating

      • No coherentsynchrotronradiation of short bunches

      • No excessivepowerconsumption

    • Problem of parasiticcollisionsautomaticallysolved due to highercrossing angle and smallerhorizontalbeamsize

    • Lesshourglassby* can be decreased


    Crab sextupoles effect

    • Crab sextupoles are strong and introduce large non-linearity, optics between them has to be linear as much as possible

    • Dynamic Aperture is greatly reduced. Solutions:

      • Design IP doublet so to compensate the kynematic (octupole) and fringing field effects

      • Locally compensate the chromaticity (Y and X separately)

      • Add octupoles and additional sextupoles to compensate for the aberrations induced by the off-phase sextupoles

      • Adjust b and phase advance between crab sextupoles

    • Done for SuperB and Italian Tau/Charm: effect is reduced (not cancelled)


    Design & operation challenges

    • Ultra low emittances (H, V)  Coupling compensation

    • Interaction Region and Final Focus design (Low b*, IP quadrupoles)

    • Dynamic aperture (with fringing fields in IP quads and crab sextupoles)

    • Tolerances to machine errors and vibrations  Low Emittance Tuning

    • Impedance budget

    • Lifetimes (bb bremsstrahlung, Touschek)  trickle charge injection

    • High backgrounds  detector protection

    • High beam currents  injection system

    • Extreme vacuum with high currents

    • Short bunch distance  kickers, feedbacks

    • Instabilities control (collective effects, b-by-b feedbacks)

    • Adequate diagnostics (SLM, BPM, BLM, b-by-b luminosity monitor…)

    • On-line tuning knobs  orbit, IP waist, dispersion, coupling, IP b, tunes, IP angles

    • ….


    Synergies

    • Most of the above topics (except for high beam currents and beam-beam issues) apply to modern design of 4th generation Synchrotron Light Sources

    • Low emittance tuning techniques (LOCO, LET, …) successfully applied

    • Record emittances measured at Diamond, SLS, ASLS (ey < 2 pm)

    • Dynamic Aperture optimization techniques (MOGA, FMA, …) give larger momentum and transverse acceptances

    • The two communities actively collaborate (see for example 3rdLOWeRING Workshop at Oxford, EuCARD2)

      http://www.physics.ox.ac.uk/lowemittance13/index.asp


    The present…


    DAFNE @ INFN-Frascati

    • First F-Factory with Large Piwinski Angle and Crab Waist collision scheme (adapted to previous IR design)

    • 3xLuminosity boost with non magnetic detector SIDDHARTA

    • Proven effectiveness of crab sextupoles (very good agreement with numerical predictions and simulations)

    • New Interaction Region for KLOE2 magnetic detector

    • Limited in beam currents (e-cloud, damaged bellows, short lifetime), but…

    • …e-cloud clearing electrodes successful in increasing threshold, and…

    • ..lot of work in 2013 for replacement/upgrade of old hardware in progress  resume operation by this Summer


    Effect of crab waist scheme

    Design Goal

    CRAB ON

    CRAB OFF


    Comparison of best runs with and without Crab-Waist

    Luminosity [1028 cm-2 s-1]

    Luminosity [1028 cm-2 s-1]


    VEPP-2000, BINP, Round Beams


    Round Beams Collisions

    • Round beams experiment:

      • geometrical factor gain

      • beam-beam limit enhancement

    • 2 pairs of superconducting focusing solenoids in the 2 Interaction Regions symmetrically with respect to IPs

    • Several combinations of solenoid polarities satisfy Round Beams condition:

      • “Normal Round” (++ --)

      • “Möbius” (++ -+)

      • “Double Möbius” (++ ++)

      • Two “Flat” combinations (+- +- or +- - +) more simple and also satisfy RBC if the betatron tunes lie on the coupling resonance

      • n1- n2 = 2

    • Small Dynamic Aperture


    Luminosity vs Energy

    Lack of e+

    DA and IBS

    lifetime

    Flip-flop

    Simulations

    VEPP-2M data

    2010-2011 run,2011-2012 run,2012-2013 run


    BEPC-II, IHEP

    • Major upgrade of BEPC in 2004

    • Presently only existing t/charm


    Luminosity tuning

    • Luminosity increased nx 0.5

    • Low ap lattice  lower e and sz


    The near Future…


    Upgrade to Belle II detector

    Colliding bunches

    New superconducting final focusing magnets near the IP

    e+ 3.6A

    e- 2.6A

    KEKB to SuperKEKB

    Redesign the lattice to squeeze the emittance (replace short dipoles with longer ones, increase wiggler cycles)

    • Nano-Beam scheme

    • extremely small by*

    • low emittance

    • Beam current double

    Reinforce RF systems for

    higher beam currents

    Replace beam pipes with TiN-coated beam pipes with antechambers

    40 times higher luminosity

    2.1x1034 --> 8x1035 cm-2s-1

    Improve monitors and control system

    Injector Linac upgrade

    Upgrade positron capture section

    DR tunnel

    Low emittance

    RF electron gun

    New e+ Damping Ring

    K. AKAI, Progress in Super B-Factories, IPAC13


    Parameters of KEKB and SuperKEKB

    Intra-beam scattering is included.

    K. AKAI, Progress in Super B-Factories, IPAC13


    • Final focus SC quads (QCS)

    • Eight final focus QCS with 40 corrector coils are to be used.

    • Fabrication of QCS-L started in July 2012, and will be completed in JFY2013.

    • Fabrication of QCS-R is scheduled in JFY2013 and 2014.

    • Prototype magnet was made at KEK. Test results show sufficient margin for operation.

    • Corrector coils are being wound at BNL under BNL/KEK collaboration.

    QC1LE prototype magnet

    Successfully tested without any quench up to 2157A, well over the design current (1560A) for nominal operation.

    [email protected] = 62.8%

    [email protected] = 87.0%

    Sufficient margin for operation

    K. AKAI, Progress in Super B-Factories, IPAC13


    Commissioning Scenario

    Commissioning Scenario

    Baseline

    Scenario

    Phase 1

    Jan. 2015 -

    ~5 months

    Phase 2

    ~4 months

    Phase 3

    First target luminosity

    1 x 1034 cm-2s-1

    TOP

    CDC

    PXD/SVD ready

    installation

    [Phase 1]No QCS, No Belle II

    • Basic machine tuning, Low emittance tuning

    • Vacuum scrubbing ( 0.5 ~ 1.0 A, >1 month)

    • DR commissioning start (~Apr. - )

      [Phase 2]With QCS, With Belle II (without Vertex Detector)

    • Small x-y coupling tuning, Collision tuning

    • by* will be gradually squeezed

    • Background study

      [Phase 3]With Full Belle II

    • Increase beam current with adding more RF

    • Increase luminosity

    K. AKAI, Progress in Super B-Factories, IPAC13


    The possible Future…


    Super t/charm proposals


    Italian t/Charm Factory

    • Evolution after cancellation of SuperB

    • Energy tunable in the range Ecm = 1-4.6 GeV

    • 1035cm-2 s-1luminosity at the t/charm threshold and upper

    • Symmetric beam energies

    • Longitudinal polarization in the electron beam (60-70%)

    • Possibility of e-e- collisions (to be studied)

      • Design based on “Large Piwinski angle & crab waist sextupoles” collision scheme

      • Low beam emittance (about 2 nm natural)

    • Wigglers needed at lower beam energy

    • Injection system scaled from the SuperB one

    • Possibility to use injection Linac + additional C-band Linac for a 6 GeV SASE-FEL facility


    t/charm parameters vs E


    t/charm @Tor Vergata (former SuperB site)

    Tau/Charm Accelerator Report just written (150 pp, not public yet)


    Summary

    • Higher luminosity colliders can still be built, profiting from:

      • experience from past successes

      • new ideas

      • new technologies

      • synergy with other communities

    • A Super Factory is being built at KEK  very important to keep alive this kind of Accelerators and Physics !

    • Several proposal for lower energy High Luminosity Flavour Factories on the market at different laboratories with experience of successful accelerators


    Aknowledgments

    • For the material presented here I’m indebted with:

      • K. Akai, Y. Funakhoshi, KEK

      • Q. Qing, Y. Zhang, IHEP

      • M. Zobov, INFN-LNF

      • A. Bogomiagkov, I. Koop, D. Schwartz, BINP

    THANK YOU FOR YOUR ATTENTION


    Spare slides


    • Beam energy from 0.5 to 2.1 GeV

    • Peak luminosity 1035 cm-2s-1 at 2 GeV and within as wide as possible energy range

    • Circumference 366 m to fit in the existent tunnel of VEPP4-M (previous design 800m)

    • Conform as much as possible to existent infrastructure

    • Longitudinal polarization at some energy points

    BINP Super cTau (2nd design)


    Parameters

    Old C-Tau, 800m

    2 cm / 0.76 mm

    10 nm

    10 mm

    7·1010

    1.7 A


    IHEP Super Tau-Charm Factory

    • Dual ring, factory like

    • 2.5-3 GeV, parasitic 3rd generation SR source

    • Crab Waist collision scheme

    • Small IP b functions

    • Small emittance using wigglers

    • High beam current

    • Electron beam polarization (e- source, 5 Siberian Snakes)

    • Top-up injection at 3 GeV, 50 Hz


    IHEP Super Tau-Charm Factory


    Turkish Accelerator Complex (TAC) SCF

    • TAC SCF presented to ECFA 2011

    • Linac (e-) + ring (e+) charm factory with L= 1.41035 cm-2 s-1

    • Synchrotron light source based on positron ring

    • Free electron laser based on electron linac

    • TDR [email protected] will be completed in 2013


    TAC Super Charm Factory parameters


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