Accelerator

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Accelerator
DAFNE crab waist experiment

• M. Biagini, LNF-INFN
• on behalf of the SuperB DAFNE Teams
• 3rd International Workshop on
  "B Factories and New Measurements"
• Atami, Jan. 24th, 2008

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Outline

• How to increase Luminosity?
• The new collision scheme
• SuperB beam-beam simulations
• SuperB parameters, layout, lattice
• DAFNE upgrade with new scheme
• DAFNE commissioning status
• Conclusions

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SuperB Accelerator Contributors

• M. E. Biagini, M. Boscolo, A. Drago, S. Guiducci,
  M. Preger, P. Raimondi, S. Tomassini,
• C. Vaccarezza, M. Zobov (INFN/LNF, Italy)
• Y. Cai, A. Fisher, S. Heifets, A. Novokhatski,
  M.T. Pivi, J. Seeman, M. Sullivan, U. Wienands
  (SLAC, US)
• T. Agoh, K. Ohmi, Y. Onhishi (KEK, Japan)
• I. Koop, S. Nikitin, E. Levichev, P. Piminov, D.
  Shatilov (BINP, Russia)
• Wolski (Liverpool University, UK)
• M. Venturini (LBNL, US)
• S. Bettoni (CERN, Geneva)
• A. Variola (LAL/Orsay, France)
• E. Paoloni (Pisa University, Italy)

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How to increase L ?
But...
Brute force method

• HOM in beam pipe
• overheating, instabilities, power costs
• Detector backgrounds increase
• Chromaticity increase
• smaller dinamic aperture
• RF voltage increase
• costs, instabilities

• Increase beam currents
• Decrease by
• Decrease bunch length

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Hourglass effect
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A new idea for L increase
P. Raimondis to focus more the beams at IP and
have a large crossing angle ? large Piwinski
angle

• Ultra-low emittance (ILC-DR like)
• Very small b at IP
• Large crossing angle
• Crab Waist scheme

• Small collision area
• Lower b is possible
• NO parasitic crossings
• NO synchro-betatron resonances due to crossing
  angle

Test at DAFNE now !!!
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Large crossing angle, small x-size
1) Head-on, Short bunches
2) Large crossing angle, long bunches
(1) and (2) have same Luminosity, but (2) has
longer bunches and smaller sx
Large Piwinski angle F tg(q)sz/sx

• Vertical waist has to be a function of x
• Z 0 for particles at sx (- sx/2q at low
  current)
• Z sx/q for particles at sx (sx/2q at low
  current)

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... and ...

• Higher luminosity with same currents and bunch
  length
• Beam instabilities are less severe
• Manageable HOM heating
• No coherent synchrotron radiation of short
  bunches
• No excessive power consumption

• Lower beam-beam tune shifts
• Relatively easier to make small sx w.r.t. short
  sz
• Parasitic collisions becomes negligible due to
  higher crossing angle and smaller sx

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IP beam distributions for KEKB
Beams are focused in the vertical plane 100 times
more than in the present factories, thanks to -
small emittances - small beta functions - larger
crossing angle Tune shifts and longitudinal
overlap are greatly reduced
IP beam distributions for SuperB
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Luminosity and blow-up vs current
M. Zobov
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Luminosity vs tunes scan
P. Raimondi, D. Shatilov, M. Zobov

• Individual contours differ by 10 in luminosity
• Design luminosity can be obtained over a wide
  tune area

(horizontal axis - nx from 0.5 to 0.65 vertical
axis ny from 0.5 to 0.65)
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Transparency condition

• Due to the large crossing angle, new conditions
  are possible, different from asymmetric currents,
  for having equal tune shifts with asymmetric
  energies
• LER and HER beams can have different emittances
  and b and equal currents

?
Present B-factories
SuperB
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?

• LER beam
• sees a shorter overlap region,
• (4/7 of the HER one)
• has a smaller by, easier to achieve in the FF
  w.r.t. HER
• has larger emittance better for Touschek
  lifetime, and tolerance for LER instabilities

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SuperB parameters (1)

• Present parameter set based on ILCDR-like
  parameters
• Same DR emittances
• Same DR bunch length
• 1.5 times DR bunch charges
• Same ILC-IP betas
• Crossing angle and crab waist to maximize
  luminosity and minimize blowup
• Presently under test at DAFNE
• Use PEP-KEK DR damping time 19 ms
• No emittance wigglers used in Phase 1

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SuperB parameters (2)

• ILC/FFTB like Final Focus
• Design based on recycling all PEP-II hardware,
  Bends, Quads and Sexts, and RF system
• Corresponds to a lot of money !
• Maximize Luminosity keeping low wall power
• Total power 17 MW, lower than PEP-II
• Simulations performed in many labs and with
  different codes
• LNF,BINP,KEK,LAL,CERN

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SuperB Parameters (Phase 1)
Transparency conditions
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Ring Layout
No polarization section here
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Final Focus

• Crossing angle to 225 mrad, L0.4 m
• Local chromaticity correction
• Horiz.beam separation at QD0 2 cm, about 180 sx
• A possible solution with a septum QD0, to avoid
  the high background rate in the detector which
  would be produced by the over-bend off-energy
  particles if a dipolar component is present, is
  being studied.
• In the novel design, based on SC helical-type
  windings, the windings generate pure quadrupole
  field as a superposition of the inner field of
  the surrounding coil and of the outer fringe
  field of the neighbor one (Bettoni, Paoloni).
  Overall thickness 8mm, leaving about 60 sx of
  beam stay-clear.

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IP layout
M.Sullivan
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Example of QD0 design
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Polarization

• Polarization of one beam is included in SuperB
• Either energy beam could be the polarized one.
• The LER would be less expensive.
• Long polarization times and short beam lifetimes
  indicate a need to inject polarized electrons in
  the vertical plane
• There are several possible IP spin rotators
• Solenoids look better at present
• Expected longitudinal polarization at the IP of
  about 87(inj) x 97(ring)85(effective)

J. Seeman, International Review Committee
Meeting, LNF, Nov.07
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DAFNE upgrade with crab waist
DAFNE Upgrade Team
D. Alesini, M. E. Biagini, C. Biscari, R. Boni,
M. Boscolo, F. Bossi, B. Buonomo, A. Clozza, G.
Delle Monache, T. Demma, E. Di Pasquale, G. Di
Pirro, A. Drago, A. Gallo, A. Ghigo, S. Guiducci,
C. Ligi, F. Marcellini, G. Mazzitelli, C.
Milardi, F. Murtas, L. Pellegrino, M. Preger, L.
Quintieri, P. Raimondi, R. Ricci, U. Rotundo, C.
Sanelli, M. Serio, F. Sgamma, B. Spataro, A.
Stecchi, A. Stella, S. Tomassini, C. Vaccarezza,
M. Zobov (INFN/LNF) I. Koop, E. Levichev, P.
Piminov, D. Shatilov, V. Smaluk (BINP) S.
Bettoni (CERN, Geneva) K. Ohmi (KEK) N. Arnaud,
D. Breton, P. Roudeau, A. Stocchi, A. Variola, B.
F. Viaud (LAL/Orsay) M. Esposito (Rome1
University) E. Paoloni (Pisa University) P.
Branchini (Roma3 University) M. Schioppa (INFN
Gruppo di Cosenza) P. Valente (INFN-Roma)
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DAFNE performances
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DAFNE Upgrade Parameters
Larger Piwinski angle
Lower vertical beta
Already achieved
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DAFNE test expected results

• The upgrade of DAFNE run the new collision scheme
  will allow for peak luminosities of 1033 cm-2 s-1
• The use of crab waist sextupoles will add a
  bonus for suppression of dangerous resonances
• Brand new IRs layout and equipments have been
  designed, constructed and installed
• This test will have the fundamental function of
  validating the simulation

Luminosity vs beam current
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Luminosity vs tunes scan
M. Zobov
Crab On ? 0.6/q
Crab Off
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Strong-Strong Simulations
Single Bunch Luminosity
Crab Waist On
Crab Waist On
Crab Waist Off
tdamping 30.000 turns
tdamping 110.000 turns
x110 bunches 1033 cm-2 s-1
(K. Ohmi, BBSS Simulations)
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Hardware modifications
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Interaction Region 2 (no collisions)
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SIDDHARTA Setup
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Commissioning status (1)

• Rings closed end November
• First beams beginning of December
• Some BPMs problems due to new RF frequency solved
• Maximum currents up to now 700/400 mA (e-/e)
• Found pm quads lower gradient (2) than expected
  ? rematched optics
• Coupling 0.4/1.1 (e-/e)
• Crab waist optics implemented, phase between
  sextupoles OK

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Commissioning status (2)

• Measured b-functions and dispersion in agreement
  with model
• Collisions started at 200 on 200 mA (e-/e), 60
  bunches
• Measured vertical IP size Sy 8.1 mm
• Tuning of all subsystems in progress
• SIDDHARTA Detector will be installed first week
  of February

Beam currents in 24 h
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Conclusions (1)

• New large Piwinski angle scheme in SuperB will
  allow for peak luminosity ³ 1036 cm-2 s-1 well
  beyond the current state-of-the-art, without a
  significant increase in beam currents or shorter
  bunch lengths
• Use of crab waist sextupoles will add a bonus
  for suppression of dangerous resonances
• Expected luminosity increase due to Crab Waist
  is
• a) a factor of 3, at least, for the DAFNE
  upgrade
• b) about 2 orders of magnitude for the
  SuperB project
• (with respect to the existing
  B-Factories)
• The principle is being tested at DA?NE

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Conclusions (2)

• There is an international interest and
  participation in SuperB
• A CDR is being reviewed by the International
  Review Committee
• In case of positive answer a TDR will be ready by
  2010
• Next issues are site, money, people

• Upgraded DAFNE is in commissioning phase
• Collisions at low current started
• Results are expected very soon