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Issues for Formation of MEIC Ion Beam

Issues for Formation of MEIC Ion Beam. Ya. Derbenev. MEIC Ion Complex Design Mini-Workshop JLab, January 27-28, 2011. O u t l I n e. Concept of high luminosity Required parameters, concepts and problems of : - High energy EC for EIC - Synchronization for EC-

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Issues for Formation of MEIC Ion Beam

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  1. Issues for Formation of MEIC Ion Beam Ya. Derbenev MEIC Ion Complex Design Mini-Workshop JLab, January 27-28, 2011

  2. O u t l I n e • Concept of high luminosity • Required parameters, concepts and problems of : - High energy EC for EIC -Synchronization for EC- - Beam emittance injected in collider ring (required) - Luminosity lifetime (due to IBS and other) - Crab Crossing - Acceleration/rebunching in collider ring - Synchronization for collisions- - Emittance vs space charge at stacking - Beam loss at re-bunching - Microwave beam stability (wakes in SRF cavities and other) - Electron cloud - Gaps

  3. Luminosity in colliders with Electron Cooling • EC in cooperation with strong HF SC field allows one to obtain: • Very short ion bunches (1cm or even shorter)  • Small transverse emittances Decrease the bunch length  designlow beta-star Decrease transverse emittances  designlow beta-star Raise the beam-beam tune shift limit: large Qs (exceeding bb tune shift) Raise repetition rate by arrangement for crab crossing to eliminate the parasitic bb -Crab crossing is effective at HF- matches short bunches ! Decrease charge/bunch- receive MW stability, reduce IBS Diminish the IBS using flat beams (non-coupled optics)

  4. Forming the ion beam • Main issues: • Initial cooling time • Bunch charge & spacing • General recommendations: • Prevent the emittance increase at beam transport (introducing a fast feedback) • Use staged cooling • Start cooling at possibly lowest energy • Use the continuous cooling during acceleration in collider ring, if necessary • Beam bunching, cooling and ramp agenda: • After stacking in collider ring, the beam under cooling can be re-bunched by high frequency SC resonators, then re-injected for coalescence (if needed), more cooling and final acceleration & cooling • The final focus could be switched on during the energy ramp, keeping the Q-values constant

  5. IBS heating mechanism: Energy exchange at intra-beam collisions leads to x-emittance increase due to energy-orbit coupling, and y-emittance increase due to x-y coupling Electron cooling is introduced to suppress beam blow up due to IBS, and maintain emittances near limits determined by beam-beam interaction. Since L 1/ xy , reduction of transverse coupling while conserving beam area, would result in decrease of impact of IBS on luminosity Electron cooling then leads to a flat equilibrium with aspect ratio of 100:1. Touschek effect: IBS at large momentum transfer (single scattering) drives particles out of the core, limiting luminosity lifetime. A phenomenological model which includes single scattering and cooling time of the scattered particles has been used to estimate an optimum set of parameters for maximum luminosity, at a given luminosity lifetime. Lifetime due to Intrabeam Scattering

  6. High Energy Electron Cooling ERL/CR based staged EC in collider ring ERL based circulator electron cooler

  7. Feasibility of High Energy Electron Cooling Advances on electron beam • SRF energy recovering linac (ERL) • Removes the linac power show-stopper • Allows for two stages cooling or even cooling while accelerating • Allows for fast varying the e-beam parameters and optics when optimizing the cooling in real time • Delivers a low longitudinal emittance of e-beam • Electron circulator-cooling ring • Eases drastically the high current and energy exposition issues of electron source and ERL • Beam transport with discontinuous solenoid • Solves the problem of combining the magnetized beam transport (necessary for efficient EC) with effective acceleration • Beam adapters • Allows one to flatten the e-beam area in order to reach the optimum cooling effect

  8. Beam-beam kicker for EC Design parameters for beam-beam kicker Kicker beam is not accelerated after the DC gun Both beams are flat in the kick section Flat beams can be obtained from magnetized sources (grid operated). A schematic of beam-beam fast kicker • Kicker beam is maintained in solenoid. It can be • flatten by imposing constant quadrupole field • Flat cooling beam is obtained applying round-to- • flat beam adapters

  9. i i Cooling section arc arc Fast kicker Fast kicker ERL 75 MeV Dumper 125 KWt Injector 5 MeVx25 mA Synchronization for EC

  10. SRF dipole F Final lens F Crab Crossing R. Palmer 1988, general idea Short bunches make feasible the Crab Crossing SRF deflectors 1.5 GHz can be used to create a proper bunch tilt Parasitic collisions are avoided without loss of luminosity

  11. Short bunches also make feasible the Crab Crossing: SRF deflectors 1.5 GHz can be used to create a proper bunch tilt Crab Crossing for EIC 2

  12. Preliminary IP layout for ion beam CCB with inserted SRF for bunching and dispersive crabbing • Dipoles bending the beam in addition to arcs • Inserted SRF resonators are sufficient for required • bunching and dispersive crabbing

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