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Space charge, electron cloud and nonlinear dynamics: Motivation and Challenges.

Space charge, electron cloud and nonlinear dynamics: Motivation and Challenges. Ingo Hofmann HHH-meeting at GSI March 30 – 31, 2006. "background" CERN PS experiments and follow-up Coherent and incoherent resonance crossing Outlook. H igh Energy H igh Intensity H adron Beams.

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Space charge, electron cloud and nonlinear dynamics: Motivation and Challenges.

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  1. Space charge, electron cloud and nonlinear dynamics: Motivation and Challenges. Ingo Hofmann HHH-meeting at GSI March 30 – 31, 2006 "background" CERN PS experiments and follow-up Coherent and incoherent resonance crossing Outlook

  2. High Energy High Intensity Hadron Beams HHH is a Networking Activity (N3) in the framework of CARE Coordinated by F. Ruggiero and W. Scandale • Main Objectives • The aim of the CARE-HHH Network is to coordinate and integrate the activities of the accelerator and particle physics communities working together, in a worldwide context, towards achieving superior High-Energy High-Intensity Hadron Beam facilities for Europe. The final objectives are: • to establish a road map for the upgrade of the European accelerator infrastructure (LHC and GSI accelerator complex) • to assemble a community capable of sustaining the technical realization and scientific exploitation of these facilities • to establish and propose the necessary accelerator R&D and experimental studies to achieve these goals

  3. Thursday

  4. Friday

  5. G. Franchetti, A. Franchi, A. Parfenova, A. Orzhekovskaya (GSI) Experiment: E. Metral a.o. from CERN P. Zenkevich (ITEP) and A. Bolshakov (ITEP) S.Y. Lee (Indiana University) G. Turchetti et al. (Bologna) S. Machida (RAL) R. Ryne, J. Qiang (LBNL) Collaborators (transverse space charge & loss)(Collective effects: see talk by Oliver)

  6. FAIR – Facility for Antiproton and Ion Research:Intensity upgrades Present Intensity in SIS12/18 2.5 x 109 U73+ -ions /cycle Planned Intensity in SIS12 Booster Operation ~1011U28+ -ions /cycle Planned Intensity in SIS100/300 ~4 x 1011 U28+ -ions /cycle The step to highest heavy ion beam intensities requires medium charge states.

  7. Nuclotron-type pulsed sc dipoles – large aperture filling

  8. Comparison SIS100 + JPARC Main Ring will work in an intermediate regime Storage of DQ ~ -0.2 and over 105 turns requires "new" approach

  9. “No one believes in simulation results except the one who performed the calculation, and everyone believes the experimental results except the one who performed the experiment.” GSI-CERN collaboration: Joint experiments started at ICFA-HB2002 with CERN-PS-group (2002-04) Montague resonance + octupole & space charge driven beam loss ( test of new "resonance trapping" model) Application of "resonance trapping" model to FAIR SIS100 design Benchmarking with other codes (2004/05) In 2005 F. Zimmermann suggested that this "resonance trapping" may also occur in LHC p-ecloud interaction Our approach is to understand fundamental mechanisms – not just run codes – we need to find scaling laws for applications to different scenarios Simulation & Experiments needed

  10. Measurements at CERN PS in 2003 relatively good agreement experiment-theory for measurements with "static" tunes Vertical tune = 6.21 (fixed) IMPACT code measured agree on "exact resonance"

  11.  Recently derived scaling laws for "static" case (fixed tunes) • from evaluating dispersion relations + fitting obtained "simple" laws for bandwidth and growth rates • stop-band width and exchange rate • (Nex = number of turns after which exchange occurs: • Nex ~ 35 for PS-experiment Based on analytical Vlasov theory

  12. "Dynamical" measurements remain a challenge • very slow crossing of tune through resonance (data from 2003): • 40.000 turns • mesured equal final emittances • synchrotron motion "mixing", collisions?) 2D "idealized" exchange k3= + 0 k3= + 60 k3= - 60 experiment

  13. Studied theoretically "fast" crossing • emittance exchange ~ (tune rate)-1 "linear" regime for fast crossing 1000 turns 100 turns Nex ~ 34 turns

  14.  Scaling law for "fast" crossing • self-consistentemittance exchange with "tune rate" dQ/dN (tune change per turn) found to scale quadratically with tune shift:

  15. Analogue to "homogeneous" 2Qx- 2Qy=0: Inhomogeneous 4Qy=N purely space charge driven resonance SIS18: 4Qy=12 (near Qy=3) or SNS: 4Qy=4x6 (near Qy=6) also FFAG: 4Qy=N "octupolar" space charge on harmonic 12 is strong for lattice with 12 super periods we suspect a similar scaling law applies for "fast crossing" a: should be weaker than for Montague: 2 turns 30 turns SIS18-lattice: only linear optics DQy=0.4 (initial waterbag distribution)

  16. Coherent resonance crossing implies all particles cross resonance "simultaneously" and in same direction occurs, if bunch compression in SIS18/100 with DQ getting too large working point is swept across resonance (non-scaling FFAG  S.Y. Lee) need for self-consistency not clear space charge induces a "shift" of exact resonance condition (claimed for SNS) Coherent crossing vs. incoherent crossing

  17. Coherentresonance crossing has dominated picture in high-intensity beam loss for SNS etc. (2002) (<1 synchrotron periods) • REVIEWS OF MODERN PHYSICS, VOLUME 75, OCTOBER 2003 • Jie Wei: Synchrotrons and accumulators for high-intensity proton beams • 3. Resonance-loss model • ... As the intensity increases, beam loss increases progressively upon overlapping with the half-integer coherent-resonance lines (Fedotov, Blaskiewicz, et al., 2002). Depending upon operational conditions, the behavior of the loss curve varies with the choice of working point, the nature and excitation of nearby resonance lines, and the correction of major resonances.

  18. New topic first presented at ICFAHB02: incoherent resonance crossing + trapping due tospace charge +synchrotron motion x z Bare tune Resonance Periodic crossing of a resonance

  19. occurs with synchrotron motion over many synchrotron periods important in all machines with long cycles SIS100 J-PARC main ring LHC with e-cloud was tested experimentally in CERN-PS in 2002/03 with now much improved agreement experiment-simulation on actual loss (in emittance grow regime good before): raised from 0% loss in early simulations to 16% loss in recent ones (measured 27%) ( talk by Giuliano Franchetti) recent benchmarking of trapping mechanism between Micromap and Simpsons (S. Machida) – agree analytical scaling model in development by P. Zenkevich Incoherent resonance crossing: many random resonance crossings and trapping  halo + loss

  20. Outlook • coherent space charge resonance effects á la Montague and 4Q=N • gained good theoretical understanding for static tunes • for Montague and static tunes good agreement with experiment in PS • slow crossing yet unresolved discrepancy (incoherent effects by synchrotron motion?) • fast crossing: scaling laws • derived for Montague - can we measure them in experiments in PS? • we are working on similar scaling laws for space charge 4Q=N – can we measure in SIS18? • incoherent resonance effects with trapping • experimentally confirmed with single strong resonance • multiple resonances? • so far not self-consistent • is it needed? • search for scaling laws and their experimental verification

  21. Issues for future experiments coherent resonance crossing | incoherent with trapped particles

  22. Issues for future simulations coherent resonance crossing | incoherent with trapped particles

  23. Codes participating in benchmarking code comparison started after October 2004 (ICFA-HB2004 workshop)

  24. SIS 100/300 SIS UNILAC FRS ESR HESR Super FRS CR NESR RESR FAIR – Facility for Antiproton and Ion Research Existing Future Project 100 m

  25. Response to octupolar resonance without synchrotron motion:incoherent resonance crossing absent (coasting beams limit) KV k3=125 KV: large difference self-consistent - frozen Gaussian k3=125 loss

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