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SIS18 space charge experiments

SIS18 space charge experiments. G. Franchetti 26/8/2008 GSI, Darmstadt. Overview. The high intensity mechanism for emittance growth and beam loss in long term storage. The S317 campaign and the experimental results. Outlook. The purpose. Study the beam dynamics of high intensity beams

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SIS18 space charge experiments

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  1. SIS18 space charge experiments G. Franchetti 26/8/2008 GSI, Darmstadt

  2. Overview The high intensity mechanism for emittance growth and beam loss in long term storage The S317 campaign and the experimental results Outlook G. Franchetti

  3. The purpose Study the beam dynamics of high intensity beams in a non linear synchrotron Provide data of an experiment performed in a well controlled condition Benchmarking of code prediction of space charge beam regimes find in SIS100: 1 s storage of high intensity bunch This studies are part of the process of SIS18 upgrade for reaching the FAIR parameters. G. Franchetti

  4. The beam physics case: space charge induced periodic crossing of a ring resonance x z Bare tune Ring resonance Resonance G. Franchetti

  5. Trapping/scattering into resonances Scattering into 3rd order resonance Example for SIS18: Trapping into 3rd order resonance G. Franchetti

  6. chromaticity induced stop-band large as or as function of pipe or DA intercepted emittance growth regime: large as ~ asymptotic limit larger than beam loss rate function of Kn, DQx Consequences I: transverse beam blow up and beam loss beam loss regime Emittance growth regime 1 Resonance stop-band Qx G. Franchetti

  7. p/p z Consequences II: effect of beam loss on longitudinal profile At the beginning of storage At the end of long term storage (when all trapped particles are transversally lost) p/p z Bunch shortening Correlation beam loss vs. bunch shortening G. Franchetti

  8. Precedent experimental campaign: CERN-PS R. Cappi, G. Franchetti, M. Giovannozzi, I. Hofmann, E. Metral, M. Martini, R.Steeremberg ICFA2004 4th-order resonace G. Franchetti

  9. The space charge campaign at GSI S317 Law of experimentalists: “Never replicate a successful experiment” G. Franchetti

  10. The people I. Hofmann, W. Bayer, F. Becker, U. Blell, O. Boine-Frankenheim, O. Chorniy, P. Forck, T. Giacomini, M. Kirk, V. Kornilov, T. Mohite, C. Omet, A. Parfenova, S. Paret, P. Schuett, S. Sorge, P. Spiller G. Franchetti

  11. Systematic in the experiments G. Franchetti

  12. The SIS18 synchrotron • 12 Auxiliary windings in the dipoles (only 6 works well) • 12 small vertical dipoles • 4 quadrupole correctors • 8 skew quadrupoles (independent) • 2 skew sextupoles (independent) • 12 sextupoles located every other period close to the F and D quads (independent) • 4 Qy=13 cannot be controlled (no octupoles) • Skew 3rd order: 2 Qx+ Qy=12, 3 Qy=10, 2 Qx- Qy = 5 (difficult with 2 skew) • Normal 3rd order: -Qx + 2 Qy = 2, 3 Qx = 13, Qx + 2 Qy = 11 NO octupole present in SIS18 (B. Franczak, A. Redelbach, C. Mühle) G. Franchetti

  13. The SIS18 resonances this is not a simulation G. Franchetti

  14. Choice of the working point S WP N Allocate DQ=0.075 S N Not allowed S N G. Franchetti

  15. scans in proximity of the 3rd order resonance Qy0 = 3.24 Qx0 = 4.34 G. Franchetti

  16. After correction of the closed orbit 30SI14+ At 500MeV/u Measured 955 ms after injection after acceleration. The acceleration starts at 400ms. Full chopper Windows. Vertical closed orbit corrected at injection and extraction Qx0= 4.34 Normalized units 86Kr34+ At 300ms after injection Without closed orbit correction 4th order Resonance 3rd order resonance G. Franchetti

  17. high intensity beam size smaller than SIS acceptance Experimental setup UNILAC beam optimized for high intensity Barth, Dahl, Groening Beam injection optimized (P. Spiller, P. Schuett) Goal RF capture obtained via an ‘external’ RF cycle control (O.Choriny + RF group) G. Franchetti

  18. RF control 400MeV/u extraction external RF control SIS RF control 11.4 MeV/u 1 second = 2x105 turns time O. Chorniy + RF group injection G. Franchetti

  19. Beam @ injection Ion: 40Ar+18 x ~ 6 mm-mrad y ~ 4 mm-mrad dp/p rms ~ 10-3 harmonic = 4 RF voltage = 4 KV Injection energy = 11.4 MeV/u Storage time = 1 sec. = 2x105 turns G. Franchetti

  20. Beam evolution Systematic use of the RGM for the transverse Simultaneous acquisition of transverse/longitudinal beam profiles during 1 second storage time. G. Franchetti

  21. CBL: peak tuneshift Qy = 3.245 G. Franchetti

  22. CBL: measurement of stop band Coasting beam low intensity with this measurement we detect the stop-band of the resonance 3Qx = 13 Qy = 3.245 G. Franchetti

  23. CBL: transverse evolution off the 3rd order resonance G. Franchetti

  24. CBL: transverse evolution in the 3rd order resonance G. Franchetti

  25. CBH: peak tuneshift Qy = 3.245 G. Franchetti

  26. CBH: beam loss and emittance growth Qy = 3.245 G. Franchetti

  27. Comparison CBL vs. CBH shift of the emittance peak of 0.0075 consistent with the tuneshifts Roughly: Qy = 3.245 G. Franchetti

  28. BBL: peak tune-shift Qy = 3.245 Bf = 1/3 G. Franchetti

  29. BBL: beam loss and emittance graowth bunched beam low intensity Qy = 3.245 Chromaticity compensated but a residual chromaticity remains structure resonance 2 Qx + Qy = 12 ??? G. Franchetti

  30. Comparison CBL vs. BBL Qy = 3.245 Max emittance growth ~25% The stop-band appears a little lager dashed: CBL solid: BBL G. Franchetti

  31. BBH: peak tune-shift at injection Qy = 3.245 G. Franchetti

  32. BBH: beam loss and emittance growth bunched beam high intensity Qy = 3.245 G. Franchetti

  33. Transverse evolution BBH SIS acceleration de-bunching 1 second storage RF Capture injection G. Franchetti

  34. Transverse evolution after resonance BBH G. Franchetti

  35. BBH: longitudinal evolution time evolution of the longitudinal beam distribution at Qx=4.344 (no beam loss) No bunch shortening G. Franchetti

  36. BBH: longitudinal evolution with transverse induced beam loss time evolution of the longitudinal beam distribution at Qx=4.340 (with beam loss) clear bunch shortening RF SIS controlled acceleration debunching 1 sec. bunching G. Franchetti

  37. BB: dependence on beam intensity Qx=4.340 high intensity low intensity G. Franchetti

  38. Summary G. Franchetti

  39. Conclusion/Outlook We compared 4 beams: CBL,CBH,BBL,BBH We find that only when a beam is bunched and the intensity is high the beam evolution, in terms of transverse emittance growth and beam loss and longitudinal beam shrinking, is consistent with the theoretical mechanism of particle trapping/scattering into a 3rd order resonance We have expended the experimental studies started in the CERN-PS in 2002/2003 and retrieved identical beam behavior Simulation-benchmarking of this experiment G. Franchetti

  40. G. Franchetti

  41. S317 first results after the first 2 Campaigns Bunched beam with Qx=0.03, Qx=0.04 is stored for one second. Scenario similar to SIS100 for U+28, but with space charge at least a factor 5 smaller than nominal FAIR intensity for SIS18-SIS100. Qy = 3.24 % CBL Large long term beam loss: up to 80% but always larger than 20%! Results are consistent with the theory, but the relatively large beam size do not allow for emittance increase z / z0 Intensity Bunched beam G. Franchetti

  42. Transverse measurements RGM G. Franchetti

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