1 / 55

Progress on e-cloud effects (PS and SPS)

Progress on e-cloud effects (PS and SPS). Many thanks to: G. Arduini , T. Argyropoulos , T. Bohl , F. Caspers , S. Cettour Cave, K. Cornelis , H. Damerau , M. Driss Mensi , J. Esteban Muller, S. Federmann , F. Follin , S. Gilardoni , B. Goddard, S. Hancock,

lamar
Download Presentation

Progress on e-cloud effects (PS and SPS)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Progress on e-cloud effects (PS and SPS) Many thanks to: G. Arduini, T. Argyropoulos, T. Bohl, F. Caspers, S. Cettour Cave, K. Cornelis, H. Damerau, M. DrissMensi, J. Esteban Muller, S. Federmann, F. Follin, S. Gilardoni , B. Goddard, S. Hancock, W. Hofle, M.Holz, C. Lazaridis, L. Kopylov , H. Neupert, Y. Papaphilippou, M. Pivi, S. Rioja Fuentelsaz, D. Schoerling , E. Shaposhnikova, , G. Sterbini, H. Timko and all the PS and SPS operator crews G. Iadarola, H.Bartosik, G. Rumolo, M. Taborelli, C. Yin Vallgren

  2. Outline • Electron cloud effects in the PS • Beam observation • Flat top instability • RF voltage optimization for e-cloud mitigation • Studies for the main magnets • Electron cloud effects in the SPS • Status for nominal intensity • Tests with higher intensity • “Doublet” beam for scrubbing • e-cloud measurement campaign • a-C coatings

  3. Outline • Electron cloud effects in the PS • Beam observation • Flat top instability • RF voltage optimization for e-cloud mitigation • Studies for the main magnets • Electron cloud effects in the SPS • Status for nominal intensity • Tests with higher intensity • “Doublet” beam for scrubbing • e-cloud measurement campaign • a-C coatings

  4. e-cloud in the PS h=42 b.sp.=50 ns (36 b.) h=7 b. sp. ≈ 330 ns (4 - 6 b.) h=84 b.sp.=25 ns (72 b.) h=21 b. sp.≈100 ns (18 b.) Triple splitting Double splitting Double splitting Bunch shortening

  5. e-cloud in the PS h=42 b.sp.=50 ns (36 b.) h=7 b. sp. ≈ 330 ns (4 - 6 b.) h=84 b.sp.=25 ns (72 b.) h=21 b. sp.≈100 ns (18 b.) No e-cloud Triple splitting Double splitting Double splitting Bunch shortening

  6. e-cloud in the PS h=42 b.sp. = 50 ns (36 b.) h=84 b.sp. = 25 ns (72 b.) h=7 b. sp. ≈ 330 ns (4 - 6 b.) h=21 b. sp.≈100 ns (18 b.) 4 ns 300 Double splitting 250 200 Bunch rotation 40 MHz RF Voltage [kV] 150 11 ns 100 0 b.l.≈14 ns Adiabatic shortening 50 10 20 30 40 50 60 Time [ms] Triple splitting Double splitting Double splitting Bunch shortening

  7. e-cloud in the PS h=42 b.sp. = 50 ns (36 b.) h=84 b.sp. = 25 ns (72 b.) h=7 b. sp. ≈ 330 ns (4 - 6 b.) h=21 b. sp.≈100 ns (18 b.) 4 ns 300 Double splitting E-cloud expected and observed 250 200 Bunch rotation 40 MHz RF Voltage [kV] 150 11 ns 100 0 b.l.≈14 ns Adiabatic shortening 50 10 20 30 40 50 60 Time [ms] Triple splitting Double splitting Double splitting Bunch shortening

  8. e-cloud in the PS: beam observations • Up to now e-cloud in the PS has never been a limitation for the production of the 25 ns LHC type beams • In 2012, bunch by bunch emittance measurements performed in the SPS (intensities up to 1.45e11 ppb) never revealed any e-cloud signature on the emittance pattern coming from the PS Horizontal Vertical • Measurements done on the SPS flat top with 1.45e11 ppb injected into the SPS

  9. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time 300 250 200 4 ns 150 100 40 MHz RF Voltage [kV] 50 11 ns 10 70 20 80 30 100 90 40 50 60 b.l.≈14 ns 0 Time [ms]

  10. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. 300 250 200 150 100 40 MHz RF Voltage [kV] b.l.≈ 11 ns 50 10 70 20 80 30 100 90 40 50 60 b.l.≈14 ns 0 Time [ms] First studies in: R. Cappi, M. Giovannozzi, E. Metral, G. Métral, G. Rumolo and F. Zimmermann, "Electron cloud buildup and related instability in the CERN Proton Synchrotron." Physical Review Special Topics-Accelerators and Beams 5.9 (2002): 094401.

  11. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  12. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  13. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  14. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  15. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  16. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  17. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  18. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  19. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  20. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  21. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  22. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train

  23. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  24. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  25. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  26. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  27. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  28. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  29. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  30. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  31. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  32. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible

  33. Transverse instability with “stored” beam • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible These features look compatible with an e-cloud driven instability

  34. Transverse instability with “stored” beam Good news: the new transverse feedback can delay this instability! • A possible reason of the absence of any degradation could be that the beam does not interact with the cloud for a sufficiently long time • If we “store” the beam for ~20 ms an horizontal instability is observed. • See talk by G. Sterbini • Therisetime is decreasing along the train • Coupled bunch motion is clearly visible 10 ms These features look compatible with an e-cloud driven instability

  35. Possible mitigation strategies: RF voltage program 4 ns • Together with the RF experts, we could optimize the 40MHz voltage program in order to mitigate the e-cloud without affecting the beam quality Double splitting 300 250 200 40 MHz RF Voltage [kV] 150 11 ns 100 0 b.l.≈14 ns 50 40kV 10 20 30 40 50 60 Time [ms] H. Damerau, S. Hancock, T. Kroyer, E. Mahner and M. Schokker, Electron Cloud Mitigation by Fast Bunch Compression in the CERN PS (No. CERN-AB-2008-050).

  36. Possible mitigation strategies: RF voltage program 4 ns • Together with the RF experts, we could optimize the 40MHz voltage program in order to mitigate the e-cloud without affecting the beam quality Double splitting 300 250 200 40 MHz RF Voltage [kV] 150 100 36 kV 0 50 10 20 30 40 50 60 Time [ms] H. Damerau, S. Hancock, T. Kroyer, E. Mahner and M. Schokker, Electron Cloud Mitigation by Fast Bunch Compression in the CERN PS (No. CERN-AB-2008-050).

  37. Possible mitigation strategies: RF voltage program Together with the RF experts, we could optimize the 40MHz voltage program in order to mitigate the e-cloud without affecting the beam quality 1.25e11 ppb 1.45e11 ppb 60b.  schemes with shorter train (e.g. BCMS) are less critical

  38. e-cloud in the main magnets • We need to assess if with LIU beam parameters the observed instability (or other e-cloud effects) can degrade the beams on the timescale of the production cycle. To be addressed with simulationsandmeasurementswith particular focuson main magnets: • PyECLOUD modules for the simulation combined function magnets have been developed and tested • One magnet unit will be equipped for e-cloud detection during LS1 (see talk by S. Gilardoni)

  39. e-cloud in the main magnets • We need to assess if with LIU beam parameters the observed instability (or other e-cloud effects) can degrade the beams on the timescale of the production cycle. E field - beam To be addressed with simulationsandmeasurementswith particular focuson main magnets: • PyECLOUD modules for the simulation combined function magnets have been developed and tested • One magnet unit will be equipped for e-cloud detection during LS1 (see talk by S. Gilardoni) Electron distribution

  40. e-cloud in the main magnets • We need to assess if with LIU beam parameters the observed instability (or other e-cloud effects) can degrade the beams on the timescale of the production cycle. To be addressed with simulationsandmeasurementswith particular focuson main magnets: • PyECLOUD modules for the simulation combined function magnets have been developed and tested • One magnet unit will be equipped for e-cloud detection during LS1 (see talk by S. Gilardoni) [By Teddy Capelli EN/MME]

  41. Outline • Electron cloud effects in the PS • Beam observation • Flat top instability • RF voltage optimization for e-cloud mitigation • Studies for the main magnets • Electron cloud effects in the SPS • Status for nominal intensity • Tests with higher intensity • “Doublet” beam for scrubbing • e-cloud measurement campaign • a-C coatings

  42. e-cloud in the SPS: nominal bunch intensity • In the past e-cloud has been strongly limiting the performances with 25 ns beams with detrimental effects both on vacuum and beam quality • Scrubbing runs regularly performed over the years with evident beneficial effects on dynamic pressure rise and beam quality • 2000 (1 batch 0.8x1011ppb) • Vertical emittance 400% G. Arduini, K. Cornelis et al.

  43. e-cloud in the SPS: nominal bunch intensity • In the past e-cloud has been strongly limiting the performances with 25 ns beams with detrimental effects both on vacuum and beam quality • Scrubbing runs regularly performed over the years with evident beneficial effects on dynamic pressure rise and beam quality • 2012 (4 batches 1.15x1011ppb) • Full characterization of the nominal 25 ns beams in the SPS (bunch by bunch emittance, tune, liferime vs. chrmoaticity) did not show any degradation due to e-cloud • Vertical

  44. Tests with higher intensity • In the last part of the 2012, MD sessions were dedicated to tests with higher intensity 25 ns beams (up to 1.45e11 inj.) with Q20 optics • Emittance blow up observed on trailing bunches of the last batches • But: • Machine never scrubbed for these intensities • Possible other sources still to be investigated

  45. Tests with higher intensity • In the last part of the 2012, MD sessions were dedicated to tests with higher intensity 25 ns beams (up to 1.45e11 inj.) with Q20 optics • Emittance blow up observed on trailing bunches of the last batches Two wire breakage during this tests. Bunch by bunch emittance measurements on full bunch train are extremely important to identify/study this kind of issues. Are we ready for higher intensities? • But: • Machine never scrubbed for these intensities • Possible other sources still to be investigated

  46. “Doublet” scrubbing beam • An important goal of the studies was the identification of a possible dedicated scrubbing beam, showing an e-cloud threshold lower than the 25 ns beam. • Simulations have shown that a possible candidate is 25 ns spaced train of doublets Accumulation between subsequent turns PyECLOUD simulation

  47. “Doublet” scrubbing beam • An important goal of the studies was the identification of a possible dedicated scrubbing beam, showing an e-cloud threshold lower than the 25 ns beam. • Simulations have shown that a possible candidate is 25 ns spaced train of doublets • Relatively simple production : • Inject long bunches from the PS (b. len.≈10 ns) • Capture in two SPS buckets (5 ns long)

  48. “Doublet” scrubbing beam First 500 turns after inj. 2 s after inj. • The production scheme has been successfully tested for a train of (2x)72 bunches with 1.7e11 p per doublet • The possibility to inject more than one batch from the PS has been tested in Feb. 2013 Thanks to T. Argyropoulosand J. Esteban Muller

  49. “Doublet” scrubbing beam • MBA-like Stainless Steel liner • It seems it works!!! 25ns “doublet” (1.7e11p/doublet) 25ns std. (1.6e11p/bunch) 25ns standard (1.6e11p/bunch) (1.7e11p/doublet) 25ns “doublet” • Clear enhancement observed both on e-cloud detectors and pressure in the arcs

  50. a-C coatings • In 2012, amorphous carbon coatings have been validated as an e-cloud suppression technique, to be used if scrubbing will not be sufficient • Tests showed that the dynamic pressure rise in a-C coated section is not due e-cloud in the coated parts

More Related