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Staged implementation of high bandwidth transverse feedback system in the SPS W. Hofle

Staged implementation of high bandwidth transverse feedback system in the SPS W. Hofle f or LARP - CERN SPS High bandwidth feedback team 17.11.2011. Motivation. o bjective : cure transverse “single bunch” instability by feedback two collective effects are limiting the

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Staged implementation of high bandwidth transverse feedback system in the SPS W. Hofle

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  1. Staged implementation of high bandwidth transverse feedback system in the SPS W. Hofle for LARP - CERN SPS High bandwidth feedback team 17.11.2011

  2. Motivation • objective: cure transverse “single bunch” instability by feedback • two collective effects are limiting the • SPS performance as LHC injector • e-cloud • TMCI • similarities: both effects cause vertical intra bunch instability • high chromaticity suppresses instability to a certain extent • feedback expected to permit • running at low chromaticity and at intensities beyond which • high chromaticity is a established cure • particular important to maintain small transverse emittances W. Hofle / LIU review 17.11.2011

  3. Feedback as cure • coherent signals visible for both ecloud and TMCI instability • provided reaction time (few turns) shorter than growth times • feedback in principle should work sum difference (delta) instability growing (TMCI) signals up to 1.6 GHz turns frequency R. de Maria et al. DIPAC 2009, MOPD17 W. Hofle / LIU review 17.11.2011

  4. e-cloud vertical instability sum difference (delta) quadrupolar motion (longitudinal) at injection due to voltage mismatch artifact from pick-up (beam pipe cut-off) instability growing signals up to 1.2 GHz turns frequency R. de Maria et al. DIPAC 2009, MOPD17 W. Hofle / LIU review 17.11.2011

  5. e-cloud vertical instability R. de Maria et al. DIPAC 2009, MOPD17 W. Hofle / LIU review 17.11.2011

  6. existing hardware simulated, no cables pick-up, also used as kicker since this year looking in beam direction “forward” backward (BPW 319.01) now kicker forward (BPW 321.01) simulated, with cable measured response ultra-short bunch W. Hofle / LIU review 17.11.2011

  7. Feasibility of feedback in simulations • simulations have focused up to now on ecloud instability • initial study done in 2008 with headtail (J. Thompson et al.) • this study showed feasibility in principle, but simple FB model • focused on 55 GeV (SPS injection with PS2) • repeated since using WARP code (J. L. Vay, R. Secondo et al.) • future: CMAD (C. Rivetta et al.) ? • TMCI best accessibly through headtail • due to good modeling of SPS Impedance in this code • re-launch simulations with headtail • also look at interplay of impedance and e-cloud J. Thompson et al. CERN-AB-2008-070 PAC 2009 FR5RFP076 W. Hofle / LIU review 17.11.2011

  8. Recent results (WARP code) –(1) suppression of emittance growth demonstrated high feedback gain required no feedback growth Suppressed for G=0.2 emittance increase J. L. Vay R. Secondo (LBNL) PAC 2011 W. Hofle / LIU review 17.11.2011

  9. Recent results (WARP code) – (2) suppression of emittance growth demonstrated high feedback gain required head kicks tail time (turns) J. L. Vay R. Secondo (LBNL) PAC 2011 W. Hofle / LIU review 17.11.2011

  10. Recent results (WARP code) – (3) need to review these parameters and agree on a set for the upgrade; address higher energies in the simulations J. L. Vay R. Secondo (LBNL) PAC 2011 W. Hofle / LIU review 17.11.2011

  11. Limitations of the simulations • action of feedback can only be followed over a very limited • number of turns in the simulations • difficult to quantify the impact of numerical noise on the • estimation of the required kick strength and the emittance • growth; incoherent effects in case of e-cloud hard to • quantify • multi-bunch effects neglected so far • more simulations will give us only an incremental increase in confidence with regards to the feasibility •  adopt a staged experimental approach W. Hofle / LIU review 17.11.2011

  12. R&D and staged implementation: The Path (1) Boundary conditions: LS1: 2012 LS2: 2017+ Phase 1:The demonstrator end 2012 minimum goal: damp head tail motion of single bunch existing equipment (amplifiers, BPWs as kicker and PU) electronics (LARP), close FB loop all design specifications for phase 2: end of 2012 Phase 2: New pick-up, new kicker, consolidated electronics, higher power amplifiers, preparation of LSS3 in LS1 for installation of equipment at the end of LS1 or later in a short winter shutdown post-LS1 feedback on multi-bunch beam in presence of e-cloud decide on final implementation and LSS3 vs. LSS5 before LS2 W. Hofle / LIU review 17.11.2011

  13. R&D and staged implementation: The Path (2) Phase 3:Final implementation in LS2 depending on desired energy range  upgrade power and if impossible to install in LSS3 for reasons of space or radiation  move to LSS5 add kicker modules if required design and construct final electronics (profit from latest technology) commission after LS2 W. Hofle / LIU review 17.11.2011

  14. (a) schedule go/no-go phase 2: go/no-go phase 3: Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 2011 2012 2013 2018 2014 2015 2016 2017 Phase 1: demonstrator power amplifiers for phase 2 tendering (s) new pick-up design and construction kickers design and construction Phase 2: phase 2 beam tests Phase 3: implementation

  15. New pick-up • long precision coupler (separate the “reflection”) • reserve 2 m space close to a QD in LSS3 (straight section) • free space during LS1 (reshuffle some equipment, • under discussion with Eric) • install cabling in LS1 and dummy chamber if PU not ready • for highest frequency reach go for smallest diameter • circular vacuum chamber • (define with ABP when location decided) • E. Montesinos interested in design and fabrication, • lead time (!) W. Hofle / LIU review 17.11.2011

  16. E. Montesinos PU kicker

  17. New kickers • short striplines, or split band approach ? • location: dispersion suppressor, flat chamber • frequency reach < 1.5 GHz • cabling in LS1, preparation of space W. Hofle / LIU review 17.11.2011

  18. Questions ? W. Hofle / LIU review 17.11.2011

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