ABP & LIU meeting 2018 - setting the scene - CERN Indico

 
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ABP & LIU meeting 2018 - setting the scene - CERN Indico
ABP & LIU meeting 2018 – setting the scene
                           H. Bartosik and G. Rumolo
 Thanks to LIU-PT and deputies: R. Alemany, G. Bellodi, D. Carloni, J. Coupard,
   H. Damerau, A. Funken, B. Goddard, K. Hanke, A. Lombardi, M. Meddahi,
             B. Mikulec, F. Pedrosa, R. Scrivens, E. Shaposhnikova

       Outline:
       • Brief recap of LIU baseline
            Proton and Pb ion beam parameters
       • Beam dynamics challenges and machine studies
ABP & LIU meeting 2018 - setting the scene - CERN Indico
Present LIU baseline I
        (main items)
• PSB
 • Connection to Linac4  New H- charge exchange injection at 160 MeV from
   Linac4 to double brightness of LHC beams
 • Acceleration to 2 GeV
   − New main power supply POPS-B
   − Replacement of C02-C04-C16 RF systems by Finemet based RF system

• Linac3 + LEIR
 • Source and Low Energy Beam Transport improvements to increase current from
   Linac3 and improve reproducibility
 • Intensive studies on Linac3-LEIR modeling and monitoring to increase reliability
   and transmission

      LIU ABP day 2018, 28 February 2018    H. Bartosik and G. Rumolo      2
ABP & LIU meeting 2018 - setting the scene - CERN Indico
Present LIU baseline II
         (main items)
• PS
 • New injection at 2 GeV for protons to mitigate space charge
 • RF improvements to improve beam quality and increase longitudinal coupled
   bunch instability threshold
   − Impedance reduction of the RF systems
   − Installation of new Finemet RF system as longitudinal feedback
 • Operational deployment of transverse feedback system

• SPS
 • 200 MHz RF system upgrade
   − Rearrangement of cavities and power upgrade
   − New LLRF including slip stacking capability
 • Electron cloud mitigation and impedance reduction to increase intensity reach
   − a-C coating of QFs + one full arc
   − QF-type flange shielding and HOM damping in 200 MHz cavities
 • New beam dump system in LSS5 and new design of protection devices to
   comply with the target HL-LHC beam parameter values
        LIU ABP day 2018, 28 February 2018     H. Bartosik and G. Rumolo   3
ABP & LIU meeting 2018 - setting the scene - CERN Indico
LIU performance reach for protons
                                             • 40 mA from Linac4 + beam loss and
                                               emittance blow up budgets

                                                      budget         PSB & PS   SPS
                                                      losses           5%       10%
                               HL-LHC
                               request               blow-up           5%       10%

                                             • PSB brightness + intensity
                                               limitations in PS and SPS inferred
                                               from simulations

                                             • Space charge limitation curves in
                                               PS and SPS based on assumed
                                               tune spreads and optimised beam
                                               parameters at transfers

                                                                       PS       SPS
                                                     DQV, max          0.31     0.21

LIU ABP day 2018, 28 February 2018       H. Bartosik and G. Rumolo               4
ABP & LIU meeting 2018 - setting the scene - CERN Indico
LIU protons – reality check
• Intensity reach
 • RF power upgrade in SPS + longitudinal impedance reduction
    − Do we have margin? E.g. damping of 200 MHz RF system HOMs, modeling of kicker impedance,
      Q22 optics
    − Are horizontal instabilities with high intensity a threat?
 • Longitudinal coupled bunch feedback system + longitudinal impedance reduction for the RF
   systems in the PS
    − Intensity presently limited to 2e11 p/b due to longitudinal instabilities along the ramp and at flat top
    − Future actions are unlikely to extend this intensity reach  Landau cavity design and construction
      added to LIU baseline, with possible implementation after LS2
    − If lower longitudinal emittance becomes feasible, do we need to check margin against e-cloud
      instability at flat top?
 • Injection of LHC beams from Linac4 over ~20 turns
    − Can we preserve the desired brightness line increasing the number of turns injected
    − Can we guarantee pre-LS2 performance of all non-LHC beams with the lower current?

       LIU ABP day 2018, 28 February 2018                  H. Bartosik and G. Rumolo                 5
LIU protons – reality check
• Brightness reach
 • Linac4 beam parameters
    − Can we gain anything from higher brightness from Linac4 (e.g. 0.3 um instead of 0.4 um)?
 • Brightness line of the PSB
    − Do we have all elements to trust simulations (including space charge) of future PSB brightness line?
      E.g. optics modeling of PSB including beta-beat during collapse of injection bump, benchmark of
      simulations with present multi-turn injection, etc
    − Are we sure that injecting at 160 MeV will not limit our WP choice due to known horizontal
      instabilities? We need transverse damper to be correctly working also during injection process
 • Blow up in PS
    − Operational beams exhibit presently a horizontal blow up around 40-50% at injection and a vertical
      blow up along the cycle
    − Several possible culprits (space charge, mismatched injection, tune swing during collapse of
      injection bump, tune drift along the cycle), but also need to confirm reliability of emittance
      measurements in PSB and PS
    − What about future operation with large longitudinal emittance beams?
 • High intensity in SPS
    − Emittance preservation in the SPS for high intensity/brightness beams to be studied further after
      2017 experience with 2e11 p/b (vertical emittance growth of >10%)

       LIU ABP day 2018, 28 February 2018               H. Bartosik and G. Rumolo               6
LIU performance reach for Pb ions
• Intensive study program in 2015-2016 across injector chain (no Pb ions in 2017)
 • Performance in 2015 was already outstanding thanks to improved LEIR performance
 • Performance in 2016 was pushed even further thanks to improvements in source + Linac3,
   continued LEIR studies, bunch splitting in PS, 7 injections in SPS

                                                                         PS

           LEIR                                    SPS

                                                    4 bunches per
                                                       injection
                                                                                     2 bunches per
                                        Pre-2015                                        injection
                           RF capture

      LIU ABP day 2018, 28 February 2018                 H. Bartosik and G. Rumolo            7
LIU performance reach for Pb ions
• Intensive study program in 2015-2016 across injector chain (no Pb ions in 2017)
 • Performance in 2015 was already outstanding thanks to improved LEIR performance
 • Performance in 2016 was pushed even further thanks to improvements in source + Linac3,
   continued LEIR studies, bunch splitting in PS, 7 injections in SPS

• Baseline LIU Pb ion parameters compliant with HL-LHC request
 • Single bunch parameters at SPS extraction from 2016 experience translate into requested ones
   when including additional losses in SPS due to longer injection plateau and slip stacking
 • Number of bunches can be achieved including slip stacking in the SPS (otherwise only 60% of
   integrated lumi target)

                                                    N
                                                               e         # of
                                                  (x 108
                                                             (mm)      bunches
                                                 ions/b)
                                     Achieved      2.2        1.5         548
                                    LIU/HL-LHC     1.9        1.5        1248

      LIU ABP day 2018, 28 February 2018                   H. Bartosik and G. Rumolo   8
Pb ions – what is left to do
• Improve reliability and reproducibility of the ion injector chain
 • Linac3 studies
    − Source auto-tuning, modeling in simulations
 • LEIR
    − Injection beam characteristics monitoring, operational procedures to ensure space charge control

• Gain margin or produce alternative schemes to mitigate the possibility of failure
  (or underperformance) of slip stacking
 • Study the full potential of three bunches in LEIR with batch compression to 75 ns in PS with Pb
 • Improve the LEIR modeling (optics, impedance, e-cooler) to further increase extracted beam
   current
 • Exploit faster injection rate in LEIR (e.g. 150 ms spacing between injections)
 • Focus on the SPS intensity limitations: Losses at flat bottom (try different optics?), losses during
   the ramp and transition crossing (ions leaking out of buckets?, instabilities?)

       LIU ABP day 2018, 28 February 2018              H. Bartosik and G. Rumolo              9
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