0

1 Alternative Options in the Injectors – Preliminary Summary H. Damerau LIU-TM#8 18 October 2013 Many thanks for discussions and input to T. Argyropoulos, M. Benedikt, H. Bartosik, T. Bohl, C. Carli, R. Garoby, S. Gilardoni, B. Goddard, S. Hancock, W. Herr, B. Mikulec, Y. Papaphilippou, G. Rumolo. E. Shaposhnikova, H. Timko, R. Tomas and many others

2 (Alternative) upgrade option overview Linac4 PSB PS SPS Basic choicesAdditional benefit/margin Faster recombination kickers PSB-PS (with 1.4 GeV) Double-batch or h=5 single batch injection 3-split, BCMS, BCS or PBC (pure batch comp.) Mini-microbatch, 8b+4e together with 3-split or BCMS Resonance compensation Special injection optics Long. flat or hollow bunches 2.0 GeV at PSB  PS transfer SPS RF upgrade: 4  3+2  4 More RF power plants: 4  2+4  3 or 10  2 Relaxed  l with 200 MHz in LHC LHC ACN cavities in SPS? Split tunes optics Special injection optics 28 GeV at PS  SPS transfer +5 % +? % +15 % +25 % +? % Vertical painting Linac4 +25 % Long. flat or hollow bunches

3 PS-SPS space charge limit, standard 3-split, 1.4 GeV BCMS BCS 3-split, 2.0 GeV PBC 3-split, 1.4 GeV 3-split, 2.0 GeV BCS BCMS PBC BCSBatch compression + split h = 9  10  20  21 BCMSBatch comp. + merge + split h = 9  10  11  12  13  14  7  21 PBCPure batch compression h = 9  10  …  20  GeV, PS: -  Q y = GeV, PS: -  Q y = 0.31 With PS at 1.4 GeV, pure batch compression reaches brightness as 2 GeV transfer  But ~15% less bunches in LHC and ~twice longer filling, but squeezed to limit (at SPS extraction, number of bun- ches per LHC ring not considered)

4 PS-SPS space charge, alternatives 3-split, 1.4 GeV h5SB 3-split, 2.0 GeV 8b+4e+BCMS 3-split, 1.4 GeV 3-split, 2.0 GeV h5SBSingle-batch h = 5 injection h = 5  10  20  21 8b+4eDouble split + empty bucket h = 7  21 (2b+1e  …  8b+4e) 8b+4e+BCMSBatch comp. + batch comp. h = 9  …  14  GeV, PS: -  Q y = 0.31 h5SP attractive only together with Linac4 and PSB-PS transfer at 1.4 GeV 8b+4e schemes approach or push brightness beyond SPS space charge limit 8b+4e 8b+4e+BCMS 2.0 GeV, PS: -  Q y = 0.31 (at SPS extraction, number of bun- ches per LHC ring not considered)

5 Larger bunch intensity from SPS?  = const, LD+PWD     Baseline upgrade: shorter cavities and 2  1.6 MW RF power N b ≈ 2 · ppb without degradation, 2.5 · ppb for 10% longer bunches  Even shorter cavities and more RF power? E. Shaposhnikova et al., LIU-TM#2 LD: Loss of Landau damp. PWD: Potential well dist. Slope? · · · Additional step of adding 2  1.6 MW: intensity gain ≈ half of first step No gain at low intensity  MWs of RF only heating the cavities  Significant uncertainty in LD+PWD line, sensitive as LD proportional to  l 5/2  Additional emittance constraints on bunch length during acceleration P old = 1.05 MW P new = 1.6 MW RF voltage at transfer to LHC Analysis still in progress

6 8b+4e scheme or 200 MHz in LHC?  = const, LD+PWD V RF for 3 MV at 200 MHz in LHC 8b+4e scheme (SPS ejection): Reduced line density due to less bunches Single bunch effects LD+PWD unchanged LD: Loss of Landau damp. PWD: Potential well dist. 200 MHz in LHC  ~ 2 ·  l ≈ 1.1 eVs No issue with LD or PWD Beam loading and matching with LHC         Analysis still in progress Significant gain from larger longitudinal emittance at transfer to LHC (assumes blow-up in SPS, to avoid bottleneck around start of acceleration) Revisit 200 MHz capture system in the LHC? Install additional 200 MHz standing wave cavities (those for LHC?) in SPS?  = const, LD+PWD

7 Preliminary summary and remarks No magic alternative to Linac GeV + SPS RF upgrade Large number of schemes to increase intensity and brightness from injectors  Linac4+PSB+PS may push SPS to space charge limit Longitudinally larger bunches in SPS would help a lot Limited reach of brute-force approach for even more RF power Interesting alternatives can be studied in injectors after LS1  PSB: Hollow bunches  PS: Flat or hollow bunches, special flat-bottom optics, pure batch compression, 8b+4e schemes, higher PS-SPS transfer energy  SPS: split tunes optics, higher intensity with slightly longer bunches Combinations of alternatives keep flexibility of injector complex to react to requests from LHC Numerous alternatives, e.g., H - injection into the PS, 400 MHz or slip stacking in SPS do not appear as studied in literature

8 8 THANK YOU FOR YOUR ATTENTION!

9 Introduction Evaluation of alternative schemes based on  ‘Common references’ document (  Assumptions presented in LIU-TM#4 ( Parameters for US1/2 with standard schemes now in good agreement with G. Rumolo’s tables ( SPS space charge limit to be revised Analysis for most of the schemes very superficial and simplified Optimization strategy: 1.Fix maximum intensity per bunch at SPS ejection 2.Calculate minimum transverse emittance backwards through the chain  Results: Transverse emittance at extraction from SPS (25 ns by default) and number of bunches per batch

10 Evaluation of injector scenarios Constraints of the injectors taken into account for evaluation: Linac + PSB  Transverse brightness  Maximum longitudinal emittance (PSB-PS transfer) PS  Space charge at flat-bottom  Various longitudinal emittance limits (RF manipulations, transition crossing, final emittance)  Coupled-bunch instability limit (with new feedback) SPS  Space charge at flat-bottom  Maximum intensity per bunch, maximum line density