1. LIU-SPS upgrade, schedule, target parameters and observed limits 1 B. Goddard, E. Shaposhnikova for LIU-SPS coordination team SPS scrubbing review 8.09.2015

2. Outline Scope SPS beam parameters Performance limitations and solutions Main upgrades baseline options Schedule Conclusions

3. SPS beam parameters: HL-LHC & LIU-SPS 25 ns beam Beam status 25 ns, 4x72b P (GeV/c) N b (10 11 ) ɛ x,y (μm) ɛ z (eVs) τ (ns) Achieved4501.22.600.41.5 LIU4502.01.90.61.7* HL-LHC4502.32.10.651.7* Other LHC beams: 50 ns spacing, BCMS *bunch length limit with present LHC 400 MHz RF Nominal LHC beams (with 50 ns and 25 ns spacing ) were successfully delivered to the LHC during run1, but twice higher intensity (even more for brightness) is needed in future for HL-LHC

4. Introduction – SPS cycle for LHC beam e-cloud longitudinal multi-bunch instability SPS budget for total losses: 10% -Losses at start of acceleration ~5% (nominal intensities ) -Transverse scraping at flat top ~3% SPS budget for emittance growth: 10% → Need to preserve high brightness along 11 s long flat bottom

5. Nominal and higher intensities beams N~1.2x10 11 p/b τ avg =1.47 ns N~1.35x10 11 p/b τ avg =1.63 ns V 200 MHz MDs → losses and bunch length increase for higher intensities - poor lifetime - horizontal instability - transv. emit. blow-up

6. Known main SPS performance limitations: 25 ns beam (288 bunches) Bunch intensity threshold LimitationEffectCuresLIU solution 4.0x10 10 longitudinal beam instability Losses, longitud. emit. blow-up - 800 MHz RF - control. blow-up - 200 MHz RF upgrade - impedance reduction* 1.2x10 11 e-cloudLosses, transverse emittance blow-up - high chromaticity - trans. damper (H) - scrubbing - aC coating (low SEY) - wideband FB* - scrubbing* 1.2x10 11 Injection kicker MKP heating High outgassing, breakdown cooling time, limiting duty cycle - Study 1.4x10 11 beam loading in 200 MHz RF system Limited V => longer bunches to LHC; losses during cycle - longer cycle(?) - bunch rotation(?) - 200 MHz RF upgrade: more shorter cavities + 2 power plants + LLRF 1.6x10 11 TMCI (single bunch)Fast losseshigh V chromaticitynew optics Q20 (done) 3.0x10 11 space charge at injection transverse emittance blow-up Working Point (WP) optimisation OK for 25 ns beam (not for 50 ns with 4x10 11 ) * not in baseline

7. SPS limitations: beam loading & instability HL-LHC After RF upgrade: → significant increase in voltage (plus 20 % impedance reduction) → voltage at flat top could be still not sufficient for HL-LHC intensity due to beam induced voltage ~ ImZ/n and emittance blow-up (long. instability) → 200 MHz RF upgrade: -rearrange existing 4 cavities to 6 shorter cavities -add 2 new power plants (1.6 MW) -pulsing mode (f rev ) -new cavity and beam control 200 MHz voltage as a function of RF current now and after RF upgrade 2015 2020 nominal beam: I b =1.4 A

8. Other limits on beam intensity or brightness: 25 ns beam (288 bunches) Bunch intensity threshold SystemEffectLimitationLIU solution 1.5x10 11 Transfer line protection devices TCDI, TED Protection of LHC, TCDI damage total intensity injected to LHC - upgraded TCDIs - new locations - new TL optics 1.7x10 11 Internal beam dump TIDVG TIDVG damagetotal circulating SPS intensity - upgraded TIDVG core - new LSS5 dump system 1.7x10 11 Extraction protection TPSG Protection of septa, TPSG damage total intensity extracted - upgraded TPSG Note: limitations for the transverse emittances in nominal scheme TCDIM

9. SPS upgrades by location BA2 BA3 BA4 ECA4 BA5 ECA5 BA6 BA7 BA1 TT40 TT41 (CNGS) TI8 (LHC) TI2 (LHC) TT20 (SPS NA) TT66 (HiRadMat) TT60 TT10 (PS) e-cloud mitigation Transverse scrapers Beam instrumentation Transfer line protection devices High bandwidth feedback Extraction protection devices 200 MHz RF power and LL Transverse damper 800 MHz RF power and LL New beam dump Beam dump core 9

10. LIU-SPS upgrade works (baseline): LS2 ActivityDuration* (months) When*Work statusRisk if not done 800 MHz RF system: LLRF and power upgrade, 1 → 2 operational cavities 122015beam commissioning Longitudinal instabilities Serigraphy of tune kicker MKQ, MKP Reduction of number of MKEs in LSS4 (1+?) 3(E)YETSFeasibility studyHeating, larger longitudinal impedance ZS septa: more pumping; reduce impedance; improve ion traps and anode circuit 3LS2designIncreased down time for LHC filling Rearrange 200 MHz RF cavities; add two 1.6 MW power plants and modify existing for 1.1 MW; power couplers 13LS2building, design, tendering, Cannot accelerate more than 1.4x10 11 p/b 200 MHz LLRF upgrade: cavity controllers, new digital beam control 13LS2Specifications under approval RF system not operational after LS2 aC coating of main magnets, LSS18LS22 cells coated, industrialisation e-cloud limit at intensity << 2.3x10 11 p/b *installation New BAF3 building for 200 MHz RF 800 MHz RF: all klystron transmitters dismantled

11. LIU-SPS upgrade works (baseline): LS2 ActivityDuration* (months) When*Work status Risk if not done Additional spares and local shielding improvement for beam scraper n/aLS2assemblyMore activation, less availability for LHC filling Upgrade and relocate collimators TCDIs in transfer lines TI2/TI8 3LS2designLimit of 144b per transfer to LHC, or risk damage to LHC SC magnets Replace septa protection TSPG4/6 by upgraded versions 3LS2studyLimit of 144b per transfer to LHC, or risk damage to MST/E septa Upgrade beam dump (TIDVG) core3LS2designLimit of 144b accelerated in SPS Reduce length of arc vacuum sectors by factor 2 6LS2cablingLonger pump-down time, longer recovery after venting Upgrade dump system (LSS5)12-18LS2studyDose to personnel, increased cost of other LSS1 system designs, injection kicker performance limits Beam instrumentation: upgrade of electronics of MOPOS; new WS; upgrade of profile monitors: BGI, BSRT, IPM & Head-Tail; BCT 12LS2study, prototype Inadequate measurements of transverse bunch profile; fast losses; orbit, instabilities. Longer commissioning, worse performance *installation TCDIM

12. LIU-SPS upgrade (options) for LS2 ActivityDuration* (months) DecisionWork status Risk if not done Scrubbing after each shutdown (alternative to aC coating) ~0.25mid- 2015 MDs, study Performance degraded Shielding or redesign of different types of vacuum flanges to reduce their impedance (~500 max) 12-18mid- 2015 study, prototype Emittance blow-up due to longitudinal instability, limit intensity < HL-LHC target New wide-band transverse damping system (CERN-LARP) 3end- 2016 study, prototype Performance limited by intra- bunch instabilities (during scrubbing); for special beams *installation Strip line kicker for WB FBvacuum flanges

13. Present SPS longitudinal impedance model Model includes: 200 MHz cavities (2+2) 800 MHz cavities (2) Kicker magnets (8 MKEs, 4 MKPs, 5 MKDs, 2 MKQs) Vacuum flanges (~500) + DR BPMs: BPH&BPV (~200) Unshielded pumping ports (~ 16 similar + 24 various) - non-conformal assumed 0 Y–chambers (2 COLDEX + 1) Beam scrappers (3 S + 4 UA9) Resistive wall AEPs (RF phase PUs, 2) ~ 0 Model doesn’t include: 6 ZSs + PMs 25 MSE/MST + PMs RF HOM Y-c BPM EM simulations of J. Varela & C. Zannini + lab measurements for RF, PPs, VFs (J. Varela et al.) VF Scrap. New contributions: HOMs in the 200 MHz and 800 MHz TW RF

14. The SPS vacuum flanges Non-enamelled QF - QF ≈ 26 Enamelled QF - MBA ≈ 97Non-shielded, enamelled BPH - QF ≈ 39 + 64 shielded Group I – 1.4 GHz Non-enamelled QD - QD ≈ 75 Enamelled QD - QD ≈ 99Enamelled BPV - Q ≈ 90 Group II

15. Impedance of vacuum flanges Vacuum Flanges Group 1: QF–QF closed flange no bellows (18+2) QF–QF closed flange (22+1+3) BPH–QF flanges (25+12) MBA–MBA flanges (12+2) QF–MBA flanges (78+2) Vacuum Flanges Group 2: QD-QD enameled flanges (99) QD-QD closed flanges (75) Shielded pumping ports – Long QD Bellows (71) Shielded pumping ports VVSA – Long QD Bellows (17) BPV–QD flanges

16. Results of impedance reduction (vacuum flanges Group 1) for a single bunch stability through (nominal) ramp 1 RF 2 MV 1 RF 6.6 MV 2 RF 2 MV 2 RF 6.6 MV In a double RF with V 800 =V 200 /10 Significant effect from removing impedance of the Group 1 flanges (QF-QF) Group 2 removal has a very small effect Multi-bunch simulations (preliminary results) show positive effect of flanges removal done together with HOMs damping Simulations of A. Lasheen with BLonD

17. Impedance reduction (vacuum flanges) -Increase in instability threshold without vacuum flanges (~2) → HL-LHC target intensity can be achieved -Beam measurements and simulations cross-checking -Design of shielding (factor 6-8 reduction) and of new flanges -Total number of flanges 529, ~10 types Decision processes and timelines (1/2) 1 RF 12 bunches 9x10 10 p/b shields Longitudinal instability during ramp: agreement between measurements and simulations 1 RF single bunch

18. Amorphous Carbon (aC) coating or scrubbing or combined - Internal review of 2014 scrubbing run - 2x1 scrubbing week -Final review: today => Possible synergy with impedance reduction Decision processes and timelines (2/2) Pressure evolution (normalized): Arc 5 SPS scrubbing process (2014) aC coating inside the SPS magnets

19. LS2 schedule for LIU (draft 2015-08-03) 15.5 months 7 months 18 months 11 weeks 8 weeks PSB PS SPS 4.5 months L4 This version of the Master Schedule includes -an extra time for the PS shutdown -an extra time for the Hardware tests of the SPS -Linac4 Master Plan Presented by Julie Coupard Schedule risks: Essential to decide remaining options in 2015 Large amount of concurrent work in LS2 Coactivity in some locations of SPS: e.g. LSS5 (aC coating workshop, new dump, cabling, instrumentation, vacuum flange shielding, HL-LHC tests, …)

20. Conclusions SPS upgrade work is in good progress, careful preparation for LS2 started Important decisions about aC coating and impedance reduction to be taken in 2015 Need to continue development of challenging technological solutions (aC coating, high power couplers, …) Intensive beam studies are planned before LS2 to address remaining issues Next challenge – increase of beam intensity by factor 2 after LS2

21. Back-up slides 21

22. Presented by Julie Coupard PSB 1.5 months of RP cooling + 15.5 months of work in the machine + 5 months of hardware tests and cold check out = 22 months + 2.5 months of beam commissioning (LHCPROBE) = 24.5 months PS 1.5 months of RP cooling + 11.5 months of work in the machine + 3 months of hardware tests (11 weeks) and cold check out (2 weeks) = 16 months + 1.5 months (6 weeks) of beam commissioning (LHCPROBE) = 17.5 months SPS 1.5 months of RP cooling + 18 months of work in the machine + 3 months of hardware tests (8 weeks) + cold check out (4 weeks) = 22.5 months + 1.5 months (6 weeks) of beam commissioning (LHCPROBE) = 24 months /!\ DSO tests for the SPS = +1 week Timeline: LS2 schedule (draft 2015-07-30) 15.5 months 11.5 months 18 months 34 weeks (8 months) 15 weeks (3.5 months) PSB PS SPS 2019

23. LIU parameter table (standard 25 ns beam) SPS injection (4 injections, 72 bunches/injection) N (10 11 p)  ,y (  m) p 0 (GeV/c)  z (eVs)  (ns)  p/p 0 (10 -3 )  Q x,y Achieved1.32.4260.43.01.5(0.05,0.07) LIU2.21.7260.43.01.5(0.09,0.16) HL-LHC2.61.9260.43.01.5(0.10,0.17)

24. SPS limitations: space charge at 26 GeV/c brightness for different bunch intensity HL-LHC 50 ns beam measurements