Outline / Executive summary

1. Motivation for 50 ns rise time injection D.Manglunki, M.Schaumannwith lots of help fromTh.Bohl, H.Damerau, J.Jowett

2. Outline / Executive summary • Ion upgrade objectives and planning: • 10 nb-1Pb-Pb after LS2 • Proposed baseline scenario and parameters: • Increase number of bunches while keeping bunch intensities and emitances constant (lumiburnoff) • 50 ns bunch & batch spacing to reach ~1200 bunches/ring • Upgrade options and improvement factors • Issues / alternative schemes • Any alternatives to 50 ns rise time injection? (75 ns , 100ns, … 225ns) • Conclusion: projections on integrated luminosity • 75 ns maximum for 10 nb-1 in Runs 3+4

3. Ion upgrade objectives and planning • ALICE Upgrade approved for 50kHz (max 6x1027 cm-2s-1) • ECFA High Luminosity LHC Experiments Workshop: • “10 nb-1Pb-Pb physics run, x10 stats of Run 2”

4. Current scheme (2011) & performance (2013) Design Intensity Design Horizontal /Vertical Emittance

5. Assuming no improvement in injectors • Using p-Pb February 2013 performance, and 2011 Pb-Pb luminosity data • Extrapolating to 6.5 TeV/c/charge • Peak L = 2.3x1027cm-2s-1

6. Proposed baseline scenario and parameters:increasing total bunch number • Increase LEIR extracted intensity by ~40% • Doubling Linac3 pulsing rate to 10Hz • Mitigating LEIR intensity limitation • Implementing new RF gymnastics in PS • Splitting followed by batch compression -> 4 bunches spaced by 50 ns • 12 (tbc) injections into SPS spaced by 50 ns • 2.4 ms train of 48 bunches spaced by 50 ns • 26 injections/ring into LHC • Taking into account 900ns for Injection Kicker and 3.3 msabort gap • 1248 bunches/ring (factor ~3.4) • >20’ filling time per ring on paper

7. Nb of bunches Harmonic number / Frequency 6injections 2 2 16 – 14 – 12 2 4 21 – 25-30-36 -42 200 MHz 48 1248 400 MHz Proposed Pb-Pb50 ns scheme for after LS2 Pb ions / (future) LHC bunch LEIR (1.6 109 Pb ions / 3.6 s) 4 108 200ns PS batch expansion 100ns PS bunch splitting followed by batch expansion(100ns bunch spacing) 12-24-21 4 50ns PS batch compression(50ns bunch spacing) 3 108 4 50ns 50ns SPS at injectionafter 12 transfers from PS, with 50ns batch spacing 2.2 108 50ns 50ns LHC at injection,after 26 transfers from SPS 1.5 108

8. Upgrade options and improvement factors • ISSUES: • LEIR intensity limitation may not be solved • Either prevents splitting and forces to keep 2 bunches out of PS, also increasing LHC filling time • Or results in lower intensity per bunch Nb • RF gymnastics in PS • Batch compression of 4 bunches to 50 ns need additional cavities • Gymnastics close to transition simulated but not demonstrated • Feasibility of 50 SPS injection kicker rise time (this review) • Hence, in parallel to longer injection kicker rise times (75, 100, …, 225 ns), we consider 3 alternative schemes, by decreasing order of resulting number of bunches in LHC: • 2 bunches spaced by 50 ns • need batch compression close to transition in PS • but can be done in one step by 13 MHz cavity for two bunches) • 4 bunches spaced by 100 ns • demonstrated, but need LEIR intensity increase, or yields lower Nb • 2 bunches spaced by 100 ns • demonstrated in February • For completeness: proposal to study stacking at low energy in PS • Vacuum issues • Necessitates accel/deceleration between injections

9. Upgrade options and improvement factors E = 7 Z TeV Intensity scaling: unsplit: = 1.15 split: = 0.85 50/50ns Max. Luminosity 50/75ns Baseline for after LS2 No Upgrade 100/225ns After LS1

10. Conclusion: Projections on integrated luminosity • 50/50ns spacing: (445h) • 50/75ns spacing: (365h) • Statu quo, 100/225ns spacing: (5h) • Assuming ~40 fills/yr, the goal of 10nb-1 can be reached in 6, 7, or 12 years.

12. Nb of bunches Harmonic number / Frequency 6injections 2 2 16 – 14 – 12 2 4 21 – 25-30-36 -42 200 MHz 48 1152 400 MHz Possible Pb-Pb 50/75 ns scheme for after LS2 Pb ions / (future) LHC bunch LEIR (1.6 109 Pb ions / 3.6 s) 4 108 200ns PS batch expansion 100ns PS bunch splitting followed by batch expansion(100ns bunch spacing) 12-24-21 4 50ns PS batch compression(50ns bunch spacing) 3 108 4 50ns 75ns SPS at injectionafter 12 transfers from PS, with 75ns batch spacing 2.2 108 50ns 75ns LHC at injection,after 24 transfers from SPS 1.5 108

13. 12 injections in SPS: intensity scaling

14. Optimum number of injections into the SPS(50/75ns)

15. Estimates for after LS1 – 2011 Scheme E = 6.5 Z TeV 2011 filling scheme with 2013 bunch performance. Max. peak luminosity

16. Estimates for after LS1 – Batch Compression • Filling schemes are not exact! • Takes into account: • Not more than 40% of the SPS is filled. • 3.3μs abort gap. • 900ns LHC kicker gap. • All bunches are colliding with an equal partner. max. Luminosity max. Intensity Max. peak luminosity

17. Estimates for after LS1 – Optimisation Scheme with max. peak luminosity 7 batches & 29 trains = 406 bunches Scheme similar as in 2011 12 batches & 18 trains = 432 bunches • 15% improvement in peak luminosity due to batch compression in the PS. • Another 10% by shortening the trains. • → 30% more as for 2011 scheme.

18. Estimates for after LS2 – 50/50ns Scheme Option with highest luminosity achievable! Flat Peak Luminosity Evolution for more than 12 batches/train.

19. Estimates for after LS2 – 50/75ns Scheme Optimal Injection Scheme: 10 PS batches, 28 LHC trains → 1120 bunches/beam

20. Luminosity Evolution w/wo SPS Kicker Upgrade • Takes into account different • initial bunch luminosities, • bunch luminosity decay times. • Without any upgrade (black curve): • Almost 50% integrated luminosity less (after 5h) compared to 50/50ns case. • 40% less compared to 50/75ns cases.

21. Luminosity Evolution w/wo SPS Kicker Upgrade Peak luminosity higher for 100ns PS spacing with unsplit bunches. → Higher brightness bunches decay faster. → Higher integrated luminosity for 50ns PS spacing with split bunches. Peak Luminosity 50/50ns split → 1200 bunches/beam 100/50ns unsplit → 748 bunches/beam Integrated Luminosity Number of Bunches/Beam