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Pb for LHC: requirements summary D.Manglunki

Pb for LHC: requirements summary D.Manglunki. Why upgrade?. ALICE Upgrade approved: Request for peak luminosity “higher tha n L=6x10 27 cm -2 .s -1 ” after LS2 Programme in coming years: HL Pb-Pb (today) Ar & Xe.

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Pb for LHC: requirements summary D.Manglunki

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  1. Pbfor LHC: requirements summaryD.Manglunki

  2. Why upgrade? • ALICE Upgrade approved: Request for peak luminosity “higher than L=6x1027cm-2.s-1” after LS2 • Programme in coming years: • HL Pb-Pb (today) • Ar & Xe

  3. Luminosity increaseNote: current brightness performance is already 2 x design • b functions at IP (/2 to 0.5m) • Transverse emittances (/2 by energy ) • Intensity per bunch (=) • Number of bunches (by reducing spacing) • Influence of LHC injection kicker (0.9ms) & abort gap (3ms) • Increase nr of injections in SPS (present limits = 12 due to ROCS; 15 due to RF) • One can shoot for L=7x1027cm-2.s-1

  4. Harmonic number Nb of bunches 6 injections 2 2 16–18-21-169 4653…4620 2 35640 48 ~912 100/50 ns scheme Pbions/bunch 5.5 108 LEIR (1.1 109 Pb ions / 3.6 s) PS batch compression + rebucketingBunch spacing = 100ns 3.8 108 100ns 2.2 108 100ns 50ns SPS at extraction,after 24 transfers from PS, Batch spacing = 50 ns 1.7 108 LHC at injection,after 19 transfers from SPS b* =0.4 m -> L = 7x1027 cm-2s-1

  5. Route to 100/50ns • Linac3 / LEIR produce similar performance as in 2013: • 2 bunches of ~5.5 108Pb54+ • PS gymnastics • Batch compression to 100ns h = 16 -> 18 -> 21(no need for new cavities, 10MHz system exists) • 2 bunches > 2 x108 Pb82+ into SPS • 24 SPS injections spaced by 50ns • Similar bunch quality as present beam • 48 bunches of ~1.7x108Pb82+ • Transverse emittances ~0.85mm • Alternating 100/50ns spacing • 19 injections / LHC ring -> 912 bunches /ring

  6. Plan B (in case no SPS injection upgrade) • Double current from Linac 3 (~50mA) • LEIR • Produce 2 bunches of ~1.1 109Pb54+ in same emittance(i.e. twice today) • PS gymnastics • As “old nominal scheme” 4bunches > 1.4 x108 Pb82+ • OR Batch compression to 100ns h = 16 -> 18 -> 21Splitting to 50 ns; 4 bunches > 1.4 x108 Pb82+ into SPS • Issues: • splitting to 50ns at high energy imposes some gamma-transition distortion • splitting to 50ns at low energy imposes acceleration at 20MHz

  7. Luminosity scaling (%) vs SPS injection kicker rise time (ns), 24 PS injections into SPS

  8. Actions/Issues since 2012 “Brainstorm” • Is the ECR source the bottleneck? • RFQ rematching • Multiple charge acceleration: Study still to be reactivated • Faster repetition rate • OK for source and Linac • Power supplies & magnets in ETL, planned for consolidation • LEIR injection to be checked Source & LINAC

  9. LEIR • Study loss at beginning of ramp (different Bdot, tunes,…) • Intensity limits (tests with longer flat bottom until higher intensity from Linac) • Vacuum (limit loss by cleaner dump) PS • Longitudinal acceptance for suggested RF gymnastics • Alternate schemes (Gamma-t jump at flat top, acceleration on 20MHz) • Vacuum SPS • Issues on flat bottom • RF noise • Space charge & IBS (Q20) • Increase number of injections • Injection kicker rise time 50ns

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