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LHC & fixed target ion requirements

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LHC & fixed target ion requirements

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  1. Ions in the SPSD.ManglunkiSpecial acknowledgements to T.Bohl, C.Carli, E.Carlier, H.Damerau, L.Ducimetière, I.Efthymiopoulos, R.Garoby, M.Gazdzicki, S.Gilardoni, M.Gruwe, T.Hakulinen, S.Hancock, S.Hutchins,J.Jowett, D.Küchler,P.Odier, Y.Papaphilipou, R.Planeta, S.Reignier,…

  2. LHC & fixed target ion requirements

  3. Fixed target ion beams in the LHC era • In order to optimize the resources, it had been decided right from the start to use the LHC beams from the injector chain, and adapt them to the needs of the fixed target users, instead of designing optimized beams for every purpose. • This has allowed to gain experience in 2010 with the production of the nominal (100ns) beam in LEIR/PS/SPS while delivering the EARLY beam to the LHC • Due to unavailability of other species, fragmented Pb (Be) has been delivered to NA61 in 2011 (tests in 2010) • 13, 20, 40, 75, 150 AGeV/c • Also primary Pb at 80AGeV/c after proton stop • In 2012: fragmented Pb (Be) at 13, 20, 30AGeV/c • We will gain experience with the Ar beam for LHC in 2013 while commissioning Ar in ECR/RFQ/Linac3 (see yesterday’s talk), and delivering the FT beam to the North Area in 2014. • Two big issues: • Beam structure at extraction • Slow extraction of primary ions in the presence of high intensity protons in the complex

  4. “Fixed frequency” acceleration • 200 MHz travelling wave cavities • fixed tuned, wide-band (199.5 to 200.4 MHz), • not wide enough for Pb Ion acceleration usingfixed harmonic acceleration (198.5 to 200.4 MHz) • Variable harmonic number (fixed frequency) acceleration is used instead • Cavity/amplifier risetime ~ 1 ms, • beam ~ 6.6 ms, • Trev~23.1 ms • RF is turned on at cavity frequency as beam passes, then turned off to adjust RF phase, ready for next beam passage. • Phase adjusted using modulated frequency via VCO • At top energy, b~1, technique can be switched off – normal situation fcav VCO h frev fmin RF ON RF OFF rev

  5. Time structure • Present beam accelerated on fixed frequency and occupies ~40% of the SPS circumference in one train. • RF is turned off prior to extraction but bunch/batch structures subsists • Modifications to the beam control: • Still occupy 40% of SPS but over 2,3, or 4 equally spaced trains (as was the case for ion operation in 1990s with analog system) • Debunch at proton equivalent momentum of 26GeV/c then recapture on fixed harmonic acceleration • For low energy Ar: possibility of using fixed harmonic from the start • MDs start this year

  6. Slow extraction of primary ions in the presence of high intensity protons in the complex • In the past, heavy ion run in SPS implied no proton (Interlcok at Linac level); now in parallel with CNGS & LHC proton beams • Radiological hazard: although both highly improbable, two mechanisms could cause the extraction of a high intensity proton) beam in the North Area, while the TAX need to be open for the low intensity primary ion beam • Injection of a high intensity proton beam on the ion cycle • Slow extraction elements pulsing during a high intensity proton cycle • (Apparently) simple solution: when in “primary ion mode” • measure the circulating current • Inhibit extraction elements above given threshold (2x1011 charges) • …which turned out to be a large integration project (BE, TE, EN, GS, DGS…) over large part of SPS (BA5, BA3, BA2) • All actors very conscious of constraints for personnel protection • Technical specification (eventually) starting to converge • Equipments ordered or delivered; BCT will be installed in next TS • Project can be completed in LS1 provided cabling can be performed

  7. Technical specification EDMS 1146023 • For redundancy, 2 new BCTs installed in BA5 (+1 Fast BCT for calibration) • 2 independent ways of communication (fiber optics & copper) • Acting on MST and MSE power supplies • If intensity over 2x1011charges, Inhibit MSE and MST: • if requested current =0 OK • If requested current >0, force zero, trip power supply on non-resetable fault (DSO), dump beam. • Additional DCCTs in power supply for current self-check • Connection with LOKN for protons

  8. Future beams for LHC • Pb-p in 2012 and later • Schemes for 200ns and 100ns bunch spacing • Increased luminosity Pb-Pb after LS1 • Limited to +25% with current hardware • (+50% with 150 ns batch spacing) • Ar-Ar in 2021 (at the earliest) • HL Pb-Pb after LS3 • List of upgrades

  9. Harmonic number / Frequency Harmonic number / Frequency Nb of bunches Nb of bunches 2 2 2 2+1 9-10 16–14-12-24 20-21-84 24-21-169 2 2 200 MHz 200 MHz 24 24 p-Pb 200ns scheme in 2012 1.5 1010 PSB (3 1010 protons) PS batch compressionbunch spacing = 200ns 1.2 1010 SPS at extraction,after 12 transfers from PS, Batch spacing = 225 ns minimum note: minimum batch spacing of 225ns dictated by protons injection at 26GeV/c LEIR (9 108 Pb ions / 3.6 s) PS batch expansion bunch spacing = 200ns 1.4 108 SPS at extraction,after 12 transfers from PS, Batch spacing = 225 ns minimum

  10. Harmonic number / Frequency Nb of bunches Nb of bunches 9-10 2 2 20-21-84 16–14-12-24 24-21-169 4 4 200 MHz 48 48 p-Pb 100ns scheme in 2012 3 1010 Harmonic number / Frequency PSB (6 1010 protons ) 2 PS batch compression+splitting ; bunch spacing = 100ns 1.2 1010 SPS at extraction,after 12 transfers from PS, Minimum batch spacing = 225 ns Note: minimum batch spacing of 225ns dictated by protons injection at 26GeV/c 4.5 108 LEIR (9 108 Pb ions / 3.6 s) PS batch expansion+splitting ; bunch spacing = 100ns 1.4 108 SPS at extraction,after 12 transfers from PS, Minimum batch spacing = 225 ns

  11. Luminosity increaseNote: current brightness performance is already 2 x design • b functions at IP • Transverse emittances • Intensity per bunch • Number of bunches -> reduce spacing • Nominal was 100 ns / 225 ns • Present scheme is 200 ns / 200 ns • ALICE asks for 50ns …but number of bunches will not be x4 • Influence of LHC injection kicker (0.9ms) & abort gap (3ms) • Effect of SPS kicker rise time: • 12 injections in SPS (present limit due to ROCS) • Scaling Luminosity as NB x IB2

  12. Luminosity scaling (%) vs SPS injection kicker rise time (ns)

  13. Possible scheme for Pb-Pb in 2015 • Same beam from Linac 3 (20mA) into LEIR into PS (2 bunches…) • PS gymnastics • Batch compression h = 16 -> 18 -> 21 (100 ns) • 12 SPS injections • Spaced by 200 ns (resp. 150 ns) • Resulting beam • SPS train: 24 bunches of 1.4 x108 Pb82+ • Transverse emittances ~0.85mm • Spacing 3x100 ns + 1x200 (resp. 150) ns • 460 (resp. 530) bunches per LHC ring in 19 (resp. 22) injections from SPS • Luminosity increase ~25% (resp. 47%)

  14. Harmonic number / Frequency Nb of bunches 7 injections 2 2 16–18-21 -169 2 200 MHz 24 400 MHz ~460(530) Possible scheme for Pb-Pb in 2015 Pb ions / (future) LHC bunch LEIR (9 108 Pb ions / 3.6 s) PS batch compression bunch spacing = 100ns 1.4 108 SPS at extraction,after 12 transfers from PS, Batch spacing = 200 ns ( resp 150ns) 1.2 108 LHC at injection,after 19 (resp 22) transfers from SPS b* =0.5 m -> L =2.5x1027 cm-2s-1(resp L= 3.0x1027 cm-2 s-1)

  15. Possible route to 50ns for HL Pb-Pb • Design current from Linac 3 (~50mA) • LEIR • Produce 2 bunches of ~109 Pb54+ in same emittance (i.e. twice today) • PS gymnastics • Batch compression to 100ns h = 16 -> 18 -> 21(no need for new cavities, 10MHz system exists) • Splitting h = 21 -> 42 (20MHz system exists but VRF acceptance to be checked) • 4 bunches > 1.4 x108 Pb82+ into SPS • 12 SPS injections spaced by 50ns • Similar bunch quality as present beam • 48 bunches of ~1.4x108 Pb82+ • Transverse emittances ~0.85mm • But with 50ns spacing and hopefully less spread in bunch population • Note: longer LHC injection time

  16. SPS MKP upgrade • Design: 225ns with four modules • Operating with only three modules allows to operate just below 200ns • Possibility to go down to 150ns with help of transverse damper? • Note with Q20 we are presently limited to minimum 200ns • PFL or “PFN cable” was foreseen for 115ns at g=5.45 , now g=7.31, PFN operate just under 200ns • 50ns @ g=7.31“not excluded” but also ~30 new, shorter magnets (time, money, manpower)

  17. Present issue in the SPS for the LHC beam • RF Noise, IBS & DQ on SPS flat bottom • First batch suffers 40 more seconds on flat bottom:lower intensity/bunch, transverse emittanceblowup • Can Q20 help? (larger beam sizes, smaller IBS & DQ ) • RF Noise? • Splitting to bunchlets& Reinstall 100 MHz system(cavities, amplifiers, beam control)?

  18. Conclusions • Ar and Xe will be available after LS1 for fixed target experiments • Cabling the beam interlock system during LS1 is vital for the parallel operation of protons and FT ions in 2014 and beyond. • With the present injector complex, increasing the number of bunches is the only route for a marginally higher luminosity, and at the expense of a longer LHC filling time • If we are to implement the suggested improvements in order to reach the required Pb-Pbluminosity, RnD has to start on • MKP • Reassess advantage of splitting to bunchlets • Possibility of more injections/longer cycle • …and of course other parts of the complex

  19. Previously on the LHC ion injector chain… • “Nominal beam” in Design report • L = 1027cm-2s-1 at 7 TeV/c/charge • ~600 bunches of 7x107 Pb82+ ions • eH,V= 1.2mm • b* = 0.5m • To combat IBS and space charge on SPS flat bottom, Complicated gymnastics in PS & SPS (splitting in bunchlets in PS, recombining in SPS using 100MHz system). • Scheme questioned in Chamonix XII (2003) • Decision to start with “EARLY” scheme, single bunch from LEIR > PS > SPS • Assumed possibility of up to 13 PS injections into SPS

  20. Pb ions / (future) LHC bunch Nb of bunches Harmonic number / Frequency 4 injections 2 2 2.25 108 16–14-12-24 4 1.2 108 Bunch splitting & el Blow-up 24-21-169-423 4 pairs • QSPS= 0.05 200 MHz 52 (32, 8) pairs 9 107 100 MHz + 200 MHz 52 (32, 8) 7 107 400 MHz 592 Nominal scheme LEIR (9 108 Pb ions / 3.6 s) PS after 1st splitting PS after 2nd splitting SPS at injection (43.2 s flat-bot),after 13 (12, 8) transfers from PS SPS at extraction LHC at injection,after 12 transfers from SPS b* = 0.5 m -> L = 1027 cm-2 s-1

  21. Present scheme (“intermediate” in 2011) • LEIR • 7 multiturn injections of Linac3 pulse (~15-20mA) • 2 bunches of 4.5x108 Pb54+ • PS (similar gymnastics as nominal, minus splittings) • Batch expansion h = 16 -> 14 -> 12 • Rebucketing (was splitting) h = 12 -> 24 • Batch expansion h = 24 ->21 • Rebucketing h = 21 -> 169 • After stripping, 2 bunches of ~3x108 Pb82+bunch spacing 200 ns • SPS • 12 injections of PS batches, batch spacing 200 ns • 24 bunches of ~1.4x108 Pb82+ (0.9x108 design) • Transverse emittances ~0.85mm (1.2 design)

  22. Lumi scaling vs SPS injection kicker rise time

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