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LEIR Commissioning

LEIR Commissioning. C. Carli on behalf of the LEIR commissioning team. Introduction Recap on LEIR General comments Situation at the time of the first MAC presentation (15 th December 2005) Completion of LEIR Commissioning : January 2006 “shutdown”, Summary,

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LEIR Commissioning

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  1. LEIR Commissioning C. Carli on behalf of the LEIR commissioning team • Introduction • Recap on LEIR • General comments • Situation at the time of the first MAC presentation (15th December 2005) • Completion of LEIR Commissioning : • January 2006 “shutdown”, • Summary, • Expected and unexpected Problems, • LEIR Status • Conclusions and Outlook LEIR Commissioning

  2. Many people have contributed to construct LEIR and in LEIR commissioning: • I-LHC project leader(s) : S. Maury (and before K. Schindl) • LEIR project leader : M. Chanel • Commissioning team : P. Belochitskii, L. Bojtar, C. Carli, M. Chanel, K. Cornelis, B. Dupuy, J. Duran, T. Eriksson, S. Gilardoni, D. Manglunki, E. Matli, C. Oliveira, S. Pasinelli, J. Pasternak, F. Roncarolo, G. Tranquille • Many people from several departments and many groups have constructed and installed all the equipment we use: • despite a lot of pressure mostly in time, • Impossible to compile a list of all contributors (more than 100 contributors are on the I-LHC mailing list). LEIR Commissioning

  3. IntroductionRecap on LEIR • Pre-LHC ion accelerator chain cannot be provided the bright LHC beams needed. • Upgrades of the ion chain: • New ion source, • Low Energy Ion Ring LEIR accumulating ions: • Elaborate multiturn injections:(70 turns > 50% efficiency), • Electron cooling (BINP):(cools within 200 to 400ms) • Transforms long (200 µs) Linac 3 pulses to short(200 ns) bright bunches. • RF gymnastics in PS …… . RF Ejection Injection Electron Cooler (from BINP) LEIR in autumn 2005 (few days after first circulating beam) LEIR Commissioning

  4. IntroductionGeneral comments • Aim of LEIR Commissioning : • Provide beam needed for first LHC runs with less bunches and luminosity (less demanding for injectors and LHC) : • Shorter cycle lasting 2.4 s each one delivering one bunch with 2.25 108 ions, • Transverse (normalized RMS) emittances 0.7 µm, • Longitudinal emittance 0.025 eVs/u. • Commissioning in Phases : • Lines in May and June 2005, • LEIR ring in autumn 2005 and beginning of 2006. • First Phase of LEIR Ring Commissioning with O4+ : • Beam rigidity very close to Pb54+, • Longer life-time expected (is that true ?) and cooling times, • Simpler for diagnostics. • Early LHC ion beam in PS and SPS in 2006 and 2007, respectively. LEIR Commissioning

  5. IntroductionSituation at the time of the last MAC presentation • Successful commissioning of: • Injection line, • Injection, lattice, many beam diagnostics instruments, RF …. • Difficulties with first cooling and accumulation: • Short life-times, explainable by high pressure in some regions (problems with recuperated bellows (?) and an ionization profile monitor), • Barely no increase in local density. • Recommendation of the MAC: • Consider O8+ for first commissioning, • After some reflections, we decided to continue with Pb54+ • Risky, but still the possibility to switch to O8+ in case of problems, • Only way to keep a chance to complete LEIR commissioning on time, • Faster cooling makes life-time less critical, • Turned out to be the right choice. LEIR Commissioning

  6. Completion of LEIR CommissioningJanuary 2006 “shutdown” • LEIR Commissioning on hold in January 2006 (access system …) • Opportunity to open vacuum sector 5 (known difficulties, broken ionization profile monitor): • Traces of ion impact on ionization profile monitor (-> addition of Au coated plates) • Definite cure of pick-up cable problem: insulate head amplifier box from bending • Everything ready to restart at mid of February Wire reducing the aperture Au coated plates Looking opposite to beam direction Traces from ion impact LEIR Commissioning

  7. Completion of LEIR CommissioningSummary • Restart at middle of February 2006 • Problems (expected) again with controls (magnetic cycle): • good collaboration with controls experts. • Circulating Pb54+ beam obtained quickly, • Improved beam life-time !! • Again serious difficulties with injection line. • Electron Cooling without particular difficulties on 3rd March 2006: • Accumulation very soon afterwards. • First synchronization and ejection on 11th April • Short life-time (1s to 3s instead of up to 14s) observed on 20th April: • No reason identified, disappeared over a ~1 week for PS interventions. • Beam in front of PS injection on 24th April 2006 • Last phase (extension) perturbed by PS (and SPS) restart • Commissioning completed on 12th May 2006: • Profile monitors in ejection line available during last week only, • “Early LHC ion beam” by accumulation of two Linac 3 (low beam current traded for stability) shots. LEIR Commissioning

  8. Completion of LEIR CommissioningExpected and unexpected Problems • Controls: • LEIR as testbed for LHC controls, • Difficulties –often recurrent- as expected (magnetic cyle generation …), • Good collaboration with controls experts, • Working (not yet perfect) control system, • No migration to another control system in near future. • Injection line matching: • Problems with Pb54+ similar to O4+, • Updated optics model based on measurements. • Electron cooling and accumulation: • Some worries after experience at the end of 2005, • No particular difficulty to set up cooling and accumulation in 2006. • Difficulties cured by upgrades during January shutdown ?, LEIR Commissioning

  9. Completion of LEIR CommissioningExpected and unexpected Problems Transverse beam dynamics on ramp: • Reason: • C-shaped bending magnets & chamber connected to ground at several locations, • Ramp induces net Eddy current & gradient, • Optics perturbations • Cure: • Compensation by adding currents to five main quad families, • One parameter (conversion of ramp to gradient) optimized, • Good acceleration efficiency. Compensation increases current Measured Quadrupole currents along the machine cycle with compensation of gradients in bends during ramp LEIR Commissioning

  10. Completion of LEIR CommissioningExpected and unexpected Problems • “Dynamic vacuum” and collimation: • Vacuum degradation due to lost ions limited proof experiment in 1997, • Upgrades based on systematic measurements at Linac 3: • Au (low outgassing) coated Collimators (fixed and movable), • Additional pumping (NEGs wherever possible). • Sufficient life-time (up 14 s – interaction with rest gas and cooler) without difficulties and movable collimators in “parking position”. • Short life-time (1s to 3s instead of up to 14s): • Suddenly observed on 20th April 2006, no reason identified, • Disappeared over a ~1 week stop for PS interventions – Unfortunately not understood !!! LEIR Commissioning

  11. LEIR status Acceleration within 0.8 s (instead of 1s) Injection with efficiencies up to 50% (~design) (17 μA from Linac -> two injections) ~2.3E8 ions at ejection Longer plateau & accumulation of two shots needed Circulating beam intensity (yellow) and magnetic field (purple) vs time. “Early LHC ion beam” produced on a 2.4 s machine cycle LEIR Commissioning

  12. LEIR statusElectron cooling and accumulation t (s) 0.6 0.4 0.2 0 accumulated stack (ready for bunching) Start acceleration 2nd injection cooled stack Bunching 1st injection -2 0 2 ∆p/p (10-3) Injections Time evolution of longitudinal Schottky spectra -> time evolution of long. distribution -> observation of long. cooling and accumulation white …… zero density red …… highest densities Horizontal beam size evolution measured with an ionization profile monitor (long cycle with 400ms between injections) LEIR Commissioning

  13. LEIR statusEjection and Transfer Ejection: Last TV of the ejection line (~5m before PS injection region) - Ejection kicker (green), - Sum (yellow) and difference (purple) of ring PU, - Ejection line beam curremnt transformer (blue) SE (wires) profile monitors in the ejection line: - transverse emittances (rms normalized) : ~0.26μm - matching: (almost) no horizontal mismatch, vertical mismatch should be corrected. Vertical mismatch (at ejection point) LEIR Commissioning

  14. LEIR statusTowards the nominal LHC ion beam Towards nominal LEIR beam : • No systematic investigations: • not aim of commissioning and no time available. • Accumulation tests with very long plateaus (yellow trace shows intensity): • Intensities well above the nominal ones (after very long accumulation), • Dynamic beam life-time after accumulation (and losses) ~14s, • Good sign for “nominal LEIR beam”. LEIR Commissioning

  15. Summary, Conclusions and Outlook • The required “early LHC ion beam” has been produced: • Two injections needed (-> acceleration in 0.8s instead of 1s), • Parameter of ejected beam well within specifications, • Successful tests of Controls developed for LHC. • LEIR construction and commissioning completed: • (almost) on time -> big success of the whole LEIR team, • LEIR can provide the “early LHC ion beam”, • Cures for all difficulties implemented. • Outlook: • Still some work to make LEIR fully operational (Schottky diagnostics, final version of digital low level RF, broken ionization profile monitor, controls …), • LEIR Re-start (from the “CERN Control Centre” CCC ?) in autumn 2006, • Provide beam for “Early LHC Ion Beam” Commissioning of the PS in autumn 2006, • Provide beam for “Early LHC Ion Beam” Commissioning of the SPS in 2007 • Prepare the Nominal LHC Ion Beam in LEIR and further downstream. LEIR Commissioning

  16. LEIR Commissioning

  17. Ejection ETL.MTV10 PS ring ETL.MTV40 ITE loop LEIR ring ETL line ER.MTV12 Linac 3 Injection LEIR Commissioning

  18. LHC ion injector chain overview Repetition rate up to 5 Hz After acceleration and stripping : - 200 mA Pb54+at 4.2 MeV/n - >120 ms long pulses Energy ramping cavity Dp/p ~0.4% (needed for LEIR injection) 200 mA Pb25+at 2.5 keV/n Pb27+ Pb54+ LEIR • Each ring filled (during ~10 min): * with 12 SPS batches, * total 592 bunches per ring. • Design : * Luminosity 1027 cm-2s-1, * Collision energy 2.76 TeV/n. • Limited by collimation and ECPP ? Accumulation of ~4 Linac pulses : - Multiturn injection (transverse+longit.) (70 turns with 50 % eff). - New electron cooler constructed by BINP. Bunching, acceleration and transfer to PS. Two bunches corresponding to 4 LHC bunches at 72 MeV/n every 3.6 s. • RF gymnastics to obtain 4 LHC bunches spaced by 100 ns. • 4 LHC bunches at 5.9 GeV/n every 3.6s. • Accumulation of up to 13 LEIR/PS batches on a ~40s plateau. • “Variable (non-integer) harmonic” acceleration. • Direct space charge and IBS limit ? - Up to 52 LHC bunches per cycle at 177 GeV/n Al Stripper Pb54+ to Pb82+: low-beta insertion LEIR Commissioning

  19. Outlook until Completion of LEIR CommissioningExpected Problems Intercepted by absorbers : • Reduced outgassing with Au coating, • Efficient scrubbing due to small surface “Dynamic life-time” Avalanche-like pressure rise : • ions lost due to rest gas electron capture (or loss) (Pb54+-> Pb53+), • every lost ion desorbs some 104 molecules, • Observed in POP in 1997. LEIR upgrades based on measurement at Linac 3 NEG coatings in straight sections to improve vacuum there Injection Cooler Loss pattern of Pb53+ ions around the LEIR ring with collimators and homogeneous gas density LEIR Commissioning

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