Accumulation in the LEIR Ring

1. Extraction Bunching, acceleration Injections momentum (or field) Electron cooler on 0 time (s) 3.6 Accumulation in the LEIR Ring Ejection Injection D=10m RF Ejection kicker E-Cooling D=0m Accumulation alternates : - Multiturn injection with horizontal, vertical and longitudinal stacking : 70 turns with >50% efficiency every 200 ms to 400 ms, • Fast electron cooling with a new state-of-the-art cooler constructed by a BINP team. Aim of commissioning : provide Pb54+ beam for the first LHC ion run(s). LEIR ring during installations (spring 2005) Cooler not yet in place, tripletts in cooler section and opposite doublets in injection section and opposite LEIR Commissioning – AB/LII section meeting

2. Overview of LEIR ring commissioning • Situation at the beginning of October : • Lines already commissioned until beginning of July, • Hardware ready to start commissioning (but not all installations completed) • At the beginning quite some control problems, amongst them : • Sometimes (in a rather erratic manner) working sets and knobs (our main interface for remote control) became filled with error messages, • Persistency problems, • Some equipments not yet controllable remotely (not the most annoying), GFA problems. • Polarity tests : • Proved to be very useful (a few hardware errors, e.g. wrong polarity of two quadrupoles) have been found), • Perturbed as well by controls problems, • Heavily perturbed by new security rule which are not clear (contradictory informations) and without official transition scheme. • First injections (expected to be a critical milestone) on October 11th : • Little adjustments (one day between one turn and stable beam) for first injection, but skew quads for reproducibility ! LEIR Commissioning – AB/LII section meeting

3. Overview of LEIR ring commissioning Circulating intensity (blue), injection bumper (red) and arriving beam (green) Transverse Schottky spectrum Members of the commissioning team with first Longitudinal Schottky Spectra (Photo published on the first page of the bulletin announcing first beam in LEIR) LEIR Commissioning – AB/LII section meeting

4. Overview of LEIR ring commissioning • Commissioning resumed on October 26th : • Again rather quickly circulating beam (low intensity !) was established • Bunching and first orbit measurements : • First bunching on October 27th • Orbit acquisitions right from the beginning (corrections worked, but due to doubts on the orbits, we did not send them • Momentum ramping set up on Nov 1st : • Needed to obtain good injection efficiencies, • Clear increase of intensity with nominal settings, • Nearly 50 % injection efficiency after few adjustments. • First Orbit response measurements : • Lattice without cooling -> some losses due to measurements • LEIR optics reasonably close to expectations (all gradients found with orbit response smaller than expected). LEIR Commissioning – AB/LII section meeting

5. Overview of LEIR Ring Commissioning • Position Pick-up cable problem (discovered on November 2nd) : • C-shaped bending magnet -> electric fields induced during the ramp, • Current on cable (on outer conductor) between pick-up and amplifier damaged the cable !! • Only ideas on cures. • First “start-up” (after week-end & Linac failure) without local intervention on November 15th. • First acquisitions by Tomoscope on November 16th (see image). • Surprising chromaticity measurements (vertical not as expected) • Electron cooler preparations : • Quite some installations during commissioning, • First electron beam on November 15th (after long technical difficulties), • First signs of cooling on November 16th, • Magnetic cycle with corrections (and long plateaus) for cooling more or less ready. LEIR Commissioning – AB/LII section meeting

6. LEIR Commissioning Status • Despite some problems (vacuum problem, controls problems -situation improved-, many installations for the cooler, RFQ problem), a lot of progress since beginning of October : • Injection with good efficiency (-> injection line setting that works), • A lot of beam diagnostics (TVs, MTRs, Schottky, Tunes …) works, • Bunching and orbit works, • Lattice : reasonably close to theory, cooler compensations work. • Next steps to come : • Systematic investigations on cooling (very soon, Ionization Profile Monitors needed), • Acceleration up to nominal field (latticeproblems expected), • Switch to Pb54+ (putting the vacuum system and the collimation to a test), • Ejection (not before February), • Transfer towards the PS (and check of performance). • LEIR commissioning : • is in full swing now (but January will be “shutdown”), • Aims at providing the beam first LHC ion run(s), • and may (if progress is like during the last ) be completed on time until end of March or beginning of April Order not yet decided LEIR Commissioning – AB/LII section meeting

7. LHC (Ion) Injector Chain • Overview of the LHC injector chains • Accumulation in the LEIR Ring • Electron Cooling • Injector Chain for (nominal) LHC Pb Ion Operation • LEIR Issues : • Increase accumulation rate (missing factor 3) w.r.t. 1997 experiment, • Control beam induced vacuum degradation, • Keep reasonable lattice during acceleration LEIR Commissioning – AB/LII section meeting

8. Overview of the LHC Injector chains(for Protons and Ions) LHC – operated with Protons (red) and ions (green) • LHC will run with protons and ions (Pb approved ), • Injectors chains for both beams needed : • Start with a source and a linear accelerator : • fast acceleration, • Little time with problems due to direct space charge, ….. . • Several Synchrotrons : • To reach higher and higher energies, • Avoid very small magnetic fields, • Focussing structure and aperture adapted to energy (beam shrinks with energy) • No Ion Beam useful for LHC with Previous chain (without LEIR), • Add Low Energy Ion Ring LEIR : • Transforms several long Linac pulses into short and dense bunches • Elaborate multiturn injection, electron cooling LEIR Commissioning – AB/LII section meeting

9. Electron Cooling electron gun (up to 40 kV) solenoid 6 kG Basic Principle (Analogy with mixing of gases) : • In co-moving coordinates: chaotic motion of ions = temperature. • Mixture (“hot” ion beam and “cold” electrons) tends to an equilibrium temperature, • Continuous renewal of electrons -> electron beam “stays cold”. • Cooling reduces : • Reduces Emittance (accelerator jargon), • Reduces transverse beam sizes, • Increases density collector Cooler constructed at INP Novosibirsk LEIR Commissioning – AB/LII section meeting

10. Injector Chain for (nominal) LHC Pb Ion Operation 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 – AB/LII section meeting

11. LEIR Issues (1/2) Nominal intensity to be provided by LEIR • Increase accumulation rate (missing factor 3) w.r.t. 1997 experiment: • New ion source, • Multiturn injection with stacking in vertical phase space as well, • Faster cooling (new cooler from BINP) and higher Linac repetition, • Confidence to meet requirements thanks to a safety factor. 8 108 ions 6 4 2 0 Poor life-time with beam: mainly due to beam-loss induced outgassing 1/3 of the intensity needed after 4 Linac pulses 0 2 4 6 8 10 sec 12 Intensity accumulated in LEAR versus time during a proof of principle experiment in 1997 LEIR Commissioning – AB/LII section meeting

12. LEIR Issues (2/2) :(Beam induced Vacuum Degradation) Intercepted by absorbers : • Reduced outgassing with Au coating, • Efficient scrubbing due to small surface Avalanche-like pressure rise : • ions lost due to rest gas electron capture (or loss) (Pb54+-> Pb53+), • every lost ion desorbs some 104 molecules . LEIR upgrades based on measurement at Linac 3: • Au (low outgassing yield) absorbers to intercept. • NEG coatings reduce pressure rise, • “Scrubbing” (continuous bombardment reduces outgassing) if needed. 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 – AB/LII section meeting

13. LHC Ion Injector Chain Status • New source and Linac 3 : operational • LEIR : • Construction completed, • Commissioning underway (Injection line and injection o.k.) until April 2006 (beam for first LHC ion run). • Commissioning of the LHC ion beam in the PS and SPS in 2006 and 2007, respectively • First LHC Pb ion run at beginning 2008 LEIR construction (Photo taken in spring 2006) LEIR Commissioning – AB/LII section meeting