Oxygen pilot run in LHC in 2022 Injectors

Oxygen pilot run in LHC in 2022: Injectors perspective R. Scrivens, D. Kuchler, R. Alemany for the ion team Acknowledgment: D. Manglunki

Atomic number Atomic mass 8 16 17 18 Q/A 0. 5 0. 47 0. 44 Stable Oxygen is a support gas for Pb: Pb 26+/O 2+ Q A 2 Pb 53+ Q/A 0. 5 8 4 Q/A 16 0. 25 0. 125 0. 255 Makes things simpler

Brief history of Oxygen in the injector complex • In 2005, after the installation of the GTSLHC ECR ion source, O 4+ was delivered to LEIR for transfer line and ring commissioning [Ref. 1] • In parallel, Linac 3 beam transport studies were performed [Ref. 2] • O 4+ extrapolations from LEAR observations with O 8+ and O 6+: O 4+ longer life time (4 e- vs 28 e- in Pb 54+) and Q/A ≈ Pb 54+ To LEIR ITH ITL ITM ITF ITH 2 O 4+ injections in LEIR + capture + acceleration

Charge state options Option 2 Option 1 O 2+ Stripper Pb 54+/Pb 82+ stripper O 8+ Fully stripped ions IT H To LEIR O 8 + O 4 +

Pros & Cons Option 1: O 2+ O 8+ before LEIR SOURCE Already optimized for the maximum extracted intensity; ~ 400 eµA after stripping to O 8+ Less setting up time, ~ 1 day L 3 Needs very high fields in the tanks, therefore more X-ray production could potentially restrict the access to some areas of L 3 if NOMINAL beam requested; no issue if EARLY is requested Stripper Optimized stripper, no loss of beam intensity After stripping Everything after the stripper changes out of the linear regime (including ramping and debunching) LEIR Fully strip ions e- stripping from no beam-gas interaction better life time Lifetime in LEAR for 08+ at K=11. 5 Me. V/u = 600 minutes with stochasting cooling, K=200 -250 minutes witout stochasting cooling [Ref. 4] Option 2: O 4+ O 8+ in TT 2 Needs full retuning of the source to get ~ 200 – 300 eµA More setting up time, ~ 3 days Lower fields in the tanks, less X-rays no access restriction might be possible O 4+ O 8+ in TT 2 with Pb stripper, might be too thick and worse stripping efficiency Stays in the linear regime (Q/AO 4+ ~ Q/APb 53+) O 4+: 4 e- left e- stripping from beam-gas interaction. 2005 commissioning report (Ref. 2) says O 4+ lifetime was poor, not clear how much this would be an issue now,

Pros & Cons Brho at LEIR injection (Tm) Option 1: O 2+ O 8+ before LEIR 0. 59 ( = ~ 400 A, the power converter or the main dipole magnets can regulate down to 120 A) 4. 78 Brho at LEIR extraction (Tm) Switch over time 1 hour (without contingency) from Pb O in source and linac 3 Option 2: O 4+ O 8+ in TT 2 1. 18 (similar to Pb 54+) 4. 78 Few hours (without contingency)

Pros & Cons Option 1: O 2+ O 8+ before LEIR Option 2: O 4+ O 8+ in TT 2 Common Neutrons are produced because of the lower charge. Simulations from RP needed and later problems on real measurements. Could restrict the access to the high-energy part of L 3 personnel protection system + beam stopper and beam interlock system to avoid sending the beam when switch yard in access Resources Grillages for access restriction in Linac 3 due to neutrons (estimate 50 KChf) estimates Beam interlock system to avoid sending the beam to switch yard when in access: beam stopper installation + beam interlock system to handle it (estimate > 100 k. CHF) 1 Fellow: operational aspects, beam parameters, settings management. Currently the ion team do not have the manpower to take care of this new run Improvement of the low energy beam instrumentation (to be defined) Caveat The feasibility of this run can be compromised if slip stacking is not commissioned in 2021 and post-poned to 2022

Proposed schedule Start the ion run with Pb up to PS (if only EARLY Oxygen beam needed or only up to LEIR if NOMINAL Oxygen beam needed) to check everything works. EARLY beam: Week 20 switch to oxygen Week 22 beam to LEIR Week 23 beam to PS Week 24 beam to SPS Week 26 beam to LHC Week 27 Pb back to the complex NOMINAL beam: Week 18 switch to oxygen Week 20 beam to LEIR Week 22 beam to PS Week 23 beam to SPS Week 26 beam to LHC Week 27 Pb back to the complex Lead Oxygen

Bibliography 1. LEIR COMMISSIONING http: //cdsweb. cern. ch/record/972341/files/lhc-project-report 923. pdf 2. Preliminary Characterization of the O 4+ Beam in Linac 3 https: //core. ac. uk/download/pdf/44163997. pdf 3. Stochastic cooling and storage tests with oxigen ions in LEAR http: //accelconf. web. cern. ch/accelconf/p 89/PDF/PAC 1989_0645. PDF 4. Oxygen ions in LEAR http: //accelconf. web. cern. ch/accelconf/e 90/PDF/EPAC 1990_0580. PDF