A First Look at the Performance for Pb-Pb and p- Pb collisions in FCC- hh

1. A First Look at the Performance for Pb-Pb and p-Pb collisions in FCC-hh Michaela Schaumann (CERN, RWTH Aachen) In collaboration with J.M. Jowett and R. Versteegen (CERN) 14th February 2014 FCC Study Kickoff Meeting, Geneva

2. Outline • General assumptions (Pre-accelerator chain, ring and beam parameters) • Estimates for: • IBSand radiation damping • Luminosity and beam evolution • Beam-beam tune shift • Power in secondary beams emerging from collision point • Parameter table • Conclusions M. Schaumann, Pb-Pb and p-Pb performance of FCC

3. General FCC-hh Parameters Based on a working p-p collider exists. M. Schaumann, Pb-Pb and p-Pb performance of FCC

4. Heavy Ion Pre-Accelerator Chain The requirements and performance of the pre-accelerator chain for FCC are not studied yet. R&D Straw-man assumption to estimate (conservative) beam parameters and luminosity: LHC, as it is today, but cycling to 3 Z TeV, is assumed to be the injector for FCC-hh. FCC LHC SPS Inject one LHC beam into 1/3 FCC, no waiting. Will see later that injector cycle time is similar to time taken to burn-off all beam in FCC. Present heavy-ion pre-injectors PS HI source + Linac 3 LEIR M. Schaumann, Pb-Pb and p-Pb performance of FCC

5. Pb Beam Parameters in LHC and FCC-hh Best injector performance achieved in 2013 p-Pb run. Average beam parameters from 2013 are assumed as VERY conservative baseline for FCC-hh! → Improvements are already under study for HL-LHC! M. Schaumann, Pb-Pb and p-Pb performance of FCC

6. Effects on the Emittance – a new regime Intra-Beam Scattering (IBS) Radiation Damping Emittance Growth Emittance Shrinkage twice as fast as for protons!! Growth rate dynamically changing with beam properties: Damping rate is constant for a given energy: IBS is weak for initial beam parameters, but increases with decreasing emittance . Fast emittance decrease at the beginning of the fill, until IBS becomes strong enough to counteract the radiation damping. M. Schaumann, Pb-Pb and p-Pb performance of FCC

7. Beam Evolution in Pb-Pb Collisions (1 Experiment) Horizontal Emittance Vertical Emittance • “Analytical calculation” considers only burn-off and radiation damping , becomes unrealistic as ! • In simulation horizontal IBS counteracts radiation damping for small emittances: • Without betatron coupling . • With coupling, horizontal IBS growth is transferred to vertical plane. • Equilibrium emittance in both planes. Intensity M. Schaumann, Pb-Pb and p-Pb performance of FCC

8. Pb-Pb Luminosity Evolution (1 Experiment) • “Analytical calculation” neglects IBS, so over-estimates luminosity peak and burn-off speed • Simulation with couplingis most realistic case. • Emittances and bunch length become very small instabilities and artificial blow-up may have to be studied. 1 experiment in collisions R&D • Very high • Is detector able to take hadronic rates > 100 kHz ? • Levelling required? • → Evolution with varying see back-up slides R&D M. Schaumann, Pb-Pb and p-Pb performance of FCC

9. Beam-Beam Tune Shift Beam-beam tune shift per experiment. For round beams : The tune shift due to beam-beam interactions remains well below assumed limit. M. Schaumann, Pb-Pb and p-Pb performance of FCC

10. p-Pb Luminosity Evolution (1 Experiment) “Analytical calculation” only! – Neglecting IBS • Initial conditions: • Pb-beam as for Pb-Pb operation. • Equal geometric beam sizes for p and Pb. • 2 = const. • = const. • → Fast Pb burn-off: Fill Length • Maximum integrated luminosity is achieved, when all Pb ions are converted into luminosity M. Schaumann, Pb-Pb and p-Pb performance of FCC

11. BFPP Beam Power Main contribution to fast Pb-Pb burn-off: Example: LHC Pb beam right of IP2 Main: 208-Pb-82+ BFPP1: 208-Pb-81+ BFPP2: 208-Pb-80+ EMD1: 207-Pb-82+ EMD2: 206-Pb-82+ Countermeasures (e.g., DS collimators) have to be considered in initial lattice & hardware design. LHC FCC-PbPb R&D peak M. Schaumann, Pb-Pb and p-Pb performance of FCC

12. Summary Table (1) M. Schaumann, Pb-Pb and p-Pb performance of FCC

13. Summary Table (2) M. Schaumann, Pb-Pb and p-Pb performance of FCC

14. Peak and Integrated Luminosity per Month Luminosity values discussed with the Ion Physics Working Group for FCC-hh. https://indico.cern.ch/event/288576/material/1/0 M. Schaumann, Pb-Pb and p-Pb performance of FCC

15. Conclusions and Outlook Strong rad. damping, small emittances and effective intensity burn-off. • High potential for luminosity improvement from injectors: • Luminosity is rather insensitive to the initial emittance coming from the injectors, due to rad. damping. • New ion source and injector chain to deliver higher beam current (higher smaller bunch spacing). • Faster cycling of injectors; more injections to increase the number of bunches. • Small emittances and bunch lengths might require artificial blow-up to prevent instabilities; could be used as levelling method. • Conservative assumptions based on existing injector-chain: • High peak luminosity ( nominal LHC) – consider levelling? • Max. int. luminosity: ~100% of particles converted into luminosity as fast as injectors can produce them. • N.B. Two experiments would share approx. same integrated luminosity. R&D Watch compatibility of evolving hadron collider design with nuclear beams. M. Schaumann, Pb-Pb and p-Pb performance of FCC

16. Thank you for your attention M. Schaumann, Pb-Pb and p-Pb performance of FCC

17. Bunch-by-Bunch Differences after Injection in the LHC E = 450 Z GeV • Structure within a train • (1st to last bunch): • increase: - intensity • - bunch length • decrease: emittance. • IBS, space charge, RF noise … at the injection plateau of the SPS: • while waiting for the 12 injections • from the PS to construct a LHC • train. • First injections sit longer at low energy • strong IBS, • emittancegrowth and particle • losses. Design Intensity 1 train Design Horizontal /Vertical Emittance M. Schaumann, Pb-Pb and p-Pb performance of FCC

18. Smooth Lattice Approximation A lattice design does not yet exist! Approximations for smooth lattice functions are used where necessary. Cell Length from aperture constraints Assume FODO cell with M. Schaumann, Pb-Pb and p-Pb performance of FCC

19. Intra-Beam Scattering A. PiwinskiFormalism for IBS growth rates: Particle Type Beam properties Energy IBS strength changes dynamically with beam properties. Lattice and beam sizes Handbook of Accelerator Physics and Engineering, 1st Edition, 3rd Print, pp. 141 M. Schaumann, Pb-Pb and p-Pb performance of FCC

20. Intra-Beam Scattering Variation of IBS growth times for initial beam conditions with FODO cell length. Injection Energy Collision Energy Expected Range Expected Range Effect of long. (hor.) IBS decreases (increases) with increasing cell length. At collision energy, IBS is weak for initial beam parameters. M. Schaumann, Pb-Pb and p-Pb performance of FCC

21. Radiation Damping Handbook of Accelerator Physics and Engineering, 1st Edition, 3rd Print, pp. 210 Damping Rates Energy Particle Type Ring Constant depending on particle’s mass and charge Radiation Integrals Isomagnetic ring with separated function magnets & M. Schaumann, Pb-Pb and p-Pb performance of FCC

22. Luminosity Evolution Consider burn off and radiation damping: IBS is weak at top energyand dominated by radiation damping: → approximate constant emittance damping time. System of two differential equations to be solved: M. Schaumann, Pb-Pb and p-Pb performance of FCC

23. Beam Evolution Simulations Dashed lines: without coupling Solid lines: with coupling Evolution of 3 typical Pb-bunches in collisions. Head Core Tail M. Schaumann, Pb-Pb and p-Pb performance of FCC

24. Pb-Pb Luminosity for varying β* CTE simulation assuming full IBS coupling. Red curve corresponds to solid red curve on slide 8. M. Schaumann, Pb-Pb and p-Pb performance of FCC

25. p-Pb Beam Evolution is assumed to be constant at approximately 100 Pbemittance damps twice as fast as p emittance; assuming exponential emittance damping with constant rad. damping rate and no IBS. M. Schaumann, Pb-Pb and p-Pb performance of FCC

26. Longitudinal Beam Parameters at top energy S.Y.Lee, Accelerator Physics, 3rd edition M. Schaumann, Pb-Pb and p-Pb performance of FCC

27. Circulating Beam Current and Stored Beam Energy Circulating beam current: Stored beam energy: M. Schaumann, Pb-Pb and p-Pb performance of FCC

28. Energy Loss per Turn Radiated power per ion: Radiated power per beam: Energy loss per ion per turn: Critical photon energy: Handbook of Accelerator Physics and Engineering, 2ndEdition, pp. 215 M. Schaumann, Pb-Pb and p-Pb performance of FCC

29. Initial Beam Current Lifetime Lifetime due to burn-off only! Total cross-section at 50Z TeV: H. Meier et al, Phys. Rev. A, vol. 63, 032713. 02/2011 M. Schaumann, Pb-Pb and p-Pb performance of FCC

30. Cycle with LHC as Last Injector 3h LHC turn around time = time between 2 injections to FCC. Luminosity lifetime FCC → Refill LHC during physics in FCC. → No waiting time for FCC due to cycling in LHC. If 2 experiments are considered, they have to be placed at opposite positions in the ring to be provided with luminosity! Intensity Evolution in FCC with 1 exp. in collisions M. Schaumann, Pb-Pb and p-Pb performance of FCC

31. Smaller Z Ions – Impact on Luminosity • New ions source & injectors  possibly higher are available. • No studies on improved heavy ion injectors done yet! • Contribution of ultra-peripheral electromagnetic processes to the total cross-section would be reduced: • Increased luminosity lifetime, more particles available for hadronic interactions. • Reduced secondary beam power emerging from collision point. • Radiation damping rate does not change much for Z>60: M. Schaumann, Pb-Pb and p-Pb performance of FCC