Upgrade Strategies for LHC Injectors: PS2 Optimization and Injector Enhancements

1. Walter Scandale, Frank Zimmermann 3rd CARE-HHH-APD Workshop LUMI’06, Valencia, October 2006 CARE-HHH Summary of LUMI06part II CERN, 18 January 2007 We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 “Structuring the European Research Area” programme (CARE, contract number RII3-CT-2003-506395).

2. Beam parameters emerging from LUMI06 +LUMI’06

3. new parameter sets have acceptable electron cloud & increased pile-up events with a modest or no increase of the beam current 25 ns spacing with ultimate beam intensity and with a considerably reduced low b* need triplets of a new generation (large gradient and aperture) D0 and small-angle crab cavities 50 ns spacing long bunches may need wire compensation of the far beam-beam effect (12.5 ns short bunches today imply unacceptable heat load -> revisit it only if there will be bunch current limitations ) Beam parameters

4. Heat load data (L. Tavian) • Ultimate scenario   add a dedicated cryoplant for RF cavities. • Long-bunch scenario  add dedicated cryoplants for RF cavities and inner triplets located at the high luminosity interaction points. • Short-bunch scenario  increase of the sector cooling capacity by a factor 4 (& local limitations in the beam screen cooling circuits).

5. Limitations in the injectors (R. Garoby)

6. Upgrade of the injectors (R. Garoby) Endorsed by the PAF

7. Parameters of the PS2 (M. Benedikt) • Twice average line density of PS • Twice longer machine • Twice extraction energy • Identical acceleration time • Shorter cycle time in some cases (LHC without double batch) • Actual performance will depend on the level of the injector upgrade • In case of staged approach: i.e. PS2 before injector upgrade • Line density limited to achievable PS density • Increased cycling time because of double batch filling from PS. Theoretically factor 8 increase in power and power density (assuming identical normalised emittances)

8. Concerns/limitations of PS2 (SPS+ and LHC) B. Goddard • Injection • High energy (3.5 GeV) H- injection system in PS2 • SPS injection system upgrade to 50/75 GeV • LHC injection system upgrade to 1 TeV • Extraction systems • Multiple extraction systems from PS2/SPS • SPS fast extraction at 1 TeV (B.dl) • Beam dumping • Aperture, dilution and absorption for SLHC dump (largeren, larger Itot, ~same E) • Machine protection for beam in gap in SPS+ and LHC+ • Radiation and “co-habitation” issues for internal dumps (PS2/SPS+) • Aperture and extraction system design for external dumps (PS2/SPS+) • Transfer lines • Bending radius and slopes for SC magnets (TI 2/8+ SPS+ to LHC+) • Kicker impedance • Already an issue in the SPS with existing kickers

9. Main area of interest for PS2 R&D B. Goddard Kicker upgrade • Impedance and shielding • Ceramic chamber coatings, surface treatments, geometries, effect on rise times • Ferrite surface treatments, stripes • Switch technology • Fast solid state high current thyristor devices • High Voltage technology • Flashover under vacuum (magnets, connectors, ceramic chambers) • Magnetic materials • High saturation ferrites • High Currie-temperature vacuum-compatible ferrites • Ultra-thin laminations, tape-wound cores • Coil technology • in-vacuum insulation • “New” beam transfer concepts • C-type extraction kickers • Beam intercepting protection devices • Materials and geometries for increased robustness • Consumable/single-use devices

10. S. Hancock

11. FODO arcs of PS2 ? J. Jowet • RF constraint on transition energy severely constrains choice of FODO cell parameters • Large dispersion (4-5 m in QF) • Increased horizontal aperture • Solution with p/2 phase advance and nbend=4 is probably most practical • Leaves adequate straight section space within twice the circumference of existing PS • Other solutions with nbend=3 • Quadrupole strengths almost independent of other choices (determined by magnets and gtr). • Further evaluation of these solutions?

12. Alternative lattice for imaginary tr Flexible Momentum Compaction J. Jowet

13. PS2 Lattice investigations J. Jowet • Straight sections increase |gtr| • FMC (and similar) arcs eat up straight section space • Revisit RF requirement on gtr to relax constraints? • Define preferred choice FODO/FMC/other … • Adapt shape of machine (and circumference?) • Provide strong enough quadrupoles (double them?) • To be done: • Matching of arc modules to dispersion-free straight sections • Likely to use flexible matching sections • Design of straight section functionality (B. Goddard’s talk …) • Injection, extraction, RF, collimation, … • Analysis of lattice stability, chromatic, non-linear behaviour, etc. • Similar calculations for other arc modules (DOFO, doublet, …)

14. PS2: which benefits for the SPS? G. Rumolo

15. SC magnets for the SPS+ G. Kirby

17. Injector complex limitations G. Arduini • Nominal LHC beam at the performance limit (PS & SPS) • Ultimate is out of range for the time being • Ambient radiation, air activation, component aging,….. • Magnet aging (coil erosion, …) is a major issue • Space charge and reduced aperture are common limitations  injection energy increase. • (The PSB will profit of the LINAC4) • TMCI in PS and SPS  |h| increase (avoid transition crossing and ginj >> gtr) • Space charge: limit at ~0.1 given the long injection plateau • Vertical physical aperture (~5 mm) is the main limitation for the high intensity beams for fixed target physics.

18. Injector complex limitations G. Arduini • Electron cloud remains THE main limitation for the SPS (and for the PS?). The only “SURE” solution is the suppression of electron multipacting by a proper design of the vacuum system. • If the priority has to be given to the PS upgrade (aging and radiation issues) we need to define the strategy for the transition to a SPS+: • Experimental verification of the scaling • Optimization of the longitudinal parameters at the transfer • How far can we extend the palliatives we have developed (scrubbing, stabilization by feedback and chromaticity, ….) • Resources and machine time issues

19. R. Assmann

20. RF issues and bunch length E. Shaposhnikova

22. ecloud heat load: LHC nominal case M. Furman heat load vs. Nb heat load vs. dmax dmax=1.7 tb=25 ns Nb=1e11 old dmax=1.7 dmax=1.5 new dmax=1.3 Solid: LTC40: ECLOUD (F. Zimmermann, LTC mtg. #40, April 2005) Dashed: new POSINST, SEY w/o rediffused dmax=1.7 heat load vs. Nb dmax=1.5 – New conclusion: ecloud less severe than before – dmax needs to be <1.3 (vs. <1.2 in the old calculation) – Very good agreement with ECLOUD if same SEY model dmax=1.3

23. ecloud heat load: LHC upgrade M. Furman heat load vs. Nb heat load vs. Nb Short bunch case (tb=12.5 ns) Longer bunch case (tb=75 ns)

24. ecloud heat load: injector upgrade SPS, Eb=50 GeV SPS+, Eb=1000 GeV M. Furman PS2, Eb=50 GeV

25. Intensity limitations in the PSB and in the SPS are the bottle necks of the injector complex The LINAC4 will mitigate the space-charge in the PSB PS2/PS2+ should be successor of PS: reliability & availability, well advanced technology optimum extraction energy, layout, & other parameters to be determined (to mitigate the SPS intensity limitations, ion acceleration, nu-physics) measures to improve the SPS until its successor will be considered Comparison PS2/PS2+ needed (eventually launch s.c. magnet R&D: superferric and 3.5-4.5 T, 2 T/s rate) superferric LER in SPS to be investigated (mitigate intensity limitations in the SPS by RF stacking in LER?) studies on space-charge compensation (e-lens) ? Check of the e-cloud in the upgraded injector to be reinvestigated and cross-checked Tentative conclusions Conclusion on injector upgrade

26. The end …dedicated to Francesco…