Task 2. 5: Beam-beam studies D. Banfi, J. Barranco, T. Pieloni, A Task 2.5: Beam-beam studies D. Banfi, J. Barranco, T. Pieloni, A. Valishev Very-Preliminary results for RLIUP scenarious Acknowledgments: LHC@home team for support!

b1, b2 30, 7.5 cm sz 7.5 cm ex, ey 2.5 mm Nb 2736 Collisions at IP1, IP5

Np (1011) x-angle (mrad) sep (s) L (1034) DA min 1.0 300 8.9 3.0 4.25 1.2 4.3 <4 350 10.4 2.7 5.3 4.0 5.2 1.4 5.4 400 11.9 5.0 1.8 8.2 2.2 12.3 1.6 450 13.4 6.0 6.2 7.7 5.5 2.0 9.4 4.6 500 14.9 5.6 6.7 7.1 6.5 8.8 550 16.4 9.9 6.1

Possible scenarios at 7 TeV: Nb coll [1011] e*coll [mm] Coll. Bunch. IP1,5 Min b* (xing / sep) [cm] B-B Sep [s] Xing angle [mrad] Lpeak [1034 cm-2s-1] Llev Lev. time [h] tlumi after Opt. Fill length Machine perf eff. 6 h fills [%] Machine per eff. opt. fills [%] Avg. Peak-pile-up density [ev./mm] Target int. Lumi [fb-1/year] PIC 1.38 1.8 2592 40/20 12 296 4.24 - 6.0 26.4 1.42 70 2.22 2736 329 3.62 8.2 6.9 28.5 28.3 1.15 US1 1.9 2.62 10 298 6.37 5.06 1.7 7.2 6.5 43.4 43.3 1.50 170 US2 2.26 15/15 450 17.6 4.3 8.4 57.8 53.6 1.21 270 2.2 2.5 473 21.3 9.0 4.13 10.2 50.6 1.24 30/7.5 335 20.0 8.7 4.57 50.8 <1.30 Bunch length 7.55cm, could be increased to 10cm for pile-up density or more with 2nd harmonic system b*= 40 cm could be relaxed to gain aperture and pile-up density B-B sep being evaluated

Beam-beam Task 2.5 Is there any filling scheme among those proposed for BCMS that could pose problems for beam-beam effects? What is the required beam-beam separation for flat optics and no BBLR? What is the dependence on intensity? BBLR position vs emittance, flat beam crossing angle with BBLR. Is it compatible with collimation?

The filling schemes are ok for us no counter-proposals! Filling schemes 25 ns Courtesy B. Gorini Filling scheme Total IP1-5 IP2 IP8 BCMS: 48b 6 Ps inj, 12 SPS inj 2604 2592 2288 2396 Standard: 72b 4 Ps inj, 12 SPS inj 2748 2736 2452 2524 The filling schemes are ok for us no counter-proposals! Just few Comments! 12 non colliding bunches for IP1 and IP5 experiment needs In case of instabilities could be problematic! Except if we take head-on collision in IP2 or IP8 Beta* leveling in IP8 but is 1 head-on stability enough? To be tested

Filling schemes 25 ns: 48 bunch trains 12 non colliding bunches for IP1 and IP5 experiment needs In case of instabilities could be problematic! Except if we take head-on collision in IP2 or IP8 Beta* leveling in IP8 but is 1 head-on stability enough? To be tested Ratio nominal/pacman different needs considerations for optimization/wire

Filling schemes 25 ns: 72 bunch trains 12 non colliding bunches for IP1 and IP5 experiment needs In case of instabilities could be problematic! Except if we take head-on collision in IP2 or IP8 Beta* leveling in IP8 but is 1 head-on stability enough? To be tested Ratio nominal/pacman different needs considerations for optimization and wire

LHC running 2012 LHC runs always above 8 s DA with imperfections! LHC nominal DA simulations 8-7 s DA for nominal intensity, nom s 1 s reduction for Intensity increase 1.1-1.6 1011 ppb LHC runs always above 8 s DA with imperfections! DA from BB and imperfections always behind collimators in LHC. We have heavy losses at DA of 3-4 s from measurements (D. Kaltchev & W. Herr) What do we define as GOOD POINT for upgrade scenarios 6 s ? 8 s ? At collimators?

Beam-beam DA studies PIC & US1 scenarios (simulations still running) DA with beam-beam only (4D&5slices and 6D) No imperfections No tune scans = no optimization DA normalized to 2.5 mm US2 DA with beam-beam (4D&5slices and 6D) DA with imperfections Tune scans on-going for 30/7.5 cm Optic Thanks to Stephane for providing initial mask file

PIC: Beam-beam interactions only 40/20 Optics 4D/5 slices BB 40-20cm Optics and beam-beam : 1.4e11 Intensity 1.4e11 Optics 40-20 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP DA in s (2.5 mm) Collimators Tune scan might improve picture PIC1: 15.8 s first encounter PIC2: 14.4 s first encounter PIC 1.38 1.8 2592 40/20 12 296 4.24 2.22 2736 329 3.62 Crossing angle between 380-420 mrad

PIC: Beam-beam interactions only 40-20cm Optics and beam-beam: 1.3 e11 Intensity 1.3e11 Optics 40-20 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Collimators DA in s (2.5 mm) Tune scan might improve picture PIC1: 15.0 s first encounter PIC2: 12.9 s first encounter PIC 1.38 1.8 2592 40/20 12 296 4.24 2.22 2736 329 3.62 Crossing angle between 350-410 mrad

PIC: Beam-beam interactions only 40-20cm Optics and beam-beam: 1.6 e11 Intensity 1.6e11 Emittance 2.62 mm Optics 40-20 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP DA in s (2.5 mm) Collimators Tune scan might improve picture US1: 13.6 s first encounter Crossing angle between 400 mrad US1 1.9 2.62 2736 40/20 10 298 6.37 5.06

Footprints and FMA Diffusion rate units of tune 296 mrad 1.8 mm 1.38e11 329 mrad 2.2 mm 1.38e11 12 s sep 12 s sep Proposed Scenarios PIC1 and PIC2

Footprints and FMA Diffusion rate units of tune 390 mrad 1.8 mm 1.38e11 390 mrad 2.2 mm 1.38e11 16 s sep 14.3 s sep 355 mrad 2.62 mm 1.6e11 420 mrad 1.54 mm 1.6e11 12 s sep 18.5 s sep

40-30/40-20/40-10 cm Optics Comparison 40/30 Optics BB 40/20 Optics BB 40/10 Optics BB Preliminary results show: Larger DA if b* sep plane larger Leveling with b* should aim to separation plane to improve DA? Reduce crossing angle? Sharper improvement with larger b* sep plane Test constant beta ratio leveling Tune scan needed!

Footprints and FMA Diffusion rate units of tune 256 mrad 1.8 mm 1.5e11 40-20 Optics 40-10 Optics 296 mrad 1.8 mm 1.38e11 256 mrad 1.8 mm 1.45e11 40-30 Optics

40-20 cm Optics: Intensity scan 4D Optics 40-20 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Collimators DA in s (2.5 mm) Intensity effect not so important for some configurations

40-20 cm Optics: Intensity scan 6D Optics 40-20 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Collimators DA in s (2.5 mm) To be understood Intensity effect not so important for some configurations

15 cm round optics Need to evaluate impact of imperfections! 15/15 Optics 4D/5 slices BB 10.6 s end of leveling Collimators Intensity scan Optics 15 cm round IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP DA in s (2.5 mm) Nominal US2 1.9 2.26 2736 15/15 10 466 16.3 5.06 2.2 2.5 490 19.8 Need to evaluate impact of imperfections! First estimates are positive

15 cm round optics 6D BB 6 D requires a bit more, Energy scaling also! 11.9 s end of leveling Collimators DA in s (2.5 mm) Intensity scan Optics 15 cm round IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Nominal 6 D requires a bit more, Energy scaling also!

15 cm round optics 15/15 Optics 590 mrad Need to understand deep at 2.2 e11 ppb Is it real? Simulations on-going ! Need also Imperfections!

30/7.5 Beam-beam interactions only 30/7.5 Optics 4D/5 slices BB 12.5 s end of leveling Collimators Intensity scan Optics 30-7.5 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Nominal This case at 7 TeV at 6.5 TeV you need 0.5 sigma more (440 mrad)

Beam-beam interactions only 30/7.5 Optics 6D Hirata 12.5 s end of leveling Collimators Nominal Intensity scan Optics 30-7.5 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Needs still some understanding! Tune scan on-going and FMA 6D beam-beam needs more separation! This case at 7 TeV at 6.5 TeV you need 0.5 sigma more (440 mrad)

Beam-beam interactions only! 30/7.5 Optics 2.2 e11 ppb Collimators Intensity scan Optics 30-7.5 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Need to clarify the 4D and 6D differences! FMA studies on-going! Imperfections have strong impact needs to be evaluated!

30/7.5 Optics 540 mrad 15cmOptics 590 mrad Results are new, need check! Tune scan could help understanding 15cmOptics 590 mrad

Tune scan Tune scan shows possible improvement of DA for higher tunes 30/7.5 Optics 2.2 e11 ppb Tune scan Optics 30-7.5 cm IP1&IP5 with crossing angle NO crab cavities IP8 off Maximum 32 long-range/IP Tune scan shows possible improvement of DA for higher tunes

Flat 30/7.5 Intensity scans All scenarios are at the limit! Here no margin! 16.5 s first encounter for 4D simulations 18 s first encounter for 6D simulations NEEDS studies to understand this effect NEEDS tune scan (on-going) Leveling in Sep plane (Larger beta in sep plane) could IMPROVE? Constant ratio of betas leveling?

BB Long range wire compensation IP1 & IP5 Head-on 15 cm round Optics HL-LHC 590 mrad crossing angle FMA and footprints tool in Sixtrack! Need official release to make them available to everyone IP1 & IP5 Head-on + LR

BB Long range wire compensation 1 Wire next to TCT IP5 1 Wire next to TCL IP1 200 A rematch2 200 A rematch3 200 A 200 A rematch1 338 A A wire exist in Sixtrack by Bela Erdelyi and Tanaji Sen (Benchmarked versus F. Zimmermann) Testing On-going preliminary results showed Need wire implemented in MADX for matching tune shift! Need MADX to Sixtrack convertion!

Summary Several results for BB only! Sorry some are still analyzed! Need to collect results faster! Preliminary results need a decision in what to define as DA minimum to define crossing angles! For flat options larger separations seems needed but not obvious to give one separation!Tunes, optics and intensity change picture Imperfections are important for low beta optics, needs some studies! Leveling with separation plane should improve things! Relax separation in crossing plane by larger beta in sep plane? Pacman families not yet studied, on-going! No intermediate optics to check impact of constant ratio leveling Past studies suggest tune scan could improve, very little for 30-7.5 optic Leveling scenario optics fundamental to study a case Wire studies are possible, need implementations in MADX! Still many things to be checked i.e. 4D versus 6D, Lifetrack vs Sixtrack for flat, B2 implementation etc.

FMA and footprints 40/20 323 mrad 1.3 e11 ppb 1.98 mm

1.38e11 1.8 mm 40/20 296mrad 390mrad

1.8mm 40/20 296mrad 390mrad