1. HL-LHC/LIU Joint workshop Goal: Progressing towards an agreed set of 450 GeV beam parameters for High Luminosity operation in LHC after LS2 & LS3. Slides available at: https://indico.cern.ch/conferenceDisplay.py?ovw=True&confId=175259https://indico.cern.ch/conferenceDisplay.py?ovw=True&confId=175259 Program: Summary and outcome of the 1st LIU-HL-LHC Brainstorming meeting - M. Lamont HL-LHC Transverse emittance blow-up and beam loss between injection and collision – 20+10 minutes - KAIN, Verena Update of required beam characteristics at injection energy in LHC – BRUNING, Oliver Micro-batch filling scheme for pacman cancellation – FARTOUKH, Stephane New ideas (e.g. pile-up levelling versus luminosity levelling schemes: potential gains and losses in performance) – ZIMMERMANN, Frank LIU talks Analysis of performance progress in the injectors in 2011 – RUMOLO, Giovanni Update of achievable beam characteristics at injection in LHC – GODDARD, Brennan About beam characteristics and LHC luminosity... – GAROBY, Roland Questions with moderators Pros-cons of 25 ns vs 50 ns, animated by J-M. Jimenez and E. Metral. Overlapping LIU accessible beam parameters (areas) with LHC beam parameters regions (bands), animated by S. Gilardoni and G. Arduini. List of questions to be answered by the end of 2012 / required MDs, animated by E. Shaposhnikova and R. Assmann. Result of the discussion session will be subject of a write-up with actions.

2. HL-LHC Performance Estimates 2 Parameternominal 25ns50ns N1.15E+112.2E+113.5E+11 nbnb 2808 1404 beam current [A]0.581.120.89 x-ing angle [  rad] 300480550 beam separation [  ] 10  * [m] 0.550.15  n [  m] 3.752.53.0  L [eVs] 2.512.5 energy spread1.20E-04 bunch length [m]7.50E-02 IBS horizontal [h]80 -> 10620.020.7 IBS longitudinal [h]61 -> 6015.813.2 Piwinski parameter0.682.542.66 geom. reduction0.830.370.35 beam-beam / IP3.10E-033.9E-035.0E-03 Peak Luminosity1 10 34 9.0 10 34 minimum  * (Leveled to 5 10 34 cm -2 s -1 and 2.5 10 34 cm -2 s -1 ) Putting it all together: Events / crossing1917134095 6.2 10 14 and 4.9 10 14 p/beam  sufficient room for leveling (with Crab Cavities) Virtual luminosity (25ns) of L = 9 / 0.37 10 34 cm -2 s -1 = 25 10 34 cm -2 s -1 (‘k’ = 5) Virtual luminosity (50ns) of L = 9 / 0.35 10 34 cm -2 s -1 = 25 10 34 cm -2 s -1 (‘k’ = 10) Oliver Brüning BE-ABP 2 nd LIU-HL-LHC Brainstorming meeting 30 March 2012

3. Tentative parameter lists (from O. Bruning for the first 2 columns, with modifications for the X-angle, first estimate by Roland for the last column) 25 ns50 nsMicro-batch (25 ns) First LIU offer for micro-batch # Bunches280814041680 p/bunch [10 11 ]2.0 (1.01 A)3.3 (0.83 A)2.8 (0.85 A)2.0 (0.61 A)  L [eV.s] 2.5  z [cm] 7.5   p/p [10 -3 ] 0.1  x,y  [  m] 2.53.0 2.0   [cm] 15 X-angle [  rad]590 (12.5  )590 (11.4  ) 460 (10.9  Loss factor0.300.33 0.34 Peak lumi [10 34 ]6.07.46.45.1 Virtual lumi [10 34 ]20.022.719.514.9 T leveling [h] @ 5E347.86.86.53.9 !!! #Pile up @5E34123247206 S. Fartoukh for the HL-LIU Brainstorming 30.03.2012 3

4. Potential improvements of the PSB beam (waiting for Linac4) Production: Day by day optimization of injection + capture Use: Alternative PS schemes (batch compression) PS performance limited by Longitudinal CBI (need feedback) In future  space charge @ injection, electron cloud, transverse instabilities SPS limitations Injection + capture losses, longitudinal stability, TMCI, emittance growth Electron cloud seems presently mitigated by years of scrubbing, but what will happen after LS1 (loss of conditioning) and with new stretched parameters? Conclusions *Best performance table (2011) 50ns25nsSingle bunch N b (10 11 ppb)  x +  y ) 2 NbNb NbNb PSB Curves emittance vs. intensity @ flat top 4.02.2 PS1.9 1.43.04.02.4 SPS nominal1.61.91.152.62.5 Q201.7?1.22.73.02.2

5. R.G. – 30/03/2012 5 HL-LHC / LIU Joint workshop Concerns & possible actions[1/2] Subject of concernRemedyPossible actions LIU estimated performance < HL-LHC request Increase injectors’ performance -More optimized adjustments (tune, resonance compensation, …) -Alternative RF gymnastics -Higher performance equipment (cavity feedbacks, dampers, kickers…) -Replace accelerators (e.g. inject at higher energy in SPS) Bring HL-LHC request within reach of LIU -Different optics -Operate differently (smaller current with shorter fills and reduced turn around time) More ideas?-?-? Turn around time / protons availability for other users Consolidate-Systematically replace with new and standardized equipment -Build spares Keep margin-Don’t expect peak performance in regular operation -Identify marginal devices and rebuild them -Design new equipment with safety margin Simplify operation-Use less RF gymnastics / less accelerators… Fill LHC faster-Reduce cycling period (basic period) -Replace accelerators (e.g. LP-SPL instead of PSB) More ideas?-?-? Actively pursued Not on the agenda Actively pursued ? ? Could be studied Not on the agenda Actively pursued Could be studied Actively pursued Could be studied Out of reach

6. R.G. – 30/03/2012 6 HL-LHC / LIU Joint workshop Concerns & possible actions[2/2] Subject of concernRemedyPossible actions Integrated luminosity is only ~3 times higher after LIU & HL-LHC* More ideas?-?-? * from LHC Performance Workshop 2012:  Estimate between LS1 and LS2 (W. Herr- session 7): ~60 fb -1  Estimate after LS3 (O. Bruning – session 9): ~200 fb -1

7. R.G. – 30/03/2012 7 HL-LHC / LIU Joint workshop Proposal for the specification of the LIU goals Announce 2 sets of beam characteristics (at injection in LHC), to be published at the end of 2012:  «Baseline» = What is considered as within reach after completion of the LIU project (immediately before LS3, assuming implementation of all the foreseen actions during LS2)  «Stretch» = What could be attained if a number of limitations are ultimately better mastered than initially estimated

8. ‘Conceivable’ improvements? Reduce losses (and SPS blowup) even further!? – Will be real challenge to achieve with x2 beam intensities – Consider as “stretch” goal - also for HL-LHC…! 2.3e11, 2.4 um (!) at SPS extraction 2.8e11, 2.6 um at SPS extraction Stretch