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1380b 50ns schemes

1380b 50ns schemes. Reminder: 25ns satellite-main collisions, why ? summer test New results from October: LDM measurements ALICE satellite-main collisions in 50ns physics Prospects for a test thursday this week see also Steve Hancock's presentation LMC_101.

jonah-contreras
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1380b 50ns schemes

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  1. 1380b 50ns schemes Reminder: 25ns satellite-main collisions, why ? summer test New results from October: LDM measurements ALICE satellite-main collisions in 50ns physics Prospects for a test thursday this week see also Steve Hancock's presentation LMC_101

  2. The current "sat-main" 1380b scheme • The intermediate 12b batch is shifted by 25ns such as to collide in IP8 (not IP2) • SPS injection gap: 250ns instead of 225ns • No more space for keeping the pilot => overinject

  3. Attempt in 12jul to 26jul was not conclusive (see LBOC 23 Aug 2011) main-sat IP2 collisions 1380b 1380b N=1.05 1092b normal scheme 840b 264b 48b

  4. Why bother ? all small gains, but all real • Benefits: • ALICE luminosity diluted over all 25 ns slots: perfect, minimize pile-up! • More collisions in ATLAS (1%), CMS (1%) and LHCb (2%) • SPS 250ns gap: "more relaxed operation" w.r.t. 225ns gaps • Prospects: • PS RF (Steve Hancock): potentially could control the 25ns satellite intensity! • Next year: could squeeze ALICE according to achievable population of 25ns satellites, • e.g. b*=1m would allow operating with current satellite populations • with 1-2% satellites could operate at 10m and tune lumi by separation • Upgrade LHC: if choose 50ns and if 3 main-main collisions are too much (beam-beam limits ?), this trick would maybe allow upgrade operation with ATLAS / CMS / LHCb (5e34 vs 2e33 luminosities)

  5. Fill 2222 25ns satellite distribution LDM, EnricoBravin first 50 minutes last 50 minutes fill average all central RF buckets of the nominal 25ns slots After removing those more than 1 slot away from a main bunch (exact definition ?)

  6. Fill 2220 25ns satellite distribution LDM, EnricoBravin

  7. Fill 2219 25ns satellite distribution LDM, EnricoBravin

  8. Fill 2218 25ns satellite distribution LDM, EnricoBravin

  9. Fill 2217 25ns satellite distribution LDM, EnricoBravin

  10. Fill 2216 25ns satellite distribution LDM, EnricoBravin

  11. Fill 2215 25ns satellite distribution LDM, EnricoBravin

  12. Fill 2210 25ns satellite distribution LDM, EnricoBravin

  13. Fill 2208 25ns satellite distribution LDM, EnricoBravin

  14. Fill 2204 25ns satellite distribution LDM, EnricoBravin

  15. 25ns bucket population products LDM, EnricoBravin 2222 2220 bucket_product to luminosity conversion is approximately (for 0 separation): L[i]=bucket_product[i]*3.4e26 Hz/cm2 assuming 100um beams All 25ns slots, but cut at 0.01for filling the histograms N1*N2*1e9  N1tot*N2tot 2219 2218

  16. 25ns bucket population products LDM, EnricoBravin 2217 2216 2215 2210

  17. 25ns bucket population products LDM, EnricoBravin 2204 2208

  18. Summary from LDM • All in all, the satellite populations are reasonably stable! (never believe in your machine colleagues' pessimism...) For the relevant satellites (those which collide with a main) • Mean population: 1.3 - 2.0 x10-3 (I take the start of fill) • RMS population: 0.6 - 1.2 x10-3 • Mean population product: 0.4 - 1.0 • RMS population product: 0.4 - 0.7

  19. ALICE: Vertex timing Paolo Martinengo & Co From fill 2217 onward, ALICE has pure "sat-main" collisions (i.e. is asking, I suppose) for zero separation Fill 2216, main-main V0 vertex Fill 2222, main-sat V0 vertex Lateral peaks due to background

  20. ALICE: Timing correlations Paolo Martinengo & Co Fill 2216, main-main T0 vertex Fill 2222, main-sat T0 vertex

  21. ALICE: Vertex distribution in XY plane Paolo Martinengo & Co Main-sat Main-Main

  22. ALICE: Vertex distribution along Z Paolo Martinengo & Co Main-sat Main-main FWHM FWHM

  23. Approximately expected total luminosity bucket_product to luminosity conversion is approximately (for 0 separation): L[i]=bucket_product[i]*3.4e26 Hz/cm2 assuming 100um beams. Here I used for the approximaley expected total luminosity: L = L[i]_mean * L[i]_entries 2217 and beyond Get 0.5-0.9 1030 Hz/cm2 ALICE wish to have up to 2x1030 Hz/cm2

  24. ALICE lumi from TIMBER • At start of fill, fair agreement with the approximately expected! • But too small lumi head-on => no levelling possible ALICE operating lumi (levelled) 2217 and beyond 0.5-0.9 1030 Hz/cm2 ALICE operating lumi (levelled)

  25. What now ? LMC 101 minutes: "DECISION: LMC gave the green light for an artificial satellite-bunch trial in the LHC" What would be desirable: • Prepare PS and SPS enhanced 25ns satellite beams just before an injection of a 50ns fill • about 1-2% satellite fraction is OK (essentially, anything you want which is bigger than 0.2% and smaller than 5%...) • Inject into LHC • check with LDM in the LHC • if OK, use for physics fill • Mike: "There might be a little cost in ATLAS/CMS peak lumi" => Fine for one fill, then we evaluate • Shouldn't cost more than, say, about 2h of LHC beam time • The window for this test is very narrow: Thursday morning to Friday morning, or saturday morning to sunday afternoon Would be nice to achieve this before end of the proton run!!

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