Run 3 performance estimate

General comments:

  • Usual caveats very much apply
  • 2021 - recommissioning after LS2 for operation at 7 TeV - short year
  • ABP will get imaginative with the optics: flat, ATS, bunch configuration... expect the potential peak to go up.

Assumptions

  • 140 days of proton physics in standard including intensity ramp-up
  • Assume 4 weeks for commissioning with beam and intensity ramp-up in standard year - double this after a long shutdown
  • BCMS as standard operational choice, should be able to inject 240 bunches after transfer line collimator upgrades in LS2
  • Levelling (crossing angle and beta* will squeeze another 3-4% integrated per fill)

Limitations

  • Maximum luminosity ~2e34 cm-2s-1 from triplet cooling limitations. Confirmed by measurements performed by cryogenics team in 2017. The limit was confirmed to be 270 W (± 10%)
  • Heat load from electron cloud remains an issue - hence natural choice is BCMS now confirmed as an option, assume injection of 240 bunch injection. BCMS beam with 2556b reaches 160 W/hc limit at ~1.2×10^11 ppb
  • Injectors following LIU will potentially offer higher bunch intensities - SPS perhaps still limited by RF power at least initially. Could push bunch intensity but of course limited by peak luminosity and pile-up in experiments.

 

 

Assumed parameters

Parameter BCMS

BCMS pushed a bit

Nominal - pushed Comments
Energy [TeV] 7.0 7.0 7.0  
β* (1/2/5/8) [m] 0.3 / 10 / 0.3 / 3 0.3/ 10 / 0.3 / 3 0.3/ 10 / 0.3 / 3 Plus beta* levelling to 25 cm
Long-range separation [sigma] - assumed emittance 9.2 sigma - 2.5 um 9.2 sigma - 2.5 um 9.2 sigma - 2.5 um  
Initial Half X-angle (1/2/5/8) [μrad] -160 / 120 / 160 / -150 -160 / 120 / 160 / -150 -205 / 120 / 205 / -150

Anti-levelled to 130 urad

Number of colliding bunches (1/5) 2592 2592 2748 BCMS - 240 bunches/injection from SPS
Bunch population 1.3e11 1.4e11 1.7e11* * ruled out, initialy at least, by e-cloud heat load
Emittance into Stable Beams [μm] 2.5 2.6 3.0  
Bunch length [ns] - 4 sigma 1.1 1.1 1.1  
Virtual Luminosity (L0) 2.3e34 2.6e34 3.2e34  
Levelling time (hours) 2.0 3.8 7.9  
Luminosity per 12 hour fill (burn only) 0.65 0.7 0.8  
Luminosity lifetime (tauL) - end levelling 13 hours 14 hours 15 hours Approx. - assuming burn only
Integrated/140 day year (fb-1) 65 - 70 70 - 75 85 - 90 NB Ballpark!
  • Higher virtual means longer levelling
  • Higher levelled - short levelled time for given virtual - marginal gains given posted limits

 

Time in Stable Beams

  • Assume a physics efficiency 50%.
  • 150 days with 50% of the time in Stable Beams - 6.5 million seconds

 

 

 

Updated May 2018 - Mike Lamont