R. Bruce, F.Carra, M. D’Andrea, C. Hernalsteens, J. Jowett, S. La Naour, A.Lechner, D. Mirarchi, A.Perillo, S. Redaelli, V. Rodin, B. Salvachua, A.Verweij, D.Wollmann, 

BLM threshold strategy for the 2023 Pb run (in view of power deposition), Anton Lechner

• The baseline for 2023 heavy ion run is the crystal-assisted collimation. 
• Set of BLM thresholds is performance-oriented and probe dynamically the quench margin. Set the thresholds above the quench level. 
• Expected steady-state quench limits for MBs at 6.8 Z TeV not higher than 15 mW/cm3
• IR7 Betatron power loss based on 2022 crystal loss maps with:
  • crystals in channeling: 15 mW/cm3 would correspond to 35-50 kW.
  • crystals in amorphous: 5-6 worse cleaning, 15 mW/cm3 would correspond to 7-10 kW.
  • Standard collimation: 
• IR7 protons: RS08-RS10 500kW, RS11 239 kW, RS12 100 kW - similar factors applied to ions
• IR6: observed losses in cold magnets originated at TCSP L6 B2 at B2H loss maps. Could this be mitigated by asymmetric jaw setup of TCSP - so that no BLMs need to be updated. 
• IR1 TCTs - could this be mitigated with asymmetric jaw settings in IR7
• Power load on crystal absorbers remains smaller than for protons, also for the coating (although it depends strongly on the impact parameter).
• Collision losses in IRs and DS: no correction for hadronic or EMD products, local correction for BFPP via Monitor Factor. 
• IR2 BFPP - TCLD and MQ.11 need to be aligned via Monitor Factor to allow for 160 W. 

Loss maps for crystal-assisted Pb collimation, Marco D’Andrea

• Configuration tested in 2022 at 6.8 Z TeV:
  • Channelling at 4.75 sigmas in optimal channeling orientation, everything else at nominal settings
  • Amorphous at 4.75 sigmas with large angular misalignment, everything else at nominal settings
  • Standard collimation
• Configuration tested in 2022 at 450 Z TeV
  • Channeling at 5.7 sigma in optimal channeling, TCPs and TCSGs upstream of absorber of channelled halo retracted, everything else at nominal settings
  • Standard collimation
• Marco calculated the response factors for the different configurations , i.e BLM expected signals in Gy/charge. These are used to scale to the different power loads discussed. 

BLM thresholds and families for the 2023 Pb run, B.Salvachua

• Expected store energies of 20 MJ at 6.8 Z TeV and 1.3 MJ at 450 Z GeV
• Thresholds at collimators will cover:
  • Crystal in channeling (60kW average in master thresholds) and in amorphous (15-20 kW average master thresholds) with the proposed set of families.
  • Standard collimation with two families pre-set so that only moving of monitors is needed if crystal collimation is not used. 
  • Factors needed implemented in a step function injection, 2 TeV and 6.8TeV.
• Thresholds changes proposed:
  • IR7 DS: Increase of thresholds for a list of monitors in the IR7 DS to the signal during the quench test of 2015. List in LHC-BLM-ECR-0070, plus 2 additional monitors and increase of 20% of two families. 
  • IR7 Collimation: at least 2 monitors per beam and plane, table with the expected numbers. 
  • IR1 and IR5 BFPP: 8 monitors to be increased via Monitor Factor from 0.333 to 1.0 
  • IR8 BFPP: no change proposed but to be checked during loss maps and intensity ramp-up
  • IR2 BFPP: no change proposed but to be checked during loss maps and intensity ramp-up.
  • IR4 WS: no change but wire-scanner ion intensity limit to be defined. 
• pp-ref run 
  • Extend flat top corrections in IP8 to EL at 2 TeV
  • MF in IR8/IR1/IR5 to be checked during ramp up

General discussion and conclusions:

• Propose to align on average to a power loss of 60 kW in IR7 for crystal in channeling.
• IR6 losses for B2H: Collimation will investigate the possibility to mitigate these losses adjusting the TCSP settings.
• IR1 TCTs losses: Collimation will investigate the possibility to mitigate these losses adjusting asymmetric jaw settings.
• F.Carra confirms that power load on collimators and coating are below specifications and therefore accepted. 
• Carefully check BFPP bumps, in particular IR8 as the quench limit is not far. To be noted that LHCb is not interested to push up the Inst. luminosity further than 1.4-1.5e27 cm-1 s-2
• IR2 BFPP - TCLD and MQ.11 need to be aligned via Monitor Factor to allow for 160 W. 
• Sandrine and Arjan have no objections to the proposed approach, they understand that quenching of magnets in the DS can occur, in this case the relevant signals will be analysed. 
• D.Mirarchi comments that TCSG.D4 has coating.
• Thresholds to be re-checked with final loss maps in 2023
• J.Jowett commented that it would be interesting to seletively intercept EMD1 losses with the TCLDs at IP2 in order to check the effect on losses in Ir3 and possibly elsewhere. 
• Agreement to setup:
  • Collimators master thresholds in channeling at 60 kW
  • Collimators master thresholds in amorphous at 15 kW 
  • Collimators master thresholds in standard at 25 kW
  • Start with MF in collimation and DS IR7 of 0.4 , then increase in steps of 0.2 (0.4 -> 0.6->0.8->1.0) 
  • Check-point needs to be defined.