Participants: Alexandros, Belen, Daniele, Roderik, John, Jorge

Belen's talk

• First discussions in 2015 -> Scale of thresholds from another family with a material factor
• Simulations of BLM response for different layout --> Small impact on the BLM orientation (V/H) but large impact on the distance to the beam pipe
• Thermomechanical simulations --> both cases acceptable
  • 40us 2.13e9 p at 3.5TeV
  • Steady 80 s of 3.13e9/s at 6.8 TeV
• One more point
• 0.1Gy/s in BLM equivalent to 2.5kW (3.1kW) power deposition in impacted jaw (deep impact beam loss simulation)
• Simulation scenarios
  • Halo deep impact and accidental scraping - 0.1 - 20 seconds (3-15kW deposited in jaw)
  • Then asked to include also from 0.01 seconds 
    • For very fast RS, energy deposition up to 300kW also discussed 
• BLM response calculated from fluka simulations --> to estimate how much we are allowing with the present thresholds 
• TCT measured BLM response at injection and top energy
• Some considerations
  • TCTs made on W, 1m, with BPMs, being the least robust collimators
  • Protect triplet aperture, located around the colliding IRs in cell 4
  • BLM layout at TCTs not uniform --> different BLM response 
    • Preparing integration to put BLMs in same positions for all TCT collimators during LS3 for IP1 and IP5
      • Action --> Start discussions to do the same in IP2 and IP8
• BLM response 
  • Depends on beam loss scenarios
  • Depends on BLM location
  • Could be simulated and measured 
• Maximum loss rate
  • Validated with maximum energy depositions, temperatures and stresses 
  • Need to be probed for full range of RS times
  • Need to be probed for full range of energy levels 
• FLUKA simulation of 2 loss scenarios
  • Halo leakage of ions from IR7 to TCTPV (deep impact)
    • Very similar for sixtrack or just larger beam size in fluke 
  • Accidental impact on TCTs (beam scraping)
  • Maximum energy deposition on the case 1a
• Why different energy deposition on both jaws? (Daniele)
  • Slightly different beam 
  • Very focused impact on one jaw, not really halo of point 7
  • 9mm impact of full gaussian beam, why is it called halo?
  • Roderik remembers that this is a conservative scenario that covers all scenarios
  • Scraping scenario by simulating collimator going towards the beam and recording impacts
• Allowing case of 3kW 
• Good agreement between simulations and measurements 
• Many corrections on top of THRI_TCT model --> thresholds 
• We want to check the power deposition that is allowed by the master thresholds 
• BLM thresholds model should cover
  • 32 energy limits
  • 12 RS
  • Damage limits for these ranges are needed
• 1 pilot at top energy could damage a TCT (fast loss, direct impact)
• What is the safe energy deposition for RS01-RS06?
• Is the material of the TCTPX the same? Can the studies we reused? Jaw still W
  • What happens in the jaw is the same, to study what happens between the jaw and the BLM
  • A bit different design, but should not impact much what happens
• Action --> remeasure BLM response, or resimulate with correct BLM positions 
• Some TCT thresholds were updated around IP2, due to degraded vacuum conditions higher signal on BLMs
• One TCT open at one side of ALICE at injection, on one side we dump on 

Alexandros' presentation

• Two scenarios simulated for power deposition on TCTs
• Model --> two maps with different mesh that are imported from FLUKA to ANSYS
  • Fine mesh for the inermet blocks, where the beam is concentrated
  • Coarse mesh for the full jaw 
• Case 1a most critical --> larger percentage of the impacting power is deposited to the jaw
• objective stay below 90MPa
• 267 degrees a good threshold from thermomechanical point of view 
• 300kW deposited for 0.1, but temperature in the jaw a bit in the limit, although due to low time, stresses on the pipe still low 
  • Not acceptable case, 0.01 right in the limit
• Scraping case --> max stress on the pipe acceptable
• Objective of the talk
  • Check thermomechanical simulations in lower time scales
  • Limit of 250 degrees on the inert blocks 
• 1kJ acceptable at RS01 and 0.01s 
  • Energy of 10kJ exceeds the temperature limits
    • Already above damage
• 250 degrees reached at approximately 2.5kJ deposited energy at 40us
  • Not a hard limit on the temperature, to give an order of magnitude 
• 2.5kJ estimation of limit for low running sums
• Case 2 extended to RS12
  • Check of structural 
  • Considered acceptable
• RS01 - RS06 --> Limit of 2.5kJ
• Safety margin in this 2.5kJ?
  • Yes and no... for the pipes yes, but for the W...
  • Maybe 1.5 safety factor?
• From test 5e9

• What is missing? Fluka simulations to see energy depositions from different particles and energies?
• Case 1a the worst case scenario 
• Protons in principle should not we worse than ions