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114th BLM Thresholds WG meeting (Pb ion, HI, TCTs)

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865/1-B03 (CERN)

865/1-B03

CERN

12
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Belen Maria Salvachua Ferrando (CERN), Daniele Mirarchi (CERN), Sara Morales Vigo (CERN)
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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 

 

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