ad-hoc BLMTWG (IR6 Q4/Q5 protons)

Friday 9 May 2025, 10:45 → 11:15 Europe/Zurich

Daniele, Anton, Belen, Sara, Fabian, Kate

• Simulations of standalone super-conducting magents 4.5K Q4/Q5 CERN-THESIS-2023-043
• Response factors from simulations for primary impacts at the TCDQ (1-side collimator - 9m) and TCSP (2-jaws collimator - 1m).
• Checked what would be the expected primary impacts at the present applied thresholds (MF=0.4).
• Checked expected energy deposition peak at the Q4 and Q5 and compared with the limit of 30-40 mW/cm3.
• This shows that a factor 2 could still be safe, but larger factor is discarded without further studies. 
• File from A.Apollonio 2018 with quench levels - stored in the BLMTWG cernbox.

 

If/when implemented this, we need to check:

• how to align it with the master thresholds and monitor factor used
• what happends with B2 that has lower response

1 Q4/Q5 Fluka simulations

Speaker: Anton Lechner (CERN)

BLMTWG_energydepQ4Q5inIR6_09052025.pdf

BLMTWG_energydepQ4Q5inIR6_09052025.pptx

• Higher leakage to IR6 from IR7 in B1H loss maps from 18cm beta star
• Simulation of BLM responses in Q4 and Q5 from impacts on TCSP/TCDQ collimators, to see if there is risk of quenching the magnets
• Belen says that in 2023 ion run there was also observed higher signals in IR6 with B2, at that moment the TCSP jaw was opened to alleviate the losses
  • A possible increase of up to a factor of 5 for RS09 was agreed
• TCDQ only has one jaw (9 meters long), TCSP has two (only one meter down)
• Some meters below a mask, TCDQM, then the first superconducting magnet Q4, some more meters downstream (about 20) the Q5
• Impacts on TCDQ: 2e-12 Gy/p Q4, 1e-12 Gy/p Q5
• Impacts on TCSP: 6e-12 Gy/p Q4 and Q5
  • Makes sense as TCSP is shorter, so less absorbing, higher BLM response expected downstream
• MF = 0.4 for the BLMs at Q4, Q5
• TCSP and TCDQ losses at Q4/Q5 dump threshold estimated (for applied thresholds)
• Q4 has the mask, so power deposition per proton lost is lower than in Q5
• Q5 has a peak of power deposition in beginning of magnet
• Both magnets of the MQY type at 4.5K
  • Q5 gets to 3500A
  • Q4 gets between 2500 and 3000A
• Maximum power deposition in Q4 and Q5 at which we are expected to dump calculated, higher for Q5 as different BLM response
  • Quench level depends on magnet current
  • There should be some margin, but there is still some uncertainty
  • Could allow for a factor of 2 probably, a factor 5 would be too much
  • From document from Andrea 
    • 37 mW/cm3 quench level for 3000A at 7 TeV, will have to check for 6.8 TeV
• See how to apply this change -> so that master threshold is at quench level?
• Anton shows Run 2 studies that show that the leakage to IR6 from IR7 seems to decrease with higher loss rates
• Daniele asks why for B2H it is not expected to reach the thresholds at the same IR7 power loss even though there seems to be similar inefficiency during loss maps
  • Fabian shows that for the equivalent B2 BLM, the response during B2H loss map seems to be around 3 times lower
  • Belen and Anton remind that one should also consider that the responses in IR7 also vary for B1 and B2