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110th BLM Thresholds WG meeting (IR3 Thresholds Proposal)
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Europe/Zurich
874/R-018 - MEETING ROOM PRIORITY BE OP (CERN)
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Participants: B.Karslen-Baeck, D.Mirarchi, S.Morales, B.Salvachua, J.Wenninger
S.Morales - BLM response for off-momentum losses (injection and top energy)
- Losses at the start of the energy ramp reaching BLM thresholds in IR3 during some fills in Run 3 --> Caused by off-momentum losses
- Loss plane decomposition algorithm developed to quantify sharing between IR3 and IR7 losses
- Main limitation in the 2024 proton run at the start of ramp was in RS10 of the Q6L3 BLM
- Thresholds increased by around a factor of 2 as a temporary measure before any further studies
- Main limitation now in the same detector but RS09 --> Around 60kW
- Next limitation in the RS08 of TCLA.A5R3.B1 and TCLA.A5L3.B2 --> Around 120kW
- IR3 BLM thresholds model not reviewed since LHC LS1
- Proposal to update the model similarly to what was done in IR7 during LS2
- Need to calculate the allowed number of charge impacts on the TCPs (allowed power loss) and the BLM responses to off-momentum losses
- Green light from different teams and equipment owners to probe up to 500kW losses in IR3 at injection energy
- Test done only in B2 --> B1 start of ramp losses in 2025 in IR7
- BLM thresholds in IR3 modified for the test to allow up to 600kW losses (500kW + 20%) based on start-of-ramp scaling
- First attempt limited to around 300kW due to a different loss pattern appearing around TCLAs when increasing losses
- IR3 BLM thresholds increased further according to the found loss pattern for the second attempt
- Multiple attempts reaching around 500kW losses, no magnet quench observed
- BLM responses to off-momentum losses underestimated in BLMs at TCLAs and TCSGs in cells 4 and 5 (L3 and R3) if calculated from collimator scraping
- Negative off-momentum loss map at injection reproduces well the loss pattern at the start of the energy ramp
- Decision to calculate IR3 BLM responses at injection from 2024 negative off-momentum loss maps at injection (2025 loss maps with B1 losses in IR7)
- Good agreement between responses calculated during the MD test for B2
- Negative off-momentum loss maps at top energy does not show the same loss pattern as with top energy scraping
- Calculation of IR3 BLM response from loss maps, same case as with injection
- Daniele asks to analyze also with positive off-momentum loss map what would be the allowed power loss
- Belen and Sara clarify that the allowed beam power loss will be analyzed for the commissioning loss maps
B.Salvachua - Proposal for BLM thresholds modification in IR3
- The goal is to increase BLM thresholds to allow up to 500kW beam losses in IR3 at injection
- Address BLM thresholds at collimators, warm magnets and MQTL
- Proposal to change IR3 collimator model similarly to what was done in IR7 during LS2
- Warm magnets and Q6 --> Apply a correction at injection, but do not modify the model
- During MD test, no thresholds were reached even with 500kW losses
- Maximum reached 63% of the threshold
- IR3 BLM thresholds reviewed and updated in 2012, considering all losses during off-momentum loss maps happened in IR3 (which today we know is not the case)
- Update of IR7 damage limits in LS2
- LS2 IR7 model keeps the maximum power loss constant over different energies and then calculates the equivalent number of protons
- For IR3, the maximum power loss limit at injection and top energy cannot be constant
- For TCP and TCSG in IR3, ok to have 500kW at injection and top energy
- For TCLA in IR3, 500kW cannot be reached at top energy
- Daniele asks about the power deposition in MQW, Belen says that we only have to look at injection, and Pierre did the study and agreed to increase the limit at injection
- Power deposition in IR7 TCLA most exposed validated for 500kW in LS2
- Power deposition in IR3 TCLA most exposed would be higher than validated if 500kW IR3 losses are allowed, only validated for 100kW losses in IR3
- If we group BLMs in 3 families -> Large difference in response, large difference in triggering
- Proposal to split TCSG and TCLA BLMs in High and low response families -> Increase redundancy
- For TCLA low response family, proposal to add 20% response to these responses, to be more relaxed
- Daniele asks how the curve goes if we go from 500kW at injection and 100kW at top energy, is it safe for example at 6 TeV? Belen says that comparing the present and proposed thresholds, during the ramp it is reduced
- New model in newly created families
- During loss maps this year we will recheck the limits
- The 2026 run starts with MF = 0.4.
- Proposal to implement the new collimation model and corrections during this week
- Follow up studies for TCLA power deposition limits
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