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108th BLM Thresholds WG meeting (Preparation of Ion Run)
Participants: D. Mirarchi, B. Salvachua, S. Morales, K. Taylor, N. Triantafyllou, F. Titz, C. Hernalsteens, J. Wenninger, R.Bruce
Overview
- Meeting objective: define actions and needs for setting BLM thresholds for the next ion run (Nov)
- Expected schedule: 4 days of commissioning and 2 days of MD.
- Previous loss maps will be used as a reference for scaling.
Ion Run 5 Configuration - Roderik Bruce
- Optics and Setup:
- Smaller β* in IR8.
- Reverse polarity (RP) in IR5 triplet.
- Crossing angles remain unchanged.
- Luminosity: Expected to be similar, but levelling time for IR8 will be longer.
- 2025 ion cycle to remain same as 2024 with additional squeeze step
- Collimation performance :
- Simulations show losses consistent with 2024 configuration.
- Summary
- RP in IR5, non-RP in IR1
- Dispersion correction added in IR2 and IR8 (new bumps introduced).
- IR8 squeeze to 1 m with new corrections and Q-bump.
- Discussion:
- Full collimation and background checks to be done with ALICE.
- If issues arise, will revert stepwise during commissioning.
- Polarity differences between IR1 and IR5 should not significantly affect loss maps. Crossing angle remains the same.
- Dispersion useful for crystal optimization, particularly for ALICE (IR2/IR8) - now no dispersion in IR7 - may be blind on crystal optimsation - to be verified.
- Commissioning:
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- Full collimation and background checks to be done with ALICE.
- If issues arise, will revert stepwise during commissioning.
-
BLM Threshold Recap - Sara Morales Vigo
- Changes needed going from protons to ion, due to different losses in IR7 due to crystal collimation.
- Crystal collimation reduced DS leakage but increased local losses (TCTs, TCLDs).
- Thresholds initially defined via 15 kW quench test.
- Crystal collimation can see up to 30–50 kW losses (depending on channelling mode).
- IR7 Thresholds:
- 2023: 5 families for channelling, 2 for amorphous (no VR).
- 2024: similar families, updated corrections and lower leakage via TCLA (11σ → 8σ).
- 2025: proposal to keep same setup pending final loss maps - consider though TCSG.A6R7.B2
- DS Strategy:
- Keep 2015 Pb-based thresholds; scaling confirmed adequate.
- Review Q6 family (BLMs detect fragment leakage from IR7).
- Updated thresholds from FLUKA studies; increased MF for RS families.
- IR3:
- Dedicated Q6 family added in 2018, no additional changes
- Thresholds increased by 30% (2023) and x2 (2024) to avoid limitations.
- RF@12 MV de-bunched beam tests stopped BLM warnings seperately.
- TCT/TCLD:
- No major change; thresholds adjusted based on loss maps.
- Collision Losses:
- BFPP losses managed by orbit bumps (IR1/5 to cryostat, IR2 to TCLD, IR8 more distributed).
- Quadrupole downstream losses under review.
- 14R8 anomalies under investigation (not fully understood).
Discussion
- Loss Maps & Commissioning:
- Need loss maps (CH, AM, VR) before the technical stop to scale and verify thresholds.
- No major configuration changes expected elsewhere.
- Quench Tests:
- Future quench test may be shifted to next year (possibly during p–Pb run).
- No change in master thresholds anticipated; only MF may be tuned.
- 14R8 Losses
- Cause of losses uncertain
- TCT.8 BLM Threshold Review
- 1m squeeze in IR8 results in tighter settings for TCT.8, probable increase in losses and so BLM thresholds could be reviewed.
Conclusions & Next Steps
- Maintain 2024 thresholds and configurations unless loss maps indicate a need for revision.
- Prepare updated loss maps for all modes (CH, AM, VR) and for injection.
- Plan for a follow-up meeting once loss maps are available to finalize MF and BLM thresholds.
- Keep monitoring IR8 losses; simulations don’t fully match data yet.
- Possible review of BLM thresholds for TCT.8
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