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LHC Operational Highlights: January 25th, 2023 Beam Dumps and Injection Tests

On January 25, 2023, the LHC experienced multiple beam dumps and injection tests. Stable beam fills numbered 3490 to 3494 were achieved, with an initial luminosity of 1e29 cm⁻²s⁻¹. Beam dumps were attributed to noisy signals from BPMS devices as ion intensity decreased. Adjustments were made to interlock parameters, although effectiveness is uncertain. Injection steering strategies and RF batch-by-batch blow-up testing were conducted to optimize beam stability and transverse emittance. Continuous monitoring is necessary due to ongoing calibration challenges.

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LHC Operational Highlights: January 25th, 2023 Beam Dumps and Injection Tests

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  1. Friday 25th and night 04:30 Stable beams fill 3490 Initial lumi: 1e29 cm-2s-1 10:35 ALICE colliding head-on. 10:58 Beams dumped by BPMS. 1.4 nb-1 in 6h29m. 13:00 Injection steering and simultaneous tests of RF bbb blow-up to reduce transverse blow-up at injection 14:30 Start filling for physics... but PS POPS is down 17:30 Injecting again 19:49 Stable beams fill 3493, Initial lumi:1e29 cm-2s-1 01:06 Dump due to BPMS after 5h17m, about 1 nb-1 02:46 Injecting for physics 04:46 Stable beams fill 3494, still hanging in… LHC 9:00 meeting

  2. BPMS • Reasons of dumps • First 3 fills dumped due to noisy signal when ion intensity getting low (3 – 4 e9 charges) on BPMSA.B4R6.B2 • On the BPMS increased interlock window from 500/100 to 2000/100 • However, when signal becomes noisy, changing the interlock window not likely to be very effective • Dump at 22:42 of 24thJanuary. This time it seems that the channel that triggered was a different one: the BPMSB.B4L6.B2-horizontal but with smaller bunch charges: 2.85e9p/bunch. • Dump at 10:58, 25th January, again BPMSB.B4L6.B2 – same as previous dump. • Conclusion: after increasing the interlock count, the beam has been dumped on a different BPMS, but not clear if this is by chance or due to the change. • Dump bunch intensity has gone down from 4e10 to about 3e10 LHC 9:00 meeting

  3. RF batch-by-batch blow-up • At injection, to reduce increase of transverse emittance • 1.4 ns target • Worked after some testing during injection steering • Observables • Initial lumi: does not seem to be match larger. Not really gained. • BSRT / BGI: needs further analysis, no absolute calibration LHC 9:00 meeting

  4. Fill 3493 ? • RF bbb blow-up • IQC green for B1 after ‘pilot masking. B2 TL (?) latches. • Roman Pots moved in, both, with sequence • Many dI/dt plots by DB • Conclusion? • Dumped BPMS just above 3e9 intensity LHC 9:00 meeting

  5. Fill 3494 • Some problems with the BPM calibration before injection, requiring a reboot of cfv-sr6-bpmint2 • Losses MBB 9L7 and 11L7 during ramp and squeeze. • RF B2 increased to 14MV, as in previous fills, to improve lifetime • Lifetimes B2 in collision not very good • Improvement by tune trim LHC 9:00 meeting

  6. 2 nb-1 per day Will be a bit lower per fill from now on because of more burn-off by going head-on in ALICE LHC 9:00 meeting

  7. Various • Wire scanners not to be used until checked in tunnel • ALICE polarity change on Sunday • V/d Meer scans next week Mon/Tue • LHCb polarity change after V/d Meer scans LHC 9:00 meeting

  8. Access requests – getting long • Long list but none urgent • Priority to accumulate lumi before polarity change • Access requests: • Wire scanner, J.Emery, point 4, 2 hours. • Collimators UJ33, test position sensors, M. di Castro, A.Masi, 20 minutes. • “Train”, B.Feral, D. Paulic, PM56/UL55, 1 h during working hours • BGI, M.Sapinski, R4, ½ h • LHCf has a problem in a part of the frontend electronics placed in the tunnel, we would like to ask a two hours access at the next opportunity in the shadow of the other activity. Takashi Sako • Quench Test on Q6.L8 – the scope is not yet in place, 1h in the UA. Mateusz Bednarek • CMS cryogenics – filter to be cleaned • LudovicMourier 165232 Restore pump for QRL insulation vacuum in sector 45 (which has a leak) • LHCb – 3 hours LHC 9:00 meeting

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