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LHC Operations Update: TDI Alignment and BPMS Interlock Checks Post-Intervention

On January 12, significant progress was made in the LHC operations, including the successful completion of TDI alignment following an intervention and extensive BPMS interlock checks. After beam intensities were verified, the interlock systems passed testing with minor acceptable errors. Technical issues arose, including a mains perturbation and an electrical fire incident, prompting ongoing repair efforts. Effective management of system calibrations and adjustments will facilitate the upcoming pPb run, with further troubleshooting planned for stuck TDIs and unstable filter systems.

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LHC Operations Update: TDI Alignment and BPMS Interlock Checks Post-Intervention

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  1. Saturday 12th January 01:00 - 05:00 squeeze in steps down to 80cm 05:42 Dump beam at 4 TeV, end of beta beat measurements over squeeze 06:48 Start TDI alignment following intervention on TDI during TS 13:30 TDI alignment finished successfully 13:30 Start of BPMS interlock check after installation of new attenuators during TS 16:30 Interlock checks finished successfully 16:30 Check of BPMS intensity limit with  a single bunch: 1.5e9 17:30 Start check of BPMS with bunch trains at injection 19:15 Mains ‘perturbation’, cryogenics lost… and a lot more 22:03 Confirmation that an electrical rack has caught fire in RE88. 00:20 Cryoconditions 01:30 UPS repair ongoing LHC 9:00 meeting

  2. TDI alignment Chiara & Wolfgang • Part of the mechanics of the left(upper) jaw of TDIs in IP2 and IP8 were replaced during Xmas stop and LVDTs re-calibrated • References no more valid and new setup needed. • Procedure • Defined orbit with indiv • Checked alignment with pilot (all 4 jaws checked) • Defined new settings plus position and energy interlocks: • Results • TDI.IP2: Left (=upper) jaw: -3.03 mm & 0 uradRight (=lower) jaw: -4.39 mm & -840 urad • TDI.IP8: Left jaw: 3.19 mm & -157 uradRight jaw: 1.59 mm & -175 urad • Checked retraction with respect to TCP (X-measurement): • TDI.IP2 both jaws at 6.4 sigma (nominal 6.8 sigma) • TDI.IP8 both jaws at 6.9 sigma (nominal 6.8 sigma) LHC 9:00 meeting

  3. BPMS checks Eva • BPMSs interlock the beam position +/- 3 mm relative to reference to be sure that the beam passes through the beam dump channel. • Filters changed during TS so cross-over between high and low sensitivity mode is not at 2e10 p+, which is where we expect to be working for the coming pPb run. • Interlocking was checked • All channels interlock correctly, with an error of up to 0.5 mm • This error was smaller in the past, 0.1 mm, but is still acceptable • Checked with single bunch minimum intensity • At 1.45e9 interlock channels triggered • Plan was to check multiple bunches of 1 – 2 e10 p+ • Difficult: injection oscillations but no IQC data. Injected beam lost after few turns. ADT still adjusted for high intensity bunches…. • Did not get very far on this as -> LHC 9:00 meeting

  4. 19:15 Mains perturbation • Explosion of a circuit breaker on the stable filter in BE9 • This effects mainly the SPS. Repair most likely on Monday. Have to see if SPS can deliver some beam without this filter • Main damage on the LHC side is a UPS in point 8 and point 7 • Fixable, but also needs external company • Repairs ongoing at this moment • Trips • ‘All’ circuits lost including Experimental Magnets • Cryogenics OK lost – but compressors stayed on • RF lost • QPS in fault • Injection and beam dump kickers in fault • ... LHC 9:00 meeting

  5. Outstanding • Problems to be fixed • LHC: UPS interventions ongoing UJ76 and RE88. To be finished early evening. Then pre-cycle and sanity check. • LHC: BLM CPU problem point 2 – intervention this morning • LHC: TDIs stuck – to be investigated • SPS: ‘Stable Filter’ not operational till Monday. • SPS: Beam dump errors on energy tracking • SPS: For the moment no protons from the SPS • Ramp up experimental magnets • ATLAS in the evening • If beam back, start with optics corrections through the squeeze. • Access requests (could be done this morning) • Ralph Steinhagen to change BBQ sensitivity LHC 9:00 meeting

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