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    LS3 IVO meeting

    → Europe/Zurich
    30/2-005 (CERN)

    30/2-005

    CERN

    15
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    1. Meeting organisation

    The proposed format for future IVO LS3 meetings was agreed:

    • Review the planning covering approximately the previous two weeks and next four weeks, completed and upcoming activities by machine. Identify resource conflicts, missing activities and technical problems.
    • Review outstanding workshop/MME activities.
    • Keep meeting minutes to maintain a searchable record of discussions and decisions.
    • The agenda should preferably be circulated about one week in advance. Presentations should remain short and informal.

    2. LHC / insulation vacuum

    Current status

    • Warm-up activities are essentially complete. Global leak testing of the helium circuits is close to completion. Envelope leak testing remains ongoing.

    L8 triplet investigation

    Observations:

    • Helium background is above normal but decreases slowly with time. Changing cryogenic conditions by pumping or pressurising lines has not produced the expected response.
    • The current working hypothesis is a double leak associated with a multiply bellows/interspace: helium circuit → interspace; interspace → isolation vacuum.
    • Helium accumulated during operation could produce a masking effect. The characteristic decay discussed is very slow, approximately 14 days.

    To improve localisation:

    • Additional pumping points are to be installed using available blank-flange locations. The relevant flange is a non-standard size for the usual CERN installation. Adapters are therefore being manufactured urgently rather than waiting for standard components. Once installed, additional measurements should improve spatial localisation of the suspected leak.

    3. SPS

    TI2 Consolidation

    • The SPS consolidation work discussed is almost complete from the vacuum side. Pump replacement has largely been carried out. Some blank flanges still need preparation/cleaning and installation.
    • Delays in the associated jack work are not currently considered critical for vacuum activities because the vacuum work is not on the critical path.

    Workshop activities

    • Approximately five workshop jobs were discussed as open.
    • The chamber orders have now been reviewed, and the situation is considered under control.

     Cleaning and leak detection

    An important procedural point was identified:

    • Cleaning and leak detection must be explicitly requested on workshop jobs.
    • The appropriate job documentation/form records whether cleaning and leak detection are required/performed.

    Leak-test MBS chamber

    The MBS chamber was identified as one of the major upcoming workshop activities.

    The chamber needs to be leak-tested before final assembly/welding. The chamber discussed is approximately:

    • 4 m long, fabricated from approximately 10 mm stainless steel and temporarily closed using top and bottom plates during leak testing.

    Several sealing methods were considered:

    • mastic
    • aluminium tape combined with mastic;
    • Viton sheet

    A key concern is the substantial atmospheric load generated during evacuation. The discussion estimated a load on the order of 20 tonnes over the relevant area.

    The existing plates came from the original tooling, which provides some confidence that the approach is mechanically viable. Nevertheless, chamber movement and plate alignment need attention.

    4. PS / PSB activities

    PS SMH57 removal

    The SMH57 intervention was completed, but significant difficulties were encountered. The area was significantly hotter radiologically than expected.

    Upcoming PS work

    Activities discussed for the following period include:

    • replacement of clamps on KFA 71 and 79;
    • possible replacement of ion pumps depending on radiation levels;
    • leak detection around the BTP/septum zone;

    5. BTY

    • Most vacuum equipment required for the ongoing work has been removed or disconnected.
    • Civil engineering work, including concrete cutting, has started.
    • Remaining chambers/equipment have been protected against dust.
    • Existing chambers have been retained temporarily as contingency spares in case a problem occurs with new components.

    Concern was raised regarding the schedule for the new chambers.

    The working target discussed was to have the chambers available by summer 2027.

    This would allow:

    • installation during Q3 2027;
    • some contingency into Q4 if difficulties occur.

    However, Q4 2027 should be considered the point at which systems need to start being closed, so further delay would become critical.

    7. PSB

    Quad consolidation

    The refurbishment campaign should begin with the more difficult components:

    1. split chambers;
    2. high-radiation areas;
    3. remaining units according to condition/priority.

    Starting with the difficult cases provides time to develop and validate the working method.

    Other tasks

    A relatively recent pump in the PSB suffered an unexpected electrical short circuit.

    • Electrical checks indicate that the fault is in the pump itself rather than the feedthrough. No obvious internal debris was visible. The pump has been removed and brought to the lab for further investigation.

     

    The bellows compression tooling is operational, although its operation is not considered particularly smooth/simple;

    Two of six new Inconel chambers had been bagged, leak-tested and cycled 20 times without evidence of a leak.

    8. New pipe-cutting tool

    A new workshop pipe cutter was presented.

    Characteristics discussed:

    • applicable diameter range approximately 35–254 mm;
    • uses a mechanical guide to maintain circularity during cutting;
    • ratchet mechanism means complete access around the pipe is not necessary;
    • produces no significant swarf/dust compared with conventional cutting;
    • the resulting pipe can potentially be reused and welded again;
    • approximately 80 mm clearance appears necessary for the guide.

    Potential advantage:

    • particularly interesting for interventions where contamination or swarf should be minimised;
    • useful where an existing chamber should subsequently be rewelded.

    9. Unexplained valve failures at ELENA

    Repeated leakage has occurred at particular vertical installations despite:

    • low cycle counts;
    • apparently normal mechanical configuration;
    • attempts to modify valve orientation;
    • replacement with a smaller valve.

    The cause remains unclear because similar valves in comparable orientations elsewhere do not exhibit the same behaviour.

    Further investigation during the shutdown was considered necessary.

    Refurbishment strategy

    Three possibilities were discussed:

    1. Send valves to VAT for refurbishment.
    2. Buy refurbishment kits and perform maintenance internally.
    3. Replace valves where refurbishment is not economically justified.

    Past external refurbishment had created logistical difficulties, particularly for radioactive components.

    Internal refurbishment could also provide useful workshop/lab work when machine access is unavailable.

    However, the economics need to be established first.

    10. FSU Resources

    • The current FSU support is considered useful and they were reported to be learning quickly.
    • In the meantime, the objective is to give them useful work and develop their experience.
    • Prepare a list of jobs to organise activities between cPS and SPS

    11. Next meeting / presentations

    Possible subjects proposed for upcoming meetings:

    Next meeting

    • cavity study;
    • septum module.

    Following meeting

    • AD cooler activities;

    The intention is to keep presentations short and practical rather than seminar-style.

    Action list

    • LHC ITL8: Complete adapters/additional pumping connections and continue localisation of the triplet helium leak.
    • Leak detection: Share access/information for the leak-detector logging application.
    • PS: Proceed with KFA clamp work and intended leak-detection activities
    • BTY: Continue follow-up of drawings, orders and new-chamber manufacturing schedule.
    • Workshop jobs: Explicitly specify cleaning and leak detection on future chamber requests.
    • MBS: Finalise the temporary sealing method for the first chamber leak test and evaluate a reusable solution for the series.
    • Bellows: Develop/produce suitable supports or protections for bellows during evacuation/leak testing.
    • Lab: Investigate the cause of the short-circuited pump.
    • Pipe cutter: Identify standard chamber diameters, manufacture appropriate guides and organise trials.
    • VAT valves: Inventory candidate valves and obtain a quotation for 10 refurbishment kits before deciding between internal and external refurbishment.

     

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