LSS4 bumpers + Extraction sextupoles - follow-up 2

Friday 18 Jul 2025, 11:00 → 12:00 Europe/Zurich

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A. Colinet, R. Murillo Garcia, D. Nisbet, J. Ridewood, I. Romera Ramirez, F. Maria Velotti

PC renovation in LS3

Certain PCs will be fully renovated (power part + FGC3). Others will only have renovated controls (FGC3).

In the draft ECR, only around half of the bumpers will be renovated (the horizontal ones, and not the vertical).

Extraction sextupoles

Ok to have no LSA settings for non-SX cycles.

Ok to have a fixed non-PPM tolerance for these PCs as they don't need sub-percent regulation.

Only 4 extraction sextupoles are used for operation: LSE.10602, LSE.22402, LSE.40602, LSE.52402. The others are only used for specific MDs, and are not planned to be used in the near future. Only the operational ones will be connected to the BIS, and the spares will be routed to the racks hosting the concentrators, but left disconnected.

Conclusion:

These devices will all have a fixed non-PPM tolerance, and will be interlocked all the time. That means that they can be connected to the SPS ring BIS.
All sextupoles cables will be pulled in LS3. Only the operational ones will be connected to the concentrators. The spare ones will be commissionned but left disconnected while unused.
Action Francesco: Confirm regulation tolerance requirements for the extraction sextupoles with absolute values in Amps.

Extraction bumpers

These devices require a much finer regulation in the order of 0.1%-0.2% (i.e. 1000ppm - 2000ppm). Action Francesco: Confirm the requirements for the LSS2/4/6 bumpers with absolute values in Amps.

Not following the function will certainly lead to high losses + can very quickly become hazardous to the machine.

As they are ramping with the beam, i.e. reasonably slowly, David thinks that the PCs should be able to follow the programmed functions during ramp up within the requested tolerance. This should at least be the case with the latest PCs (Polaris), planned to be installed in LS3. Not all extraction bumpers will be renovated though.

Action David + Raul: Confirm the point above once the tolerances are available from Francesco.

PPM thresholds

Note: when using a PPM threshold without LSA settings, there is no regulation evaluation for this user, and in this case the User Permit is True.

There are really only two options for the settings:

either a single non-PPM threshold
or PPM thresholds with the requirement to have settings for all users.

Windowed tolerance

Following circulation of EDMS 3253361, EPC (Ivan) will give feedback next week to see if windowed tolerances are indeed required based on the performance of the new PCs.

There are minutes attached to this event. Show them.

- 11:00 → 11:20
  
  LSS4 bumpers + Extraction sextupoles - follow-up 2 20m
  
  Questions:
  - Required maximum regulation errors for all extraction sextupoles, LSS2 bumpers and LSS4 bumpers at flat top?
  - What is the regulation error for these elements during ramp?
  - Kevin’s question: If we have windowed tolerances along the cycle and the PC regulates at the last known value, could it also take the last known tolerance if a user is not defined?
  - Interlocks to Ring BIS, or not to Ring BIS?
  
  Speaker: Antoine Colinet (CERN)
  
  NA_HI_LSS4_bumpers.pdf
  
  NA_HI_LSS4_bumpers.pptx

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