The meeting took place on Friday, November 7^th^, 2025, 10.00h-11.00h, in 874/R-018 and on Zoom.

Participants: A. Butterworth, A. Colinet, C. Lannoy, K. Li, B. Mikulec, L. Nevay, I. Ramirez, R. Secondo, J. Uythoven, C. Wiesner, D. Wollmann, C. Zamantzas.

The slides of all presentations can be found on the website of the Machine Protection Panel and on Indico.

Minutes and actions

D. Wollmann welcomed the participants and reviewed the actions from the 262^nd^ and 263^rd^ MPP meetings.

C. Zamantzas reported that the proposal to add extra BLMs in the north area after the T2-TBIU incident on 16.07.2025 is blocked because installation still requires manual cable disconnection, which would expose personnel to radiation. Although three additional detectors are planned for LS3, only fully robotic intervention is permitted, making the current approach unsuitable. The issue remains open and is being followed by WP2.

ACTION (C. Zamantzas / Integration): Continue working on North Area BLM detector installation solution (cable connection without human intervention).

C. Zamantzas indicated that the API change for the BLM threshold GUI is now scheduled during the YETS, after the ion run, following discussions with B. Salvachua.

Proposal for the connection of the SPS extraction sextupoles and bumpers to the BIS post-LS3 (A. Colinet)

Summary:

• New Beam Interlock System (BIS) to be installed in LS3 to protect North Area.

• Engineering Change Request (ECR) and Engineering Specification of the North Area BIS documents available on EDMS. You are welcome to review these documents and provide feedback.

• Multiple MPP presentations planned to get expert feedback on key protection points.

• Today's presentation focuses on SPS extraction sextupoles and bumpers, which are located in the SPS ring with Power Converter (PC) in BA1, 2, 4, 5, 6.

Extraction Sextupoles:

• Used to put beam in resonance in SPS for slow extraction.

Extraction Bumpers:

• BA4 and BA6: Send beam to LHC, AWAKE, and HiRadMat.

• BA2: Extract beam to North Area.

Current Implementation (Pre-LS3):

• Interlocks exist for extraction to TT40 and TT60.

• LSS4/6 extraction bumpers are controlled by MUGEF, which provides the FEI to the SPS extraction BICs. They perform a current evaluation at flat top, and these interlocks can be masked when the intensity is below 5×10¹¹ p.

• BIS does not trigger SPS beam dump but only inhibit extraction kicker.

• Beam dumped at end of flat top or potentially on beam losses if the resulting orbit shift triggers the BLMs in the SPS.

• Extraction elements for slow extraction have SIS interlocks. Maskable at any beam intensity (acceptable from operational perspective).

• Masked interlocks (in SIS and BIS) reported to the SPS logbook at end of every shift.

Post-LS3 Requirements:

• All extraction sextupoles and all BA2, BA4 bumpers must be interlocked for North Area cycles.

• All PCs will be equipped with renovated FGC3 controls (replacing MUGEF).

• New FGC3 feature to be developed by EPC: Multiple thresholds throughout cycle.

• Certain selected PCs will also have renovated power parts (Polaris).

• Operational aspects:

  • Elements are part of SPS ring beamline, they see beam in any cycle.

  • Must verify PC regulation in all cycles regardless of destination.

  • However, we should have the ability to mask interlocks to resume operation to unaffected areas.

  • Example: Issue with one extraction sextupole shouldn't stop all SPS operation (LHC, Awake, unaffected areas should continue).

Proposed LS3 Implementation:

• For LSS4 and LSS6 Extraction Interlocks (to LHC/AWAKE/HiRadMat): Keep extraction bumpers connected to SPS extraction BICs (as today, evaluation at flat top, maskable when intensity < 5×10¹¹p).

• In addition, it is proposed to interlock all elements (bumpers and sextupoles) with the SPS ring BIS. They would be connected to the BIS through dedicated concentrator User Interface boards (CIBFX) and would be maskable. The Setup Beam Flag governing maskability in the SPS is permanently set to true, meaning these interlocks can be masked independently of the beam intensity.

Pros of proposal:

• Higher protection level than today (elements monitored in all cycles).

• Earlier beam dump capability resulting in less energy deposited on the SBDS (act on SPS beam dump, not just inhibit extraction kicker).

• More logical than initial proposal to connect all elements to North Area BIS (would require extensive fiber runs around ring to BA2).

Limitations:

• Loss of SPS availability if one element faults. Mitigation: Keep maskability option.

• Maskability regardless of intensity (reduced safety). Mitigation: Software check to prevent playing North Area cycle if any North Area interlocks are masked.

Discussions:

J. Uythoven noted that the combination of operator checks, which involve masking unused elements, together with software checks that block North Area extraction if an interlock is masked, works well. However, he highlighted a weak point: a pressured operator could both mask interlocks and adjust the SIS. To prevent this, he proposes introducing role-based access controls so that the same operator cannot perform both actions.

D. Wollmann remarked that this approach breaks the traditional assumption that nothing safety-relevant should reside in the SIS.

Decision:

The Machine Protection Panel agreed that the proposal represents a good compromise between safety and operational flexibility and is better than the current situation, where no protection is in place.

ACTION (K. Li): Implement role-based access for masking in the SIS, requiring approval from a second person and preventing a single operator from masking interlocks and adjusting the SIS.

ACTION (K. Li, EPC, OP, ABT): Define the strategy for cycles without function settings, choosing between a non-ppm (global) threshold or a per-user threshold approach.

ACTION (All): Read the Engineering Specification of the North Area BIS document and give feedback before beginning of December 2025.

With no AOB, Daniel thanked all participants and closed the meeting.