Reminder on Technical Motivations,Objectives and Plans

E.Carlier, B. Goddard, V. Mertens

Technical Review on UPS power distributionof the LHC beam dumping system (LBDS)

20 June 2012

Outline:• Technical motivation

o LBDS reliability requirementso 2012 incidents

• Planso System modificationso Testing, analysis, reviews

• Review objectives

Energy in ‘ultimate’ 7 TeV LHC beam is > 500 MJ Already running with above 100 MJ Massive damage potential if uncontrolled beam loss LBDS MUST work if beam permit loop opens

Reliability requirement for the whole machine protection systems (including LBDS, BIS, QPS, BLM, PIC, …) is SIL3.Reliability calculation (2006) “unsafety/year” (LBDS alone) of 2.4×10-7 (x 2 for 2 beams), largely SIL 4 (if post-dump checks to rec. “as good as new” state).

LBDS reliability requirements

V.Mertens / LBDS UPS power distribution review, introduction / 20.6.2012

Severe damage to SPS TT40 magnet vacuum chamber following uncontrolled loss of 2 MJ 450 GeV p+ beam.

Powering failures/weaknesses observed in 2012 which were not expected from previous analyses:

Type 1: Faults of crate power supplies, propagating through the electrical distribution and switching off groups of subsystems (consequence in case of beam would be asynchronous dump).

Type 2: Finding (on test bed) that stable short circuit of +12 V triggering and synchronisation crate would prevent ANY trigger from propagating to the dump kickers (= NO dump, consequence in case of beam almost certainly severe machine damage).

2012 incidents

V.Mertens / LBDS UPS power distribution review, introduction / 20.6.2012

Testing: • Powering failure mode scenarios (UPS & mains) to be fully tested at the end of LS1

(has not been possible in 2006).Analyses: • Impact of powering failures to be reevaluated within reliability analysis of the LBDS.Reviews: • UPS powering: today • Overall LBDS system: end 2012 • Triggering and BIS link (date ?)• Overall LHC MP, requested by LMC (date ?)

Plans for system modifications

V.Mertens / LBDS UPS power distribution review, introduction / 20.6.2012

Plans for further testing, analyses, reviews

Powering system modifications, against type 1 issues:• Short term: fixes already in place (described later)• LS1: all crates connected to completely indep. electrical feed for full redundancy• All WIENER crates to be replaced by crates with internal protection (BE-CO)

TSDS powering modifications, against type 2 issues:• Short term: surveillance of 12 V + connection to retriggering system (consol. in TS2)• LS1: separation of the two TSU into independent VME crates

No major system changes (in powering and triggering) foreseen beyond LS1

Provide focus for LBDS team to investigate powering aspects of system

Get input from other system experts, who will have different experience and viewpoints

Foster cross-system technical knowledge sharing

Validate proposed LS1 technical changes

Answer specific questions:

Is the system analysis sufficient ?

Are the HW testing and validation sufficient ?

Is the present system design (with modifications) solid ?

Are there still any potential issues or risk items ?

Are the underlying assumptions well-founded ?

Are the documentation and change procedures adequate ?

Review objectives

V.Mertens / LBDS UPS power distribution review, introduction / 20.6.2012