LHC BLM threshold modification reports

Information on the external LHC BLM audit


  • Critical System first summary presentation [ppt]
  • Critical System final summary [pdf]
  • MPP talk summary and comments to the review [pptx]

On-site visit presentasions and plan:

  • Indico page: [url]



Critical Systems Labs, Inc.
#618 - 475 Howe Street Vancouver,
B.C. Canada V6C 2B3  

Scope of the audit:

CERN internal reviews have been performed in the past and these reviews focused primarily on the analogue parts of the system design. Therefore CSL review will focus more on the digital parts and more particularly on the programmable parts of this system. The essential and foremost question that will drive CSL technical review is:
Are the digital and programmable parts of the BLM system going to perform as they are intended to in the context of the BLM system?

     This review will seek to:

  • assess the adequacy of the overall BLM system design with a focus on the programmable parts
  • identify possible weaknesses in the programmable parts of the mission-critical BLM
  • suggest activities that could increase the level of confidence that the programmable parts of BLM system performs as intended
  • suggest potential improvements of the BLM
  • provide a general comparison of the BLM with approaches in industrial systems.

      The scope of this review is also limited to a consideration of:

  • Potential sources of unsafety within the BLM, where the detection of an amount of particle losses that has the potential to quench the magnet is not relayed to the Beam Interlock System, resulting in a ‘missed generation of beam dump trigger’ and potentially machine damage.
  • Potential sources of unavailability, where failure of the BLM leads to a request to the Beam Interlock System to dump the beam, resulting in a ‘false dump trigger’ and some machine downtime.


The following table shows a tentative schedule for this review. 




16th August 2010


Delivery of project documentation

6th September 2010


Finalization of site-visit agenda

13th to 16th September 2010


On-Site visit - 4 full days

18th October 2010


Delivery of written report


Official Documents:

  • Motivation from BI/BL for the Review (pdf)

  • Proposal from CSL for the Review (pdf)


Project Code:


All source code to build the binary firmware for all FPGAs employed can be found in the BI-BL SubVersion repository (SVN).

(for CERN authenticated users: https://svnweb.cern.ch/cern/wsvn/bi-bl/)


TAR blobs of the latest production commits are added here for easiness:




BLM system introduction:

  • Beam Loss Monitor Specification (EDMS)

  • B.Dehning, Beam Loss Monitor System for Machine Protection, DIPAC05 (paper)

  • B.Dehning et al, First Experience with the LHC BLM system, PAC09 (paper)


  • Ionization chamber, energy deposition simulation:

    • M. Stockner, Beam Loss Calibration Studies for High Energy Proton Accelerators, PhD Thesis (10.2007),  (pdf)

    • M. Hodgson, Ionisation chamber design studies thesis, Master Thesis, [pdf]

  • Secondary Emission Monitor:

    • D.Kramer et al, Very High Radiation Detector for the LHC BLM System Based on Secondary Electron Emission, IEEE NSS 2007, (presentation, paper)

  • Ionization chamber and secondary emission monitor testing

    • E. B. Holzer et al, Development, production and testing of 4500 beam loss monitors, CERN-AB-2008-054, (paper)

Front-end electronics:

  • W. Friesenbichler, CFC, Diploma thesis [pdf.gz] (5.2002)
  • E. Effinger et al, Single Gain Radiation Tolerant LHC Beam Loss Acquisition Card, DIPAC, (poster (pdf, odp), paper)
  • E. Effinger et al, The LHC beam loss monitoring system’s data acquisition card, LECC,  (talk, paper)
  • J. Emery et al, Functional and Linearity Test System for the LHC Beam Loss Monitoring Data Acquisition Card, LECC, (poster, paper)

Back-end electronics:

  • C. Zamantzas, The Real-Time Data Analysis and Decision System for Particle Flux Detection in the LHC Accelerator at CERN., Brunel University, CERN-THESIS-2006-037. (pdf)

  • C. Zamantzas et al, An FPGA Based Implementation for Real-Time Processing of the LHC Beam Loss Monitoring System’s Data, IEEE NSS 2006 (poster, paper)

  • C. Zamantzas et al, The LHC Beam Loss Monitoring System's Surface Building Installation, LECC 2006, (paper)

  • C. Zamantzas et al, The LHC Beam Loss Monitoring System's Data Contribution to other Systems, IEEE NSS 2007, (presentation, paper)

Combiner and interfaces to machine protection and energy receiver, connectivity check (or HV modulation) and sanity checks:

  • J. Emery slides, (presentation), Combiner and Survey Card (schematics)

  • J. Emery et al, LHC BLM single channel connectivity test using the standard installation, DIPAC, (poster, paper)

  • J. Emery et al, First experiences with the LHC BLM sanity checks, TWEPP, (poster, paper)


  • M. Sapinski, (pdf, doc), Database specification

Software tools:

  • C. Zamantzas et al, The LHC Beam Loss Monitoring System's Data Contribution to other Systems, IEEE NSS 2007, (presentation, paper)

  • C. Zamantzas et al, Configuration and Validation of the LHC Beam Loss Monitoring System, DIPAC 2009 (paper)

Reliability and availability of the system:

  • G. Guaglio, BLMS Dependability, PhD Thesis, (Presentation.ppt, Thesis.pdf)

  • G. Guaglio, Reliability study of the BLM system, AB seminar, (pdf), (4.2006)

Test and start-up procedures:

MPS and Settings:

  • MPS aspects of the BLM system (edms)

  • Management of the BLM settings (edms)

  • ECR (engineering change request) (example)




Machine name




Beam loss monitoring system



Secondary emission monitor



Ionization chamber



Current to frequency converter (includes an FPGA), front end electronics, tunnel and alcoves

Threshold comparator


Data processing and Threshold comparison  (includes an FPGA), backend electronics, surface buildings



Combiner and survey card (includes an FPGA), backend electronics, surface buildings




Test unit for the BLECF cards (includes an FPGA)

Vertical Slice BLEVS Test unit for the BLM system



Manufacturing and Test Folders travellers database



LHC Software Architecture database

Layout DB


LHC Layout database

Meas DB


Measurement database

Logging DB 






CISV   Safe LHC Parameters receiver board (including the beam energy)
BIS   Beam Interlock System
BIC   Beam Interlock Controller
CIBUS   Controls Interlocks Beam User Single (Both beams with one input)



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