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CERN , the LHC collider and studies on its dependability. R.Schmidt (CERN und TU Darmstadt) Seminarvortrag Universität Stuttgart, 16 Oktober 2012. What is CERN ? What are the principles of accelerators ? What is the L arge H adron C ollider (LHC) ?

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CERN, the LHC collider and studies on its dependability

R.Schmidt (CERN und TU Darmstadt)

Seminarvortrag Universität Stuttgart, 16 Oktober 2012


What is CERN ?

What are the principles of accelerators ?

What is the Large Hadron Collider (LHC) ?

What risks at CERN … and for the LHC ?


CERN Mission: Research, technology, collaboration, education

  • The motivation for CERN is basic research: Seeking and finding answers to questions about the Universe
  • To perform this research needs innovation in technology (such as the WWW): Advancing the frontiers of technology
  • Collaborating: Bringing nations together through science
  • Education: Training the scientists of tomorrow
a global endeavour
A global endeavour

20 Member States


Fundedbythe12 European States

…most of the EU…

8 Observer States and Organisations

…Japan, Russia, USA…

580 Institutes World Wide

2500 Staff

10000 Visiting Scientists

35 Non-Member States

…Australia, Canada, New Zealand…

ConseilEuropéenpour la RechercheNucléaire

EuropeanCentrefor NuclearResearch

understanding our universe many thousand scientists are fascinated about research at cern
Understanding our universemany thousand scientists are fascinated about research at CERN


  • The Universe is governed byforcesand is made out ofelementary particles
  • Understand the forcesgoverning nature: Gravitation, Electro-Magnetic forces, Forces in the nucleus (Strong Force holding the nucleus together, and Weak Force related to radioactivity)
  • The basic constituents of matter are elementary particles (electrons, protons, neutrons, photons, …)
  • Understand the Origin of Mass:finding the HIGGS particle

Particle Physics: these questions are related to elementary particles physics. We need some clues! The LHC started to provide it….

cern infrastructure accelerators and experiments
CERN infrastructure: Accelerators and experiments


  • CERN provides the world’s largest and most complex scientific instruments to study the elementary particles
  • These instruments are particle accelerators and experiments
  • Accelerators boost beams of elementary particles to high energies before they are made to collide with each other
  • Experimentsobserve and record the results of these collisions

Our flag-ship project is theLargeHadronCollider…


CERN Accelerator Complex

Lake Geneva



CERN LAB 2 (France)

CERN LAB 1 (Switzerland)


CERN Accelerator Complex

Large Hadron Collider

(LHC, 2008)

27km long

150m underground

Lake Geneva



Super Proton Synchrotron

(SPS, 1976)

Proton Synchrotron

(PS, 1959)


CERN Accelerator Complex

Four LHC experiments: huge detectors were constructed by thousands of scientists in international collaboration





a different kind of particle accelerator
Protons are accelerated by radio waves to an energy of 7 TeV while kept on a circle with strong magnetic fields from superconducting magnets operating at 8.3 TA different kind of particle accelerator…

The protons make 7 Million turns, and are accelerated with one Million Volt per turn to the speed of light (300000 km/second)

the lhc a 50 years long adventure
The LHC: A 50 Years long Adventure
  • 1984: Kick off meeting to discuss ideas for an accelerator to collide protons at very high energy
  • 1996: Final decision for the LHC, the most complex scientific instrument ever constructed
  • 10 September 2008: Start of commissioning with beam
  • 19 September 2008: Serious accident and damage
  • 19 November 2009: Restart of beam operation

Since 2009: successful operation, providing billions of particle collisions for the LHC experiments


  • About 2030: The LHC physics programme to be finished ? Upgrade of LHC to higher energy?


Beam dump blocks


The arcs:



Beam dumping system


  • 27 km long
  • 2 beams
  • 11000 turns per second
  • 8 arcs
  • 8 straight sections






the lhc tunnel with dipole magnets
The LHC tunnel with dipole magnets

beam tubes

Looking into the arc

risks for the lhc
Risks for the LHC
  • Not to complete the construction of the accelerator
    • Happened to other projects, the most expensive was the Superconducting Super Collider in Texas / USA with a length of ~80 km
    • Cost increase from 4.4 Billion US$ to 12 Billion US$, US congress stopped the project in 1993 after having invested more the 2 Billion US$
  • Not to be able to operate the accelerator
  • Damage to the accelerator beyond repair due to an accident


risks for particle physics
Risks for particle physics



Future of Particle Physics compromised

energy and risk
Energy and risk
  • Energy stored in any system can cause damage, when the energy is released accidentally
  • For an accelerator, risks are coming from energy stored in the magnets system and in the beams

Energy of a car with 1.4 tons driving at 50 km/h: 135000 Joule

energy stored in the magnet system
Energy stored in the magnet system

Stored energy in the magnet circuits is 9 GJoule

Kinetic Energy of Aircraft Carrier at 50 km/h ≈ 9 GJoule

….can melt 14 tons of copper


Picture source:

Shared as: public domain

energy stored in one beam
Energy stored in one beam

31014protons in each beam

Kinetic Energyof 200 mTrain at 155 km/h ≈ 360 MJoule

Stored energyper beam is360 MJoule

Picture source:

Shared as:


energy stored in one beam1
Energy stored in one beam

360 Million Joule =

10 kg of Swiss Chocolate

360 Million Joule =

90 kg of explosives

..think of you fuel tank


first beam on 10 september 2008

250 journalists

30 television stations

Millions of viewers

“we attempted to do something for the first time, live, with absolutely no guarantee of success”

The idea was to send a right and a left hand beam to the LHC and obtain at least one turn around the accelerator…

Risk: performing an experiment that might not work, in the presence of Millions of spectators

First beam on 10 September 2008LHC start up with beam – 10 September 2008


the incident of 19 september 2008
The incident of 19 September 2008

10000 high current superconducting cable joints – all soldered in situ in the tunnel and one of these connections was defective

One joint ruptured, with 600 MJ stored in the magnets – 70% of this energy was dissipated in the tunnel, electric arcs, vaporizing material, and moving magnets around

the damage
The damage

...and collateral damage

what has been done about it
What has been done about it….

Analysethe accident, to exactly understand the causes

Establish a plan for repair

Improve the systems to prevent that this can happen again

Invite internationalexperts to review risks and proposed improvements

The LHC had worked very well and 99% were still ok – pull yourself together, face the problems and work towards a solution

First priority is to solve the problem, and not too look for the “culprit”….

lhc operation a success
LHC operation…. ….a success

ATLAS Collaboration, Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC


CMS Collaboration,

Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC


but still some way to go
…….but still some way to go

The performance of LHC was substantially increased from 2009 to 2012

The energy stored in one beam is about 145 MJoule, the LHC operates at 4 TeV

The objective operation with beams of 362 MJoule at 7 TeV

To be done after a long shutdown 20113/14

risk of damage from beam
Risk of damage from beam

Beams with the 360 MJ are running through the beam tube with the speed of light

10000 magnets keep the beams in the center of the beam tube

In case of magnet failure, the beams hit the accelerator equipment in a very short time, 1/1000 of a second

This must never happen: Managing risks is relying on the Machine Protection Systems

sps experiment beam damage with 450 gev proton beam
Controlled SPS experiment

81012 protons clear damage

beam size σx/y = 1.1mm/0.6mm

above damage limit for copper

stainless steel no damage

21012 protons

below damage limit for copper

SPS experiment: Beam damage with 450 GeV proton beam

25 cm

6 cm

  • Damage limit ~200 kJoule
  • 0.1 % of the full LHC 7 TeV beams
  • factor of ~10 below the energy in a bunch train injected into LHC


V.Kain et al



Beam dump blocks


Failures in such complex accelerator cannot be avoided

Beam dumping system


They must be detected

The beams shall be extracted into the beam dump blocks

This must happen within less than 1 ms






strategy for machine protection
Strategy for machine protection

Beam Cleaning System

  • Definition of aperture by collimators.

Powering Interlocks

Fast Magnet Current change Monitor

  • Early detection of equipment failures generates dump request, possibly before beam is affected.
  • Active monitoring of the beams detects abnormal beam conditions and generates beam dump requests down to a single machine turn.

Beam Loss Monitors

Other Beam Monitors

In total, many 10 thousand interlock channels than can trigger a beam dump

  • Reliable operation of beam dumping system for dump requests or internal faults, safely extract the beams onto the external dump blocks.

Beam Dumping System

  • Reliable transmission of beam dump requests to beam dumping system. Active signal required for operation, absence of signal is considered as beam dump request and injection inhibit.

Beam Interlock System

  • Passive protection by beam absorbers and collimators for specific failure cases.

Collimator and Beam Absorbers

lhc first accelerator with the potential of damage beyond repair
LHC: first accelerator with the potential of damage beyond repair
  • Dependability: new challenge for accelerator laboratories
  • Requires different approach in engineering, operation and management
  • Safety culture: has been developed over the last, say, 10 years
    • Largely helped by the accident in 2008
  • Excellent experience: no damage, no near miss
  • Continuous effort to safely operate that LHC
  • Availability is acceptable, but we are working on further increasing availability
  • Lessons to be learned for future accelerators to ensure safe operation with high availability (e.g. Accelerator Driven Spallation)
accidental beam losses risks and protection
Accidental beam losses: Risks and protection
  • Protection is required since there is some risk
  • Risk = probability of an accident (in number of accidents per year)consequences(in Euro, downtime, radiation dose to people)
  • Probability of an accidental beam loss
    • What are the failure modes the lead to beam loss into equipment?
    • What is the probability for the most likely failures (there is an practical infinite number of mechanisms to lose the beam)?
  • Consequences of an accidental beam loss
    • Damage to equipment
    • Downtime of the accelerator for repair (spare parts available?)
    • Activation of material, might lead to downtime since access to equipment is delayed
  • The higher the risk, the more protection becomes important
d esign principles for protection systems
Design principles for protection systems
  • Failsafe design
    • detect internal faults
    • possibility for remote testing, for example between two runs
    • if the protection system does not work, better stop operation rather than damage equipment
  • Critical equipment should be redundant (possibly diverse)
  • Critical processes not by software (no operating system)
    • no remote changes of most critical parameters
  • Demonstrate safety / availability / reliability
    • use established methods to analyse critical systems and to predict failure rate
  • Managing interlocks
    • disabling of interlocks is common practice (keep track !)
    • LHC: masking of some interlocks possible for low intensity / low energy beams
iec 61508 safety lifecycle
‘A model for structuring safety management activities throughout the life cycle of safety- related systems’IEC 61508 Safety Lifecycle

Handout​ Principles of System Safety Engineering and Management,

Workshop, CERN 2011​, Redmill Consultancy, London​

Sigrid Wagner

safety case
Safety case
  • The MPS was designed considering a large number of possible failures of LHC equipment
  • The knowledge of these failures and of the machine protection functions implemented to cover these failures is distributed over the different teams involved in the design and operation of the LHC
  • A recent project (Sigrid Wagner and Andrea Apollonio) aims at bringing together this knowledge in a common failure catalogue.
  • The objective is to create a “safety case”
    • documentation ‘ to go to court with’
    • including, claim, argument, evidence
  • Details can be discussed if of interest
hazard and risk analysis and protection requirements
Hazard and Risk Analysis and Protection requirements

Proceeding in lifecycle from hazard chains to definition of protection functions

Sigrid Wagner

comment to lhc machine protection
Comment to LHC Machine Protection
  • Some protection systems were considered early in the project (beam dumping system, magnet protection, beam loss monitors)
  • Consideration for coherent approach on machine protection started in 2000 – done by the team working in interlocks that links all systems
  • Lot of work since then (e.g. 10-20 PhD theses on machine protection)
  • Stated to use “formal methods” since ~2004 (calculation of reliability, availability etc.)
  • Together with design and construction of systems considerations for documentation, commissioning etc.
  • Very important: diagnostics for protection (what stopped the beam?)
some remarks
Some remarks
  • Citation: “Prioritizing risk management too highly could keep an organisation from ever completing a project or even getting started” – particular true for research(Wikipedia, Risk Management)
  • Do not address all possible risks at the same time….
  • Prioritise the risks
  • Address the most urgent risk now
  • Accept some risks – there will be problems for a complex one-off machine… sometime completely unforeseen
  • Risk management at CERN is novel for such institutes: we learned during construction and operation, and continue learning
  • Our approach is unconventional and less formal compared to other domains, others (institutes and industry) are interested in our new ideas
some phd theses on dependability
S.Wagner, LHC MachineProtection System: MethodforBalancingMachineSafetyand Beam Availability, CERN-THESIS-2010-215 , ETH Zurich, 2010

A.Vergara-Fernández, A ReliabilityoftheQuenchProtection System forthe LHC Superconducting Elements, CERN-THESIS-2004-019

G.Guaglio, Reliabilityofthe Beam Loss Monitors System forthe Large Hadron Collider at CERN, CERN-THESIS-2006-012, Clermont-Ferrand

R. Filippini, Dependabilityanalysisof a safetycriticalsystem : the LHC beam dumpingsystemat CERN, CERN-THESIS-2006-054, Pisa U.,

F.Perisse et al., Reliabilitydeterminationofaluminiumelectrolyticcapacitors by themeanofvariousmethods, 2004 - Published in: Microelectron. Reliab. 44 (2004) 1757-1762 (shortversionoftheses)

M.Rampl, Study for a failsafetriggergenerationsystemforthe LHC beam dumpkickermagnets, CERN-THESIS-99-056, 1999

B. Todd, A Beam Interlock System for CERN High Energy Accelerators,CERN-THESIS-2007-019 - West London: Brunel U.

Some PhD theses on dependability
selection of o ther publications
S. Wagner et al., A Failure Catalogue for the LHC, 2nd International Particle Accelerator Conference, San Sebastian, Spain, Sep 2011

R.Filippini et al., Reliability Assessment ofthe LHC MachineProtection System, LHC-Project-Report-812; CERN, 14 Jun 2005

E.Carlier et al., Reliability Analysis ofthe LHC Beam Dumping System, CERN-LHC-Project-Report-811, CERN, 14 Jun 2005

J.H.Dieperink et al. Design aspectsrelatedtothereliabilityofthe LHC beam dumpkickersystem, PAC 1997, Vancouver

C.Garion et al., Reliabilityorientedoptimum design ofthe Large Hadron Collider magnet-to-magnet interconnections, CERN-LHC-Project-Report-631, CERN, 3 Apr 2003

C.Garion, B.Skoczen, Reliabilityorientedoptimum design ofthe LHC interconnections - Part I: Mechanicalcompensationsystem LHC, PROJECT-NOTE-245 (2000)

L.Scibile, P.Ninin, S.Grau, FunctionalSafety, A total qualityapproach, CERN-ST-2001-055 (2001)

W.Hees, R.Trant, Evaluation ofElectroPneumaticValvePositionersfor LHC Cryogenics, LHC-PROJECT-NOTE-190 (1999)

comment on cern
Comment on CERN

Is CERN a playground for thousands of (particle) physicists all hoping to discover the secrets of the universe and getting the Nobel Prize?

  • Indeed, these are the visitor (incl. students and post docs) from many hundred universities around the globe

Is CERN the laboratory for thousand engineers (incl. a few applied physicists) from many different fields to design, construct and operate the most complex scientific instruments ever conceived (particle accelerators and detectors)?

  • Indeed, the engineers are the CERN staff members, working together well students (e.g. about 140 PhD students), post docs and other external collaborators, mostly from the CERN member states
the end
…the end

Thank you for your attention