Workshop on Machine Protection, focusing on Linear Accelerator complexes : 6th - 8th June, 2012

6 Jun 2012, 08:00 → 8 Jun 2012, 18:30 Europe/Zurich

30/7-018 - Kjell Johnsen Auditorium (CERN)

Daniel Schulte (CERN), Hermann Schmickler (CERN), Marc Ross (Fermilab), Michael Jonker (CERN), Rudiger Schmidt (CERN), Steinar Stapnes (CERN)

The objective of the workshop is to bring together experts working on machine protection systems for accelerator facilities with high brilliance or large stored beam energies, with the main focus on linear accelerators and their injectors. The workshop should establish a coherent view of failure modes and consequences for linear accelerators and review the current state of the art in machine protection systems. The participants will benefit from the experience of colleagues who have designed, commissioned and operated such systems. The workshop will provide input to the design of machine protection systems at future accelerators, in particular for CLIC and ILC. It also should promote synergies in the development of protection systems at different accelerators.

Linac'12 Paper THPB091.pdf

Linac'12 Poster THPB091_poster.pdf

Wednesday 6 June

Introduction; Machine protection, experience and challenges: Review of existing solutions and challenges faced by future installations

Convener: Mr Rudiger Schmidt (CERN)

1 Welcome

Speaker: Steinar Stapnes (CERN)

Slides MPWS2012_WS_intro.pptx

2 Purpose of machine protection, risks, challenges, issues and objectives

Speaker: Michael Jonker (CERN)

Slides MPWS2012_introduction.pptx

3 Experience from MP in LHC

The LHC machine protection system (MPS) has been constantly evolving over the past decade, to assure safe machine operation whilst avoiding additional downtime due to the required complex architecture of protection and interlock systems. An overview of the present machine protection architecture will be presented, along with experience in operating the MPS systems throughout the various commissioning phases and early years of beam operation. Encountered and outstanding issues for LHC machine protection and potential lessons for CLIC will be highlighted.

Speaker: Dr Markus Zerlauth (CERN)

Slides CLIC-LHC-MPS.pdf CLIC-LHC-MPS.pptx

4 Experience from MP in Flash, lessons for XFEL

This presentation gives an overview of the Machine Protection System (MPS) for the Free electron LASer at Hamburg FLASH. It describes MPS components and functionality, development over the years. FLASH started as a test facility, had been extended and is now operated as a user facility. Similarities and differences of the MPS for FLASH and XFEL will be presented as well as operation experiences at FLASH. Especially the high current test runs for ILC revealed a few disadvantages in the design and gave lessons for XFEL MPS.

Speaker: Martin Staack

Slides M.Staack_XFEL_MPS_CERN.pdf

10:30 Coffee Break

5 Machine protection at the Jefferson Lab 1MW CEBAF electron accelerator

Jefferson Lab accelerators include the 1MW CEBAF electron machine as well as the high intensity Free Electron Laser. Borrowing risk management practices from the military, aerospace and chemical processing industries, Jefferson Lab manages a graded approach to identify and manage risk presented by beam operations. Constraints are then incorporated in to system level requirements across multiple subsystems. This talk will describe the engineering transition of the Jefferson Lab CEBAF and FEL accelerator machine protection systems to a risk based systems engineering approach. The approach addresses the traditional goals of maximum machine availability, minimal short and long term damage, and configurability. In addition, a systems engineering approach also addresses enabling and supporting processes like project management, controls infrastructure, personnel competency, and long term system effectiveness. We will conclude with a brief look at ongoing work to integrate the systems, software, and cyber security assurance practices.

Speaker: Mr Kelly Mahoney (TJNAF)

Slides CERN_MPS__K.Mahoney.pdf CERN_MPS__K.Mahoney.pptx

6 Machine protection plans in ESS

The European Spallation Source (ESS) aims to be the brightest source of neutrons in the world for scientific research. Located in Lund, Sweden, it is currently in the pre-construction phase with a plan to deliver first neutrons in 2019. The baseline specification is for a 5 MW proton power, long pulse facility delivering neutrons to 22 independent instruments that will foster major advances from aging and health, materials technology for sustainable and renewable energy, to experiments in quantum physics, biomaterials and nano-science. High beam power, which can severely damage accelerator or target components as well as the beam pipe itself, demands fast and reliable Machine Protection System (MPS). The goal of the MPS is to improve the operation safety by reducing the risk of damage to the components of the machine. Hundreds of diagnostic devices will monitor the machine and the beam health and in case of excessive beam loss or other critical malfunction the beam will be shut down. Only few microseconds are available for MPS to trigger mitigation, therefore very fast interlock system needs to be designed. MPS will provide time-stamping and logging of all input changes. All logs will be synchronized and will serve as a vital input to post-mortem analysis. Support for commissioning and different machine modes will be embedded. Important part of the MPS will be a Beam Permit System (BPS) with a task to check that the facility is configured and secured appropriately, and that all relevant equipment is operating and within the desired setpoint ranges for the operator-selected mode.

Speaker: Gregor Čuk (CosyLab)

Slides Cuk-MPS_plans_in_ESS.pdf Cuk-MPS_plans_in_ESS.pptx

7 Machine protection challenges in ILC,

The ILC Machine Protection System (MPS) is that collection of devices intended to keep the beam from damaging machine components. With nominal average beam power of 20 MW, consisting of 14000 bunches of 2e10 ppb each per second, and typical beam sizes near 10 x 1 micron, both the damage caused by a single bunch and the residual radiation or heating caused by small (fractional) losses of a many bunches are important for MPS. The MPS consists of 1) a single bunch damage mitigation system, 2) an average beam loss limiting system, 3) a series of abort kickers and dumps, 4) a restart ramp sequence, 5) a beam permit system, 6) a fault analysis recorder system, 7) a strategy for limiting the rate with which magnetic fields (and insertable device positions) can change, 8) a sequencing system that provides for the appropriate level of protection depending on machine mode or state, and 9) a protection collimator system. The systems listed must be tightly integrated in order to minimize time lost to aberrant beams and associated faults

Speaker: Marc Ross (Fermilab)

Slides MPS_mcr_20120606.pdf MPS_mcr_20120606.pptx

8 Machine protection challenges in CLIC

The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy of 48 high intensity, low energy drive beam trains is extracted and transferred to 2 low intensity, high energy main beams. A single drive beam-train has a damage potential that is two orders of magnitude above the level causing structural damage in copper. The extreme charge density due to the microscopic beam size gives the main beam already at low energies a damage potential four orders of magnitude above the safe level. The machine protection system in CLIC has to cope with a wide variety of failures, from real time failures (RF breakdowns, kickers misfiring), to equipment failures, to beam instabilities (caused by e.g. temperature drifts, slow ground motions). This presentation introduced the baseline for the CLIC machine protection philosophy based on passive, active and permit based protection.

Speaker: Michael Jonker (CERN)

Slides MPWS2012_CLIC.pptx

12:50 Lunch Break

Beam loss mechanisms

Experience of existing and previsions for future accelerator complexes, addressing three types of beam losses and their potential impacts:
- Operational beam losses: quasi continuous losses (e.g. beam gas induced) that form the loss background that has a major impact on the radiation environment in the accelerator.
- Equipment failure induced beam losses, which – if ill controlled – may lead to major damage of the accelerator structures.
- Transient beam losses, or beam losses related to changing environment (temperature drift, ground motion, ufo, others).

Convener: Daniel Schulte (CERN)

9 Status of the ASTA Facility Machine Protection System at Fermilab

Speaker: Arden Warner (Fermilab)

Slides ASTA_Overview.pdf ASTA_Overview.ppt

10 Beam loss mechanisms in Flash/Desy

The Free Electron Laser in Hamburg (FLASH) is based on a linac with superconducting RF technology. The linac is designed to produce high power electron beams. Loss of only a fraction of the beam can damage the machine. Machine Protection System of FLASH controls modes of operation and prevents dangerous conditions. The Dark Current of the FLASH gun is the largest source of lost particles. Operational issues related to the FLASH gun dark current and dynamics of cavity beam loading will be presented.

Speaker: Alexander Kaukher (DESY)

Slides MPS_Workshop_A.Kaukher.pdf

11 Halo formation and losses in CLIC

The talk will shortly review our knowledge of halo production by standard processes and in particular beam-gas scattering. Analytic estimates and simulation tools (PLACET+HTGEN) exist and have been used to predict the halo for the drive beam, LINAC and beam delivery systems of CLIC. This allows to show that halo and losses from halo should be rather low in CLIC under design conditions and provides insight in which energy range and location in the system are more critical for halo production and losses.

Speaker: Dr Helmut Burkhardt (CERN)

Slides CLIC_Losses_2012_06_06.pdf

12 Beam loss experience from CTF3

CTF3 tests the drive beam generation for CLIC, as well as the two-beam acceleration. Although the beam power and the damage potential are considerably lower than at CLIC, it can give important insight to considerations for the machine protection at CLIC. The presentation will show the experience at CTF3 for different loss mechanisms and their consequences, as well as the results of a dedicated experiment to measure the effects of RF breakdown induced kicks on the beam, and will give a short description of interlocks to reduce losses.

Speaker: Frank Tecker (CERN)

Slides 2012_MP_workshop-tecker.pdf 2012_MP_workshop-tecker.pptx

16:00 Coffee Break

13 Beam loss mechanisms : observation from the LHC

After 2 years of operation pushing the beam parameters, we gained some experience on the different beam loss mechanisms observed in the LHC. Some of these mechanisms are expected, like the losses during injection process, some others have been discovered with the higher intensities like the UFOs. This talk will address the three types of losses (operational, equipment failure and transient beam losses) as seen in the LHC and in the transfer to LHC.

Speaker: Laurette Ponce (CERN)

Slides BeamLossMechanismLHCV2.pdf BeamLossMechanismLHCV2.ppt

14 Overview of Failure Mode Studies for ILC and CLIC

Failures in the ILC and in the CLIC can lead to beam loss, or even damage the machine. Also failures that do not lead to beam loss can affect the luminosity performance, in particular since some time is required to recover from them. During the last years several different failures scenarios have been investigated, and their impact on the machine performance has been being studied. At this purpose, a number of simulation codes have been developed, perfected, and utilized: to track the beam including effects such as wakefields and dynamical machine alignment; to simulate halo and tail generation; to evaluate energy deposition and beam-halo interaction with collimators. A review of the main studies is presented, including a short description of the principal tools.

Speaker: Dr Andrea Latina (CERN)

Slides Workshop.pdf

15 Failure studies at CLIC main Linac and Beam Delivery System

The CERN TE-MPE group has the mission to develop and maintain the systems to protect machine components from damage caused by ill controlled conditions. Various failure scenarios were studied and the potential damage these failures could cause to the machine structures was estimated. First results of the beam response to kick induced failures in the main LINAC and in the beam delivery system (BDS) sections are presented together with possible collimator damage scenarios.

Speaker: Carlos Omar Maidana

Slides MAIDANA_MP_workshop_June_6_2012.pdf

Thursday 7 June

Failure detection

This section will address the detection of failures that may lead to uncontrolled beams.
- Beam Quality Assessments (for active systems and Post Pulse Analysis)
- Equipment failure detection

Convener: Dr Hermann Schmickler (CERN)

16 Beam loss detection

The ILC or CLIC beam loss detection will have to function as a protection and tuning system of the beams. Losses need to be measured at numerous locations and depending on limits action have to be initiated by the system. With the triggering of automatic actions the aspects of reliability and on the other side the consequences of wrongly initiated actions have to be regarded. The talk will concentrate on these subjects using examples from the LHC system and the experience from its operation.

Speaker: Bernd Dehning (CERN)

Slides Dehning_BLM_CLIC_MP_workshop_20120606.pdf Dehning_BLM_CLIC_MP_workshop_20120606.pptx

17 Studies for the CLIC TBM BLM System

The CLIC 21 km main linac and corresponding 24 drive beam decelerators are arranged into modular structures referred to as the 'two beam modules'. The baseline technology choice for the CLIC Beam Loss Monitoring system (as presented in the conceptual design report) is based on ionization chambers for the two beam modules. However, a more cost effective BLM design, based on Cherenkov light generated in optical fibers is being investigated. A model for light production and propagation has been developed and validated with measurements. Monte Carlo simulations of loss scenarios in the CLIC tunnel have been performed, to determine the suitability of an optical fiber system in terms of sensitivity and dynamic range. The ability to distinguish between losses from each of the two beams will also be presented. Issues specifically related to the use of Cherenkov fibers such as the achievable longitudinal position resolution for long pulses and radiation hardness will be discussed.

Speaker: Sophie Mallows (University of Liverpool (GB))

Slides smallows_MPworkshopJune2012.pdf smallows_MPworkshopJune2012.pptx

18 Diagnostics for Machine Protection at FERMI@Elettra

The talk presents the design and performance of the main diagnostic subsystems of the MPS for the FERMI@Elettra free-electron laser: Beam loss position monitors based on the detection of Cherenkov light in quartz fibers with multi-pixel photon counters, conventional ionization chambers with a novel frontend electronics package, and solid-state RADFET dosimeters providing an online measurement of the absorbed dose in undulator magnets.

Speaker: Lars Fröhlich (Sincrotrone Trieste)

Slides Diagnostics_for_Machine_Protection_at_FERMI@Elettra.pdf Diagnostics_for_Machine_Protection_at_FERMI@Elettra.pptx

10:30 Coffee Break

19 Equipment fault detection

The organization and the setup of the equipment interlocks are described through the CERN Beam Interlock System (BIS) solution. The latter is the common solution to protect various types of CERN accelerators: ring (LHC, SPS...), linear (Linac4) or transfer lines. The BIS is more than a protection system, it is the key element to get efficient beam operation, to enhance machine availability and to perform self testing. These aspects are illustrated through the main features provided by the Beam Interlock System.

Speaker: Mr Bruno Puccio (CERN)

Slides BIS-as-Eqpt-fault-Detection-Sequence_MP-Workshop(June2012)_1v0.pdf BIS-as-Eqpt-fault-Detection-Sequence_MP-Workshop(June2012)_1v0.pptx

20 Beam Quality Assessment for the LHC beams real time and post-mortem

The LHC has stringent requirements on transverse and longitudinal beam quality to avoid beam instabilities, maximize transmission and performance. Dedicated automatic quality checks are carried out in the last LHC injector and in the LHC after each injection. These systems have successfully indicated problems with beam quality at many occasions and guarantee the required excellent performance from the injectors. The monitored parameters, analysis and infrastructure of the automatic analysis systems are described. The importance of logging. long time storage together with appropriate tools to display trends of monitored parameters will also be discussed. Missing aspects of the current quality checks will be mentioned.

Speaker: Verena Kain (CERN)

Slides BeamQualityAssessment-CLICMPS-June2012_v1.pdf BeamQualityAssessment-CLICMPS-June2012_v1.ppt

12:30 Lunch Time

Failure mitigation

Reviews of various types of failure mitigation:
- Passive protection (masks , materials, collimators, non linear optics)
- RT protection
- Safe by design
- Interlock systems (equipment and post pulse assessment)

Convener: Michael Jonker (CERN)

21 Beam Loss Mechanisms and Mitigation at SLC

The SLAC Linear Collider (SLC) was intended in part to demonstrate that linear colliders could work. Even though it did not meet luminosity goals, physics goals were met and remain comparable to LEP results. Stabilizing the SLC was the most difficult challenge and transitions in beam power, caused by frequent machine protect system faults were the most serious source of instability. MPS faults, in turn, were caused through amplification of relatively small damping ring impedance-related longitudinal instabilities in a kind of chain reaction that involved the ring, bunch compressor, normal-conducting linac and collimation systems.

Speaker: Marc Ross (Fermilab)

Slides MPSSLC_mcr_20120607.pdf MPSSLC_mcr_20120607.pptx

22 The post-LINAC collimation system of CLIC: Machine Protection Aspects

The main functions of the post-linac collimation system for future linear colliders are: the cleaning of the beam halo particles which potentially can generate detector background at the Interaction Point (IP); and the protection of the Beam Delivery System (BDS) by minimising the activation and damage of downstream equipment. In this presentation we focus mainly on the machine protection function of the energy collimation section against errant or miss-steered beams due to failure modes in the main linac. In order to investigate and identify critical scenarios, we have performed simulations of failure modes in the main linac, and evaluated their impact in terms of collimator damage. In addition, a thermo-mechanical analysis of the energy spoiler has been performed using the simulation codes FLUKA and ANSYS. The results of these studies are discussed in this presentation. Finally, we also discuss some alternative collimation schemes, such as nonlinear optical layouts, which could help to guarantee the survivability of the collimators in case of beam impact.

Speakers: Javier Resta Lopez (IFIC, Valencia University), Rogelio Tomas Garcia (CERN)

Slides CLIC_collimation_studies2.pdf CLIC_collimation_studies2.ppt

23 Novel advanced materials for next-generation Beam Intercepting Devices

The introduction of new, extremely energetic particle accelerators has brought about the need for advanced cleaning and protection systems in order to safely increase the beam energy and intensity to unprecedented levels. A new family of materials, combining the physical, thermal, electrical and mechanical properties which are required by the extreme working conditions existing in high energy/high intensity accelerators is being developed: Metal Matrix Composites with Diamond or Graphite reinforcements. These materials are to combine the outstanding thermal and physical properties of diamond and graphite with the electrical and mechanical properties of metals. Materials being produced and characterized include Copper-Diamond, Silver-Diamond, Molybdenum-Diamond and Molybdenum-Graphite. A comprehensive material testing program, including a first-of-its-kind experiment submitting materials to intense proton beams, is being deployed. These activities are complemented by advanced numerical simulations allowing to study the extreme phenomena which these materials may undergo.

Speaker: Alessandro Bertarelli (CERN)

Slides AdvancedMaterialsForNextGenerationBID_v1.pdf AdvancedMaterialsForNextGenerationBID_v1.pptx

15:30 Coffee Break

24 Reliable beam extraction

Beam extraction systems are used in a linear accelerator complex at the combiner rings, at the damping rings, for beam distribution and for emergency dumps if the bunch spacing allows. The highly brilliant beams used have a large damage potential in case of extraction failures. The failures can be categorised in trigger errors, timing errors and amplitude errors. The LHC beam dumping system is taken as an example on how to obtain safe extraction systems by using redundancy, surveillance, mitigation and automated post mortem system. The second example shows the present development for the extraction system of the CLIC damping rings using an inductive adder.

Speaker: Dr Jan Uythoven (CERN)

Slides CLC_MP_workshop_7June2012.pdf CLC_MP_workshop_7June2012.pptx

25 Safe by design Clic powering

A large number of magnet powering systems are required for the CLIC machine complex. Several studies have been made to ensure a reliable and safe powering system that meets the CLIC technical requirements. The presentation will introduce the powering concepts proposed for the drive beam and main beam magnets to ensure appropriate machine availability, and introduce the methods used to estimate the reliability for the system.

Speaker: David Nisbet (CERN)

Slides Safe_by_Design_CLIC_Powering.pdf Safe_by_Design_CLIC_Powering.ppt

26 CLIC Interlock system: preliminary study

This presentation gives an overview of the CLIC interlock system study. From the Machine Protection strategy, there is a need to cover some anticipated failures. This leads to a necessity of an Interlock system. An explanation of the two principles that are comprised by this system is given. The main challenges and the current solution planned are then described. Finally, the ongoing works to validate this solution are addressed.

Speaker: Patrice Denis Eric Nouvel (Insitut National Polytechnique de Toulouse (FR))

Slides CLIC_Interlock_System_MP_Workshop.pdf CLIC_Interlock_System_MP_Workshop.pptx

Friday 8 June

Operational aspects

• Operational aspects (commissioning, intensity ramp, machine availability)
• Risk assessment: management and tools

Convener: Marc Ross (Fermilab)

27 RF breakdown recovery

The breakdown rate for the CLIC main linac rf system must be less than 3x10-7/pulse/m in order to ensure that less than 1% of all machine pulses lose luminosity due to beam deflections caused by the breakdowns. What’s known so far about the statistics of breakdown is reviewed and an operational scenario for reacting to breakdown on following pulses is described.

Speaker: Walter Wuensch (CERN)

Slides rf_breakdown_wuensch_final.pdf rf_breakdown_wuensch_final.pptx

28 Clic Intensity rampup

The permit based machine protection system of CLIC depends on the measured performance of the machine during the previous cycle. This presentation addresses the bootstrap procedure which, starting from safe beams, stepwise increases the beam intensities.

Speaker: Michael Jonker (CERN)

Slides MPWS2012_intensity_rampup.pdf MPWS2012_intensity_rampup.pptx

29 'AvailSim' - Simulating the Operation and Maintenance of an Accelerator Complex

AvailSim is a Monte-Carlo simulation tool that uses Excel and Matlab to show a timeline of operation of a large accelerator complex. The simulation uses and table listing all key accelerator components with mean time to fail (MTBF) and mean time to repair (MTTR) data taken from data recorded at DESY, Fermilab and SLAC from the 1990's. The model includes the full segmentation of the machine so that repairs can be done in one segment while necessary machine development is done upstream. A key parameter in the model is the time to recover operation after a downtime. AvailSim has been a useful tool to aid in the machine design, especially aspects such as equipment location (in /out of tunnel), access and operations segmentation and redundancy.

Speaker: Marc Ross (Fermilab)

Slides lc_availability.pdf schaetzel_ilc_060329.pdf

10:30 Coffee Break

30 Reliability of the CERN Beam Interlock System: Past, Present and Future

The Beam Interlock System (BIS) is a high-speed, high-dependability interlock system used throughout the CERN accelerator complex. It has been designed to provide the required protection level whilst having a minimal impact on machine availability. This talk explains the methods used to predict the reliability of the BIS during the design phase, the observed system performance with respect to predictions, and an outlook for reliability considerations in dependable systems.

Speaker: Dr Benjamin Todd (CERN)

Slides BIS_2012_1v1.pptx

31 Risk assessment in Linac-4, management and tools

In high energy accelerators the need for Protections Systems is essential to protect the machines from possible failures. As the beam energy increases, beam-induced damage can cause serious consequences in terms of repair costs and down-time of the accelerator. Hence the risk associated to a failure has to be estimated for all possible failure scenarios. The present work shows the adopted approach and the considerations done to derive a complete failure catalogue for the future injector complex (Linac4-transfer lines-PSB). A dedicated website has been created in order to make the acquired knowledge available for the public.

Speaker: Andrea Apollonio (Vienna University of Technology (AT))

Slides MPWORKSHOP862012_AndreaApollonio.pdf MPWORKSHOP862012_AndreaApollonio.pptx

32 A Systems Engineering Approach to Machine Protection

Jefferson Lab accelerators include the 1MW CEBAF electron machine as well as the high intensity Free Electron Laser. Borrowing risk management practices from the military, aerospace and chemical processing industries, Jefferson Lab manages a graded approach to identify and manage risk presented by beam operations. Constraints are then incorporated in to system level requirements across multiple subsystems. This talk will describe the engineering transition of the Jefferson Lab CEBAF and FEL accelerator machine protection systems to a risk based systems engineering approach. The approach addresses the traditional goals of maximum machine availability, minimal short and long term damage, and configurability. In addition, a systems engineering approach also addresses enabling and supporting processes like project management, controls infrastructure, personnel competency, and long term system effectiveness. We will conclude with a brief look at ongoing work to integrate the systems, software, and cyber security assurance practices.

Speaker: Mr Kelly Mahoney (TJNAF)

Slides CERN_MPS_Workshop_-_Presentation_2_Formatted.pdf CERN_MPS_Workshop_-_Presentation_2_Formatted.pptx

12:30 Lunch Break

Summing up and conclusions

Convener: Steinar Stapnes (CERN)

33 Machine protection and operational availability, issues and solutions

Speaker: Mr Rudiger Schmidt (CERN)

Slides CLIC-MP.pptx

34 Beam loss mechanisms

Speaker: Daniel Schulte (CERN)

Slides MP3.pdf MP3.pptx

35 Failure onset detection

Speaker: Dr Hermann Schmickler (CERN)

Slides Summary_HS.pdf Summary_HS.pptx

36 Failure mitigation

Speaker: Michael Jonker (CERN)

Slides MPWS2012_Summary_Session_4.pptx

37 Operational aspects

Speaker: Marc Ross (Fermilab)

Slides MPSOPSA_mcr_20120608.pdf MPSOPSA_mcr_20120608.pptx

38 Conclusions and closure

Speaker: Steinar Stapnes (CERN)

Slides MPWS2012_close.pdf MPWS2012_close.pptx