04 Beam Loss Monitors and Machine Protection
Paper Title Page
TU2T1 Collimation and Machine Protection for Low Emittance Rings 196
  • J.C. Dooling, M. Borland, A.M. Grannan, C.J. Graziani, Y. Lee, R.R. Lindberg, G. Navrotski
    ANL, Lemont, Illinois, USA
  • N.M. Cook
    RadiaSoft LLC, Boulder, Colorado, USA
  • D.W. Lee
    UCSC, Santa Cruz, California, USA
  Funding: Work supported by Hard X-ray Sciences LDRD Project 2021-0119 and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The reduced emittance and concomitant increase in electron beam intensity in Fourth Generation Storage Ring (4GSR) light sources lead to the challenging machine protection problem of how to safely dispose of the circulating charge during unplanned whole-beam loss events. Two recent experiments conducted to study the effects of 4GSR whole-beam dumps showed that damage to candidate collimator materials can be severe. This is a paradigm shift for SR light source machine protection. Typically the biggest threat to the machine is from CW synchrotron radiation. The choice of collimator material is important. High-Z, high-density materials such as tungsten may appear effective for stopping the beam in static simulations; however, in reality, short radiation lengths will cause severe destructive hydrodynamic effects. In our experiments, significant damage was observed even in low-Z aluminum. Thus unplanned, whole-beam dumps cannot be stopped in a single collimator structure. In this tutorial, alternatives such as multiple collimators and fan-out abort kicker systems will be discussed. Collimator design strategy and foreseen diagnostics for their operation will also be presented.
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DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TU2T1  
About • Received ※ 08 September 2022 — Revised ※ 09 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 04 October 2022
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TU2C2 The Diamond Beam Loss Monitoring System at CERN LHC and SPS 202
  • E. Calvo Giraldo, E. Effinger, M. Gonzalez Berges, J. Martínez Samblas, S. Morales Vigo, B. Salvachúa, C. Zamantzas
    CERN, Meyrin, Switzerland
  • J. Kral
    CTUP/FNSPE, Prague, Czech Republic
  The Large Hadron Collider (LHC) and the Super Proton Synchrotron (SPS) accelerators are equipped with 17 pCVD diamond based Beam Loss detectors at strategical locations where their nanosecond resolution can provide insights into the loss mechanisms and complement the information of the standard ionization chamber type detectors. They are used at the injection and extraction lines of the LHC and SPS, to analyse the injection or extraction efficiency, and to verify the timing alignment of other elements like kicker magnets. They are used at the betatron collimation region and are being also explored as detectors to analyse slow extractions. The acquisition chain was fully renovated during the second LHC long shutdown period (from December 2018 to July 2022) to provide higher resolution measurements, real-time data processing and data reduction at the source as well as to integrate seamlessly to the controls infrastructure. This paper presents the new hardware platform, the different acquisition modes implemented, the system capabilities and initial results obtained during the commissioning and operation at the beginning of the LHC’s Run 3.  
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DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TU2C2  
About • Received ※ 06 September 2022 — Revised ※ 09 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 14 September 2022
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TU2C3 Commissioning Beam-Loss Monitors for the Superconducting Upgrade to LCLS 207
  • A.S. Fisher, G.W. Brown, E.P. Chin, C.I. Clarke, W.G. Cobau, T. Frosio, B.T. Jacobson, R.A. Kadyrov, J.A. Mock, J. Park, E. Rodriguez, P.K. Roy, M. Santana-Leitner, J.J. Welch
    SLAC, Menlo Park, California, USA
  Commissioning of the 4-GeV, 120-kW superconducting linac, an upgrade to the LCLS x-ray FEL at SLAC, began in summer 2022, by accelerating a beam through the first cryomodule to 100 MeV. This autumn the beam will accelerate along the full linac, pass through the bypass transport line above the copper linac, and end at a new high-power tune-up dump at the muon shield wall. The first beam through the undulators is expected by early 2023, at a rate well below the full 1 MHz. A new system of beam-loss detectors will provide radiation protection, machine protection, and diagnostics. Radiation-hard optical fibres span the full 4 km from the electron gun to the undulators and their beam dumps. Diamond detectors cover anticipated loss points. These replace ionization chambers previously used with the copper linac, due to concern about ion pile-up at high loss rates. Signals from the new detectors are integrated with a 500-ms time con-stant and compared to the allowed threshold. If this level is crossed, the beam stops within 0.2 ms. We report on the initial commissioning of this system and on the detection of losses of both photocurrent and of dark current from the gun and cryomodules.  
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DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TU2C3  
About • Received ※ 08 September 2022 — Revised ※ 09 September 2022 — Accepted ※ 11 September 2022 — Issue date ※ 12 October 2022
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TUP01 Commissioning of the Libera Beam Loss Monitoring System at SPEAR3 211
  • K. Tian, S. Condamoor, W.J. Corbett, N.L. Parry, J.A. Safranek, J.J. Sebek, F. Toufexis
    SLAC, Menlo Park, California, USA
  SPEAR3 is a third generation synchrotron radiation light source, which operates approximately 9 months each year with a very high reliability. The beam loss monitoring system in the storage ring has recently been upgrade to the modern Libera system from the original legacy hardware. During the initial stage of the new beam loss monitoring system deployment, it was proved to be useful for a new lattice commissioning at SPEAR3. In this paper, we will report the progress in the Libera system commissioning at SPEAR3 and present some first results.  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TUP01  
About • Received ※ 07 September 2022 — Revised ※ 09 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 03 November 2022
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TUP02 Design of High Dynamic Range Preamplifiers for a Diamond-Based Radiation Monitor System 216
  • M. Marich, S. Carrato
    University of Trieste, Trieste, Italy
  • L. Bosisio, A. Gabrielli, Y. Jin, L. Lanceri
    INFN-Trieste, Trieste, Italy
  • G. Brajnik, G. Cautero, D. Giuressi
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • L. Vitale
    Università degli Studi di Trieste, Trieste, Italy
  Regardless of the different accelerator types (light sources like FELs or synchrotrons, high energy colliders), diagnostics is an essential element for both personnel and machine protection. With each update, accelerators become more complex and require an appropriate diagnostic system capable of satisfying multiple specifications, that become more stringent as complexity increases. This paper presents prototyping work towards a possible update of the readout electronics of a system based on single-crystal chemical vapor deposition (scCVD) diamond sensors, monitoring the radiation dose-rates in the interaction region of SuperKEKB, an asymmetric-energy electron-positron collider. The present readout units digitize the output signals from the radiation monitors, process them using an FPGA, and alert the accelerator control system if the radiation reaches excessive levels. The proposed updated version introduces a new design for the analog front end that overcomes its predecessor’s limits in dynamic range thanks to high-speed switches to introduce a variable gain in transimpedance preamplifiers, controlled by an ad-hoc developed FPGA firmware.  
poster icon Poster TUP02 [1.292 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TUP02  
About • Received ※ 07 September 2022 — Revised ※ 09 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 16 October 2022
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TUP03 The Beam Loss Monitoring System after the LHC Long Shutdown 2 at CERN 220
  • M. Saccani, E. Effinger, W. Viganò, C. Zamantzas
    CERN, Meyrin, Switzerland
  Most of the LHC systems at CERN were updated during the Long Shutdown 2, from December 2018 to July 2022, to prepare the accelerator for High-Luminosity. The Beam Loss Monitoring system is a key part of the LHC’s instrumentation for machine protection and beam optimisation by producing continuous and reliable measurements of beam losses along the accelerator. The BLM system update during LS2 aims at providing better gateware portability to future evolutions, improving significantly the data rate in the back-end processing and the software efficiency, and adding remote command capability for the tunnel electronics. This paper first recalls the Run 1 and Run 2 BLM system achievements, then reviews the main changes brought during LS2, before focusing on the commissioning phase of Run 3 and future expectations.  
poster icon Poster TUP03 [2.871 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TUP03  
About • Received ※ 05 September 2022 — Revised ※ 10 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 29 October 2022
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TUP04 Beam Loss Monitor for Polish Free Electron Laser (PolFEL): Design and Tests 225
  • R. Kwiatkowski, R. Nietubyc, J. Szewiński, D.R. Zaloga
    NCBJ, Świerk/Otwock, Poland
  • A.I. Wawrzyniak
    NSRC SOLARIS, Kraków, Poland
  Funding: European Regional Development Fund in the framework of the Smart Growth Operational Programme and Regional Operational Programme for Mazowieckie Voivodeship.
The Beam Loss Monitor (BLM) system is primarily used for machine protection and is especially important in the case of high energy density of accelerated beam, when such a beam could cause serious damages due to uncontrolled loss. PolFEL linear accelerator is designed with the beam parameters, which made BLM an essential system for machine protection. The design of BLM system for PolFEL is composed of several scintillation probes placed along and around the accelerator. The paper reports on design and first tests of prototype detector, which is planned to be used for PolFEL project. The prototype was tested in NCBJ and SOLARIS, using radioactive calibration samples and linear electron accelerator as a sources. We also present results of numerical investigation of radiation generated due to interaction of fast electrons with accelerator components.
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TUP04  
About • Received ※ 07 September 2022 — Revised ※ 10 September 2022 — Accepted ※ 13 September 2022 — Issue date ※ 19 October 2022
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TUP05 Experience with Machine Protection Systems at PIP2IT 229
  • A. Warner, M.R. Austin, L.R. Carmichael, J.-P. Carneiro, B.M. Hanna, E.R. Harms, M.A. Ibrahim, R. Neswold, L.R. Prost, R.A. Rivera, A.V. Shemyakin, J.Y. Wu
    Fermilab, Batavia, Illinois, USA
  Funding: * This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The PIP2IT accelerator was assembled in multiple stages in 2014 - 2021 to test concepts and components of the future PIP-II linac that is being constructed at Fermilab. In its final configuration, PIP2IT accelerated a 0.55 ms x 20 Hz x 2 mA H beam to 16 MeV. To protect elements of the beam line, a Machine Protection System (MPS) was implemented and commissioned. The beam was interrupted faster than 10 µs when excessive beam loss was detected. The paper describes the MPS architecture, methods of the loss detection, procedure of the beam interruption, and operational experience at PIP2IT.
poster icon Poster TUP05 [1.233 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TUP05  
About • Received ※ 05 September 2022 — Revised ※ 09 September 2022 — Accepted ※ 11 September 2022 — Issue date ※ 18 September 2022
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WEP04 Dual channel FMC High-Voltage Supply 383
  • W. Viganò, J. Emery, M. Saccani
    CERN, Meyrin, Switzerland
  The Beam Loss Monitoring (BLM) detectors and electronics are installed along the CERN accelerators to provide measurements of the beam loss as well as protection from them when excessive. Majority of the BLM detector types require voltage biasing up to 2000VDC with the possibility to generate voltage modulation patterns to verify the connection chain of the detectors to the front-ends. Currently, the power supply solution consists of COTS large format power supplies with additional custom electronics and various interconnections to provide monitoring and remote control. For this reason, a market search has been done to identify a high reliability module suitable for dedicated BLM installations composed by a few detectors. The outcome of the market search has justified the need to design a low cost custom board, compatible with the CERN infrastructure and different detector types, as well as allow easy customization to cover various installation architectures and voltage range needs. Main characteristics could be summarized with the following points: completely remote controlled and autonomous system, common hardware for different applications, only need to change DC\DC converter.
Other characteristics: few more components for different application and make a model smaller than what is currently used as high voltage power supplies.
poster icon Poster WEP04 [1.216 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-WEP04  
About • Received ※ 06 September 2022 — Revised ※ 10 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 05 November 2022
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Online Machine Learning Version of the SNS Differential Beam Current Monitor  
  • W. Blokland, F. Liu, N.R. Miniskar, P. Ramuhalli, A.R. Young, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
  • K. Rajput, M. Schram
    JLab, Newport News, Virginia, USA
  • Y.A. Yucesan
    ORNL RAD, Oak Ridge, Tennessee, USA
  Funding: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE).
We have duplicated the Spallation Neutron Source (SNS) Differential beam Current Monitor (DCM) and included Machine Learning algorithms to observe the beam condition by looking for errant beam event precursors. The new system runs in parallel to the existing operational system and receives the same beam current signals but can be modified without affecting Operations. The archived data from the operational DCM was used to prove the existence of precursors and to generate the models. The new system has implemented Siamese Twin models on the real-time OS and a Random Forest model in the FPGA of the system. The system can also stream all acquired data at full rates to a data server for archival and online analysis. We discuss the setup and initial results.
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WEP06 An LHC Protection System Based on Fast Beam Intensity Drops 387
  • M. Gąsior, T.E. Levens
    CERN, Meyrin, Switzerland
  The Large Hadron Collider (LHC) is protected against potentially dangerous beam losses by a distributed system based on some four thousand beam loss monitors. To provide an additional level of safety, the LHC has been equipped with a system to detect fast beam intensity drops and trigger a beam dump for potentially dangerous rates. This paper describes the architecture of the system and its signal processing, optimized to cope with dump thresholds in the order of 0.01 % of the circulating beam intensity. The performance of the installed system is presented based upon beam measurements.  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-WEP06  
About • Received ※ 10 September 2022 — Revised ※ 11 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 22 November 2022
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WEP07 Influence of the Beam Induced Irradiation on the Critical Current Phenomena in Superconducting Elements 391
  • J. Sosnowski
    NCBJ, Świerk/Otwock, Poland
  Currently developed nuclear accelerators more and more widely use superconducting elements especially in windings of superconducting electromagnets and current leads to them. These elements are however sensitive to the irradiation caused by primary beam as well as by secondary particles, as it is the case for PolFEL. In the paper it is discussed how this irradiation damages the subtle structure of superconducting materials, leading to columnar defects formation in 2D HTc superconductors. It is analysed, in which way created nano-sized structural defects influence the critical current properties of the superconducting materials, in the process of capturing of the magnetic pancake vortices. Various initial positions of the captured vortices are analysed; their movement leads to potential barrier variations. Influence of the irradiation effects on the current-voltage characteristics of superconductors are investigated then and maximal current density detected as the function of irradiation dose, nano-defects size and physical parameters as magnetic field and temperature.  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-WEP07  
About • Received ※ 07 September 2022 — Revised ※ 13 September 2022 — Accepted ※ 15 September 2022 — Issue date ※ 11 December 2022
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