Low level RF
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TH1AA06 Low Level RF Control Algorithms for the CERN Proton LINAC4 673
  • P. Baudrenghien, B. Bielawski, R.B. Borner
    CERN, Meyrin, Switzerland
  The CERN Linac4 Low Level RF (LLRF) uses a Linear Gaussian Regulator and an Adaptive Feed Forward to regulate the accelerating field in the cavities in the presence of strong beam loading. A Klystron Polar Loop is also implemented to compensate the RF perturbations caused by the ripples and droop in the klystron High Voltage supply. The talk presents the important parts of the regulation, shows results as the system has evolved from first prototype (2013) to operational beams (2020), and mentions some important issues encountered during the commissioning and the first years of operation, with their mitigations.  
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slides icon Slides TH1AA06 [4.183 MB]  
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About • Received ※ 24 August 2022 — Revised ※ 31 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 06 September 2022
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THPOPA12 Development and Integration of a New Low-Level RF System for MedAustron 764
  • M. Wolf, M. Cerv, C. Kurfürst, G. Muyan, S. Myalski, M. Repovž, C. Schmitzer
    EBG MedAustron, Wr. Neustadt, Austria
  • A. Bardorfer, B. Baričevič, P. Paglovec, M. Škabar
    I-Tech, Solkan, Slovenia
  The MedAustron Ion Therapy Centre is a synchrotron-based particle therapy facility, which delivers proton and carbon beams for clinical treatments. Currently, the facility treats 40 patients per day and is improving its systems and workflows to further increase this number. Although MedAustron is a young and modern center, the life-cycle of certain crucial control electronics is near end-of-life and needs to be addressed. This paper presents the 216MHz injector Low-Level Radio Frequency (iLLRF) system with option of use for the synchrotron Low-Level Radio Frequency (sLLRF - 0.4-10MHz). The developed system will unify the cavity regulation for both LLRFs and will also be used for beam diagnostics (injector/synchrotron) and RF knock-out slow extraction. The new LLRF system is based on a µTCA platform which is controlled by the MedAustron Control System based on NI-PXIe. Currently, it supports fiberoptics links (SFP+), but other links (e.g. EPICS, DOOCS) can be established. The modular implementation of this LLRF allows connections to other components, such as motors, amplifiers, or interlock systems, and will increase the robustness and maintainability of the accelerator.  
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About • Received ※ 24 August 2022 — Revised ※ 25 August 2022 — Accepted ※ 31 August 2022 — Issue date ※ 01 September 2022
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THPOPA13 Superconducting Cavity and RF Control Loop Model for the SPIRAL2 Linac 767
  • F. Bouly
    LPSC, Grenoble Cedex, France
  • M. Di Giacomo, J.F. Leyge, M. Tontayeva
    GANIL, Caen, France
  The SPIRAL2 superconducting linac has been successfully commissioned with protons in 2020. During the commissioning, a model of the cavity and its LLRF control loop has been developed. The model enables to have better understanding of the system and was used to guide the tuning of the PI(D) correctors for beam loading compensation. Here we review the development of such a tool, computed with MATLAB Simulink and using the frequency domain (Laplace transfer function) to model the cavity RF and mechanical behaviours (Lorentz detuning), as well as all elements that compose the RF control loop (digital LLRF, amplifier, transmission lines, etc.). The benchmarking of the model with measurement carried out with the proton beam is also discussed in this contribution.  
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About • Received ※ 24 August 2022 — Revised ※ 01 September 2022 — Accepted ※ 03 September 2022 — Issue date ※ 15 September 2022
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THPOPA14 MTCA.4-Based LLRF System Prototype Status for MYRRHA 771
  • C. Joly, S. Berthelot, N. Gandolfo, J. Rozé, J.-F. Yaniche
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • J-L. Bolli, I. Garcia, C. Gaudin
    IOXOS Technologies, Gland, Switzerland
  • O. Bourrion, D. Tourres
    LPSC, Grenoble Cedex, France
  • S. Boussa, W. De Cock, P. Della Faille, F. Pompon, E. Verhagen
    SCK•CEN, Mol, Belgium
  Within the framework of MINERVA, the first Phase of MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) project, IN2P3 labs are in charge of the development of several accelerator elements. Among those, a fully equipped Spoke cryomodule prototype was constructed. It integrates two superconducting single spoke cavities operating at 2K, the RF power couplers and the associated cold tuning systems. On the control side, a MTCA.4-based Low Level RadioFrequency (LLRF) system prototype has been implemented by IJCLab including FPGA specific firmware, a new µRTM frequency downconverter module from the company IOxOS Technologies and EPICS developments in collaboration with the SCK•CEN. The status of the LLRF system will be shown as well as its preliminary tests results.  
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About • Received ※ 23 August 2022 — Revised ※ 26 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 01 September 2022
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THPOPA15 Anomaly Detection Based Quench Detection System for CW Operation of SRF Cavities 775
  • G. Martino, A. Bellandi, J. Branlard, A. Eichler, H. Schlarb
    DESY, Hamburg, Germany
  • S. Aderhold, A.L. Benwell, D. Gonnella, S.L. Hoobler, J. Nelson, R.D. Porter, A. Ratti, L.M. Zacarias
    SLAC, Menlo Park, California, USA
  • L.R. Doolittle
    LBNL, Berkeley, California, USA
  • G. Fey
    Hamburg University of Technology, Hamburg, Germany
  Funding: This work is supported by DASHH (Data Science in Hamburg - HELMHOLTZ Graduate School for the Structure of Matter) under Grant No.: HIDSS-0002.
Superconducting radio frequency (SRF) cavities are used in modern particle accelerators to take advantage of their very high quality factor (Q). A higher Q means that a higher RF field can be sustained, and a higher acceleration can be produced in the cavity for length unity. However, in certain situations, e.g., too high RF field, the SRF cavities can experience quenches that risk creating damage due to the rapid increase in the heat load. This is especially negative in continuous wave (CW) operation due to the impossibility of the system to recover during the off-load period. The design goal of a quench-detection system is to protect the system without being a limiting factor during the operation. In this paper, we compare two different classification approaches for improving a quench detection system. We perform tests using traces recorded from LCLS-II and show that the ARSENAL classifier outperforms a CNN classifier in terms of accuracy.
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About • Received ※ 24 August 2022 — Accepted ※ 25 August 2022 — Issue date ※ 23 September 2022  
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THPOPA18 Development of a Tuner Control System for Low-Energy Superconducting Linac at RAON 778
  • H. Kim, M.O. Hyun, H. Jang, M.S. Kim, Y. Kim
    IBS, Daejeon, Republic of Korea
  Funding: This research was supported by the RISP of ibs funded by the Ministry of Science and the National Research Foundation (NRF) of the Republic of Korea under Contract 2013M7A1A1075764.
We propose a tuner control system for low-energy superconducting linac at RAON. The frequency error of the superconducting cavities must be smaller than a few of Hz to operate in beam acceleration mode. To minimize the freuqency error as much as possible, the error is calculated in the low-level RF(LLRF), and the proposed tuner control system changes the superconducting cavity frequency by using a mechanical tuner and a motor attached to the cavity directly. This control system deals with not only the initial frequency error of the cavity but also the frequency drift of the cavity induced by external disturbance such as the slow fluctuation helium pressure automatically. In addition, an automatic proportional gain calibration technique is also proposed. In this paper, the detailed operation and techniques will be described.
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About • Received ※ 13 August 2022 — Revised ※ 23 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 11 September 2022
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THPOPA19 Initial High Power RF Driving Test Using Digital LLRF for RF Conditioning of 1 MeV/n RFQ at KOMAC 781
  • H.S. Jeong, W.-H. Jung, D.-H. Kim, H.S. Kim, J.H. Kim, K.H. Kim, S.G. Kim, H.-J. Kwon, P. Lee, Y.G. Song
    KOMAC, KAERI, Gyeongju, Republic of Korea
  Funding: This work was supported through the KOMAC operation fund by the Ministry of Science and ICT of Korean government.
As a part of R&D toward the RFQ based heavy ion irradiation system, the 1 MeV/n RFQ was designed, brazed, installed and commissioned by staff researchers and engineers at KOMAC of KAERI. This 1 MeV/n RFQ system includes the microwave ion source, EBIS, RFQ, quadrupole magnets, switching magnet and the target systems. The digital based Low-Level RF was developed to provide the stable accelerating field to the RFQ. This Low-Level RF has features such as direct RF detection/generation without mixer, non-IQ sampling, PI feedback control, iterative learning based feed-forward control, and the digital RF interlock. In this paper, the characteristics of Low-Level RF are described, as well as the processes and results of an initial RF driving test for the RFQ’s RF conditioning.
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About • Received ※ 22 August 2022 — Revised ※ 28 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 15 September 2022
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THPOPA21 Narrow Bandwidth Active Noise Control for Microphonics Rejection in Superconducting Cavities at LCLS-II 785
SUPCPA06   use link to see paper's listing under its alternate paper code  
  • A. Bellandi, J. Branlard
    DESY, Hamburg, Germany
  • S. Aderhold, A.L. Benwell, A. Brachmann, J.A. Diaz Cruz, D. Gonnella, S.L. Hoobler, J. Nelson, A. Ratti, L.M. Zacarias
    SLAC, Menlo Park, California, USA
  • J.A. Diaz Cruz
    UNM-ECE, Albuquerque, USA
  • R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  LCLS-II is an X-Ray Free Electron Laser (XFEL) under commissioning at SLAC, being the first Continuous Wave (CW) hard XFEL in the world to come into operation. To accelerate the electron beam to an energy of 4 GeV, 280 superconducting cavities of the TESLA types are used. A Loaded Q (QL) value of 4x107 is used to drive the cavities at a power level of a few kilowatts. For this QL value, the RF cavity bandwidth is equal to 32 Hz. Therefore, keeping the cavity resonance frequency within such bandwidth is imperative to avoid a significant increase in the required RF power. In superconducting accelerators, resonance frequency variations are produced by mechanical microphonic vibrations of the cavities. One source of microphonics noise is rotary machinery such as vacuum pumps or HVAC equipment. A possible method to reject these disturbances is to use Narrowband Active Noise Control (NANC) techniques. Such a technique was already tested at DESY/CMTB and Cornell/CBETA. This proceeding presents the implementation of a NANC controller in the LCLS-II Low Level RF (LLRF) control system. Tests on the rejection of LCLS-II microphonics disturbances are also presented.  
poster icon Poster THPOPA21 [1.843 MB]  
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About • Received ※ 24 August 2022 — Revised ※ 30 August 2022 — Accepted ※ 02 September 2022 — Issue date ※ 26 September 2022
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THPOPA22 C-Band Low Level RF System Using COTS Components 789
  • J.P. Edelen
    RadiaSoft LLC, Boulder, Colorado, USA
  • R.D. Berry, A. Diego, D.I. Gavryushkin, A.Yu. Smirnov
    RadiaBeam, Santa Monica, California, USA
  • J. Krasna
    COSYLAB, Control System Laboratory, Ljubljana, Slovenia
  Low Level RF systems have historically fallen into two categories. Custom systems developed at national laboratories or industrial systems using custom hardware specifically designed for LLRF. Recently however advances in RF technology accompanied by demand from applications like quantum computing have led to commercially available systems that are viable for building a modular low-level RF system. Here we present an overview of a Keysight based digital LLRF system. Our system employs analog upconversion and downconversion with an intermediate frequency of 100MHz. We discuss our phase-reference system and provide initial results on the system performance.  
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About • Received ※ 25 August 2022 — Revised ※ 01 September 2022 — Accepted ※ 02 September 2022 — Issue date ※ 03 September 2022
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THPOPA23 Digital LLRF System Development and Implementation at the APS Linac 792
  • Y. Yang, J.M. Byrd, G.I. Fystro, D.A. Meyer, A. Nassiri, A.F. Pietryla, T.L. Smith, Y. Sun
    ANL, Lemont, Illinois, USA
  • B. Baričevič
    I-Tech, Solkan, Slovenia
  The current analog LLRF systems which have supported the APS linac operation for over 25 years, will be replaced with digital LLRF systems utilizing the latest commercially available electronics technology. A customized LLRF system has been developed as the next-generation APS linac controller. Two systems have been manufactured and delivered to the APS. On-site tests demonstrated they met the APS linac operation requirements with the first system expected to be integrated into APS linac operation this year.  
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About • Received ※ 22 August 2022 — Revised ※ 29 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 15 September 2022
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THPOPA24 First SELAP Algorithm Operational Experience of the New LLRF 3.0 RF Control System 795
  • T.E. Plawski, R. Bachimanchi, S. Higgins, C. Hovater, J. Latshaw, C.I. Mounts
    JLab, Newport News, Virgina, USA
  The JLAB LLRF 3.0 system has been developed and is replacing the 30-year-old LLRF systems in the CEBAF accelerator. The LLRF system builds upon 25 years of design and operational RF control experience (digital and analog), and our recent collaboration in the design of the LCLSII LLRF system. The new system also incorporates a cavity control algorithm using a fully functional phase and amplitude locked Self Exciting Loop (SELAP). The first system (controlling 8 cavities) was installed and commissioned in August of 2021. Since then the new LLRF system has been operating with cavity gradients up to 20 MV/m, and electron beam currents up to 350 uA. This paper discusses the operational experience of the LLRF 3.0 SELAP algorithm along with other software and firmware tools like cavity and klystron characterization and quench detection.
T. E. Plawski et al., ’JLAB LLRF 3.0 Development and Tests’, in Proc. 12th Int. Particle Accelerator Conf. (IPAC’21), Campinas, Brazil, May 2021, pp
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About • Received ※ 10 August 2022 — Revised ※ 01 September 2022 — Accepted ※ 07 September 2022 — Issue date ※ 12 October 2022
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THPOPA26 Machine Learning Assisted Cavity Quench Identification at the European XFEL 798
THOPA09   use link to see paper's listing under its alternate paper code  
  • J. Branlard, A. Eichler, J.H.K. Timm, N. Walker
    DESY, Hamburg, Germany
  A server-based quench detection system is used since the beginning of operation at the European XFEL (2017) to stop driving superconducting cavities if they experience a quench. While this approach effectively detects quenches, it also generates false positives, tripping the accelerating stations when failures other than quenches occur. Using the post-mortem data snapshots generated for every trip, an additional signal (referred to as residual) is systematically computed based on the standard cavity model. Following an initial training on a set of such residuals derived from quench as well as non-quench events, two independent machine learning engines analyze routinely the trip snapshots and their residuals to identify if a trip was indeed triggered by a quench or has another root cause. The outcome of the analysis is automatically appended to the data snapshots and distributed to a team of experts. This constitutes a fully deployed example of machine-learning-assisted failure classification to identify quenches, supporting experts in their daily routine of monitoring and documenting the accelerator uptime and availability.  
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poster icon Poster THPOPA26 [0.975 MB]  
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About • Received ※ 19 August 2022 — Revised ※ 24 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 01 September 2022
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