RF power sources and power couplers
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TUPOPA15 Multipactor Studies: Simulations and Measurements on the RF Coaxial Resonator Test Bench 445
  • Y. Gómez Martínez, J. Angot, M.A. Baylac, T. Cabanel, M. Meyer
    LPSC, Grenoble Cedex, France
  • D. Longuevergne, G. Sattonnay
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  Multipactor is an undesired phenomenon triggered by electromagnetic fields in accelerator components and more specifically in RF structures, such as accelerating cavities and power couplers, and may lead to Electron Cloud build up in beam tubes. The accelerator group at LPSC has developed an experimental setup dedicated to multipactor studies. It consists in a coaxial resonator, tunable and operational between 100 MHz and 1 GHz. It allows to characterize under real conditions the efficiency of surface treatment mitigation processes (coatings, cleaning procedures) at room temperature. This paper presents the experimental measurements performed with this setup confronted to simulations.  
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About • Received ※ 12 August 2022 — Revised ※ 30 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 16 September 2022
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TUPOPA16 Complete Study of the Multipactor Phenomenon for the MYRRHA 80 kW CW RF Couplers 448
  • Y. Gómez Martínez, P.-O. Dumont, M. Meyer
    LPSC, Grenoble Cedex, France
  • P. Duchesne, C. Joly, W. Kaabi
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  MYRRHA [1] (Multi Purpose Hybrid Reactor for High Tech Applications) is an Accelerator Driven System (ADS) project. Its superconducting linac will provide a 600 MeV - 4 mA proton beam. The first project phase based on a 100 MeV linac is launched. The Radio-Frequency (RF) couplers have been designed to handle 80 kW CW (Continuous Wave) at 352.2 MHz. This paper describes the multipacting studies on couplers.  
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About • Received ※ 12 August 2022 — Revised ※ 22 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 05 September 2022
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TUPOPA17 Solving the USB Communication Problem of the High-Voltage Modulator Control System in the European XFEL 451
  • M. Bousonville, S. Choroba, T. Grevsmühl, S. Göller, A. Hauberg, T. Weinhausen
    DESY, Hamburg, Germany
  Since the commissioning of the modulators in the European XFEL in 2016, it happened from time to time that the modulator control system hung up. The reason for the problem was unknown at that time. Initially, the MTBF (Mean Time Between Failure) was 104 days, which was so rare that other problems with the RF system clearly dominated and were addressed first. Over the next 2 years, the error became more frequent and occurred on average every 18 days. After the winter shutdown of the XFEL in 2020, the problem became absolutely dominant, with an MTBF of 2 days. Therefore, the fault was investigated with top priority and was finally identified. Two units of the control electronics communicate via USB 2.0 with the main server. Using special measurement technology, it was possible to prove that weak signal levels in the USB signal led to bit errors and thus to the crash of the control electronics. This article describes the troubleshooting process, how to measure the signal quality of USB signals and how the problem was solved in the end.  
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About • Received ※ 22 August 2022 — Revised ※ 19 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 15 September 2022
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TUPOPA18 Test and Commissioning of the HELIAC Power Coupler 454
  • J. List, K. Aulenbacher, W.A. Barth, M. Basten, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, M. Miski-Oglu, S. Yaramyshev
    HIM, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, F.D. Dziuba, S. Lauber, J. List
    KPH, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, M. Basten, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, S. Yaramyshev
    GSI, Darmstadt, Germany
  • T. Conrad, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  The superconducting continuous wave (cw) heavy ion HElmholtz LInear ACcelerator (HELIAC) is intended to be built at GSI in Darmstadt. With its high average beam current and repetition rate, the HELIAC is designed to fulfill the requirements of the super heavy element (SHE) research user program and the material sciences community at GSI. The accelerating cavities are of the superconducting Crossbar H-mode (CH) type, developed by GUF. Within the Advanced Demonstrator project, the first cryomodule, consisting of four cavities is scheduled for commissioning with beam in 2023. The former RF power couplers introduced a high heat input into the cryostat. Therefore, the coupler is redesigned at HIM in order to not only reduce the heat input but to provide an overall improved power coupler for the HELIAC. It is designed for maximal power of 5 kW cw at the frequency of 216.816 MHz. A prototype has been tested and commissioned recently. This includes several RF-tests at room temperature and in cryogenic environments. The results of these tests will be presented in this paper.  
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About • Received ※ 20 August 2022 — Revised ※ 21 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 01 September 2022
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TUPOPA24 Design of an X-Band Bunching and Accelerating System for AWAKE Run 2 458
  • J.M. Arnesano, S. Döbert
    CERN, Meyrin, Switzerland
  The AWAKE experiment at CERN demonstrated in its Run 1 that it is possible to accelerate electrons in plasma wakefields driven by a self-modulated proton bunch. In Run2, AWAKE aims to increase the accelerating gradient in the plasma even further and demonstrate beam quality in order to be ready for high-energy physics experiments. In this framework, a new electron injector, consisting of an S-band RF-gun and a subsequent X-band bunching and accelerating section, capable of producing very short bunches with a small emittance, has been designed. In this paper, two different configurations of the X-band section and their corresponding high-power distribution systems are presented. The first one consists of three identical cavities to bunch and accelerate the beam while the second one uses a separate short structure for velocity bunching followed by three long, pure accelerating structures. A discussion of the strengths and weaknesses of each configuration is carried out and beam dynamics aspects are analyzed. Finally the X-Band power distribution systems are described with particular attention to the choice of the klystron, the pulse compression system and the waveguide distribution.  
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About • Received ※ 12 August 2022 — Revised ※ 21 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 16 September 2022
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TUPOPA25 Design, Manufacturing, Assembly, Testing, and Lessons Learned of the Prototype 650 MHz Couplers 462
  • J. Helsper, S.K. Chandrasekaran, F. Furuta, B.M. Hanna, S. Kazakov, J.P. Ozelis, K.S. Premo, N. Solyak, G. Wu
    Fermilab, Batavia, Illinois, USA
  Funding: Work supported, in part, by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under U.S. DOE Contract No. DE-AC02-07CH11359.
Six 650 MHz high-power couplers will be integrated into the prototype High Beta 650 MHz (HB650) cryomodule for the PIP-II project at Fermilab. The design of the coupler is described, including design optimizations from the previous generation. This paper then describes the coupler life-cycle, including manufacturing, assembly, testing, conditioning and the lessons learned at each stage.
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About • Received ※ 24 August 2022 — Revised ※ 25 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 02 September 2022
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TUPOPA27 Conceptual Analysis of a Compact High Efficiency Klystron 466
  • J.P. Edelen, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • K.E. Nichols
    LANL, Los Alamos, New Mexico, USA
  Traditional klystron efficiencies are limited by the output electron beam harmonic current and energy spread. Increasing the amount of harmonic current produced in the klystron requires increasing the velocity bunching in the input cavity. Additional cavities may be used to improve the bunching, however they do so at additional cost and space requirements for the klystron. Moreover, at higher currents space charge counteracts this velocity bunching reducing the amount of harmonic current that can be produced. Our concept resolves these challenges by employing a new type of high-efficiency, multi-beam klystron. Our design consists of a single two-frequency input cavity, a wiggler, and an output cavity. The two-frequency input cavity approximates a linear function in time thereby increasing the harmonic content of the beam, while the wiggler provides strong longitudinal focusing to mitigate the effects of space charge. In this paper we provide the theoretical foundation for our design and present initial numerical calculations showing improved bunching from the harmonic mode and the wiggler.  
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About • Received ※ 14 August 2022 — Revised ※ 24 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 31 August 2022
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TUPOPA29 Design Enhancements for the SNS RFQ Coaxial Coupler 469
  • G.D. Toby, C.N. Barbier, Y.W. Kang, S.W. Lee, J.S. Moss
    ORNL, Oak Ridge, Tennessee, USA
  • A.H. Narayan
    ORNL RAD, Oak Ridge, Tennessee, USA
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science.
The H ion linear accelerator at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory operates with reliability that routinely surpasses 90% during scheduled beam operation. With the ambitious goal of eventually achieving at least 95% availability, several upgrade and improvement projects are ongoing. One such project is the modification of the coaxial couplers that transfer radio frequency (RF) power to the accelerator’s Radio Frequency Quadrupole (RFQ). The proposed modification utilizes stub sections and capacitive coupling to construct a physically separable assembly with DC isolation. With a separated coupler assembly, the section that includes the magnetic coupling loop can be permanently mounted to the RFQ which would eliminate the need to re-adjust the couplers after maintenance activities, upgrades, and repairs. Additionally, the modified design would provide increased multipaction suppression with DC biasing and potentially lower thermal gradients across the device. This paper presents the design and simulation results of the project.
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About • Received ※ 23 August 2022 — Revised ※ 29 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 01 September 2022
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TUPOPA30 Innovative Magnetron Power Sources for SRF Linacs 473
TUOPA05   use link to see paper's listing under its alternate paper code  
  • M. Popovic, M.A. Cummings, A. Dudas, R.P. Johnson, R.R. Lentz, M.L. Neubauer, T. Wynn
    Muons, Inc, Illinois, USA
  • T. Blassick, J.K. Wessel
    Richardson Electronics Ltd, Lafox, Illinois, USA
  • K. Jordan, R.A. Rimmer, H. Wang
    JLab, Newport News, Virginia, USA
  Funding: Supported in part by US Department of Energy Nuclear Physics SBIR Grant DE-SC0022484
Magnetron RF power sources for single cavities can cost much less and operate at much higher efficiency than klystrons, but they do not have the phase and amplitude control, or the lifetime, needed to drive SRF cavities for superconducting particle accelerators. Existing magnetrons that are typically used to study methods of control or lifetime improvements for SRF accelerators are built for much different applications such as kitchen microwave ovens (1kW, 2.45 GHz) or industrial heating (100 kW, 915 MHz). Muons, Inc. is working with Richardson Electronics LLC to develop fast and flexible manufacturing techniques to allow many ideas to be tested for construction variations that enable new phase and amplitude injection locking control methods, longer lifetime, and inexpensive refurbishing resulting in the lowest possible life-cycle costs. A magnetron suitable for 1497 MHz klystron replacements at Jefferson Lab has been designed, constructed, and tested.
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About • Received ※ 16 August 2022 — Revised ※ 26 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 01 September 2022
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