07 Accelerator Technology
T08 RF Power Sources
Paper Title Page
MOYGB1 Status and Future Strategy for Advanced High Power Microwave Sources for Accelerators 12
  • F. Gerigk
    CERN, Geneva, Switzerland
  The need for more energy efficient high power microwave devices for accelerator applications continues to increase. This is important for development of cost effective accelerator designs that are coming up in the near future. Efforts are already in place to design new devices that could stretch the limits of RF power conversion to the highest levels possible. Devices including new technologies and design innovations like multi beam, increased number of cavities designs are being considered. Advances in the application of solid state amplifiers to accelerators are also being realized. This invited talk will cover the recent advances and status of such efforts. It will discuss future needs and a strategy for pursuing these efforts on a faster time scale for the benefit of the accelerator community.  
slides icon Slides MOYGB1 [11.580 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOYGB1  
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WEXGBF3 RF System for FRIB Accelerator 1765
  • D.G. Morris, J. Brandon, N.K. Bultman, K.D. Davidson, A. Facco, P.E. Gibson, L. Hodges, M.G. Konrad, T.L. Larter, H. Maniar, P. Morrison, P.N. Ostroumov, J.T. Popielarski, G. Pozdeyev, H.T. Ren, T. Russo, K. Schrock, R. Walker, J. Wei, T. Xu, Y. Xu, S. Zhao
    FRIB, East Lansing, USA
  • A. Facco
    INFN/LNL, Legnaro (PD), Italy
  The RF system of the FRIB driver accelerator includes solid state amplifiers up to 18 kW operating at frequencies from 80.5 MHz to 322 MHz. Much higher power is required for the normal conducting RFQ, ~100 kW, and it is based on vacuum tubes. This invited talk presents the performance of solid state amplifiers and LLRF in off-line testing and on-line testing of the RFQ amplifier.  
slides icon Slides WEXGBF3 [14.111 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEXGBF3  
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WEPMF002 Operational Experience with IOTs at Alba Synchrotron 2372
  • J.R. Ocampo, B. Bravo, R. Fos, F. Pérez, A. Salom, P. Solans
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • S. Bethuys, A. Beunas, M. Grezaud, P. Reynaud
    TED, Velizy-Villacoublay, France
  • M. Boyle, J. Cipolla, W.F. Coyle, H. Schult
    L-3, Williamsport, Pennsylvania, USA
  ALBA is a 3 GeV Synchrotron light source in operation since 2012. The RF systems are based in Inductive Output Tube (IOT) transmitters. A total of 13 80 kW IOT amplifiers are used to power the Storage Ring and Booster cavities at 500 MHz. The transmitters were initially configured to operate the TH-793-1 and TH-794 IOT from THALES Electron devices. On 2015, the amplifiers have been adapted to operate also the TH-795 from THALES and the L4444-C from L3 Communications. In this paper, a brief overview of the differences between these IOT models will be presented, as well as operation results for each type of IOT from the point of view of performance, reliability and durability.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF002  
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WEPMF005 Design and Testing of a 12 kW, 352 MHz Solid State rf System at the Advanced Photon Source 2378
  • D. Horan, D.J. Bromberek, A. Goel, T.J. Madden, A. Nassiri, G.J. Waldschmidt
    ANL, Argonne, Illinois, USA
  A 12 kW, 352 MHz rf power amplifier system was designed and constructed at the Advanced Photon Source as a research and development test bed for eventual development of a 200 kW cw rf system capable of supporting accelerator beam operation. The system utilizes six 2 kW laterally diffused metal oxide field effect transistor (MOSFET) rf amplifiers, an output cavity combiner terminated with a WR2300 waveguide output flange, and a monitoring system based on programmable logic controller technology. The combining cavity has a total capacity of 108 two-kilowatt inputs to support eventual operation up to 216kW maximum output power. Design details and operational performance of the 12 kW system will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF005  
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WEPMF009 Influence of Argon-Ion Irradiation on Field Emission from Polycrystalline Cu and Large-Grain NB Surfaces 2384
  • S. Soykarci
    University of Wuppertal, Wuppertal, Germany
  • D. Lützenkirchen-Hecht, V. Porshyn, P. Serbun
    Bergische Universität Wuppertal, Wuppertal, Germany
  Funding: This work is funded by the BMBF project 05H15PXRB1.
In the present work, systematic investigations of the enhanced field emission (EFE) from polycrystalline copper and large grain niobium surfaces before and after argon-ion irradiation with an energy of 5 keV were performed with a variation of the irradiation time. Results show that the suppression of the EFE might be achievable.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF009  
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WEPMF010 Laser Treatment of Niobium Surface for SRF Aplications 2387
  • V. Porshyn, D. Lützenkirchen-Hecht, P. Serbun
    Bergische Universität Wuppertal, Wuppertal, Germany
  • H. Bürger, S. Soykarci
    University of Wuppertal, Wuppertal, Germany
  Funding: The research was funded by the German Federal Ministry of Education and Research (BMBF) under project number 05H15PXRB1.
We report on a laser surface treatment of high purity niobium (110) single crystals. Typical surface defects like scratches, pits, sharp rims and holes were eliminated by a focused pulsed ns-laser beam. A laser fluence of about 0.68 J/cm2 and 40 - 80 pulses per spot were required to induce well detectable surface modifications. The remelted surface was sufficiently smooth, but exhibited also a number of wave structures. Thus, the surface roughness slightly increased with increasing number of pulses. Finally, boiling traces and µm-deep ablation were observed and studied as well. Local field electron emission measurements showed no emission up to 700 MV/m from a moderate remelted area below the boiling point.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF010  
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WEPMF030 Optimization of Klystron Efficiency with MOGA 2419
  • C. Meng, X. He, S. Pei, S.C. Wang, O. Xiao, Z.S. Zhou
    IHEP, Beijing, People's Republic of China
  As the very important element of accelerator the klystron provide power to cavities for accelerating. Considering the accelerator cost of construction and running, the improvement of klystron efficiency is one developing hotspot of klystron research. In this paper the optimization method of klystron efficiency with MOGA based on 1D simulation program is proposed and the influences on klystron efficiency will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF030  
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WEPMF065 High Efficiency, High Power, Resonant Cavity Amplifier For PIP-II 2518
  • M.P.J. Gaudreau, N. Butler, D.B. Cope, P. H. Gordon, E.G. Johnson, M.K. Kempkes, R.E. Simpson
    Diversified Technologies, Inc., Bedford, Massachusetts, USA
  Funding: Funded under US DOE grant no. DE-SC0015780
Diversified Technologies, Inc. (DTI) is developing an integrated resonant-cavity combined solid-state amplifier for the Proton Improvement Plan-II (PIP-II) at Fermilab. The prototype has demonstrated multiple-transistor combining at 71% efficiency, at 675 watts per transistor at 650 MHz. The design simplifies solid-state transmitters to create straightforward scaling to high power levels. A crucial innovation is the reliable "soft-failure" mode of operation; a failure in one or more of these myriad combined transistors has negligible performance impact. The design couples the transistor drains directly to the cavity without first transforming to 50 Ohms, avoiding the otherwise-necessary multitude of circulators, cables, and connectors. DTI's design increases the power level at which it is cost-effective to employ a solid-state transmitter. DTI is upgrading the system to accommodate more transistors in each cavity module, and then will design and build a complete 100 kW-class transmitter which will consist of four such cavity modules and a combiner.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF065  
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WEPMF074 High Power Conditioning of X-Band RF Components 2545
  • N. Catalán Lasheras, H. Damerau, R.L. Gerard, A. Grudiev, G. McMonagle, J. Paszkiewicz, A. Solodko, I. Syratchev, B.J. Woolley, W. Wuensch, V. del Pozo Romano
    CERN, Geneva, Switzerland
  • T.G. Lucas, M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
  • S. Pitman
    Lancaster University, Lancaster, United Kingdom
  • A. Vnuchenko
    IFIC, Valencia, Spain
  As part of the effort to qualify CLIC accelerating struc-tures prototypes, new X-band test facilities have been built and commissioned at CERN in the last years. In this context, a number of RF components have been designed and manufactured aiming at stable operation above 50 MW peak power and several kW of average power. All of them have been tested now in the X-band facility at CERN either as part of the facility or in dedicated tests. Here, we describe shortly the main design and manufac-turing steps for each component, the testing and eventual conditioning as well as the final performance they achieved.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF074  
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THPAL025 New Drift-Tube Linac RF Systems at LANSCE 3680
  • J.T.M. Lyles, R.E. Bratton, M.S. Prokop, D. Rees
    LANL, Los Alamos, New Mexico, USA
  Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
LANSCE has restored the proton drift-tube linac (DTL) to high-power capability after the original RF-power tube manufacturer could no longer supply devices that consistently met our high-average power requirement. Thales TH628L Diacrodes® now supply RF power to three of the four DTL tanks. These tetrodes reused the existing infrastructure including water-cooling systems, coaxial transmission lines, high-voltage power supplies and capacitor banks. Each transmitter uses a combined pair of power amplifiers to produce up to 3- MW peak and 360- kW of mean power. A new intermediate power amplifier was simultaneously developed using a TH781 tetrode. Design and prototype testing of the high-power stages was completed in 2012, with commercialization following in 2013. Each installation was accomplished during a 4 to 5 month beam outage each year from 2014-2016. A new digital low-level RF control system was designed, built and placed into operation in 2016. The interaction of the dual power amplifiers, the I/Q LLRF, and the DTL cavities provided many challenges that were overcome. The replacement RF systems have completely met our accelerator requirements.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL025  
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THPAL038 Phase Grouping of Larmor Electrons by a Synchronous Wave in Controlled Magnetrons 3723
  • G.M. Kazakevich, R.P. Johnson
    Muons, Inc, Illinois, USA
  • V.A. Lebedev, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  A simplified analytical model based on the charge drift approximation has been developed. It considers the resonant interaction of the synchronous wave with the flow of Larmor electrons in a magnetron. The model predicts stable coherent generation of the tube above and below the threshold of self-excitation. This occurs if the magnetron is driven by a sufficient resonant injected signal (up to -10 dB). The model substantiates precise stability, high efficiency and low noise at the range of the magnetron power control over 10 dB by variation of the magnetron current. The model and the verifying experiments with 2.45 GHz, 1 kW magnetrons are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL038  
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THPAL039 Improved Magnetron Stability and Reduced Noise in Efficient Transmitters for Superconducting Accelerators 3726
  • G.M. Kazakevich, R.P. Johnson
    Muons, Inc, Illinois, USA
  • V.A. Lebedev, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  State of the art high-current superconducting accelerators require efficient RF sources with a fast dynamic phase and power control. This allows for compensation of the phase and amplitude deviations of the accelerating volt-age in the Superconducting RF (SRF) cavities caused by microphonics, etc. Efficient magnetron transmitters with fast phase and power control are attractive RF sources for this application. They are more cost effective than traditional RF sources such as klystrons, IOTs and solid-state amplifiers used with large scale accelerator projects. However, unlike traditional RF sources, controlled magnetrons operate as forced oscillators. Study of the impact of the controlling signal on magnetron stability, noise and efficiency is therefore important. This paper discusses experiments with 2.45 GHz, 1 kW tubes and verifies our analytical model which is based on the charge drift approximation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL039  
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THPAL042 Injection Locked 1497 MHz Magnetron 3736
  • M.L. Neubauer, A. Dudas, S.A. Kahn
    Muons, Inc, Illinois, USA
  • R.A. Rimmer, H. Wang
    JLab, Newport News, Virginia, USA
  A novel injection-locked 1497 MHz 13 kW AM magnetron design is presented. The anode design to minimized eddy currents due to the changing magnetic field is presented. Thermal calculations of two design options are also presented. An extra degree of freedom in the anode construction is made possible by the fact that the magnetron is injection locked. This fact presents some additional design details that can be utilized in the cooling network for the magnetron anode.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL042  
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THPAL046 Energy-Savings for the TPS Booster RF System at the NSRRC in Taiwan 3748
  • F.-T. Chung, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, Y.T. Li, M.-C. Lin, Z.K. Liu, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  In this paper, we discuss an energy-savings control sys-tem for the Taiwan Photon Source (TPS) booster RF sys-tem. During top-up storage ring operation, a timing con-trol is activated to reduce the booster RF transmitter en-ergy consumption when no injection is required. When-ever injection into the TPS storage ring is needed, the booster RF transmitter is immediately adjusted to operat-ing conditions. This timing-control system will save an energy of 380, 000 kWh annually.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL046  
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THPAL053 Perveance Measurement of the TLS-Linac Klystron and the Evaluation of Its Operation Performance 3763
  • H.H. Chen, C.H. Kuo, K.-K. Lin, Y.-H. Liu
    NSRRC, Hsinchu, Taiwan
  The high power klystron is a radio frequency amplifier for TLS linac operation. It is a crucial device for electron acceleration in linac. How to evaluate its efficiency, lifetime and performance of klystron in operation is one of the major concern in this report. The key klystron parameter perveance is introduced and used for performance evaluation and operation status monitoring. It is important to execute periodic monitoring on perveance for ensuring a stable linac operation. Klystron characteristics diagnostics can be achieved through perveance measurement. A couple of klystron diagnostic parameters concerning perveance are explored for field examination purpose. Perveance comparison with factory acceptance test data is also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL053  
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THPAL060 Advanced Modeling of Klystrons by the Tesla-Family of Large-Signal Codes 3785
  • I.A. Chernyavskiy, D.K. Abe, B. Levush, A.N. Vlasov
    NRL, Washington, DC, USA
  • T.M. Antonsen
    UMD, College Park, Maryland, USA
  • T.M. Antonsen
    Leidos Corp, Billerica, MA, USA
  • J. Rodgers
    Naval Research Laboratory (NRL), Washington, USA
  Funding: US Office of the Naval Research
Klystrons and IOTs are widely used or proposed to be used in accelerators as high-power RF sources. Development and optimization of klystron and IOT designs is aided by the use of different simulation tools, including highly efficient large-signal codes. We present an overview of the advances in the code development and modeling using Naval Research Laboratory (NRL) set of TESLA-family of large-signal codes, suitable for the modeling of single-beam and multiple beam klystrons and IOTs. Original 2D large-signal algorithm of the code TESLA* was developed for the modeling of klystrons based on (relatively) high Q resonators and is applicable to the multiple-beam devices in an approximation of identical beams/beam-tunnels. Parallel extension of TESLA algorithm (code TESLA-MB**) enabled an accurate, quasi-3D modeling of multiple-beam devices with non-identical beams/beam-tunnels. Recently developed more general TESLA-Z algorithm*** is based on the impedance matrix approach and enabled geometry-driven large-signal modeling. Examples of applications of TESLA-family of codes to the modeling of advanced single-beam and multiple-beam klystrons (and IOTs) will be presented.
*A.N. Vlasov, et al,IEEE TPS, v.30(3), 1277-1291, June 2002
**I.A. Chernyavskiy, et al.,IEEE TPS, v.36(3), 670-681, June 2008
***I.A. Chernyavskiy, et al.,IEEE TED, v.64(2), 536-542, Feb 2017
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL060  
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THPAL073 Progress on 1.5 GHz Multi-kW CW Amplifier 3821
  • A.V. Smirnov, R.B. Agustsson, S. Boucher, A.Y. Murokh, A.Yu. Smirnov
    RadiaBeam Systems, Santa Monica, California, USA
  • M.A. Ahmadi, P. Blanchard, M.D. Mccann, C. Nguen, P.B. Peter, J. Zabek
    Microsemi Corporation, Aliso Viejo, USA
  • G.R. Branner, K.S. Yuk
    UC Davis, Davis, USA
  • J.J. Hartzell, K.J. Hoyt, T.J. Villabona
    RadiaBeam, Santa Monica, California, USA
  • V. Khodos
    Sierra Nevada Corporation, Irvine, USA
  Funding: Work supported by the U.S. Department of Energy (award No. DE-SC0013136)
JLab upgrade program foresees new CW amplifiers operating at 1497 MHz and significantly increased efficiency vs. existing VKL-7811 klystron. One of possibilities for the replacement is usage of high electron mobility packaged GaN transistors applied in array of highly efficient amplifiers using precise in-phase, low-loss combiners-dividers. We present here performance of novel, compact 300 W pallets developed at MicroSemi specifically for this project including their new GaN transistor, as well as significantly upgraded divider and combiner. Design features and challenges related to amplifier modules (pallets), broadband 21-way dividers/combiners, as well construction and assembling of the entire system are discussed including measurements.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL073  
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THPAL148 Status of High Efficiency Klystron Development in TETD 3993
  • Y. Okubo, S. Fujii, K. Suzuki, T.E. Tanaka
    Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan
  TETD (Toshiba Electron Tubes and Devices Co., Ltd.) has been developing a high efficiency klystron improved bunch quality by the multi-stage of core oscillation design. For feasibility study, an S-band 7.5 MW klystron has been designed with the efficiency of more than 60% at 1.8μperveance. The first prototype was fabricated by modifying the interaction section of a commercial model to enhance the efficiency from 45% to 60%. The klystron was tested in June 2017, and 57% of efficiency at 6 MW output power was demonstrated. We are developing the second prototype which has the improved design for the higher efficiency at 7.5 WM output power. The design details and the test results of the first prototypes are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL148  
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