02 Photon Sources and Electron Accelerators
A08 Linear Accelerators
Paper Title Page
MOZGBD3 Performance of the First LCLS-II Cryomodules: Issues and Solutions 34
 
  • N. Solyak, E. Cullerton, J. Einstein-Curtis, E.R. Harms, B.D. Hartsell, J.P. Holzbauer, T.N. Khabiboulline, A. Lunin, Y.M. Pischalnikov, R.P. Stanek, G. Wu
    Fermilab, Batavia, Illinois, USA
  • O. Napoly
    CEA/DSM/IRFU, France
 
  LCLS-II 4 GeV linac is on the middle production stage. Linac contains 40 cryomodules of 1.3 GHz and 3 cryomodules of 3.9 GHz, including spares. Fermilab and JLAB share responsibility for cryomodule design, assembly and test. Paper will overview the performance of the cryomodules it the tests, lessons learned and modifications in design to improve performance.  
slides icon Slides MOZGBD3 [8.634 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBD3  
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TUPMF032 RF Conceptual Design of Normal Conducting Cavity for an eRHIC Rapid Cycling Synchrotron 1316
 
  • B. P. Xiao, M. Blaskiewicz, J.M. Brennan, D. Holmes, K.S. Smith, T. Xin, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Rapid Cycling Synchrotron (RCS) for the eRHIC Ring-Ring design will provide on energy injection (up to 18 GeV) of high charge, polarized electron bunches to the eRHIC electron storage ring. The RF system comprises a large number of 563MHz fundamental cavities, providing up to 45MV per turn. The cavities will operate in pulsed mode with <20% duty factor, at a repetition rate of 1 Hz. In this paper we report the conceptual RF design of the cavity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF032  
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TUPMF034 Measuring the Electrical Center and Field Flatness of 704 MHz Deflecting Cavity for LEReC with Wire Stretching System 1320
 
  • T. Xin, J.M. Brennan, J.C.B. Brutus, K. Mernick, K.S. Smith, B. P. Xiao, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • W. Johnson
    SBU, Stony Brook, New York, USA
  • H. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
704 MHz deflecting cavity was designed for the Low Energy RHIC electron Cooling (LEReC) project. The cavity will serve as a major component in diagnostic line. In LEReC project the requirement on the energy spread of the electron beam is extremely high (better than 10-4) and the diagnostic system has to to be designed accordingly. The 704 MHz transverse deflecting cavity provides the vertical kick to the beam after it passes through the dispersion dipole so that we can measure the energy spread of the core of the bunch. Traditional way of determining the electrical center of the cavity involves the needle pulling and integration of the signal which is prone to the cumulative error. We present the measurement result from a wire stretching system that is much more efficient and accurate compared to the bead/needle pulling method. Both simulation and experimental results are shown in this paper and the potential in further application is discussed at the end.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF034  
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TUPMF060 Design of Bunch Lengthening System in Electron Linac 1401
 
  • C. Meng, Y. Jiao, J.L. Li, S. Pei, Y.M. Peng, H.S. Xu
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a linac and a full energy booster. To increase the threshold of TMCI in the booster, the HEPS linac design has been evolved with several iterations. The important middle-version design is a 300 MeV linac with rms bunch length larger than 20 ps. One bunch lengthening system is proposed and discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF060  
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TUPMF061 Physical Design of the 500 MeV Electron Linac for the High Energy Photon Source 1404
 
  • S. Pei, D.Y. He, X. He, J.L. Li, J. Liu, X. Ma, C. Meng, X. Wang, O. Xiao, J.R. Zhang, Z.S. Zhou
    IHEP, Beijing, People's Republic of China
  • S. Shu
    Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
 
  Funding: Work supported by the HEPS project and the National Natural Science Foundation of China (11475201). peisl@ihep.ac.cn
The High Energy Photon Source (HEPS) is a 6 GeV light source with ultra-low emittance, it is proposed to be built at Huairou district, northeast suburb of Beijing, China. A 500 MeV electron linac will be used to generate the electron beam for injection into the booster. Here the preliminary physical design of the electron linac is presented.
 
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TUPMF086 Status of the ARES RF Gun at SINBAD: From its Characterization and Installation towards Commissioning 1474
 
  • B. Marchetti, R.W. Aßmann, S. Baark, F. Burkart, U. Dorda, K. Flöttmann, I. Hartl, J. Hauser, J. Herrmann, M. Hüning, K. Knebel, O. Krebs, G. Kube, W. Kuropka, S. Lederer, F. Lemery, F. Ludwig, D. Marx, F. Mayet, M. Pelzer, I. Peperkorn, F. Poblotzki, S. Pumpe, J. Rothenburg, H. Schlarb, M. Titberidze, G. Vashchenko, T. Vinatier, P.A. Walker, L. Winkelmann, K. Wittenburg, S. Yamin, J. Zhu
    DESY, Hamburg, Germany
 
  The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to host multiple experiments relating to the production of ultra-short electron bunches and novel high gradient acceleration techniques. The SINBAD-ARES linac will be a conventional S-band linear RF accelerator allowing the production of low charge (0.5 pC - tens pC) ultra-short electron bunches (FWHM length =< 1 fs - few fs) with 100 MeV energy. The installation of the linac will proceed in stages. In this paper we report on the status of the characterization of the ARES RF gun and the installations of the related infrastructure.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF086  
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TUPML003 Design of an L-band Accelerating Structure for the Argonne Wakefield Accelerator Facility Witness Beam Line Energy Upgrade 1533
 
  • J.H. Shao, M.E. Conde, D.S. Doran, J.F. Power
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  The Argonne Wakefield Accelerator (AWA) facility has been devoting much effort to the fundamental R&D of two-beam acceleration (TBA) technology with two parallel L-band beam lines. Beginning from the 70 MeV drive beam line, the high frequency (C-band and above) rf power is extracted from the beam by a decelerating structure (a.k.a. power extractor), transferred to an accelerating structure in the witness beam line, and used to accelerate the 15 MeV main beam. These high frequency accelerating structures usually have a small aperture to obtain high gradient and high efficiency, making it difficult for the low energy main beam to pass. To address this issue, one proposal is to increase the main beam energy to above 30 MeV by replacing the current witness linac. A 9-cell 𝜋-mode L-band standing-wave accelerating structure has therefore been designed to meet the high shunt impedance and low cost requirements. In addition, the single-feed coupling cell has been optimized with additional symmetrical ports to eliminate field distortion. The detailed design of the new accelerating structure will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML003  
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WEYGBD1 12 GeV CEBAF Initial Operational Experience and Challenges 1771
 
  • M. F. Spata
    JLab, Newport News, Virginia, USA
 
  The 12 GeV Upgrade for the Continuous Electron Beam Accelerator Facility (CEBAF) achieved CD-4B, or Project Completion, on September 27, 2017. The 13-year $338M project doubled the beam energy of the CEBAF accelerator while also adding a fourth experimental hall. The scope of work for the accelerator complex was completed in 2014. Over the subsequent three years the upgrades for the experimental halls were completed, beamlines and spectrometers commissioned and transitions made to production running for the Nuclear Physics program. This paper will present an overview of the operational experience gained during initial accelerator commissioning through the recent achievements of simultaneous 4-Hall operations at full beam power.  
slides icon Slides WEYGBD1 [15.183 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEYGBD1  
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THPMF001 Beam Dynamics Studies for Beam Focusing and Solenoid Alignment at SINBAD 4026
SUSPF020   use link to see paper's listing under its alternate paper code  
 
  • S. Yamin, R.W. Aßmann, B. Marchetti, J. Zhu
    DESY, Hamburg, Germany
 
  SINBAD (Short INnovative Bunches and Accelerators at DESY) facility under construction at DESY plans to host several experiments for the production of ultra-short bunches and will be a test facility for high-gradient compact novel acceleration techniques. The ARES (Accelerator Research Experiment at SINBAD) linac is foreseen to produce ultra-short bunches to be injected e.g. into Novel Dielectric Laser Acceleration structures or Laser Wake-Field Acceleration experiments. The work presented in this paper is based on optimization of the focusing system consisting of solenoids for the ARES, which have been studied earlier in detail but is revisited for updated beamline. Moreover tolerances for the possible misalignment of solenoids are presented investigating the effect on the beam properties during the gun commissioning.
* J. Zhu, R. Assmann, U. Dorda, B. Marchetti, "Matching sub-fs electron bunches for laser-driven plasma acceleration at SINBAD", Nucl. Instrum. Methods Phys. Res., Sect. A 829, 229 (2016)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF001  
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THPMF014 First Experiments at the CLEAR User Facility 4066
 
  • R. Corsini, A. Curcio, S. Curt, S. Döbert, W. Farabolini, D. Gamba, R. Garcia Alia, T. Lefèvre, G. McMonagle, P.K. Skowroński, M. Tali, F. Tecker
    CERN, Geneva, Switzerland
  • E. Adli, C.A. Lindstrøm, K.N. Sjobak
    University of Oslo, Oslo, Norway
  • R.M. Jones, A. Lagzda
    UMAN, Manchester, United Kingdom
 
  The new "CERN Linear Electron Accelerator for Research" (CLEAR) facility at CERN started its operation in fall 2017. CLEAR results from the conversion of the CALIFES beam line of the former CLIC Test Facility (CTF3) into a new testbed for general accelerator R&D and component studies for existing and possible future accelerator applications. CLEAR can provide a stable and reliable electron beam from 60 to 220 MeV in single or multi bunch configuration at 1.5 GHz. The experimental program includes studies for high gradient acceleration methods, e.g. for CLIC X-band and plasma technology, prototyping and validation of accelerator components, e.g. for the HL-LHC upgrade, and irradiation test capabilities for characterization of electronic components and for medical applications. An overview of the facility capabilities and a summary of the latest results will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF014  
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THPMF024 Commissioning and Operation of FAST Electron Linac at Fermilab 4096
 
  • A.L. Romanov, C.M. Baffes, D.R. Broemmelsiek, K. Carlson, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, J. Hurd, M.J. Kucera, J.R. Leibfritz, I.L. Rakhno, J. Reid, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari, R.M. Thurman-Keup, A. Valishev, A. Warner
    Fermilab, Batavia, Illinois, USA
 
  We report results of the beam commissioning and first operation of the 1.3 GHz superconducting RF electron linear accelerator at Fermilab Accelerator Science and Technology (FAST) facility. Construction of the linac was completed and the machine was commissioned with beam in 2017. The maximum total beam energy of about 300 MeV was achieved with the record energy gain of 250 MeV in the ILC-type SRF cryomodule. The pho-toinjector was tuned to produce trains of 200 pC bunches with a frequency of 3 MHz at a repetition rate of 1 Hz. This report describes the aspects of machine commission-ing such as tuning of the SRF cryomodule and beam optics optimization. We also present highlights of an experimental program carried out parasitically during the two-month run, including studies of wake-fields, and advanced beam phase space manipulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF024  
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THPMF025 Emittance Measurements at FAST Facility 4100
 
  • J. Ruan, D.R. Broemmelsiek, D.J. Crawford, A.L. Edelen, J.P. Edelen, D.R. Edstrom, A.H. Lumpkin, P. Piot, A.L. Romanov, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
 
  Funding: *Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The FAST facility at Fermilab recently been commissioned has demonstrated the generation of electron beam within a wide range of parameter (energy, charge) suitable for accelerator-science and beam-physics experiments. This accelerator consists of a photo-electron gun, injector, ILC-type cryomodules, and multiple downstream beam-lines. It will mainly serve as injector for the upcoming Integrable Optical Test Accelerator (IOTA). At the same time we will also carry out a LINAC based intense gamma ray experiment based on the Inverse Compton scattering. It is essential to understand the beam emittance for both experiments. A number of techniques are used to characaterizing the beam emittance including slit based method and quad scan method. An on-line emittance measurement based on multi-slit method is developed so the emittance measured will be immediately available to support further beam optimization. In this report we will present the results from the emittance studies using this tool. We will also present the emittance measurement based on quads scan technique for the high energy beam line.
 
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THPMF045 Synchronized Beam Position Measurement for SuperKEKB Injector Linac 4159
 
  • M. Satoh, F. Miyahara, T. Suwada
    KEK, Ibaraki, Japan
  • T. Kudou, S. Kusano
    Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
  • T. Ohfusa, H.S. Saotome, M. Takagi
    Kanto Information Service (KIS), Accelerator Group, Ibaraki, Japan
 
  Toward SuperKEKB project, the injector linac upgrade is ongoing for aiming at the stable beam operation with low emittance and high intensity bunch charge. One of the key challenges is a low emittance preservation of electron beam because the vertical emittance of 20 mm.mrad or less should be transported to the main ring without a damping ring. For this purpose, the fine alignment of accelerator components is a crucial issue since the linac alignment was badly damaged by the big earthquake in 2011. From the simulation results of emittance growth, the alignment of the quadrupole magnets and accelerating structures should be conducted at the level of 300 um in rms along the 600-m-long linac. In addition, we are aiming at the level of 100 um alignment in rms within the short range distance of 100 m long. Even after the fine component alignment can be achieved, the fine beam orbit manipulation is necessary for low emittance preservation. For these reasons, we have developed the new BPM readout system based on VME64x. The new system has improved the precision of beam position measurement up to 3 um from 25 um. We will describe the software development of the new BPM readout system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF045  
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THPMF046 Precision Charge Measurement of 40~MeV Electron-Beam to Calibrate Air Fluorescence Telescope for Cosmic Ray Observation 4163
 
  • T. Shibata
    KEK, Ibaraki, Japan
  • O.C. Shin
    OCU, Osaka, Japan
 
  The Telescope Array (TA) is ultra-high energy cosmic ray observation (UHECR). TA is using the fluorescence detectors (FD) for observation the air fluorescence(AFY) which are emitted in the cascade generated by an UHECR in atmosphere. One of the important observables is primary energy of UHECR, however it has 21% systematic uncertainty. For reduction of the uncertainty, we have been operated an 40-MeV electron linear accelerator from 2010 which we have constructed for absolute energy calibration. The accelerator is located at 100 m from FD station, and can shot electron beam which the direction is vertical into the air, the energy is 40-MeV, the pulse width is 1 micro-second, and the beam charge is 160 pC. The AFY efficiency and FD calibration parameters can be calibrated, which means energy scale of UHECR, by observation of the AFY which are generated by the electron beam in the air. The most important beam parameter is beam charge. The requirement of the accuracy of charge measurement is a few %, then we have developed the double faraday cups and one current transfer system. We calibrated the current transfer by the double faraday cups, and we could achieve about 1% accuracy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF046  
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THPMF048 Bunch Length Measurements Using CTR at the AWA with Comparison to Simulation 4166
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • J.G. Power, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
In this paper we present electron bunch length measurements at the Argonne Wakefield Accelerator (AWA) photoinjector facility. The AWA accelerator has a large dynamic charge density range, with electron beam charge varying between 0.1 nC - 100 nC, and laser spot size diameter at the cathode between 0.1 mm - 18 mm. The bunch length measurements were taken at different charge densities using a metallic screen and a Martin-Puplett interferometer to perform autocorrelation scans of the corresponding coherent transition radiation (CTR). A liquid helium-cooled 4K bolometer was used to register the interferometer signal. The experimental results are compared with Impact-T and OPAL-T numerical simulations.
 
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THPMF049 Photoinjector Optimization Studies at the AWA 4169
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • J. Larson, J.G. Power
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
With a variable charge range of 0.1 nC - 100 nC, the Argonne Wakefield Accelerator facility (AWA) has a unique and dynamic set of operating parameters. Adjustment of the optics and occasionally the rf phases is required each time the bunch charge is changed. Presently, these adjustments are done by the operator during each experiment. This is time consuming and inefficient, more so at high charge and for complex experimental set ups. In an attempt to reduce the amount of time spent adjusting parameters by hand, several optimization methods in simulation are being explored. This includes using the well-known Genetic Algorithm (NSGA-II), incorporated into OPAL-T. We have also investigated a model-based method and novel structure based algorithms developed at ANL. Ongoing efforts include using these optimization methods to improve operations at the AWA. Simulation results will be compared to measured beam parameters at the AWA, and one optimization method will be selected for use in guiding operations going forward.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF049  
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THPMF064 Beam Based Alignment of SRF Cavities in an Electron Injector Linac 4219
 
  • F. Hug
    KPH, Mainz, Germany
  • M. Arnold, T. Bahlo, J. Pforr, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
 
  Funding: Funded by DFG through Cluster of Excellence EXC 1098/2014 "PRISMA" and RTG 2128 "AccelencE" and by the European Union's Horizon 2020 Research and Innovation programme under Grant Agreement No 730871
Proper alignment of accelerating cavities is an important issue concerning beam quality of accelerators. In particular SRF cavities of injector linacs using high accelerating gradients on low beta electron beams can affect the beam quality significantly when not aligned perfectly. On the other hand knowing the exact position of every cavity after several cool-down cycles of a cryomodule can be difficult depending on the cryomodule design. We will report on operational experience on the SC injector of the Darmstadt superconducting linac and ERL (S-DALINAC) showing unexpected effects on beam dynamics and beam quality. Operators could observe transverse beam deflections by changing accelerating phases of the injector SRF-cavities while a growth of tranverse emittance occurred at the same time. As beam currents in the S-DALINAC injector do never exceed 100 µA and the effects could even be observed at nA beam currents space-charge effects could be eliminated to be the reason for these observations. In this work we will report on the possibility to align SRF cavities after cooldown by measuring the transverse deflection of the beam and compare results with beam dynamics simulations.
 
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THPMF068 Commissioning Status of FLUTE 4229
 
  • A. Malygin, A. Bernhard, E. Bründermann, A. Böhm, S. Funkner, S. Marsching, W. Mexner, A. Mochihashi, A.-S. Müller, M.J. Nasse, G. Niehues, R. Ruprecht, T. Schmelzer, M. Schuh, N.J. Smale, P. Wesolowski, M. Yan
    KIT, Karlsruhe, Germany
  • I. Križnar
    Cosylab, Ljubljana, Slovenia
  • M. Schwarz
    CERN, Geneva, Switzerland
 
  FLUTE (Ferninfrarot Linac- Und Test-Experiment) will be a new compact versatile linear accelerator at the KIT. Its primary goal is to serve as a platform for a variety of accelerator studies as well as to generate strong ultra-short THz pulses for photon science. The phase I of the project, which includes the RF photo injector providing electrons at beam energy of 7 MeV and a corresponding diagnostics section, is currently being commissioned. In this contribution, we report on the latest progress of the commissioning phase. The status of the gun conditioning will be given, followed by an overview of the RF system and the laser system.  
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THPMF074 Study of the Saturation of Radiation Energy Caused by the Space Charge Effect in a Compact THz Coherent Radiation Source 4245
SUSPF018   use link to see paper's listing under its alternate paper code  
 
  • S. Krainara, Chatani, S. Chatani, T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
 
  Funding: Institute of Advanced Energy, Kyoto University
To generate an intense quasi-monochromatic Terahertz Coherent Undulator Radiation (THz-CUR), a compact linac system, which employs a magnetic electron bunch compressor with a beam energy of 4.6 MeV, has been constructed at Kyoto University. The THz-CUR has suc-cessfully been generated in a frequency range from 0.16 to 0.65 THz with a bunch charge of 60 pC. The maximum micro-pulse energy of THz radiation was observed higher than 1 µJ at 0.16 THz with 160 pC. However, when a bunch charge was higher than 80 pC, the micro-pulse energy of THz radiation gradually went to the saturation and obviously at the bunch charge higher than 110 pC because of the bunch lengthening and degradation of electron beam quality due to the space charge effect. The dependence of a bunch length on a bunch charge has been studied by GPT simulation and compared with CTR and CUR experiments. The trends of the measured results from CUR and CTR are in good agreement with the GPT simulation.
 
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THPMF090 Linac Design Elements for Spaceborne Accelerators 4291
 
  • J.W. Lewellen, C.E. Buechler, G.E. Dale, M.A. Holloway, D.C. Nguyen, D. Patrick
    LANL, Los Alamos, New Mexico, USA
  • V.A. Dolgashev, E.N. Jongewaard, J. Neilson, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • J-.M. Lauenstein
    NASA Goddard Space Flight Center, Greenbelt, USA
 
  Funding: Los Alamos National Laboratory LDRD and Program Development
Los Alamos National Laboratory, in collaboration with SLAC and Goddard Space Flight Center, have begun developing a high-duty-factor, MeV-range linear accelerator intended for use on satellites, specifically to probe the magnetosphere-ionosphere linkage. The design makes use of low-beta C-band cavities operating at moderate gradients, individually powered by 500-W RF amplifier chips. We present the current state of the design, and technology maturation efforts including RF amplifier performance studies, cavity tuner design and an initial acceleration test using a DC beam source and single RF cavity.
 
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THPMK033 PAL-XFEL Linac RF System Status 4369
 
  • H.-S. Lee, Heo, J.Y. Heo, J.H. Hong, H.-S. Kang, K.H. Kim, S.H. Kim, D.H. Na, S.S. Park, Y.J. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Funding: Ministry of Science and ICT
The PAL-XFEL Linear Accelerator began user support in March 2017 after one year of RF conditioning in 2016. The energy jitter was 0.013% when operating the H-X linear accelerator with 46 modulators, Klystron, LLRF, SSA and vacuum system at 6.838 GeV energy during user support period. So far, we have replaced four klystrons and 10 thyratron switches. We also measured the influence of temperature changes of RF components according to repetition rates of the machine. We will report on the measurement results of this operating experience and performance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK033  
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THPMK048 The Design and Construction of a Novel Dual-Mode Dual-Frequency Linac Design 4391
SUSPF045   use link to see paper's listing under its alternate paper code  
 
  • M.H. Nasr, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  One promising approach in boosting accelerators efficiency is dual-mode simultaneous operation. In our work, the topic of dual-mode acceleration is studied from a wider perspective with new approaches and tools. We present a new type of accelerator structures that operates simultaneously with two modes and two frequencies. The frequencies are not constrained to be harmonically related, but rather have a common sub-harmonic. These designs will utilize a newly developed parallel-feeding network that feeds each individual accelerating cell independently using a distributed feeding network. As a result, the design problem converges to a single-cell design with identical cells. The cells are designed for maximum efficiency using new geometrical optimization that utilizes nonuniform rational B-spline (NURBS) with a series of control points. We will present a study on the topic for S-band simultaneous operation with C-band or X-band.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK048  
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THPMK049 New Geometrical-Optimization Approach using Splines for Enhanced Accelerator Cavities' Performance 4395
 
  • M.H. Nasr, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Over the past decades accelerator scientists made a huge effort in advancing the technology of particle accelerators, which lead to state-of-the-art fabrication techniques as well as simulation tools. Combining these advancements with the large boosting in computing speed provides large flexibility and motivation to investigate new accelerator geometries. In this paper, we describe a new optimization approach for the geometry of accelerating cells. This approach uses a set of control points with variable positions to control a non-uniform rational B-spline (NURBS), which describes the cavity shape. The positions of the control points are then optimized using differential-evolution optimization to maximize/minimize a defined optimization function, which is defined by the user and depends on the cavity parameters such as the shunt impedance, wall losses, peak surface fields…etc. This optimization approach leads to accelerator geometries with enhanced performance and very smooth surface fields.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK049  
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THPMK058 RF Design of the X-band Linac for the EuPRAXIA@SPARC_LAB Project 4422
SUSPF016   use link to see paper's listing under its alternate paper code  
 
  • M. Diomede
    Sapienza University of Rome, Rome, Italy
  • D. Alesini, M. Bellaveglia, B. Buonomo, F. Cardelli, E. Chiadroni, G. Di Raddo, R.D. Di Raddo, M. Diomede, M. Ferrario, A. Gallo, A. Ghigo, A. Giribono, V.L. Lollo, L. Piersanti, B. Spataro, C. Vaccarezza
    INFN/LNF, Frascati (Roma), Italy
  • N. Catalán Lasheras, A. Grudiev, W. Wuensch
    CERN, Geneva, Switzerland
 
  We illustrate the RF design of the X-band linac for the upgrade of the SPARC_LAB facility at INFN-LNF (EuPRAXIA@SPARC_LAB). The structures are travelling wave (TW) cavities, working on the 2π/3 mode, fed by klystrons with pulse compressor systems. The tapering of the cells along the structure and the cell profiles have been optimized to maximize the effective shunt impedance keeping under control the maximum value of the modified Poynting vector, while the couplers have been designed to have a symmetric feeding and a reduced pulsed heating. In the paper we also present the RF power distribution layout of the accelerating module and a preliminary mechanical design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK058  
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THPMK084 E-field Measurement of 9.3 GHz RF cavity for 6 MeV LINAC 4496
SUSPF017   use link to see paper's listing under its alternate paper code  
 
  • D.H. Ha, J.-S. Chai, M. Ghergherehchi, H.S. Kim, J.C. Lee, H. Namgoong, J.H. Seo, Shin, S.W. Shin
    SKKU, Suwon, Republic of Korea
 
  In order to achieve performance close to the design value, fabricated cavity was tuned at Sunkyunkwan university. Tuning was done in two step: each cell tuning and bead-pull system. Each cell tuning was used to determine the status of each cell and to remove the stop-band. Bead-pull system was used to measure the E-field distribution and obtain the required field flatness. This paper describes each cell measurement data and bead-pull measurement system and data.
x-band, linac, measurement
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK084  
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THPMK090 First RF Test Results of Two-Cavities Accelerating Cryomodule for ARIEL eLinac at TRIUMF 4512
 
  • Y. Ma, Z.T. Ang, K. Fong, J.J. Keir, D. Kishi, D. Lang, R.E. Laxdal, R.R. Nagimov, B.S. Waraich, Z.Y. Yao, V. Zvyagintsev
    TRIUMF, Vancouver, Canada
 
  The Advanced Rare Isotope Laboratory (ARIEL) pro-ject requires a 50 MeV, 10 mA continuous-wave (CW) electron linear accelerator (e-Linac) as a driver accelera-tor. Now the stage of the 30MeV portion of the e-Linac is under commissioning which includes an injector cry-omodule(ICM) and the 1st accelerator cryomodules (ACM1) with two cavities configuration. A single 290kW klystron is used to feed the two ACM1 cavities in vector sum closed-loop control. In this paper the initial commis-sioning results of the ACM1 RF system will be present.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK090  
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THPMK103 Initial Testing of Techniques for Large Scale Rf Conditioning for the Compact Linear Collider 4548
SUSPF019   use link to see paper's listing under its alternate paper code  
 
  • T.G. Lucas, M.J. Boland, P.J. Giansiracusa, R.P. Rassool, M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
  • N. Catalán Lasheras, A. Grudiev, T. Lefèvre, G. McMonagle, I. Syratchev, B.J. Woolley, W. Wuensch, V. del Pozo Romano
    CERN, Geneva, Switzerland
  • J. Paszkiewicz
    University of Oxford, Oxford, United Kingdom
  • C. Serpico
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • A. Vnuchenko
    IFIC, Valencia, Spain
  • R. Zennaro
    PSI, Villigen PSI, Switzerland
 
  Nominal operating conditions for the Compact Linear Collider (CLIC) 380 GeV requires 72 MV/m loaded accelerating gradients for a 180 ns flat-top pulse. Achieving this requires extensive RF conditioning which past tests have demonstrated can take several months per structure, when conditioned at the nominal repetition rate of 50 Hz. At CERN there are three individual X-band test stands currently operational, testing up to 6 structures concurrently. For CLIC's 380 GeV design, 28,000 accelerating structures will make up the main linac. For a large scale conditioning programme, it is important to understand the RF conditioning process and to optimise the time taken for conditioning. In this paper, we review recent X-band testing results from CERN's test stands. With these results we investigate how to optimise the conditioning process and demonstrate the feasibility of pre-conditioning the structures at a higher repetition rate before installation into the main linac.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK103  
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THPMK104 High Power and High Repetition Rate X-band Power Source Using Multiple Klystrons 4552
 
  • M. Volpi, M.J. Boland, P.J. Giansiracusa, T.G. Lucas, R.P. Rassool
    The University of Melbourne, Melbourne, Victoria, Australia
  • N. Catalán Lasheras, A. Grudiev, G. McMonagle, I. Syratchev, B.J. Woolley, W. Wuensch, V. del Pozo Romano
    CERN, Geneva, Switzerland
  • J. Paszkiewicz
    University of Oxford, Oxford, United Kingdom
  • C. Serpico
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • A. Vnuchenko
    IFIC, Valencia, Spain
 
  In July 2016, the first X-band test facility operating with two interwoven, 6 MW klystron pulses was commissioned at CERN. Outputting up to 46 MW after pulse compression, the new test stand allows testing of two structures concurrently with repetition rates up to 400 Hz in each line. RF commissioning of all four lines has been completed and testing of high gradient accelerating structures for the Compact Linear Collider has commenced. Operations have been ongoing for more than a year, where dedicated control algorithms have been developed to conditioning the structure and to keep the pulse compressors tuned. Significant progress has been made in understanding the conditioning of two structures that are sharing an interlock and vacuum system. The high repetition rate is already showing the significantly reduced time needed to condition accelerating structures.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK104  
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THPML063 Micro-Bunched Beam Production at FAST for Narrow Band THz Generation Using a Slit-Mask 4784
 
  • J. Hyun
    Sokendai, Ibaraki, Japan
  • D.J. Crawford, D.R. Edstrom, J. Ruan, J.K. Santucci, T. Sen, J.C.T. Thangaraj, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
 
  We discuss simulations and experiments on creating micro-bunch beams for generating narrow band THz radiation at the Fermilab Accelerator Science and Technology (FAST) facility. The low-energy electron beamline at FAST consists of a photoinjector-based RF gun, two L-band superconducting accelerating cavities, a chicane, and a beam dump. The electron bunches are lengthened with cavity phases set off-crest for better longitudinal separation and then micro-bunched with a slit-mask installed in the chicane. We carried out the experiments with 30 MeV electron beams and detected signals of the micro-bunching using a skew quadrupole magnet in the chicane. In this paper, the details of micro-bunch beam production, the detection of micro-bunching and comparison with simulations are described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML063  
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THPML092 Electromagnetic and Mechanical Design of High Gradient S-Band Accelerator in TTX 4876
 
  • D.Z. Cao, H.B. Chen, Y. C. Du, W. Gai, W.-H. Huang, J. Shi, C.-X. Tang, P. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  Thomson scattering x-ray source is an essential scien-tific research tool in x-ray imaging technology for vari-ous fields. Upgrading plan of replacing the 3-meter S-band linac with a shorter structure operating at higher gradient in Tsinghua Thomson scattering X-ray source (TTX) is undergoing so far, aiming to enhance the accel-erating gradient from 15 MV/m to 30 MV/m. Detailed parameters of couplers and mechanical design of acceler-ation structure are presented in this work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML092  
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THPML125 Efficiency Analysis of High Average Power Linacs for Environmental and Industrial Applications 4970
 
  • M. Shumail, V.A. Dolgashev
    SLAC, Menlo Park, California, USA
 
  Funding: U.S. Department of Energy, HEP under Research Opportunities in Accelerator Stewardship: LAB 16-1438.
We present comprehensive efficiency equations and useful scaling laws to optimally determine design parameters for high efficiency rf linacs. For the first time we have incorporated the parasitic losses due to the higher order cavity modes into the efficiency analysis of the standing wave (SW) and travelling wave (TW) accelerators. We have also derived the efficiency equations for a new kind of attenuation-independent-impedance travelling wave (ATW) accelerators where the shunt impedance can be optimized independent of the group velocity. We have obtained scaling laws which relate the rf to beam efficiency to the linac length, beam aperture radius , phase advance per cell, and the type of accelerating structure: SW versus TW, disk-loaded (DL) versus nose-cone (NC). We give an example of using these scaling laws to determine a feasible set of parameters for a 10 MeV, 10 MW linac with 97.2% efficiency.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML125  
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