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MOPGW002 Longitudinal Kicker Design for Sirius Light Source cavity, kicker, HOM, feedback 57
 
  • H.O.C. Duarte, A. Barros
    LNLS, Campinas, Brazil
 
  An overloaded cavity kicker for the Sirius longitudinal bunch-by-bunch feedback system will be presented in this contribution. 4th generation light sources’ lower aperture of vacuum chambers lead to higher cutoff frequencies, jeopardizing the electromagnetic performance of cavities by trapping higher order modes (HOMs) inside the structure. With the objective of damping longitudinal and transverse HOMs without compromising the kicker shunt impedance, solutions as cavity radius reduction, tapered transitions and other geometry changes are discussed herein.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW002  
About • paper received ※ 15 May 2019       paper accepted ※ 17 May 2019       issue date ※ 21 June 2019  
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MOPGW004 Microphonics Suppression in ARIEL ACM1 Cryomodule cavity, cryomodule, linac, pick-up 65
 
  • Y. Ma, K. Fong, J.J. Keir, D. Kishi, S.R. Koscielniak, D. Lang, R.E. Laxdal, R.S. Sekhon
    TRIUMF, Vancouver, Canada
 
  Now the stage of the 30MeV portion of ARIEL (The Advanced Rare Isotope Laboratory) e-Linac is under commissioning which includes an injector cryomodule (ICM) and the 1st accelerator cryomodule (ACM1) with two cavities configuration. The two ACM1 cavities are driven by a single klystron with vector-sum control and running in CW mode. During the commissioning, the ACM1 cavities gradient and stability was limited by ponderomotive effect. Acoustic noise from the environment vibration generated by cooling water system, cryogenic system and vacuum system have been identified to certain external source and some damping has been installed. In this paper, the progress of the microphonics suppression of ACM1 is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW004  
About • paper received ※ 01 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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MOPGW047 Analysis and Simulation of the "After-Pulse" RF Breakdown cavity, simulation, timing, experiment 196
 
  • X. Lin, H.B. Chen, Z.N. Liu, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
  • X.W. Wu
    CERN, Meyrin, Switzerland
 
  During the high power experiment of a single-cell standing-wave accelerating structure, it was observed that many RF breakdowns happen when the field inside cavity is decaying after the input rf pulse is off. The distribution of breakdown timing shows a peak at the moment of RF power switches off. A series of simulation was performed to study the after-pulse breakdown effect in such a standing-wave structure. A method of calculating poynting vector over time is proposed in this article to study the modified poynting vector at critical points in the cavity. Field simulation and thermal simulation were also carried out to analyse possible reasons for the after-pulse breakdown effect.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW047  
About • paper received ※ 14 May 2019       paper accepted ※ 17 May 2019       issue date ※ 21 June 2019  
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MOPGW061 Radiation from a Dielectrically Loaded Waveguide with Open End vacuum, radiation, embedded, acceleration 228
 
  • S.N. Galyamin, A.A. Grigoreva, A.V. Tyukhtin, V.V. Vorobev
    Saint Petersburg State University, Saint Petersburg, Russia
  • A. Aryshev
    KEK, Ibaraki, Japan
 
  Funding: Work supported by Russian Science Foundation (Grant No. 18-72-10137).
Open-ended waveguide structures with dielectric loading excited by specially prepared electron bunches are considered as promising candidates for development of contemporary sources of Terahertz (THz) radiation. Despite of the fact that both ordinary vacuum THz devices (e.g., backward wave oscillator) are widely available and other mechanisms for THz generation are discussed, beam driven sources are still extremely attractive due to the extraordinary peak power of THz radiation*. In this report, we study electromagnetic (EM) field produced by a charged particle bunch exiting an open-ended circular waveguide with dielectric filling placed inside collinear vacuum waveguide of a larger radius. Based on the previously developed theory**, we mainly investigate Cherenkov radiation generated penetrated vacuum regions of the structure due to the diffraction mechanism. We pay attention to the case of a train of short bunches resulting in high-order Cherenkov modes excitation. We also develop analytical procedure allowing performing the limiting process to the case of infinite radius of the outer waveguide.
* B.D. O’Shea et al., Nature Communications, Vol. 7, P. 12763, (2016).
** S.N. Galyamin et al., J. Instrumentation, Vol. 13, P. C02012 (2018).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW061  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW064 On Wakefield in Dielectric Waveguide with Shallow Corrugation of Metallic Wall radiation, ECR, wakefield, impedance 237
 
  • A.V. Tyukhtin, E.R. Akhmatova, T.Yu. Alekhina, S.N. Galyamin, V.V. Vorobev
    Saint Petersburg State University, Saint Petersburg, Russia
 
  Funding: This work was supported by the Russian Science Foundation (Grant # 18-72-10137).
Bunch radiation in periodical waveguides was mainly analyzed for situations when wavelengths are comparable to the structure period (Smith-Purcell emission). However, it is also of interest to study the "long-wave radiation" with wavelengths which are much larger than the structure period*,**. In such situation, the exact boundary conditions on the complicated periodic surface can be replaced with the equivalent boundary conditions (EBC) which must be fulfilled on the smooth surface. Earlier we considered with this approach radiation of the bunch moving along the axis of circular vacuum corrugated waveguide**. Comparison of analytical results with COMSOL simulations showed high accuracy of the EBC method. Here we analyze an analogous problem for the waveguide with corrugated wall and dielectric filling under condition that Cherenkov effect takes place in the dielectric. Due to this fact the radiation differs radically from that in the vacuum waveguide. At the same time, the radiation has essential differences from the one in the usual dielectric waveguide. The radiation properties in the waveguide under consideration and its differences from the radiation in the waveguide with smooth wall are analyzed.
* G. Stupakov, K. Bane, Phys. Rev. ST-AB, 15 (2012) 124401.
** A.V. Tyukhtin et al, J. of Instrumentation, 13 (2018) C04009.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW064  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW067 On Coordinate Systems in Beam Dynamics simulation, experiment, acceleration, FEL 243
 
  • E. Laface
    ESS, Lund, Sweden
 
  Any description of the beam dynamics calculation and simulation relies on the proper choice of a coordinate system in order to minimize the computational complexity and to apply different level of approximations in the calculations. This need generates a large number of reference systems, especially to describe the longitudinal dynamics of a particle beam like(z, z′),(t,∆P/P),(z, φ), etc. In this paper we summarize the rules to change coordinates systems, which system is canonical and how the Hamiltonian of the beam transforms according to the chosen coordinate system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW067  
About • paper received ※ 10 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW114 Bayesian Approach for Linear Optics Correction quadrupole, optics, lattice, distributed 390
 
  • Y. Li, W.X. Cheng, R.S. Rainer
    BNL, Upton, Long Island, New York, USA
 
  With a Bayesian approach, the linear optics correction algorithm for storage rings is revisited. In modern ring-based accelerators, optics corrections are determined from repetitive measurements which help identify systematic and random quadrupole errors in presence of various measurement noises. This process is a multivariate nonlinear regression problem driven by either a completed lattice model or a Jacobian matrix. Starting from the Bayes’ theorem, ’likelihood functions’ and ’prior probability’ distributions are extracted from a complete linear optics model. Under some assumptions, the least square algorithm and then the Jacobian matrix approach can be re-derived. The coherence of the correction algorithm is ensured through specifying a self-consistent regularization coefficient to prevent overfitting. Optimal weights for different correction objectives are obtained based on their measurement noise level. A new technique has been developed to resolve degenerated quadrupole errors when observed at a few select BPMs. A necessary condition of being distinguishable is that their optics response vectors seen at these specific BPMs should be near-orthogonal.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW114  
About • paper received ※ 18 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPRB022 Current Status of the High-Power RF Systems During Phase2 Operation in SuperKEKB klystron, cavity, operation, status 619
 
  • K. Watanabe, K. Marutsuka, Ma. Yoshida, S.I. Yoshimoto
    KEK, Ibaraki, Japan
 
  The SuperKEKB is an asymmetric-energy two-ring collider consisting of the high-energy ring (HER) for 7 GeV electrons and the low-energy ring (LER) for 4 GeV positrons at KEK. Both the electron and positron beams are injected from the Linac injector complex, which includes a newly constructed 1.1 GeV positron damping ring (DR) to supply a high-quality low emittance positron beam to the LER. The high power RF system has a role to drive the ARES cavities and the superconducting RF cavities for the SuperKEKB. The operating frequency of RF system is 508.9 MHz. The required RF power from the klystron at maximum storage beam current is ~850 kW (CW). The number of RF stations is total 31 for the main ring (MR) and DR. The status of each high power RF components, troubles of them and operation condition that occurred during phase 2 commissioning from Feb 2018 to July 2018 will be reported in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB022  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPRB056 THz Radiator Based on Photonic Band Gap Crystal for SwissFEL electron, photon, experiment, FEL 693
 
  • L. Shi, R. Ischebeck, S. Reiche
    PSI, Villigen PSI, Switzerland
 
  Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 701647.
The electromagnetic radiation in 1-20 THz has many unique properties when it interacts with matter due to its non-ionizing excitation in matter. Especially the dynamics of the excited matter can be probed with the help of X-ray pulses at a free electron laser facility, e.g. SwissFEL, to deepen our understanding of a wide range of phenomena. Due to its high research potential, various means of THz generation have been proposed and demonstrated. We investigate preliminarily here its generation based on a relativistic electron bunch and a photonic band gap crystal (PBG) made of dielectric rods. The PBG provides additional degrees of freedom for the THz pulse tuning. Additionally, the unwanted radiation parts can be damped by the structure in order to minimize the deleterious beam dynamics effects. The crystal also promises the integration of generation, filtering and coupling for transport into a single piece.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB056  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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MOPRB067 High-gradient Single Cycle Terahertz Accelerating Structures gun, acceleration, cathode, electron 731
 
  • S.P. Antipov, E. Gomez, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
 
  Recently, gradients on the order of 1 GV/m level have been obtained in a form of single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). These pulses however are broadband (0.1-5 THz) and therefore a new accelerating structure type is required. For electron beam acceleration with such pulses we propose arrays of parabolic focusing micro-mirrors with common central. These novel structures could be produced by a femtosecond laser ablation system developed at Euclid Techlabs. This technology had already been tested for production of several millimeters long, multi-cell structure which has been testing with electron beam. We also propose using of structures where necessary GV/m E-fields are excited by a drive bunch travelling in the corrugated waveguide. The radiated by drive bunch sequence of short range delayed wakes are guided in this case by metallic disks and reflected back being focused exactly at time when the witness bunch arrives.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB067  
About • paper received ※ 21 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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MOPTS010 Simulation of the Guide Field Flipping Procedure for the Frequency Domain Method lattice, simulation, sextupole, dipole 858
 
  • A.E. Aksentyev
    FZJ, Jülich, Germany
  • A.E. Aksentyev
    MEPhI, Moscow, Russia
  • A.E. Aksentyev, V. Senichev
    RAS/INR, Moscow, Russia
 
  The spin vector of a particle injected into a perfectly aligned storage ring precesses about the vertically-orientated guide field. In the presence of an Electric Dipole Moment (EDM), the spin precession axis acquires a proportional radial component. However, in an imperfect ring, rotational magnet misalignments induce a radial component to the spin precession axis, related to the Magnetic Dipole Moment (MDM). In the Frequency Domain Method, [*] this additional precession is dealt with by consecutively injecting the beam in opposite directions, and constructing the EDM estimator as the sum of the clockwise and counter-clockwise vertical plane precession frequencies. Since the radial MDM component changes sign when the magnetic field direction is reversed, it cancels in the sum, leaving only the EDM effect. In order to reproduce the guide field magnitude with precision sufficient for the cancellation of the MDM effect, we propose to calibrate the guide field via the horizontal plane precession frequency. In the present work we describe the algorithm of the field flipping procedure, and do a numerical simulation.
[*] Senichev Y, Aksentev A, Ivanov A, Valetov E. Frequency domain method of the search for the deuteron electric dipole moment in a storage ring with imperfections. arXiv:171106512. 2017 Nov 17.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS010  
About • paper received ※ 08 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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MOPTS050 VSWR Adjustment for ACS Cavity in J-PARC LINAC cavity, coupling, simulation, linac 974
 
  • J. Tamura, Y. Kondo, T. Morishita
    JAEA/J-PARC, Tokai-mura, Japan
  • F. Naito, M. Otani
    KEK, Tokai, Ibaraki, Japan
  • Y. Nemoto
    Nippon Advanced Technology Co., Ltd., Tokai, Japan
 
  In the Japan Proton Accelerator Research Complex (J-PARC) linac, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by twenty-one Annular-ring Coupled Structure (ACS) accelerating cavities. The input coupler of the ACS high-beta cavity, which is the 21st accelerating cavity (ACS21) in the order of beam acceleration, had a comparatively larger value of the Voltage Standing Wave Ratio (VSWR) than those of the other ACS cavities. To adjust the VSWR of the ACS21, we designed and fabricated a rectangular waveguide with a capacitive iris which conduces to a better matching between the cavity and the waveguide. In the 2018 summer maintenance period, we installed the newly fabricated waveguide to the ACS21 in the position between the input coupler and the RF window. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS050  
About • paper received ※ 01 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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TUXXPLM2 SRF Cavity Fault Classification Using Machine Learning at CEBAF cavity, cryomodule, SRF, operation 1167
 
  • A.D. Solopova, A. Carpenter, T. Powers, Y. Roblin, C. Tennant
    JLab, Newport News, Virginia, USA
  • K.M. Iftekharuddin, L. Vidyaratne
    ODU, Norfolk, Virginia, USA
 
  The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is the first large high power CW recirculating electron accelerator which makes use of SRF accelerating structures configured in two antiparallel linacs. Each linac consists of twenty C20/C50 cryomodules each containing eight 5-cell cavities and five C100 upgrade cryomodules each containing eight 7-cell cavities. Accurately classifying the source of cavity faults is critical for improving accelerator performance. In addition to archived signals sampled at 10 Hz, a cavity fault triggers a waveform acquisition process where 16 waveform records sampled at 5 kHz are recorded for each of the 8 cavities in the effected cryomodule. The waveform record length is sufficiently long for transient microphonic effects to be observable. Significant time is required by a subject matter expert to analyze and identify the intra-cavity signatures of imminent faults. This paper describes a path forward that utilizes machine learning for automatic fault classification. Post-training identification of the physical origins of faults are discussed, as are potential machine-trained model-free implementations of trip avoidance procedures. These methods should provide new insights into cavity fault mechanisms and facilitate intelligent optimization of cryomodule performance  
slides icon Slides TUXXPLM2 [4.404 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUXXPLM2  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP051 MULTIPACTOR SUPPRESSION BY LASER ABLATION SURFACE ENGINEERING FOR SPACE APPLICATIONS electron, laser, multipactoring, controls 1365
 
  • R. Valizadeh, A.N. Hannah, O.B. Malyshev, B.S. Sian
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.S. Colligon
    University of Huddersfield, Huddersfield, United Kingdom
  • Y. Dan
    Hitachi High-Technologies Corp., Ibaraki-ken, Japan
  • V. R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • J. Mutch
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • B.S. Sian
    UMAN, Manchester, United Kingdom
  • N. Sykes
    Micronanics Laser Solution Center, Didcot, United Kingdom
 
  Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators and space-borne RF equipment for communication purposes. In this study we report on the secondary electron yield (SEY) measured from silver coated aluminium alloy as-received and after laser ablation surface engineering (LASE). Analysis shows the SEY can be reduced by 43% using LASE. EDX and SEM analysis shows it is possible to reduce the SEY whilst maintaining the original surface composition.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP051  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPGW019 Progress of the BESSY VSR Cold String Development and Testing cavity, simulation, experiment, vacuum 1434
 
  • H.-W. Glock, V. Dürr, F. Glöckner, J. Knobloch, M. Tannert, A.V. Vélez, D. Wolk, N. Wunderer
    HZB, Berlin, Germany
  • J. Guo, R.A. Rimmer, H. Wang
    JLab, Newport News, Virginia, USA
 
  The so-called VSR (Variable Storage Ring) upgrade of the 3rd gen. light source BESSY II will provide the capability to simultaneously store long (about 20 ps rms length) and short (1 ps or less) bunches in the ring. This will be accomplished by inserting a module with four superconducting cavities, two of them operating at 1.5 GHz as the third harmonic of the 500 MHz driving RF, two at 1.75 GHz. The "cold" string of those four cavities also includes supporting and connecting devices, as there will be: - three intermediate bellows, all shielded against leaking fundamental mode cavity fields, one additionally acting as a collimator for incident synchrotron light; - two tuneable bellows at the module ends; - two warm end groups outside the module, housing toroidal dielectric wake field absorbers, another bellow and a vacuum pump connection. The recent design progress of those components will be reported, including a description of a beam test planned for the central collimating shielded bellow.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW019  
About • paper received ※ 22 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPGW098 Fabrication & Cold Tests of a Millimeter-Period RF Undulator undulator, laser, FEL, electron 1643
 
  • F. Toufexis, B. J. Angier, D. Gamzina, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
To reduce the linac energy required for an FEL radiating at a given wavelength, and hence its size, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424GHz, using a corrugated cylindrical waveguide operating at the HE11 modes. We have designed a mm-wave undulator cavity at 91.392GHz* with an equivalent undulator period of 1.75 mm. This undulator requires 1.4 MW for sub microsecond pulses for an equivalent K value of 0.1. In this work we present the mechanical design and fabrication of this 91.392 GHz RF Undulator, as well as preliminary cold test data.
* F. Toufexis and S.G. Tantawi, "A 1.75-mm Period RF-Driven Undulator", Proceedings of IPAC17.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW098  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPGW099 Superconducting Crab Cavity Options for Short X-Ray Pulse Generation in SPEAR3 cavity, sextupole, impedance, HOM 1647
 
  • F. Toufexis, V.A. Dolgashev, X. Huang, Z. Li
    SLAC, Menlo Park, California, USA
 
  Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
We are exploring methods to generate short X-ray pulses in SPEAR3 on the order of 1 ps to enable studying ultrafast processes in materials. We are developing a 2-frequency crab cavity scheme with two sets of crab cavities* at the 6th and 6.5th harmonics of the 476 MHz ring RF frequency. In previous work we studied a normal conducting crab cavity for SPEAR3**. In this work we explored two superconducting cavity options: a traditional elliptical cavity and the Quasi-waveguide Resonator***. We found that the Quasi-waveguide Resonator cannot meet our field uniformity specifications due to higher order multipole fields. We then optimized a traditional elliptical cavity with the input, Lower Order Modes, and Higher Order Modes couplers following the Argonne Advanced Photon Source design.
* A. Zholents, et al, Nucl. Instrum. Methods Phys. Res., Sect. A, Vol. 425 (1999), p. 385.
** Z. Li, et al, Proceedings of IPAC17.
*** A. Lunin, et al, Proceedings of HOMSC14.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW099  
About • paper received ※ 11 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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TUPGW108 Characterization of NEG Coatings for SLS 2.0 impedance, resonance, coupling, vacuum 1662
 
  • M.M. Dehler, A. Citterio
    PSI, Villigen PSI, Switzerland
  • S. Alberti, J.P. Hogge
    SPC-EPFL, Lausanne, Switzerland
  • M. Hahn, H.P. Marques
    ESRF, Grenoble, France
  • X.Y. Liu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  To limit desorption and ameliorate pumping of the narrow 20 mm aperture vacuum chamber of SLS2.0, it is planned to fully coat it with nonevaporable getter (NEG) material. NEG coating can be produced with different structural characteristics, from dense films to columnar growth, with corresponding distinct electrical properties affecting the machine impedance and the instability threshold of the accelerator. In order to evaluate and characterize the coating process for geometries similar to the SLS chamber, we measured the resonance properties of coated and uncoated shorted waveguide pieces. First tests were done with standard X band waveguides at 12 and 7 GHz. Test setups using elliptical cross sections are in preparation, also for higher frequencies allowing the characterization of thin NEG layers. The final goal is to have a standardized process to test of samples coated by external producers. We describe the setups and first results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW108  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPRB002 The Conceptual Design of a 36 GHz RF Undulator undulator, cavity, electron, photon 1676
 
  • D. Zhu
    ASCo, Clayton, Victoria, Australia
  • A.W. Cross, L. Zhang
    USTRAT/SUPA, Glasgow, United Kingdom
  • Y.E. Tan
    AS - ANSTO, Clayton, Australia
 
  The CompactLight project supported by European H2020 is to design a hard X-ray FEL facility beyond today’s state of the art. The project integrates photo injector, X-band acceleration and innovative compact short-period undulators together to make the machine more compact. RF undulator has an extraordinary advantage of working at very short undulator period. A conceptual design for a RF undulator at 36 GHz using a corrugated cylindrical waveguide operating in the HE11 mode is presented in this paper. Based on beam dynamics simulation and photon beam radiation simulations, the possibility of RF undulator to be used in CompactLight project is evaluated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB002  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPRB015 Cryogenic, in-Vacuum Magnetic Measurement Setup for Superconducting Undulators vacuum, undulator, detector, synchrotron 1709
 
  • A.W. Grau, S. Casalbuoni, N. Glamann, D. Saez de Jauregui
    KIT, Eggenstein-Leopoldshafen, Germany
 
  The magnetic field quality has a strong impact on the performance of insertion devices (IDs) when installed in synchrotron light sources. Superconducting IDs have the advantage to produce a higher magnetic peak field for a given gap and period length than IDs assembled with permanent magnets. Before installation of a superconducting ID in a synchrotron light source it is of fundamental importance to characterize the magnetic properties by accurate field and field integral measurements. We follow this aim within our R&D program for superconducting undulators (SCUs). In this contribution, we describe the equipment and the challenges of a cryogenic, in vacuum measurement setup to perform magnetic measurements of the local field, the field integrals and the multipole components of in vacuum SCUs assembled in the final cryostat.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB015  
About • paper received ※ 29 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPRB045 Stimulated Excitation by Seeding With Cherenkov Radiation in an Optical Cavity radiation, cavity, electron, ion-source 1785
 
  • S.M. Jiang, Z.G. He, Q.K. Jia, W.W. Li, L. Wang
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  • D. He
    Anhui Electrical Engineering Professional Technique College, Hefei, People’s Republic of China
 
  Funding: Work supported by National Foundation of Natural Sciences of China (11775216, 11705198, 11675178), and Fundamental Research Funds for the Central Universities (WK2310000061).
By seeding with narrow-band Cherenkov radiation from a dielectric loaded waveguide(DLW), stimulated excitation in an optical cavity is presented. The evolution and energy loss of the field oscillating in optical cavity is analysed by the theoretical and numerical calculation. The results show that the high order TM modes of the Cherenkov radiation can be better preserved after a large number of roundtrips in the optical cavity and this scheme offers a potential method of realizing high power Terahertz radiation source in a compact facility.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB045  
About • paper received ※ 30 April 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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TUPRB050 The Optical Resonator of CTFEL for Range of 1 to 2 THz FEL, radiation, electron, coupling 1795
 
  • X.J. Shu, Y.H. Dou
    Institute of Applied Physics and Computational Mathematics, People’s Republic of China
 
  A high power THz free electron laser (FEL) facility is under construction at China Academy of Engineering Physics (CTFEL). The radiation frequency of the FEL facility will be tuned in range of 1~3 THz and the average output power is about 10 W. The system mainly consists of a GaAs photoemission DC gun, superconductor accelerator, hybrid wiggler, optical cavity. The first lasing is obtained on Aug. 29, 2017, and CTFEL is operated in range of 2-4THz, but cannot lasing at the frequency below 1.8 THz. The optical resonator of CTFEL must be optimized to ensure lasing in range of 1 to 2 THz.. The lasing strongly depends on the performance of the optical resonator including output efficiency, gain and round-trip loss. The optical resonator consists of metal-coated reflect mirror, the centre-hole output mirror, waveguide. The influence of waveguide on the quality of optical cavity is evaluated by the 3D OSIFEL code. The waveguide size and output hole radius is optimized to different frequencies between 1 THz to 2 THz.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB050  
About • paper received ※ 13 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
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TUPRB094 New Superconducting Undulator Magnetic Measurement System for the Advanced Photon Source Upgrade undulator, photon, vacuum, storage-ring 1881
 
  • M. Kasa, E.R. Anliker, Y. Ivanyushenkov, Y. Shiroyanagi
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Magnetic measurements of existing superconducting undulators (SCUs) are performed under normal operating conditions after final assembly into the cryostat and before installation on the Advanced Photon Source (APS) storage ring. The SCU cryostat for the APS upgrade has been scaled in length from the current cryostat and will contain two SCUs. While some aspects of the current measurement system are desirable to retain, such as a room temperature measurement bore, scaling the current measurement techniques to the length required for the APS upgrade cryostat is not feasible. To address these challenges a unique system has been developed at the APS to allow measurements of the two SCU magnets in the long cryostat. The measurement system developed allows the magnets to be operated under normal operating conditions while maintaining the measurement equipment at room temperature and atmospheric pressure.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB094  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPTS065 RF Conditioning of the CLARA 400 Hz Photoinjector cavity, controls, vacuum, operation 2067
 
  • L.S. Cowie, D.J. Scott
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Automated conditioning of the 400 Hz photoinjector for CLARA was begun and the conditioning program refined. The conditioning was performed at 100 Hz. Masks were used to detect breakdowns in the reflected power and phase, and the breakdown rate was limited to 5x106 breakdowns per pulse. The cavity gradient and breakdown rate evolution over the conditioning time is presented. Post-pulse multipactor and other evidence of electron effects were detected. Possible mechanisms for this are discussed. The conditioning was interrupted by breakdown in the waveguide after reaching 2.5 MW, and will be resumed after the planned 6 month shutdown of CLARA.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS065  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPMP044 Mu2e Electrostatic Septa Volumetric Exchange of Fc-40 Dielectric in High Radiation Environments radiation, septum, cathode, extraction 2434
 
  • M.L. Alvarez, A. Deshpande, K.R. Hunden, V.P. Nagaslaev, E. Pirtle
    Fermilab, Batavia, Illinois, USA
 
  Funding: * Operated by FRA, LLC under Contract No. DEAC02-07CH11359 and Grant Award No. LAB 18-1802 with the United States Department of Energy.
Two electrostatic septa (ESS) are being designed for the slow extraction of 8 GeV proton beam for the Mu2e experiment at Fermilab. Special attention is given to the high voltage feedthrough (HVF), which energizes the cathode creating the bending field. The FC-40 dielectric fluid, surrounding the HV cable breaks down from radiation exposure, which reduces its insulating capabilities. The new HVF design focuses on effective replacement of the exposed fluid and eliminating the stagnant areas of low exchange rate. A preliminary test using a fully transparent prototype HVF and water was conducted to understand the volumetric exchange rate of the high radiation region. Here we discuss the results of these tests and further studies using the FC-40.
** malvare4@fnal.gov
*** vnagasl@fnal.gov
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP044  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPGW003 High-Level Applications for the Sirius Accelerator Control System EPICS, controls, MMI, linac 2462
 
  • X.R. Resende, L. Liu, A.C.S. Oliveira, F.H. de Sá, G.L. do Prado
    LNLS, Campinas, Brazil
 
  Sirius is the new 3 GeV low-emittance Brazilian Synchrotron Light source under installation and commissioning at LNLS. The machine control system is based on EPICS and when the installation is complete it should have a few hundred thousand process variables in use. For flexible integration and intuitive control of such sizable system a considerable number of high-level applications, input/output controllers and graphical user interfaces have been developed, mostly in Python, using a variety of libraries, such as PyEpics, PCASPy and PyDM. Common support service applications (Archiver Appliance, Olog, Apache server, a mongoDB-based configuration server, etc) are used. Matlab Middle Layer is also an available option to control EPICS applications. Currently system integration tests are being performed concomitant with initial phases of accelerator commissioning and installation. A set of functionalities is already available: Linac’s control; timing subsystem control; machine snapshots; optics measurements and correction; magnets settings and cycling; Booster orbit acquisition and correction, and so on. From the experience so far, subsystems communications have worked satisfactorily but there has been a few unexpected component performance. In this paper we discuss this experience and descrive the libraries and packages used in high-level control system , as well as the difficulties faced to implement and to operate them.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW003  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPGW045 Application of Clustering by Fast Search and Find of Density Peaks to Beam Diagnostics at SSRF SRF, storage-ring, diagnostics, electron 2581
 
  • R. Jiang, Y.B. Leng
    SSRF, Shanghai, People’s Republic of China
 
  With the increased technological complexity of accelera-tors, meeting the demand of beam diagnostics and opera-tion need more powerful and faster methods. And detect-ing the accuracy and stability of beam position moni-tors(BPMs) are important for all kinds of measurement systems and feedback systems in particle accelerator field. As an effective tool for data analysis and automa-tion, the machine learning methods had been used in accelerator physics field, recently. Among machine learn-ing methods, the clustering by fast search and find of density peaks as a typical unsupervised learning algo-rithms could be performed directly without training in arbitrary accelerator systems and could discover un-known patterns in the data. This paper used clustering by fast search and find of density peaks to detect faulty beam position monitor or monitoring beam orbit stability by analysis five typical parameters, that is beta oscilla-tion of X and Y direction(BetaX and BetaY), transverse oscillation of X and Y direction(AmpX and AmpY) and energy oscillation(AmpE). The results showed that cluster-ing by fast search and find of density peaks could classi-fy beam data into different clusters on the basis of their similarity. And that, aberrant run data points could be detected by decision graph. Morever, analysis results demonstrate the characteristic parameters AmpE, AmpX and BetaX amplitude have the same effect to distinguish the faulty BPMs and the AmpY and the BetaY amplitude are also.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW045  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPGW074 MYRRHA DAQ Development controls, EPICS, LabView, software 2645
 
  • R. Modic
    Cosy lab, Ljubljana, Slovenia
  • P. Della Faille, D. Vandeplassche
    SCK•CEN, Mol, Belgium
  • P. Mekuc
    Cosylab, Ljubljana, Slovenia
 
  An approach to a generic Data Acquisition (DAQ) solution for the MYRRHA test stand at Louvain-la-Neuve (Belgium) will be described in this paper. Need for better sampling performance, signal quality, arbitrary processing and storage of measurements was a motivation for this work. A full integration of the DAQ system in the global EPICS control environment was a strong requirement. An intermediate DAQ platform was put in place to satisfy the control and experiment needs. The NI PXI platform is selected to minimize integration and development effort. NI LabVIEW is used to create a generic DAQ application. CALab library supported by BESSY is used to connect LabVIEW and EPICS. CSS GUI provides the user with the necessary control, visualization and configuration capability. The technical and organizational approach to the collaboration will be detailed in the paper. Necessary customizations of CSS and CALab and experience on using NI PXI for DAQ platform will be explained.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW074  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPGW115 Radiation Robust RF Gas Beam Detector R&D for Intensity Frontier Experiments detector, cavity, plasma, electron 2770
 
  • K. Yonehara, A. Moretti
    Fermilab, Batavia, Illinois, USA
  • M.A. Cummings, R.P. Johnson, G.M. Kazakevich
    Muons, Inc, Illinois, USA
 
  A novel radiation robust RF gas beam detector has been demonstrated by using the Main Injector beam at Fermilab. The detector demonstrated a stable signal gain, fast response time, and high radiation resistivity with intense proton beams. The plasma process in the detector is studied to validate the plasma physics model. The result suggests that the detector is applicable for Long Baseline Neutrino Facility at Fermilab. To prepare for the LBNF, a proto type detector will be made and applied for the Neutrino at Main Injector target system. Progress of the project will be given in the presentation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW115  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPGW116 LHC Optics Measurement and Correction Software Progress and Plans optics, software, coupling, MMI 2773
 
  • R. Tomás, F.S. Carlier, J. Coello, J. Dilly, E. Fol, A. Garcia-Tabares, M. Hofer, E.H. Maclean, L. Malina, T. H. B. Persson, P.K. Skowroński, M.L. Spitznagel, A. Wegscheider, J. Wenninger
    CERN, Geneva, Switzerland
  • J.F. Cardona, Y. Rodriguez
    UNAL, Bogota D.C, Colombia
  • F.S. Carlier
    NIKHEF, Amsterdam, The Netherlands
  • D. Esperante Pereira, J. Fuster, D. Gonzalez-Iglesias
    IFIC, Valencia, Spain
  • R. Hoekstra
    KVI, Groningen, The Netherlands
 
  LHC Optics Measurements and Corrections (OMC) require efficient on-line software applications to acquire and analyze data and to compute the necessary corrections. During Run 2 various measurement and correction techniques have been merged to yield unprecedented optics quality, increasing the required number of steps to finalize the optics commissioning and the size of the software project. In turn, this calls for a higher level of automation, where machine learning techniques are being implemented. During the Long Shutdown 2 a large refactoring of the codes will be in place to improve performance, maintainability and extensibility. A description of the current status of the software and future plans is given.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW116  
About • paper received ※ 07 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB024 Low Power RF Test of a Quadrupole-free X-Band Mode Launcher for High Brightness Applications brightness, quadrupole, simulation, electron 2856
 
  • G. Torrisi, L. Celona, S. Gammino, O. Leonardi, G. Sorbello
    INFN/LNS, Catania, Italy
  • G. Castorina
    Sapienza University of Rome, Rome, Italy
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • L. Faillace
    INFN-Milano, Milano, Italy
  • G.S. Mauro
    INFN/LNL, Legnaro (PD), Italy
  • G. Sorbello
    University of Catania, Catania, Italy
  • B. Spataro
    INFN/LNF, Frascati, Italy
 
  In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB024  
About • paper received ※ 09 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB034 Study on the Design of the X-band Waveguide-damped Structure wakefield, damping, HOM, simulation 2886
 
  • X.X. Huang, W. Fang, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
  • A. Grudiev
    CERN, Meyrin, Switzerland
 
  The design of waveguide-damped structure is optimized to reduce the magnitudes of surface electromagnetic fields and strongly suppress long-range transverse wakefields of the 380 GeV Compact Linear Collider facility currently under study. The optimization is mainly discussed with the elliptical shape of the iris, the wall shape of the damping waveguides, the position of the high-order-mode damping loads and the widths of the waveguide openings of the entire sequence of damping waveguides.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB034  
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB039 Tuning of a Tapered Ridge-Loaded Waveguide Coupler for a Drift Tube LINAC of the Compact Pulsed Hadron Source coupling, DTL, linac, target 2893
 
  • Y. Lei, C.T. Du, X. Guan, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
    TUB, Beijing, People’s Republic of China
 
  This paper presents the tuning result of a tapered ridge-loaded waveguide coupler for the drift tube linac (DTL) of the compact pulsed hadron source (CPHS) at Tsinghua University. The coupler has been designed, manufactured, and mounted on the DTL cavity for the cold measurement and tuning. The iris diameter of the coupler which is related to the coupling coefficient needs to be determined in the tuning experiment, due to the difference between the designed and measured quality factors. Meanwhile, we found that the relationship between the coupling coefficient and iris diameter from the traditional analytical design method is not applicable when the iris diameter is relatively large. In this paper, the target coupling coeffi-cient is analysed, and the limit of the original analytical design is presented. The measurement method is intro-duced to improve the measurement efficiency and the tuning process of the coupling coefficient to the target value is described. After several iterations, the coupling coefficient is tuned to 1.54 which is close to the desired value of 1.56.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB039  
About • paper received ※ 30 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB042 High Power Test of the First C-band Spherical Pulse Compressor Prototype cavity, FEL, electron, linac 2896
 
  • Z.B. Li
    SINAP, Shanghai, People’s Republic of China
  • W. Fang, Q. Gu, X.X. Huang, J.H. Tan, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
 
  Funding: National Natural Science Foundation of China (No. 11675249)
Recently, a new C-band (5712 MHz) compact spherical radio frequency (RF) pulse compressor was designed and tested for Shanghai Soft X-ray Free Electron Laser Facili-ty (SXFEL). This pulse compressor utilizes one high Q0 spherical RF resonant cavity that works with two TE1, 1,3 modes and a dual-mode polarized coupler. The peak power multiply factor is 6.1 and average power gain 3.8 in theory. During the high power test, a peak power mul-tiply factor of 5.74 and average power gain of 3.77 was achieved. This paper presents the RF measurement of the C-band spherical pulse compressor and the high power test results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB042  
About • paper received ※ 19 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB043 Wakefield Suppression in the Main LINAC of the Klystron-Based First Stage of CLIC at 380 GeV wakefield, HOM, damping, linac 2899
 
  • J.Y. Liu, H.B. Chen, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
  • A. Grudiev
    CERN, Meyrin, Switzerland
 
  An alternative klystron-based scenario for the first stage of Compact Linear Collider (CLIC) at 380 GeV centre-of-mass energy was proposed. To preserve the beam stability and luminosity of CLIC, the beam-induced transverse long-range wakefield in main linac must be suppressed to an acceptable value. The design of klystron-based accelerating structure is based on waveguide damping structure (WDS). The high-order modes (HOMs) propagating into four waveguides are absorbed by HOM damping loads. In this paper, the wakefield suppression in CLIC-K based on GdfidL code simulations are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB043  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB046 Development of Flexible Waveguide for High Power High Vacuum Applications in S-band vacuum, simulation, factory, linac 2909
 
  • X. He, B. Deng, J. Lei, C. Meng, S. Pei
    IHEP, Beijing, People’s Republic of China
 
  A novel flexible waveguide is developed for S band 2856 MHz, which is a standard WR284 waveguide. The surface of the flexible waveguide is plated with Oxygen-free High Conductivity (OFHC) copper for the purpose of welding with the stainless steel flange in the vacuum furnace, for the flexible waveguide itself is made of brass. The prototype has got a certain amount of deformation which will be much more convenient for the connection between two hard waveguides. It also has a good measurement results of the lower power microwave test, and the 72 hours vacuum leakage test shows a satisfactory vacuum performance, no obvious surface collapse is observed. The high power test will be conducted after our high power test facility is available, which will tell us the maximal power level of the flexible waveguide prototype.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB046  
About • paper received ※ 13 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB047 High-Power Test of a 12 Cell Accelerating Structure Build in Halves klystron, vacuum, shielding, ECR 2912
 
  • M.M. Peng, Y.L. Jiang, J.Y. Liu, Z.N. Liu, X.C. Meng, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
 
  An X-band 12 cell travelling-wave accelerating structure has been developed and high-power tested at Tsinghua University in China. This structure works at 2⁄3 π at the frequency of 11.424 GHz. It is a 12-cell constant-impedance structure build in halves and was silver-brazed as a vacuum tight structure. The high power test was conducted at Tsinghua X-band high power test facility [1] with a 50-MW X-band klystron at a repetition rate to 40 Hz. The final input power was 51.23 MW with a 200 ns pulse width, which means an accelerating gradient of 88.58 MV/m was reached. This paper presents the high power test results including the gradient and breakdown history.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB047  
About • paper received ※ 10 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB048 Design, Fabricate, and Tuning of X-Band Deflecting Structure for CERN simulation, cavity, free-electron-laser, electron 2915
 
  • J.H. Tan, W. Fang, Q. Gu, X.X. Huang, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
 
  A 20-cell x-band deflecting structure for CERN has been finished, and now is under high power conditioning at XBOX of CERN.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB048  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB052 Design of Two Types of X-Band High Power Directional Coupler coupling, simulation, scattering, operation 2928
 
  • G. Wang, X. Lin, Y.G. Tang, C.-F. Wu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  The directional coupler is one of the most widely used components in many microwave systems, which is used to distribute the power of the input microwave signal according to a desired ratio. Directional coupler may be a three-port component or a four-port component with certain specification such as frequencies, bandwidth and structure. To meet the requirements of stable coupling degree and high directivity, we designed two types of directional coupler working at 11.424 GHz with high power handling capacity. One consists of two parallel rectangular waveguides with four holes drilled along the central line of the narrow-wall for coupling the electromagnetic power from the main-waveguide to the sub-waveguide which is called H-plane directional coupler. Simulations show that the coupling degree of H-face directional coupler is 49.9 dB and the directivity is 54.5 dB .The peak electric field is about 29MV/m while operating at 200 MW peak power. The other consists of a circular main-waveguide transmitting TM01 mode and a rectangular sub-waveguide transmitting TE10 mode, called circular-rectangle waveguide directional coupler. These two waveguide are connected by six holes drilled on the side of the circular main-waveguide and along the central line of the wide-wall of the sub-waveguide. The coupling degree of this directional coupler is 50.14 dB and the directivity is 37.93 dB due to the simulation. The bandwidth is about 800MHz. The peak electric field is 404.5V/m while operating at 200 MW peak power. Comparing with the H-plane directional coupler, peak electric field of this directional coupler is lower. Low peak electric field can reduce the risk of RF breakdown and the Multipactor effect, which ensures the stable high power operation of the directional coupler.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB052  
About • paper received ※ 27 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB058 Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures electron, multipactoring, simulation, cavity 2940
 
  • D. Banon-Caballero
    IFIC, Valencia, Spain
  • N. Catalán Lasheras, K. T. Szypula, W. Wuensch
    CERN, Geneva, Switzerland
  • A. Faus-Golfe
    LAL, Orsay, France
  • B. Gimeno
    UVEG, Burjasot (Valencia), Spain
 
  Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB058  
About • paper received ※ 27 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB060 HOM Damped Normal Conducting 1.5 GHz Cavity Design Evolution for the 3rd Harmonic System of the ALBA Storage Ring cavity, HOM, simulation, insertion 2948
 
  • A. Salom, J.M. Alvarez, B. Bravo, F. Pérez
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
 
  In a collaboration framework with CERN, ALBA has designed a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the evolution of the preliminary design of this cavity and its trans-dampers: high order modes coaxial dampers with waveguide transitions to N, which allows extracting the power of the high order modes induced by the beam outside of the cavity and to dissipate it using standard loads. This approach has two main advantages: no ferrites brazing is needed and they provide a diagnostic to analyze the beam dynamics. The new features of the design, together with electromagnetic simulations, mechanical and thermal stress analysis will be presented in this paper as well as the first stages of the prototype production status.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB060  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB064 High Power Conditioning of X-Band Variable Power Splitter and Phase Shifter simulation, klystron, ISOL, operation 2964
 
  • V. del Pozo Romano, H. Bursali, N. Catalán Lasheras, A. Grudiev, S. Pitman, I. Syratchev
    CERN, Meyrin, Switzerland
  • C. Serpico
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
 
  The three X-band test facilities currently at CERN aim at qualifying CLIC structures prototypes but are also exten- sively used to qualify X-band components operation at high power. In order to upgrade one of the facilities from a single test line to a double test line facility, a high power variable splitter and variable phase shifter have been designed and manufactured at CERN. They have been power tested, first in a dedicated test and also in their final configuration, to en- sure stable power operation before installing them together with an accelerating structure. In this paper, we broadly describe the RF and mechanical design, manufacturing and low power measurements agreement with simulations. We report the high power qualification of both components and their suitability to be used in existing and planned X-band facilities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB064  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPTS037 DC Beam Space-Charge Modeling for OpenXAL simulation, space-charge, LEBT, solenoid 3177
 
  • B.E. Bolling, N. Milas
    ESS, Lund, Sweden
 
  OpenXAL is an open source multi-purpose accelerator physics software platform based on a pure Java open source development environment used for creating accelerator physics applications, scripts and services. Currently, the software has been used with an ellipsoidal (bunched) beam to account for space-charge effects. Applications developed so far for ESS, such as the Virtual Machine for the ESS Low Energy Beam Transport (LEBT) section, would profit from a DC beam description. In this paper, the space-charge component for a continuous beam is derived taking into account beams with different transverse charge distributions (uniform, gaussian, etc). The implementation in OpenXAL and a comparison with other simulation codes is also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS037  
About • paper received ※ 14 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPTS081 An Analytic Approach to Emittance Growth from the Beam-Beam Effect with Applications to the LHeC proton, emittance, electron, collider 3307
 
  • E.A. Nissen
    JLab, Newport News, Virginia, USA
  • D. Schulte
    CERN, Meyrin, Switzerland
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, world-wide license to publish or reproduce this manuscript.
In colliders with asymmetric rigidity such as the proposed Large Hadron electron Collider, jitter in the weaker beam can cause emittance growth via coherent beam-beam interactions. The LHeC in this case would collide 7 TeV protons on 60 GeV electrons, which can be modeled using a weak-strong model. In this work we estimate the proton beam emittance growth by separating out the longitudinal angular kicks from an off-center bunch interaction and produce an analytic expression for the emittance growth per turn in systems like the LHeC.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS081  
About • paper received ※ 01 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPMP044 Radiation Hard Sensor for Reactor Applications laser, radiation, timing, detector 3545
 
  • R.J. Abrams, M.A. Cummings, R.P. Johnson, T.J. Roberts
    Muons, Inc, Illinois, USA
  • D.M. Kaplan
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  A novel method of measuring temperature of the coolant inside a reactor core is presented. The method, which is both standoff and non-invasive, is based on the interaction between an ultrasonic pulse and a delayed light pulse in the coolant. In the interaction, the light pulse, which is scattered backward by Brillouin scattering, is frequency-shifted. The frequency shift is dependent on the temperature and other parameters of the coolant. The light pulses and the ultrasound pulses are generated and detected outside of the core.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP044  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPMP046 Knowledge Exchange Within the Particle Accelerator Community via Cloud Computing simulation, software, HOM, electron 3548
 
  • D.L. Bruhwiler, D.T. Abell, N.M. Cook, C.C. Hall, M.V. Keilman, P. Moeller, R. Nagler, B. Nash
    RadiaSoft LLC, Boulder, Colorado, USA
 
  Funding: Work supported by US Department of Energy under Award Nos. DE-SC0011237, DE-SC0011340, DE-SC0018719, DE-SC0015212, DE-SC0017181 and DE-SC0017162.
The development, testing and use of particle accelerator modeling codes is a core competency of accelerator research laboratories around the world, and likewise for synchrotron radiation and X-ray optics codes at lightsource facilities. Such codes require time and training to learn a command-line workflow involving multiple input and configuration files, execution on a high-performance server or cluster, post-processing with specialized software and finally visualization. Such workflows are error prone an difficult to reproduce. Cloud computing and UI design are core competencies of RadiaSoft LLC, where the Sirepo* framework is being developed to make state of the art codes available in the browser of any desktop, laptop or tablet. We present our initial successes as real world examples of knowledge exchange (KE) between industry and the research community. This work is leading to broader knowledge exchange throughout the community by facilitating education of students and enabling instantaneous sharing of simulation details between colleagues. Sirepo design objectives include: seamless integration with legacy codes, low barrier to entry for new users, configuration transfer to command line mode, catalog of provenance to aid reproducibility, and simplified collaboration through multimodal sharing. The Sirepo Scientific Gateway** allows users to directly test the software. The combination of intuitive browser-based GUIs and Sirepo’s server-side application container technology enables simplified computational archiving and reproducibility. If embraced by the community, this could become an important asset for the design, commissioning and future upgrade of particle accelerator and X-ray beamline facilities.
* Sirepo cloud computing framework, https://github.com/radiasoft/sirepo
** Sirepo Scientific Gateway, https://sirepo.com
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP046  
About • paper received ※ 21 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPMP050 Progress on the Optics Modeling of BMI’s Ion Rapid-Cycling Medical Synchrotron at BNL dipole, optics, focusing, simulation 3561
 
  • F. Méot, P.N. Joshi, N. Tsoupas
    BNL, Upton, Long Island, New York, USA
  • J.P. Lidestri
    Best Medical International, Springfield, USA
 
  Funding: A project funded by Best Medical International, in the framework of a Technical Services Agreement (No. TSA-NF-18-50) with Brookhaven National Laboratory.
The Brookhaven National Laboratory continues to provide technical support and guidance to Best Medical International to build and test a 60 degree magnetic arc of a rapid-cycling ion synchrotron for cancer treatment. The 60 degree magnetic sector on its guirder has undergone field measurements, including the production of partial 3D field maps. Concurrently, OPERA field map computations as well as lattice and beam dynamics simulations have been performed, aimed at both preparing and analyzing the field measurements. Contingency responses aimed at adapting to non-ideal orbit and optics have been devised. These works and their outcomes are summarized here.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP050  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPGW033 Numerical Study of Photonic-Crystal-Based Dielectric Accelerators photon, acceleration, electron, impedance 3653
 
  • G. Torrisi, L. Celona, S. Gammino, D. Mascali, G. Sorbello
    INFN/LNS, Catania, Italy
  • C. De Angelis, A. Locatelli
    University of Brescia, Brescia, Italy
  • G.S. Mauro
    INFN/LNL, Legnaro (PD), Italy
  • G. Sorbello
    University of Catania, Catania, Italy
 
  All-dielectric electromagnetic band gap (EBG) waveguides structures promise significant improvement of accelerating gradient of laser-driven acceleration with the potential to miniaturize the accelerator itself. In this work we study photonic crystal structures designed for acceleration of relativistic electrons. We explore the performance of the all-dielectric EBG accelerating waveguide structures thanks to full wave electromagnetic simulations of couplers and accelerating waveguides. The characteristic interaction impedance, accelerating gradient and all the key parameters that are typically used to characterize linear accelerators are evaluated and used to compare the properties of the accelerating mode field distribution in different geometries.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW033  
About • paper received ※ 30 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPGW078 Prototyping of Brazed mm-Wave Accelerating Structures cavity, resonance, simulation, RF-structure 3764
 
  • M. A. K. Othman, B. J. Angier, A.A. Haase, E.A. Nanni, M. R. Roux, A.V. Sy
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. This work was also supported by NSF grants PHY-1734015.
Advanced fabrication and prototyping of metallic RF structures play a fundamental role in advancing accelerator technologies particularly at mm-wave and THz frequencies. With the scaling of the RF structure up to these frequencies, conventional fabrication techniques do not achieve the required accuracy and tolerances. Improved manufacturing techniques including diffusion bonding, brazing or clamping split-block geometries produce high quality structures when successfully implemented. However, in most schemes the resulting gap and irregularities at the iris result in a local field enhancement which is not desirable for high-gradient operation. Development of advanced split-block braze technique for THz accelerators was required for high quality miniature accelerators. A new braze technique was developed for W-band structures to control the flow of braze alloy, enabling fabrication of the first high-gradient brazed structures at mm-wave frequencies. This fabrication process has the potential to overcome consistent fabrication defects around the cell iris. Thin spacers were used to set the final gap between blocks during the braze process; while braze foil thickness is varied with minimal impact on the resulting frequency. To demonstrate the robustness of this technique, testing after the various manufacturing steps was done to monitor and track frequency change throughout the process. This technique is further pushed to produce G-band RF structures, operating at 300 GHz.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW078  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPGW079 THz-Based Femtosecond MeV Electron Bunch Compression electron, FEM, experiment, focusing 3766
 
  • M. A. K. Othman, M.C. Hoffmann, M.E. Kozina, R.K. Li, E.A. Nanni, X. Shen, E.J. Snively, X.J. Wang
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515.
Probing structural dynamics at atomic spatial and ultrashort temporal scales reveals unprecedented details of fundamental behavior of nature, allowing for better understanding of intricate energy-matter interaction occurring at such scales. Developing state-of-the-art technology to access these details entails utilizing X-ray free-electron lasers (XFELs), ultrafast electron diffraction (UED), and advanced electron microscopes. In particular, ultrafast diffraction science received growing attention thanks to innovation in sources, detectors and instrumentation in general. Within this context, interest in laser-generated THz wave-matter interaction has recently emerged as a new regime for controlling electrons with high temporal precision. Previously, the SLAC UED team has demonstrated attosecond electron metrology using laser-generated single-cycle THz radiation, which is intrinsically phase locked to the optical drive pulses, to manipulate multi-MeV relativistic electron beams. Here we demonstrate further steps towards achieving ultrafast timing resolution that utilizes femtosecond electron bunches. The proposed setup allows for compressing electron beam bunches down to a femtosecond using interaction with high field single-cycle THz pulses. We demonstrate a novel design of a dispersion-free parallel-plate tapered waveguide that provides focusing of THz pulses achieving >100 MV/m field strength at the interaction point as measured by electro-optical sampling for ~7 μJ of incoming THz pulse energy. The structure is being designed and built for bunch compression experiments using the SLAC UED facility.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW079  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB038 ALARM SYSTEM OF IRFEL AT NSRL FEL, controls, interface, EPICS 3896
 
  • X. Chen, C. Li, G. Liu, Z.X. Shao, Y. Song, J.G. Wang, K. Xuan
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  An InfraRed Free Electron Laser Light (IRFEL) is under commissioning at National Synchrotron Radiation Laboratory (NSRL). The control system of IRFEL is a distributed system based on Experimental Physics and Industrial Control System (EPICS). The alarm system is an essential part of the control system. It is developed based on the software Phoebus. The module named "Alarms" in Phoebus can store states and configuration information of the Process Variable (PV) in the Kafka topics. To meet our requirements, 3 kinds of alarm message distribution applications are developed, i.e. Web-Based GUI, WeChat and SMS. This paper will introduce the alarm system architecture and the implementations of the applications for alarm message distribution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB038  
About • paper received ※ 17 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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THPRB079 DC Testing and Phase Resolved Partial Discharge Measurements of the New Trigger Transformers for the LHC Beam Dump Kickers high-voltage, operation, kicker, power-supply 3998
 
  • T. Stadlbauer, A. Chmielinska, L. Ducimetière, D. Kontelis, T. Kramer, V. Senaj
    CERN, Geneva, Switzerland
 
  During LS2 the LHC beam dump kicker pulse generators will be subject to a substantial consolidation program. One major part is the replacement of the existing GTO stack trigger transformer by a new more performant one. The transformer is assembled, moulded and tested in-house. Part of the validation procedure are standard DC tests and subsequent discharge monitoring as well as newly introduced phase resolved partial discharge measurements. This paper briefly highlights the trigger transformer parameters and construction and outlines in detail the testing and partial discharge measurements. It concludes with a comparison and analysis of the results of the different measurement techniques.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB079  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB086 Design & Optimization of the Alignment Supports for the New Laminated Magnets for the CERN East Area Consolidation Project alignment, radiation, operation, secondary-beams 4020
 
  • R. Vanhoutte, D. Brethoux, A. Ebn Rahmoun, S. Evrard, F.J. Harden, E. Harrouch, M. Lazzaroni, M. Lino Diogo dos Santos, R. Lopez, D.E. Nogtikov, J. Renedo Anglada
    CERN, Meyrin, Switzerland
 
  The East Area is one of CERNs experimental area, running since its foundation in 1958. Extracting a 24GeV proton beam from the Proton Synchrotron accelerator, the primary beam is divided into different secondary beams, serving various experiments and user’s facilities such as CLOUD, CHARM, IRRAD. Due to improved optics and an energy saving scheme, the facility will go under a renovation between 2019 and 2020, including the replacement of the magnets with new laminated ones to allow a cycled powering scheme. Those magnets need improved supports, and in some cases even a new design, to optimize the alignment operations in those areas. This article will mainly address the different proposed solutions for plug-in supports as well as for conventional ones.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB086  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB112 Commission of the Transverse Bunch-by-Bunch Feedback at SPEAR3 feedback, kicker, injection, vacuum 4081
 
  • K. Tian, W.J. Corbett, X. Huang, N. Kurita, D.J. Martin, J.A. Safranek, J.J. Sebek
    SLAC, Menlo Park, California, USA
  • D. Teytelman
    Dimtel, San Jose, USA
 
  Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515.
Driven by the demand of suppressing transverse beam instabilities and developing novel short pulse operation modes in SPEAR3 storage ring, a wide-band transverse bunch-by-bunch feedback system has been recently commissioned for SPEAR3 storage ring. The system was demonstrated to be sufficient to suppress the transverse coupled bunch instabilities caused by trapped RF modes in one of the in vacuum insertion devices. A new function of beam instability interlock has been developed and is part of machine protection system for the in vacuum insertion device. In addition, the bunch-by-bunch feedback system serves as a indispensable diagnostic tool that enables us to measure machine parameters, beam impedance, and characteristics of the beam instability modes. In this paper, we describe the scheme and performance of the bunch-by-bunch feedback system at SPEAR3.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB112  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB116 Effect of Ground Motion Introduced by HL-LHC CE Work on LHC Beam Operation ground-motion, luminosity, operation, civil-engineering 4092
 
  • M. Schaumann, D. Gamba, M. Guinchard, L. Scislo, J. Wenninger
    CERN, Geneva, Switzerland
 
  Funding: Research supported by the HL-LHC project
The official groundbreaking of the civil engineering (CE) work for the high luminosity upgrade of the LHC started on 15 June 2018 parallel to LHC beam operation. Compactor work and shaft excavation around the two low beta experiments, ATLAS and CMS, were expected to induce vibrations to the accelerator magnets and cause orbit disturbance, beam loss and potentially premature beam dumps. Ground motion sensors were installed on the surface and close to the triplets, where the CE works were expected to have the largest impact on the beams. This paper discusses the observations made on the LHC beams that could be correlated to CE work.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB116  
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPTS008 Prospects of Additive Manufacturing for Accelerators cavity, vacuum, niobium, detector 4118
 
  • N. Delerue, S. Jenzer
    LAL, Orsay, France
  • H.C. Carduner
    SUBATECH, Nantes, France
  • R.L. Gerard
    CERN, Meyrin, Switzerland
  • P.M. Manil
    CEA-DRF-IRFU, France
  • P.R. Repain
    LPNHE, Paris, France
  • A. Simar
    UCL, Louvain-la-Neuve, Belgium
 
  Funding: Université Paris-SAclay, Labex P2IO and P2I departement
Additive manufacturing allows the production of mechanical components often much faster than traditional manufacturing. Several accelerators components built using additive manufacturing have already been qualified for use in accelerator. A workshop was held in Orsay in December 2018 to discuss the prospects of using additive manufacturing for particle accelerators and particle detectors. We report here on the prospects as far as accelerators are concerned.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS008  
About • paper received ※ 20 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPTS039 DESIGN OF A COMPACT VARIABLE X-BAND RF POWER SPLITTER impedance, klystron, electron, network 4194
 
  • F. Liu, H.B. Chen, J.Y. Liu, Z.N. Liu, J. Shi, H. Zha
    TUB, Beijing, People’s Republic of China
 
  This paper presents a design of a compact variable X-band RF power splitter. The RF power splitter includes one input port and two output ports, and the power divi-sion ratio can be adjusted by changing the position of a short circuit piston. This system keeps a good match (less than -40 dB) at any power division ratio. An E-bend waveguide structure is selected to make the geometry more compact (11cm in length, 3.5cm in width and 5 cm in height). Special studies was conducted to sustain a low surface electrical field (maximum 65 MV/m at 100 MW input), and large bandwidth (250MHz). This power split-ter is designed for high-power test stand at Tsinghua Uni-versity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS039  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPTS063 Development of a W-Band Power Extraction Structure cavity, undulator, electron, extraction 4252
 
  • F. Toufexis, B. J. Angier, D. Gamzina, A. McGuire, M. Shumail, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
We are modifying the X-Band Test Accelerator at SLAC to operate as an Extreme Ultra Violet (EUV) light source*. The existing photo electron gun will be replaced by a thermionic X-Band injector which utilizes RF bunch compression. The beam is accelerated up to 129 MeV using an X-Band traveling wave structure followed by a novel high shunt impedance standing wave structure. The beam then goes through a mm-wave undulator with a period of 1.75 mm, producing EUV radiation around 13.5 nm. The undulator is powered by a W-Band decelerator structure, which extracts the RF power from the electron beam. In this work we present the mechanical design and fabrication of the 91.392 GHz decelerator structure, as well as structural characterization of its cavities using SEM and 3D microscopy.
* F. Toufexis, et al, "A Compact EUV Light Source using a mm-wave Undulator", Proceedings of IPAC17.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS063  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPTS087 Micro-aligned Solenoid for Magnetized Bunched-beam Electron Cooling of 100 GeV/u Ions electron, solenoid, alignment, collider 4314
 
  • P.M. McIntyre, J. Breitschopf, J. Gerity, J.N. Kellams
    Texas A&M University, College Station, USA
  • J. Breitschopf, J. Gerity, J.N. Kellams, A. Sattarov
    ATC, College Station, Texas, USA
 
  Funding: This work is supported by grant DE-SC0018468 from the US Dept. of Energy.
Magnetized electron cooling of ion beams requires pre-cise alignment of the electron beam with the equilibrium trajectory of the ion bunch. For the parameters required for JLEIC, a solenoid with bore field ~1 T, length ~30 m, and rms alignment of ~μrad is required. Such precise alignment has never been accomplished in a 1 T solenoid. The design of a micro-aligned solenoid is presented. A gap-separated stack of thin steel washers is located inside the solenoid. The washer stack shields transverse magnet-ic fields from its interior by a factor of ~10. A 30-washer module of the structure was built and measured using ultra-sensitive capacitive probes using a coordinate meas-uring machine. The r.m.s. coplanarity of the washer gaps was measured to be <5 μm, consistent with the required micro-alignment.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS087  
About • paper received ※ 17 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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