Keyword: vacuum
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MOZBA2 Operational Experience with Superconducting Undulators at APS operation, undulator, photon, radiation 57
 
  • K.C. Harkay, L.E. Boon, M. Borland, J.C. Dooling, L. Emery, V. Sajaev, Y.P. Sun
    ANL, Lemont, Illinois, USA
  
  Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
APS has been developing superconducting undulators for over a decade. Presently, two planar and one helical device are in operation in the APS storage ring, and a number of devices will be installed in the APS Upgrade ring. All superconducting devices perform with very high reliability and have very minor effect on the storage ring operation. To achieve this, a number of storage ring modifications had to be done, such as introduction of the beam abort system to eliminate device quenches during beam dumps, and lattice and orbit modifications to allow for installation of the small horizontal aperture helical device with magnet coils in the plane of synchrotron radiation. 		 
slides icon Slides MOZBA2 [3.424 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA2  
About • paper received ※ 02 September 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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MOZBA6 The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project impedance, wakefield, simulation, cavity 74
 
  • D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini
    LBNL, Berkeley, California, USA
  • K.L.F. Bane
    SLAC, Menlo Park, California, USA
  
  Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.  
slides icon Slides MOZBA6 [8.926 MB]  
poster icon Poster MOZBA6 [3.542 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6  
About • paper received ※ 27 August 2019       paper accepted ※ 06 September 2019       issue date ※ 08 October 2019  
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MOZBB6 Measuring the Mean Transverse Energy of Pump-Probe Photoemitted Electrons electron, cathode, photon, experiment 87
 
  • C.M. Pierce, I.V. Bazarov, L. Cultrera, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Low effective mass semiconductor photocathodes have historically failed to exhibit the sub-thermal mean transverse energies (MTEs) expected of them based on their band structure. However, conservation of transverse momentum across the vacuum interface, and therefore a low MTE in these materials, has been observed in time resolved ARPES*. To help bridge this gap, we measured the MTE of the pump probe photoemitted electrons seen in the ARPES experiment using methods typical of accelerator physics. We compare the results of these measurements with those of both communities and discuss them in the context of photoemission physics.
* Kanasaki, J., Tanimura, H., & Tanimura, K. (2014). Imaging Energy-, Momentum-, and Time-Resolved Distributions of Photoinjected Hot Electrons in GaAs. Physical Review Letters, 113(23), 237401. 		 
slides icon Slides MOZBB6 [7.348 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBB6  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM06 High Voltage Design of a 350 kV DC Photogun at BNL electron, cathode, gun, high-voltage 102
 
  • W. Liu, O.H. Rahman, E. Wang
    BNL, Upton, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Brookhaven National Laboratory is constructing a 350 kV DC high voltage photogun to provide spin-polarized electron beam for the proposed eRHIC facility. The photogun employs a compact inverted-tapered-geometry ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. By operating at high voltage, the photogun will provide lower beam emittance, thereby improving the beam transmission through the injector apertures, and prolong the operating lifetime of the photogun. However, high voltage increases the field emission, which can result in high voltage breakdown and even lead to irreparable damage of the ceramic insulator. This work describes the methods to minimize the electric field near the metal-vacuum-insulator interface, and to avoid high voltage breakdown and ceramic insulator damage. The triple point junction shields are designed. The simulated electric field, field emission and beam transportation will be presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM06  
About • paper received ※ 19 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM17 Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST impedance, simulation, kicker, cavity 140
 
  • C. Yao, J. Carvelli, K.C. Harkay, L.H. Morrison
    ANL, Lemont, Illinois, USA
  • D. Hui
    University of Arizona, Tucson, Arizona, USA
  • J.S. Wang
    Dassault Systems Simulia, Waltham, Massachusetts, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS-U (APS upgrade) ring plans implement a "swap out" injection scheme, which requires a injected beam of 15.6 nC single-bunch beam. The Particle Accumulator Ring (PAR), originally designed for up to 6 nC charge, must be upgraded to provide 20 nC single bunch beam. Our studies have shown that bunch length of the PAR beam, typically 300 ps at lower charge, increases to 800 ps at high charge due to longitudinal instabilities, which causes low injection efficiency of the downstream Booster ring. We completed beam impedance of all the PAR vacuum components recently with CST wakefield solver. 3D CAD models are directly imported into CST and various techniques were explored to improve and verify the results. The results are also cross-checked with that from GdfidL and Echo simulation. We identified 23 bellow- and 24 non-bellow flanges that contribute to as much as 50% of the total loss factor. We are considering upgrade options to reduce over all beam loading and longitudinal impedance. Beam tracking simulation is in progress that including the longitudinal impedance results from the simulations. We report the results and methods of the CST impedance simulations. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM17  
About • paper received ※ 22 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLM20 Impedance Considerations for the APS Upgrade impedance, photon, cavity, simulation 147
 
  • R.R. Lindberg
    ANL, Lemont, Illinois, USA
  • A. Blednykh
    BNL, Upton, New York, USA
  
  Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The APS-Upgrade is targeting a 42 pm lattice that requires strong magnets and small vacuum chambers. Hence, impedance is of significant concern. We overview recent progress on identifying and modelling vacuum components that are important sources of impedance in the ring, including photon absorbers, BPMs, and flange joints. We also show how these impact collective dynamics in the APS-U lattice. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM20  
About • paper received ※ 27 August 2019       paper accepted ※ 01 September 2019       issue date ※ 08 October 2019  
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MOPLH17 Enhanced Robustness of GaAs-Based Photocathodes Activation by Cs, Sb, and O2 electron, cathode, polarization, extraction 210
 
  • J. Bae, L. Cultrera, A. Galdi, F. Ikponmwen
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • I.V. Bazarov, J.M. Maxson
    Cornell University, Ithaca, New York, USA
  
  Funding: This work is funded by Department of Energy: DE-SC0016203.
Operational lifetime of GaAs photocathodes is the primary limit for applications as high current spin polarized electron sources in future nuclear physics facilities, such as Electron Ion Collider. Recently, ultrathin Cs2Te on GaAs has shown a successful negative electron affinity (NEA) activation with an improved lifetime by a factor of 5 *. In this work, we report activation of GaAs with Cs, Sb and oxygen. Four different methods of introducing oxygen during the growth was investigated. Cs-Sb-O activated GaAs has shown up to a factor of 40 and 13 improvement in charge extraction lifetime and dark lifetime, respectively.
* Bae, et al. (2018). Rugged spin-polarized electron sources based on negative electron affinity GaAs photocathode with robust Cs2Te coating. Applied Physics Letters, 112(15), 154101. 		 
poster icon Poster MOPLH17 [0.926 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH17  
About • paper received ※ 28 August 2019       paper accepted ※ 01 September 2019       issue date ※ 08 October 2019  
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MOPLH24 Towards the Optimization Of Photocathode Properties Via Surface Science Techniques: A Study On Cs3Sb Thin Film Growth cathode, electron, laser, emittance 224
 
  • A. Galdi, J. Balajka, W.J.I. DeBenedetti, M. Hines
    Cornell University, Ithaca, New York, USA
  • I.V. Bazarov, L. Cultrera, F. Ikponmwen, J.M. Maxson, S.A. McBride
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: National Science Foundation Grant No. PHY-1549132
A better understanding of the properties of photocathode materials can be achieved by integrating advanced growth and surface science techniques in their synthesis and analysis. This is a main research theme of the Center for Bright Beams, whose goal is increasing the brightness of linear electron accelerators. Alkali antimonides are efficient photocathode materials and have very low intrinsic emittance at cryogenic temperatures.* A limiting factors is the surface roughness and chemical inhomogeneity of the films.** We studied the influence of growth parameters on the morphology and composition of Cs3Sb thin films. The films are codeposited using pure element sources and transferred via UHV suitcase to a STM/XPS analysis chamber, to study in particular the influence of substrate temperature and material. This platform can be expanded to more analysis and growth systems thanks to a specially designed sample holder and suitcase. An example is a new cryogenic instrument for intrinsic emittance measurements.
* L. Cultrera et al., Phys. Rev. ST ’ Acc. Beams 18 (2015) 113401
** G. Gevorkian et al., Phys. Rev. Accel. Beams, 21 (2018) 093401 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH24  
About • paper received ※ 28 August 2019       paper accepted ※ 30 August 2019       issue date ※ 08 October 2019  
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MOPLO06 Black Gun Technologies for DC Photoinjectors gun, electron, laser, scattering 247
 
  • E.J. Montgomery, C. Jing, S. Poddar
    Euclid Beamlabs LLC, Bolingbrook, USA
  • J.E. Butler
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S. Zhang
    JLab, Newport News, Virginia, USA
  
  Funding: Work supported by the US DOE Office of Science, Office of Nuclear Physics, grant number DESC0019688. Work at Argonne CNM under Contract No. DE-AC02-06CH11357.
Euclid Beamlabs is developing a new "Black Gun" concept in direct current (DC) photoinjectors. To reduce electron-stimulated desorption indirectly influenced by stray photoemission, we are testing advanced optical coatings and low-scattering optics compatible with the extreme high vacuum (XHV) environment of modern DC photoinjectors. Stray light in DC photoinjectors (in proportion to the photoemitted charge) causes off-nominal photoemission, initiating electron trajectories which intercept downstream surfaces. This causes electron-stimulated desorption of atoms, which ionize and may back-bombard the cathode, reducing its charge lifetime. Back-bombardment is key for high average current or high repetition rate. First, we report on progress developing optical skimmers based on Butler baffles to collimate both incoming and outgoing laser beams. Second, we describe candidate coatings for reduction of scattered light. Requirements for these coatings are that they be conducting, optically black at the drive laser wavelength, conformally applied to complex geometry, and XHV-compatible with negligible outgassing. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO06  
About • paper received ※ 04 September 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLO12 The RF BPM Pickup Electrodes Development for the APS-MBA Upgrade pick-up, simulation, electron, storage-ring 256
 
  • X. Sun, R.M. Lill
    ANL, Lemont, Illinois, USA
  
  Beam stability is critical for the Advanced Photon Source (APS) multi-bend achromat (MBA) lattice up-grade and will employ 560 radio frequency (RF) beam position monitors (BPMs). The RF BPMs will provide the primary measurement of the electron beam. Design goals for the BPM assembly include high sensitivity, low wakefield impedance, and ultra-mechanically stability. The design, electromagnetic simulation, manufacturing tolerance and prototype testing will be presented in this paper.
*Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO12  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLO15 Engineering and Fabrication of the High Gradient Structure for Compact Ion Therapy Linac linac, proton, operation, coupling 267
 
  • O. Chimalpopoca, R.B. Agustsson, S.V. Kutsaev, A.Yu. Smirnov, A. Verma
    RadiaBeam, Santa Monica, California, USA
  • A. Barcikowski, R.L. Fischer, B. Mustapha
    ANL, Lemont, Illinois, USA
  
  RadiaBeam is fabricating a novel ultra-high gradient linear accelerator for the Advanced Compact Carbon Ion LINAC (ACCIL) project. The ACCIL is an Argonne National Laboratory (ANL) led project, in collaboration with RadiaBeam, designed to be capable of delivering sufficiently energized carbon ions and protons while maintaining a 50 m footprint. This is made possible by the development of S-Band 50 MV/m accelerating structures for particles with beta of 0.3 or higher. Such high gradient accelerating structures require particular care in their engineering details and fabrication process to limit the RF breakdown at the operating gradients. The details of fabrication and engineering design of the accelerating structure will be presented.  
poster icon Poster MOPLO15 [1.050 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO15  
About • paper received ※ 28 August 2019       paper accepted ※ 12 September 2019       issue date ※ 08 October 2019  
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MOPLO19 Test Results of PIP2IT MEBT Vacuum Protection System cavity, cryomodule, MEBT, SRF 278
 
  • A.Z. Chen, R. Andrews, C.M. Baffes, D.D. Lambert, L.R. Prost, A.V. Shemyakin, T.J. Zuchnik
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The central part of PIP-II program of upgrades proposed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in superconducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype is installed in the PIP-II Injector Test (PIP2IT) accelerator and recently is successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO19  
About • paper received ※ 28 August 2019       paper accepted ※ 03 September 2019       issue date ※ 08 October 2019  
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TUYBB3 Final Design of the APS-Upgrade Storage Ring Vacuum System storage-ring, photon, extraction, alignment 315
 
  • J.A. Carter, B. Billett, B. Brajuskovic, M.A. Lale, A. McElderry, O.K. Mulvany, J.R. Noonan, M.M. O’Neill, R.R. Swanson, K.J. Wakefield, D.R. Walters, G.E. Wiemerslage, J. Zientek
    ANL, Lemont, Illinois, USA
  
  Funding: Argonne National Laboratory’s work was supported by the U.S. Department of Energy, Office of Science under contract DE-AC02-06CH11357.
The Advanced Photon Source Upgrade project is progressing from its final design phase into production for the future 6 GeV, 200 mA upgrade of the existing APS. The storage ring arc vacuum system will include over 2500 custom vacuum chambers ranging from 70 mm to 2.5 meters in length and typically feature a narrow 22 mm inner diameter aperture. The scope of NEG coatings was increased to 40% of the length along the e-beam path to ensure efficient conditioning and low pressure requirements can be met. The final design phase required advancing previous work to a procurement-ready level and to address local and system level challenges. Local challenges include designing thin-walled vacuum chambers with carefully controlled lengths and outer profiles and also mitigating significant radiation heat loads absorbed along vacuum chamber walls. System level challenges include planning for the complex machine assembly, networking components to utilities, managing the quality of upcoming procurements. This presentation will highlight the major design challenges and solutions for the storage ring vacuum system and also plans for production and installation. 		 
slides icon Slides TUYBB3 [10.852 MB]  
poster icon Poster TUYBB3 [5.028 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB3  
About • paper received ※ 27 August 2019       paper accepted ※ 30 August 2019       issue date ※ 08 October 2019  
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TUPLM25 Connecting Gas-Scattering Lifetime and Ion Instabilities scattering, experiment, electron, storage-ring 430
 
  • B. Podobedov, M. Blaskiewicz
    BNL, Upton, New York, USA
  
  Recently there is a renewed interest in fast ion instability (FII) which is of concern for future low-emittance electron storage rings, such as MBA light sources and colliders, i.e. eRHIC. While analytical theories and numerical codes exist to model the effect, due to various assumptions and limitations, accurate experimental verification is often desirable. Unfortunately, one of the most critical parameters for FII (as well as the classical "trapped-ion" instability), the residual ion concentration, is usually the most uncertain. Vacuum gauges and residual gas analyzers (RGAs) provide some useful data, but they are often not accurate enough, and, more importantly, they cannot directly probe the ion concentration along the beam orbit. In this paper we show how one could use gas-scattering lifetime measurements to infer the residual gas concentration suitable for ion instability experiment modelling.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM25  
About • paper received ※ 21 September 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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TUPLM36 Temperature Measurements of the NSLS-II Vacuum Components impedance, experiment, cavity, detector 443
 
  • A. Blednykh, G. Bassi, C. Hetzel, B.N. Kosciuk, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang
    BNL, Upton, New York, USA
  
  This paper is dedicated to the analysis of our recent experience from ramp-up of operating current at NSLS-II from 25 mA at the end of commissioning in 2014 to 475 mA achieved in studies today. To approach the design level of the ring intensity we had to solve major problems in overheating of the chamber components. Since the beginning of the NSLS-II commissioning, the temperature of the vacuum components has been monitored by the Resistance Temperature Detectors located predominantly outside of the vacuum chamber and attached to the chamber body. A couple of vacuum components were designed with the possibility for internal temperature measurements under the vacuum as diagnostic assemblies. Temperature map helps us to control overheating of the vacuum components around the ring especially during the current ramp-up. The average current of 475mA has been achieved with two main 500MHz RF cavities and w/o any harmonic cavities. In this paper we discuss the heating results for a 15ps bunch length (at low current) of the following vacuum components: Large Aperture BPM, Small Aperture BPM, Bellows, Flanges, Ceramics Chambers and Stripline Kickers.  
poster icon Poster TUPLM36 [3.696 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM36  
About • paper received ※ 28 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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TUPLS02 APS Upgrade Insertion Device Vacuum Chamber Design alignment, storage-ring, photon, distributed 450
 
  • J.E. Lerch, T.J. Bender, O.K. Mulvany, M.E. Szubert
    ANL, Lemont, Illinois, USA
  
  A straight section vacuum system (nominally 5.363 meters long) has been designed for the APS upgrade project. This vacuum system will be used in straight sections equipped with hybrid permanent magnet undulators (HPMU). The vacuum system assembly consists of the insertion device vacuum chamber (IDVC), the vacuum chamber distributed support, and the photon absorber. Numerous functional requirements constrained the IDVC design. These constraints included incorporation of the beam aperture transition into the end of the aluminium vacuum chamber extrusion (storage ring aperture to IDVC aperture), thin walls (~600 microns) surrounding the beam aperture to allow for as small a magnetic gap as possible, and complicated weld paths to ensure a continuous beam surface to minimize impedance. Additionally, extensive FEA and raytrace analysis were performed to ensure that the chamber would not fail due to structural or thermal perturbations.  
poster icon Poster TUPLS02 [3.816 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS02  
About • paper received ※ 26 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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TUPLS03 Advanced Photon Source Upgrade photon, storage-ring, operation, undulator 453
 
  • M.E. Szubert, E.R. Anliker, T.J. Bender, J.E. Lerch
    ANL, Lemont, Illinois, USA
  
  The Advanced Photon Source Upgrade (APS-U) in-cludes four straight sections equipped with full length Superconducting Undulators (SCUs). These sections require vacuum systems that must span 5.383 meters at nominal length, accommodate the SCU device, and ac-commodate additional magnets for the canted configura-tions. In the direction of the beam, the upstream portion of the vacuum system is a copper chamber doubling as a photon absorber with a design that is manufactured to allow a 13.5 mm canting magnet gap. This portion of the vacuum system operates at room temperature and shad-ows the length of the vacuum chamber that operates within the cryostat at 20K. The vacuum chamber inside the cryostat is a weldment including a machined alumi-num extrusion allowing for an 8mm magnetic gap, stain-less steel thermal insulators, copper shields, and bel-lows/flange assembly. The vacuum system includes an-other room temperature copper chamber and absorber on the downstream end of the straight section. The vacuum system provides Ultra-high Vacuum (UHV) continuity through the straight section, connecting the storage ring vacuum systems.  
poster icon Poster TUPLS03 [0.974 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS03  
About • paper received ※ 26 August 2019       paper accepted ※ 13 September 2019       issue date ※ 08 October 2019  
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TUPLS04 Re-Evaluation of the NSLS-II Active Interlock Window insertion, insertion-device, wiggler, undulator 456
 
  • R.P. Fliller, III, C. Hetzel, Y. Hidaka, T. Tanabe
    BNL, Upton, New York, USA
  
  Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy
The NSLS-II Active Interlock is the system which protects the NSLS-II Storage Ring vacuum chamber from damage due to synchrotron radiation. The Active Interlock measures the beam position and angle at all insertion devices and issues a beam dump if the beam is outside of the pre-defined window. The window is determined by thermal analysis of vacuum apertures and considers the effects of local magnets such as canting magnets, etc. Recently, it was realized that the insertion device correction coils where not considered in the initial evaluation of the envelope. The purpose of these coils is to correct for the orbit deviations caused by imperfections in the insertion devices that steer the beam. The usual effect is to negate any angle induced by the device, however, if the coil is not set properly the beam may have a larger angle than permitted by the Active Interlock even though the angle calculation does not show it. In this paper we discuss the effect of the insertion device coils on the electron beam and the steps taken to account for this effect in the Active Interlock. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS04  
About • paper received ※ 27 August 2019       paper accepted ※ 16 November 2020       issue date ※ 08 October 2019  
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TUPLS11 NEG-Coated Copper Vacuum Chambers for the APS-Upgrade Storage Ring Vacuum System storage-ring, photon, radiation, operation 477
 
  • O.K. Mulvany, B. Billett, B. Brajuskovic, J.A. Carter, A. McElderry, K.J. Wakefield
    ANL, Lemont, Illinois, USA
  
  Funding: Argonne National Laboratory’s work was supported by the U.S. Department of Energy, Office of Science under contract DE-AC02-06CH11357.
The APS-Upgrade (APS-U) storage ring features a diverse group of vacuum chambers including seven distinctive, non-evaporable getter (NEG)-coated copper vacuum chambers per each of the 40 sectors. These chambers feature a 22-millimeter diameter aperture along the electron-beam path, with two vacuum chambers permitting photon extraction through a keyhole-shaped extension to this aperture. The chambers range from 0.3-meters to 1.7-meters in length and fit within the narrow envelope of quadrupole and sextupole magnets. Six of the seven copper vacuum chambers intercept significant heat loads from synchrotron radiation; five of these designs are fabricated entirely from OFS copper extrusions and are equipped with a compact Glidcop® photon absorber. A hybrid vacuum chamber, fabricated from OFS copper extrusion and a copper chromium zirconium (CuCrZr) keyhole transition, also intercepts synchrotron radiation. The seventh vacuum chamber design features a keyhole aperture across its length and is entirely fabricated from CuCrZr. This paper details the careful balance of vacuum chamber functionality, manufacturability, and the overall design process followed to achieve the final designs. 		 
poster icon Poster TUPLS11 [4.941 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS11  
About • paper received ※ 27 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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TUPLS12 Final Design of NEG-Coated Aluminum Vacuum Chambers & Stainless Steel Keyhole Vacuum Chambers for the APS-U Storage Ring storage-ring, photon, radiation, quadrupole 480
 
  • A. McElderry, B. Billett, J.A. Carter, K.J. Wakefield
    ANL, Lemont, Illinois, USA
  
  Funding: Argonne National Laboratory’s work was supported by the U.S. Department of Energy, Office of Science under contract DE-AC02-06CH11357.
The APS-Upgrade storage ring features a diverse group of vacuum chambers which includes eight NEG (non-evaporable getter) coated aluminum chambers and two copper coated stainless steel keyhole-shaped chambers per sector (40 total). Each chamber contains a 22 mm diameter electron beam aperture; the keyhole chambers also include a photon extraction antechamber. The chambers vary in length of approximately 289 ’ 792 mm and fit within the narrow envelope of quadrupole and sextupole magnets. Each design is a balance of functionality, manufacturability, and installation space. An innovative CAD skeleton model system and ray tracing layout accurately determined synchrotron radiation heat loads on built-in photon absorbers and the internal envelope of the keyhole antechamber. Chamber designs were optimized using thermal-structural FEA for operating and bakeout conditions. The group of chambers require complex manufacturing processes including EDM, explosion-bonded metals, furnace brazing, and welding with minimal space. This paper describes the design process and manufacturing plan for these vacuum chambers including details about FEA, fabrication plans, and cooling/bakeout strategies. 		 
poster icon Poster TUPLS12 [2.581 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS12  
About • paper received ※ 27 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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TUPLH10 Fabrication Progress of a Superconducting Helical Undulator with Superimposed Focusing Gradient for High Efficiency Tapered X-Ray FELs undulator, FEL, quadrupole, focusing 509
 
  • S.M. Lynam, R.B. Agustsson, I.I. Gadjev, A.Yu. Smirnov
    RadiaBeam, Santa Monica, California, USA
  • F.H. O’Shea
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  Funding: This work is supported by DOE grant no. DE-SC0017072, "Superconducting Helical Undulator with Superimposed Focusing Gradient for High Efficiency Tapered X-Ray FELs"
The Advanced Gradient Undulator (AGU) represents a potentially significant advancement in x-ray conversion efficiency for x-ray FELs. This increase in efficiency would have broad implications on the capabilities of x-ray light sources. To achieve this high conversion efficiency, the inner diameter of the undulator coil is a mere 7mm, even with the use of superconducting coils. To accommodate the beamline at the Advanced Photon Source this yields in a chamber with a wall thickness of 0.5mm fabricated from Aluminum. With a period of 2cm and a conductor position tolerance of <100 µm over a length of >80cm at 4.2K, the engineering and fabrication challenges for the undulator alone are substantial. We will discuss these fabrication challenges and present solutions to meet the tolerances required for desired performance, and provide an update on current progress of the construction of a section of the AGU insertion device. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH10  
About • paper received ※ 28 August 2019       paper accepted ※ 16 November 2020       issue date ※ 08 October 2019  
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TUPLO03 RHIC Beam Abort System Upgrade Options kicker, proton, operation, heavy-ion 536
 
  • W. Fischer, M. Blaskiewicz, M. Mapes, M.G. Minty, C. Montag, S.K. Nayak, V. Ptitsyn, J. Sandberg, P. Thieberger, N. Tsoupas, J.E. Tuozzolo, K. Yip
    BNL, Upton, New York, USA
  
  Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
The RHIC ion (polarized proton) beam intensity has increased to 4x (1.1x) of the original design specifications. In 2013 proton beam currents overcame the eddy current reduction design features in the RHIC beam abort system kicker magnets causing ferrite heating and resulting in a reduction of the kicker strength. In 2014, the abort kicker ferrites were changed, the eddy current reduction design was upgraded, and an active ferrite cooling loop installed to prevent heating. For ions the beam dump vacuum window was changed from stainless steel to a titanium alloy and the adjacent beam diffuser block carbon material was changed to allow for higher ion intensities. A thicker beam pipe was installed to prevent secondaries from quenching the adjacent superconducting quadrupole. With these upgrades there is at least a factor 2 of safety margin for the demonstrated intensities to date. For a further increase in the intensity for RHIC and eRHIC we evaluate upgrade options for the beam abort system. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO03  
About • paper received ※ 26 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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TUPLE05 Optical System for Observation of FRIB Target target, radiation, shielding, neutron 570
 
  • I.N. Nesterenko, G. Bollen, M. Hausmann, A. Hussain, S.M. Lidia, S. Rodriguez Esparza
    FRIB, East Lansing, Michigan, USA
  • G. Bollen
    NSCL, East Lansing, Michigan, USA
  • G. Bollen
    MSU, East Lansing, Michigan, USA
  • I.N. Nesterenko
    BINP SB RAS, Novosibirsk, Russia
  
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
Facility for Rare Isotope Beams (FRIB) is a next-generation rare-isotope research facility under construction at Michigan State University (MSU). FRIB will produce rare-isotope beams of unprecedented intensities by impinging a 400 kW heavy-ion beam on a production target and by collecting and purifying the rare isotopes of interest with a fragment separator. A thermal imaging system (TIS) has been developed to monitor the beam spot on the production target. The main features and characteristics of optical system is presented. The prototype of optical system has been tested. 		 
poster icon Poster TUPLE05 [1.840 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE05  
About • paper received ※ 27 August 2019       paper accepted ※ 06 November 2020       issue date ※ 08 October 2019  
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TUPLE06 Skimmer-Nozzle Configuration Measurements for a Gas Sheet Beam Profile Monitor injection, detector, cathode, background 573
 
  • S. Szustkowski, S. Chattopadhyay, B.T. Freemire
    Northern Illinois University, DeKalb, Illinois, USA
  • S. Chattopadhyay, D.J. Crawford, B.T. Freemire
    Fermilab, Batavia, Illinois, USA
  
  Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program
Understanding the characteristics of the gas sheet being produced and optimal configuration of the gas injection system is essential to the the performance of a gas sheet beam profile monitor. A gas injection system test stand has been built at Fermilab to test various nozzle and slit configurations. The distance between the nozzle and slit can be changed to find an optimal configuration. Using a moveable cold cathode gauge the gas profile is measured. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE06  
About • paper received ※ 28 August 2019       paper accepted ※ 03 September 2019       issue date ※ 08 October 2019  
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WEYBB4 Progress of Liquid Lithium Stripper for FRIB operation, MMI, electron, gun 636
 
  • T. Kanemura, J. Gao, R. Madendorp, F. Marti, Y. Momozaki
    FRIB, East Lansing, Michigan, USA
  • M.J. LaVere
    MSU, East Lansing, Michigan, USA
  • Y. Momozaki
    ANL, Lemont, Illinois, USA
  
  Funding: This work is supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB) at Michigan State University is building a heavy ion linear accelerator (linac) to produce rare isotopes by the fragmentation method. At energies between 16 and 20 MeV/u ions are further stripped by a charge stripper increasing the energy gain downstream in the linac. The main challenges in the stripper design are high power deposited by the ions in the stripping media and radiation damage to the media itself. To overcome these challenges, self-recovering stripper media are the most suitable solutions. The FRIB baseline choice is a high-velocity thin film of liquid lithium*. Because liquid lithium is highly reactive with air, we have implemented rigorous safety measures. Since May 2018, the lithium stripper system has been operated safely at an offline test site to accumulate operational experience. Recently, we successfully completed a 10-day long unattended continuous operation without any issue, which proved the reliability of the system. The next step is to characterize the lithium film stability with diagnostics. In 2020, we plan to bring the lithium stripper into the accelerator tunnel and commission it with ion beams.
*Jie Wei, et al., TU1A04, Proceedings of LINAC 2012, Tel-Aviv, Israel 		 
slides icon Slides WEYBB4 [6.012 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBB4  
About • paper received ※ 03 September 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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WEPLM11 Closed Loop Modeling of the APS-U Orbit Feedback System controls, feedback, power-supply, simulation 683
 
  • P.S. Kallakuri, A.R. Brill, J. Carwardine, N. Sereno
    ANL, Lemont, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357.
Orbit stabilization to 10% of the expected small beam sizes for Advanced Photon Source Upgrade (APS-U) requires pushing the state of the art in fast orbit feedback (FOFB) control, both in the spatial domain and in dynamical performance. We are building a Matlab/Simulink fast orbit feedback system model to guide decisions about APS-U fast orbit feedback system implementation and to provide a test bench for optimal-control methodologies and orbit correction algorithms applicable to the APS-U. A transfer function model was built from open-loop frequency-response and step-response measurements of the present APS and subsequently validated against closed-loop measurements. A corresponding model for APS-U fast orbit feedback was generated by substituting measured responses of APS-U prototype corrector magnets and power supplies into this same model. Stabilizing PID gains are designed using model, and simulated dynamic performance of the new controller is validated through experiments. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM11  
About • paper received ※ 27 August 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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WEPLM56 Development of Helium Gas Charge Stripper with Plasma Window plasma, cathode, heavy-ion, experiment 720
 
  • J. Gao, F. Marti
    FRIB, East Lansing, Michigan, USA
  • A. Lajoie
    NSCL, East Lansing, Michigan, USA
  
  Funding: This work is supported by NSF Award PHY-1565546.
The cascade arc discharge, also called "plasma window", was suggested to be used as an interface to provide an effective separation between atmosphere and vacuum [1]. As suggested by Thieberger and Hershcovitch at Facility for Rare Isotope Beams (FRIB) workshop in 2009, helium plasma window offers an alternative to a large pumping system used in helium gas charge stripper for high intensity heavy ion beam accelerator facilities [2]. In this report, we present the recent progress on the development of helium plasma window with both 6mm and 10 mm diameter apparatus [3]. The size dependent sealing performance of helium plasma window has been investigated. Various diagnostics tools have been developed to improve our understanding of underlying physics. Over 140 hours continuous unattended operation of helium plasma window in recirculating gas system has been achieved, which suggests our system to be a feasible charge stripper solution for heavy ion beam accelerators. We also discuss anticipated future developments of plasma window.
[1] A. Hershcovitch, Phys. Plasma 5, 2130 (1998).
[2] H. Imao, et al., Phys. Rev. ST Accel. Beams 15, 123501 (2012).
[3] A. LaJoie, J. Gao and F. Marti, IEEE Transactions on Plasma Science (2019)
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM56  
About • paper received ※ 27 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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WEPLM57 200 kW, 350 - 700 MHz RF Sources using Multiple Beam Triodes cavity, cathode, electron, klystron 724
 
  • R.L. Ives, T. Bui, D. Marsden, M.E. Read
    CCR, San Mateo, California, USA
  • B. Henderson, L. Higgins, R. Ho
    CPI, Palo Alto, California, USA
  
  Funding: U.S. Department of Energy Grant No. DE-SC0018838
Calabazas Creek Research, Inc. and Communications & Power Industries, LLC are developing multiple beam triodes to produce more than 200 kW of RF power at extremely low cost and efficiencies exceeding 85%. RF power is achieved by installing the triode inside coaxial input and output cavities at the desired frequency. The multiple beam triodes developed in this program will provide RF power from 350 MHz to 700 MHz using the appropriate, tuned, resonant cavities. This program is using eight grid-cathode assemblies to achieve 200 kW with a target efficiency exceeding 80%. A 350 MHz RF source would be approximately 36 inches high, 18 inches in diameter and weigh approximately 150 pounds. This is significantly smaller than any other RF source at this frequency and power level. The gain is limited to approximately 14 dB, so a single beam triode-based source will serve as a driver. The combined cost and efficiency will still exceed the performance of other comparable RF sources, including solid state sources. Design issues, include grid cooling, uniformity of RF electric fields on the grids, and efficiency, will be discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM57  
About • paper received ※ 27 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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WEPLM64 High Dynamic Voltage Range Studies of Piezoelectric Multilayer Actuators at Low Temperatures linac, cavity, operation, SRF 739
 
  • C. Contreras-Martinez
    FRIB, East Lansing, Michigan, USA
  • Y.M. Pischalnikov, J.C. Yun
    Fermilab, Batavia, Illinois, USA
  
  Piezo actuators are used for resonance control in superconducting linacs. In high accelerating gradients linacs, such as those operated in a pulsed mode, the piezos require a large operating voltage. This is due to the Lorentz forced detuning which causes a large frequency shift and is compensated with an active piezo-tuning system. In this high dynamic voltage range the piezo is expected to warm up drastically due to it being in an insulated vacuum. This study characterizes the dielectric properties (capacitance, dielectric losses), the piezo stroke (from geophone), and thermal properties such as heating. Results obtained in the temperature range of 20K to 300K will be presented and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM64  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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WEPLH07 Commissioning of the FRIB/NSCL New ReA3 4-Rod Radio Frequency Quadrupole Accelerator rfq, operation, MMI, cavity 817
 
  • S. Nash, J.F. Brandon, D.B. Crisp, T. Summers, A.C.C. Villari, Q. Zhao
    NSCL, East Lansing, Michigan, USA
  • P.N. Ostroumov, A.S. Plastun
    FRIB, East Lansing, Michigan, USA
  
  Funding: This work was supported by the National Science Foundation under Grant PHY-15-65546
The reaccelerator facility ReA3 at the National Superconducting Cyclotron Laboratory is a state-of-the-art accelerator for ions of rare and stable isotopes. The first stage of acceleration is provided by a 4-rod radio-frequency quadrupole (RFQ) at 80.5 MHz, which accelerates ions from 12 keV/u to 530 keV/u. The internal copper acceleration structure of the RFQ was re-designed. The goal was to improve transmission while allowing to operate the RFQ in CW and accelerating ions with A/Q from 2 to 5. In this paper, we summarize the steps involved in the disassembly of the existing structure, preparation work on the retrofitted vacuum vessel, installation of the new components, acceptance testing, and commissioning of the completed RFQ. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH07  
About • paper received ※ 29 August 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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THYBA3 Use of Solid Xenon as a Beam Dump Material for 4th-Generation Storage Rings electron, emittance, simulation, storage-ring 927
 
  • M. Borland, H. Cease, J.C. Dooling
    ANL, Lemont, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Damage to tungsten beam dumps has been observed in the Advanced Photon Source due to the high charge (368 nC/store), high energy (7 GeV), and short loss time (about 15 microseconds). Owing to the higher charge (736 nC/store) and much lower emittance (42 pm vs 2.5 nm), this issue is expected to be much more severe in the APS Upgrade. This strongly suggests that such dumps are necessary in 4th-generation electron storage rings to prevent catastrophic damage to vacuum systems when, for example, rf systems trip. However, it also implies that the dump will be damaged by each strike and will thus need to be "refreshed," perhaps by moving the dump surface vertically to expose undamaged material. Xenon, a gas that solidifies at 161K, is an intriguing possibility for a beam dump material. Calculations suggest that as the beam spirals in toward a dump in a high-dispersion area the tails of the electron beam would vaporize sufficient xenon to rapidly diffuse the beam and render it harmless. The dump surface could be periodically reformed without breaking vacuum. Issues with the concept include the need to protect the frozen xenon from wakefield heating. 		 
slides icon Slides THYBA3 [2.451 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA3  
About • paper received ※ 27 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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THYBB3 Compact 1 MeV Electron Accelerator cavity, GUI, gun, electron 942
 
  • S.V. Kuzikov
    IAP/RAS, Nizhny Novgorod, Russia
  • S.P. Antipov, P.V. Avrakhov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  The cost of the accelerating structure in modern medical accelerators and industrial linacs is substantial. This comes to no surprise, as the accelerating waveguide is a set of diamond-turned copper resonators brazed together. Such a multistep manufacturing process is not only expensive, but also prone to manufacturing errors, which decrease the production yield. In the big picture, the cost of the accelerating waveguide precludes the use of accelerators as a replacement option for radioactive sources. Here we present a new cheap brazeless electron accelerating structure made out of two copper plates tightened together by means of an additional stainless steel plate. This additional plate, having sharp blades, is aimed to provide vacuum inside the whole system. The designed X-band 1 MeV structure consists of eight different length cells and accelerates field-emitted electrons from copper cathode. The structure is fed by 9 GHz magnetron which produces 240 kW, 1 µs pulses. The average gradient is as high as 10.6 MV/m, maximum surface fields do not exceed 50 MV/m.  
slides icon Slides THYBB3 [19.559 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBB3  
About • paper received ※ 27 August 2019       paper accepted ※ 15 September 2019       issue date ※ 08 October 2019  
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