Keyword: HOM
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MOPAB043 Validation of APS-U Beam Dynamics Using 6-GeV APS Beam simulation, cavity, lattice, impedance 189
 
  • L. Emery, P.S. Kallakuri, R.R. Lindberg, A. Xiao
    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.
Several beam measurements at the Advanced Photon Sources were done with a lowered-energy beam of 6 GeV in order to verify or validate calculation codes and some predictions for the APS-U. Though the APS lattice is obviously different from that of the APS-U some aspects of the beams at 6 GeV are similar, for example, the synchrotron radiation damping rate. At 6 GeV, one can also store more current and run with a higher rf bucket allowing the characterization of larger momentum aperture lattices. We report measurements (or plans of measurements) on general instabilities thresholds, lifetime, and other subtle effects. The important topic of ion instabilities at 6 GeV is covered in a separate paper by J. Calvey at this conference.
 
poster icon Poster MOPAB043 [0.829 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB043  
About • paper received ※ 20 May 2021       paper accepted ※ 23 June 2021       issue date ※ 10 August 2021  
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MOPAB088 Beam-Based Measurement on the Performance of Ferrite Dampers in an In-Vacuum Undulator damping, feedback, radiation, vacuum 331
 
  • K. Tian, A. Ringwall, J.J. Sebek
    SLAC, Menlo Park, California, USA
 
  In this paper, we first present the tracking studies for SPEAR3 with the new BL17 ID and estimate its impact on the dynamic aperture of the low emittance lattice. Then the ferrite dampers installations in the device is briefly reviewed. After that, we will show that, based on beam-based measurements, the performance of the dampers is as being expected from earlier numerical studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB088  
About • paper received ※ 19 May 2021       paper accepted ※ 18 June 2021       issue date ※ 24 August 2021  
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MOPAB107 RF Plans for the Diamond-II Upgrade cavity, linac, booster, gun 391
 
  • C. Christou, P. Gu, P.J. Marten, S.A. Pande, A.F. Rankin
    DLS, Oxfordshire, United Kingdom
 
  The RF system for the proposed Diamond-II upgrade will be based on normal-conducting EU HOM-damped cavities powered by high powered solid state amplifiers and controlled by digital low level RF systems built on the microTCA platform. Reasons for these design choices are discussed, and experience of the selected technologies in the Diamond-I ring are reviewed. The storage ring will also include a third harmonic cavity, and the different design options for this device are discussed. RF design of the booster ring is presented, and details are given of an upgraded linac and gun design intended to improve the charge delivered for top-up.  
poster icon Poster MOPAB107 [1.703 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB107  
About • paper received ※ 18 May 2021       paper accepted ※ 20 May 2021       issue date ※ 12 August 2021  
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MOPAB108 ESRF-EBS 352.37 MHz Radio Frequency System cavity, SRF, operation, MMI 395
 
  • J. Jacob, P.B. Borowiec, A. D’Elia, G. Gautier, V. Serrière
    ESRF, Grenoble, France
 
  The ESRF 352 MHz Radio Frequency (RF) system has been upgraded and tailored to the new 4th Generation Extremely Brilliant Source EBS, that was installed in 2019 and commissioned in 2020. The five former five-cell cavities were replaced with 13 single cell strongly HOM damped cavities that were developed in house, 10 of which are powered from existing 1 MW klystron transmitters. The remaining three cavities are individually fed by three 150 kW solid state amplifiers. All this required a reconstruction in record time of an elaborate WR2300 waveguide network. The low level RF system as well as the cavity and transmitter control system have been rebuilt. The RF design, commissioning and operation experience will be reported, including plans for a 4th harmonic RF system for bunch lengthening to further improve the performance of the new EBS ring.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB108  
About • paper received ※ 19 May 2021       paper accepted ※ 27 May 2021       issue date ※ 02 September 2021  
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MOPAB232 Observation of Polarization-Dependent Changes in Higher-Order Mode Responses as a Function of Transverse Beam Position in Tesla-Type Cavities at FAST cavity, electron, dipole, cryomodule 756
 
  • R.M. Thurman-Keup, D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan
    Fermilab, Batavia, Illinois, USA
  • J.A. Diaz Cruz
    UNM-ECE, Albuquerque, USA
  • J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou
    SLAC, Menlo Park, California, USA
 
  Funding: FNAL supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-07CH11359. SLAC supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-76SF00515.
Higher-order modes (HOMs) in superconducting rf cavities present problems for an electron bunch traversing the cavity in the form of long-range wakefields from previous bunches. These may dilute the emittance of the macropulse average, especially with low emittance beams at facilities such as the European X-ray Free-electron Laser (XFEL) and the upgraded Linac Coherent Light Source (LCLS-II). Here we present observations of HOMs driven by the beam at the Fermilab Accelerator Science and Technology (FAST) facility. The FAST facility features two independent TESLA-type cavities (CC1 and CC2) after a photocathode rf gun followed by an 8-cavity cryomodule. The HOM signals were acquired from cavities using bandpass filters of 1.75 ± 0.15 GHz, 2.5 ± 0.2 GHz, and 3.25 ± 0.2 GHz and recorded using an 8-GHz, 20 GSa/s oscilloscope. The frequency resolution obtained is sufficient to separate polarization components of many of the HOMs. These HOM signals were captured from CC1 and cavities 1 and 8 of the cryomodule for various initial trajectories through the cavities, and we observe correlations between trajectory, HOM signals, and which polarization component of a mode is affected.
 
poster icon Poster MOPAB232 [2.144 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB232  
About • paper received ※ 20 May 2021       paper accepted ※ 25 May 2021       issue date ※ 10 August 2021  
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MOPAB283 Simulations of Space-Charge and Guiding Fields Effects on the Performance of Gas Jet Profile Monitoring electron, simulation, collimation, GUI 898
 
  • O. Sedláček, N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang
    The University of Liverpool, Liverpool, United Kingdom
  • P. Forck, S. Udrea
    GSI, Darmstadt, Germany
  • N. Kumar, A. Salehilashkajani, O. Sedláček, C.P. Welsch, H.D. Zhang
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • S. Mazzoni, O. Sedláček
    CERN, Geneva, Switzerland
 
  Gas jet based profile monitors inject a usually curtain shaped gas jet across a charged particle beam and exploit the results of the minimally invasive beam-gas interaction to provide information about the beam’s transversal profile. Such monitor will be installed as part of the High Luminosity LHC upgrade at CERN in the Hollow Electron Lens (HEL). The HEL represents a new collimation stage increasing the diffusion rate of halo particles by placing a high intensity hollow electron beam concentrically around the LHC beam. The gas jet monitor will use the fluorescence radiation resulting due to the beam-gas interaction to create an image of the profiles of both hollow electron and LHC beams However, the high beam space-charge and strong guiding magnetic field of the electron beam cause significant displacements of the excited molecules, as they are also ionized, and thus image distortions. This work presents preliminary simulation results showing expected fluorescence images of the hollow electron profile as affected by space-charge and guiding fields using simulation tools such as IPMsim. The influence of the estimated electron beam and gas jet curtain parameters are investigated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB283  
About • paper received ※ 18 May 2021       paper accepted ※ 28 July 2021       issue date ※ 19 August 2021  
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MOPAB289 Machine Learning Training for HOM reduction and Emittance Preservation in a TESLA-type Cryomodule at FAST cavity, emittance, electron, controls 916
 
  • J.A. Diaz Cruz
    UNM-ECE, Albuquerque, USA
  • J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, J.P. Sikora
    SLAC, Menlo Park, California, USA
  • D.R. Edstrom, A.H. Lumpkin, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
 
  Low emittance electron beams are of high importance at facilities like the LCLS-II at SLAC. Emittance dilution effects due to off-axis beam transport for a TESLA-type cryomodule (CM) have been shown at the Fermilab Accelerator Science and Technology facility. The results showed the correlation between the electron beam-induced cavity high-order modes (HOMs) and submacropulse centroid slewing and oscillation downstream of the CM. Mitigation of emittance dilution can be achieved by reducing the HOM signals and the variances in the submacropulse beam positions downstream of the CM. Here we present a Machine Learning based optimization and model construction for HOM signal level reduction using Neural Networks and Gaussian Processes. To gather training data we performed experiments using single bunch and 50 bunch electron beams with charges up to 125 pC/b. We measured HOM signals of all cavities and beam position with a set of BPMs downstream of the CM. The beam trajectory was changed using V/H125 corrector set located upstream of the CM. The results presented here will inform the LCLS-II injector commissioning and will serve as a prototype for HOM reduction and emittance preservation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB289  
About • paper received ※ 19 May 2021       paper accepted ※ 09 June 2021       issue date ※ 14 August 2021  
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MOPAB323 Commissioning of the LCLS-II Prototype HOM Detectors with Tesla-Type Cavities at Fast cavity, electron, cryomodule, detector 996
 
  • J.P. Sikora, J.A. Diaz Cruz, B.T. Jacobson
    SLAC, Menlo Park, California, USA
  • J.A. Diaz Cruz
    UNM-ECE, Albuquerque, USA
  • D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
 
  Funding: *Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. **Work supported by the U.S. Department of Energy, contract DE-AC02-76SF00515.
Experiments at the Fermilab Accelerator Science and Technology* (FAST) facility detected electron beam-induced high order mode (HOM) signals from Tesla superconducting cavities. This paper describes some of the signal detection hardware used in this experiment, as well as measurements of the HOM signal magnitude versus beam trajectory. These measurements were made both with a single bunch and with a train of 50 bunches at bunch charges from 400 pC/b down to 10 pC/b. The detection hardware is designed for use with the Tesla superconducting cavities of LCLS-II at SLAC** and is based on a prototype already in use at Fermilab. The HOM signal passes through a bandpass filter that is centered on several cavity dipole modes and a zero bias Schottky diode detects its magnitude. Direct comparisons were made between the FNAL chassis and the SLAC prototype for identical beam steering conditions. To support measurements with bunch charges as low as 10 pC, the SLAC detector has RF amplification between the bandpass filter and the diode detector. With this hardware, usable HOM signal measurements are obtained with a single bunch of 10 pC in cryomodule cavities as will be needed for LCLS-II.
 
poster icon Poster MOPAB323 [2.076 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB323  
About • paper received ※ 17 May 2021       paper accepted ※ 07 June 2021       issue date ※ 14 August 2021  
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MOPAB332 Design of 4th Harmonic RF Cavities for ESRF-EBS cavity, SRF, impedance, coupling 1031
 
  • A. D’Elia, J. Jacob, V. Serrière, X.W. Zhu
    ESRF, Grenoble, France
 
  Funding: European Union’s Horizon 2020 research and innovation program under grant #871072
An active 4th harmonic RF system for bunch lengthening is under study at the ESRF to improve the performance of the new EBS storage ring, mainly for few bunch operation with high currents per bunch, by reducing Touschek and intrabeam scattering, thereby increasing the lifetime and limiting the emittance growth. It will also reduce impedance heating of the vacuum chambers. The 4th Harmonic 1.41 GHz normal conducting cavity design takes inspiration from the KEK idea of using a TM020 mode exhibiting a reduced R/Q but a higher unloaded Q with respect to TM010. We propose to use multicell cavities for their compactness, the reduced number of required ancillaries and the ease of control for a reduced number of cavities. The drawback is the complexity of the model and the necessity to damp the lower order TM010 mode (LOM) as well as the higher order modes (HOM). The RF design of a 4th harmonic multicell damped cavity will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB332  
About • paper received ※ 19 May 2021       paper accepted ※ 17 August 2021       issue date ※ 16 August 2021  
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MOPAB333 ESRF-EBS 352 MHz HOM Damped RF Cavities cavity, SRF, impedance, MMI 1034
 
  • A. D’Elia, J. Jacob, V. Serrière
    ESRF, Grenoble, France
 
  For the new ESRF-EBS Storage Ring (SR), HOM damped RF cavities were needed to cope with the reduced thresholds for Longitudinal Coupled Bunch Instabilities (LCBI). The 352 MHz cavities were designed at the ESRF based on an improved version of the 500 MHz EU/ALBA/BESSY structures. A short description of the cavity design will be presented as well as an overview of the fabrication, the preparation and the performance of 13 such cavities for the ESRF-EBS SR. A study of the impedance of a whole cavity equipped with its ancillaries (HOM absorbers, ion pump and tuner) will be presented. One of the three HOM absorbers, the smaller one on top of the cavity, was finally not installed on the machine. The reasons and a detailed analysis in terms of HOM impedances that justifies this choice will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB333  
About • paper received ※ 19 May 2021       paper accepted ※ 07 June 2021       issue date ※ 02 September 2021  
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MOPAB358 Design and Measurement of the 1.4 GHz Cavity for LEReC Linac cavity, electron, resonance, GUI 1113
 
  • B.P. Xiao, J.C. Brutus, J.M. Fite, K. Hamdi, D. Holmes, K. Mernick, K.S. Smith, J.E. Tuozzolo, T. Xin, A. Zaltsman
    BNL, Upton, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration of electron bunches. To further improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, a normal conducting RF cavity at 1.4 GHz was designed and fabricated for the LINAC that will provide longer electron bunches for the LEReC. It is a single-cell cavity with an effective cavity length shorter than half of the 1.4 GHz wavelength. This cavity was fabricated and tested on-site at BNL to verify RF properties, i.e. the resonance frequency, FPC coupling strength, tuner system performance, and high power tests. In this paper, we report the RF test results for this cavity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB358  
About • paper received ※ 17 May 2021       paper accepted ※ 25 June 2021       issue date ※ 24 August 2021  
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MOPAB385 An Overview of RF Systems for the EIC cavity, SRF, electron, luminosity 1179
 
  • R.A. Rimmer, J.P. Preble
    JLab, Newport News, Virginia, USA
  • K.S. Smith, A. Zaltsman
    BNL, Upton, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under DOE Contract No. DE-SC0012704, by Jefferson Science Associates under contract DE-SC0002769, and by SLAC under Contract No. DE-AC02-76SF00515.
The Electron Ion Collider (EIC) to be constructed at Brookhaven National Laboratory in the USA will be a complex system of accelerators providing high luminosity, high polarization, variable center of mass energy collisions between electrons and protons or ions. To achieve this a variety of RF systems are required. They must provide for capture, formation and storage of Ampere-class beams in the electron and hadron storage rings (ESR and HSR), fast acceleration of high-charge polarized electron bunches in the rapid cycling synchrotron (RCS), provision of cold high current electron bunches in the high-energy cooler ERL and precise high-gradient crabbing of electrons and hadrons either side of the interaction point. The challenges include strong HOM damping in the storage ring cavities and cooler ERL, very high fundamental mode power in the ESR and cooler injector, extremely stable low-noise operation of the crab cavities, mitigation of transient beam loading from gaps, and operating over a wide range of energies and beam currents. We describe the high-level system parameters and principal design choices made and progress on the R&D plan to develop these state of the art systems.
 
poster icon Poster MOPAB385 [1.268 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB385  
About • paper received ※ 18 May 2021       paper accepted ※ 31 May 2021       issue date ※ 30 August 2021  
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MOPAB393 Design of an RF-Dipole Crabbing Cavity System for the Electron-Ion Collider cavity, cryomodule, impedance, electron 1200
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • J. Henry, F. Marhauser, H. Park, R.A. Rimmer
    JLab, Newport News, Virginia, USA
 
  The Electron-Ion Collider requires several crabbing systems to facilitate head-on collisions between electron and proton beams in increasing the luminosity at the interaction point. One of the critical rf systems is the 197 MHz crabbing system that will be used in crabbing the proton beam. Many factors such as the low operating frequency, large transverse voltage requirement, tight longitudinal and transverse impedance thresholds, and limited beam line space makes the crabbing cavity design challenging. The rf-dipole cavity design is considered as one of the crabbing cavity options for the 197 MHz crabbing system. The cavity is designed including the HOM couplers, FPC and other ancillaries. This paper presents the detailed electromagnetic design, mechanical analysis, and conceptual cryomodule design of the crabbing system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB393  
About • paper received ※ 26 May 2021       paper accepted ※ 02 June 2021       issue date ※ 26 August 2021  
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TUXA05 Measurements of Beam-Beam Interactions in Gear-Changing Collisions in DESIREE experiment, collider, beam-beam-effects, framework 1283
 
  • E.A. Nissen
    JLab, Newport News, Virginia, USA
  • A. Källberg, A. Simonsson
    Stockholm University, Stockholm, Sweden
 
  Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a license to publish or reproduce this manuscript.
In this work, we perform measurements on the interactions of colliding beams in a gear-changing system. Gear-changing was first demonstrated in DESIREE in May of 2020 and showed several promising avenues to measure beam-beam effects. DESIREE has a unique collision scheme where the beams are moving in the same direction, which provides for unique interactions. This experiment used a 4 on 3 gear changing system with one bucket in each ring left empty, this allows us to see the bunch profile while undergoing collisions. We then measured the bunch length over time and used a Fourier transform to extract longitudinal evolution data and compared it to baseline data of uncollided beams.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA05  
About • paper received ※ 21 May 2021       paper accepted ※ 14 June 2021       issue date ※ 26 August 2021  
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TUPAB038 Simulation of the Filling Pattern Dependent Regenerative Beam Breakup Instabilities in Energy Recover Linacs cavity, linac, simulation, electron 1431
 
  • S. Setiniyaz, P.H. Williams
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • R. Apsimon
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  The interaction of a transversely displaced beam with the higher modes (HOM) of the accelerating cavities causes building up HOM voltages in the cavity, which in turn kicks the beam and increases the offset further. This is known as regenerative beam breakup (BBU) instability and it sets the beam threshold current for the stable beam operation. A study by Setiniyaz et al.~[Setiniyaz2020] showed the filling pattern and recombination schemes of multi-turn energy recovery linacs (ERLs) can create many different beam loading transients, which can have a big impact on the cavity fundamental mode voltage and RF stabilizes. In this work, we extend the study of the filling pattern and recombination schemes to the BBU instabilities and threshold current. In the ERLs, the accelerated and decelerated bunches can be ordered differently while they pass through the cavity and form different filling patterns. Each pattern has a unique bunch energy sequence and bunch arrival times and hence interacts with cavity uniquely and thus drives BBU differently. In this paper, we introduce a simulation tool to investigate the filling pattern dependence of the ERL BBU instability.
* S. Setiniyaz, R. Apsimon, and P. H. Williams, Phys. Rev. Accel. Beams 23, 072002, 2020.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB038  
About • paper received ※ 20 May 2021       paper accepted ※ 09 June 2021       issue date ※ 15 August 2021  
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TUPAB053 Design Progress of ALS-U 3rd-Harmonic Cavity cavity, damping, impedance, simulation 1481
 
  • T.H. Luo, K.M. Baptiste, S. De Santis, D. Li, J.W. Staples, M. Venturini
    LBNL, Berkeley, California, USA
  • H.Q. Feng
    TUB, Beijing, People’s Republic of China
 
  Funding: Director, Office of Science, Office of Basic Energy Sciences, and LDRD Program of Lawrence Berkeley National Laboratory, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A higher-harmonic rf cavity (HHC) system is required in the ALS-U storage ring to lengthen the bunches, reduce intrabeam-scattering effects, and improve Touschek beam lifetime. A 3rd harmonic, normal conducting, passive-cavity system has been chosen based on beam-dynamics requirements and cost considerations. We have explored two options for ALS-U 3HC system: a high-R/Q re-entrant cavity with waveguide HOM dampers, and a low-R/Q system with two elliptical cavities and HOM beam line absorbers. In this paper, we present the recent progress on the cavity design and related beam dynamics studies.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB053  
About • paper received ※ 19 May 2021       paper accepted ※ 11 June 2021       issue date ※ 14 August 2021  
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TUPAB087 Full Characterization of the Bunch-Compressor Dipoles for FLUTE dipole, electron, linac, controls 1585
 
  • Y. Nie, A. Bernhard, E. Bründermann, A.-S. Müller, M.J. Nasse, R. Ruprecht, J. Schäfer, M. Schuh, Y. Tong
    KIT, Karlsruhe, Germany
 
  Funding: This work is supported by the BMBF project 05H18VKRB1 HIRING (Federal Ministry of Education and Research).
The Ferninfrarot Linac- Und Test-Experiment (FLUTE) is a KIT-operated linac-based test facility for accelerator research and development as well as a compact, ultra-broadband and short-pulse terahertz (THz) source. As a key component of FLUTE, the bunch compressor (chicane) consisting of four specially designed dipoles will be used to compress the 40-50 MeV electron bunches after the linac down to single fs bunch length. The maximum vertical magnetic field of the dipoles reach 0.22 T, with an effective length of 200 mm. The good field region is ±40 mm and ±10.5 mm in the horizontal and vertical direction, respectively. The latest measurement results of the dipoles in terms of field homogeneity, excitation and field reproducibility within the good field regions will be reported, which meet the predefined specifications. The measured 3D magnetic field distributions have been used to perform beam dynamics simulations of the bunch compressor. Effects of the real field properties on the beam dynamics, which are different from that of the ASTRA built-in dipole field, will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB087  
About • paper received ※ 10 May 2021       paper accepted ※ 27 May 2021       issue date ※ 01 September 2021  
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TUPAB177 Simulating Magnetized Electron Cooling for EIC with JSPEC electron, scattering, simulation, target 1813
 
  • S.J. Coleman, D.L. Bruhwiler, B. Nash, I.V. Pogorelov
    RadiaSoft LLC, Boulder, Colorado, USA
  • H. Zhang
    JLab, Newport News, Virginia, USA
 
  We present a possible electron cooling configuration for the proposed Electron Ion Collider (EIC) facility, developed using a Nelder-Mead Simplex optimization procedure built into JSPEC, an electron cooling code developed at Jefferson Lab. We show the time evolution of the emittance of the ion beam in the presence of this cooler evaluated assuming the ion distribution remains Gaussian. We also show that bi-gaussian distributions emerge in simulations of ion macro-particles. We show how intra-beam scattering can be treated with a core-tail model in simulations of ion macro-particles. The Sirepo/JSPEC* and Sirepo/Jupyter** apps will be presented, with instructions enabling the community to reproduce our simulations.
* https://www.sirepo.com/jspec
** https://www.sirepo.com/jupyter
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB177  
About • paper received ※ 19 May 2021       paper accepted ※ 15 June 2021       issue date ※ 16 August 2021  
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TUPAB225 3D Magnetic Field Analysis of LHC Final Focus Quadrupoles with Beam Screen quadrupole, octupole, focusing, database 1952
 
  • T. Pugnat, B. Dalena, C. Lorin
    CEA-IRFU, Gif-sur-Yvette, France
  • S. Bagnis
    CEA-DRF-IRFU, France
 
  During the LHC commissioning, a discrepancy in the non-linear corrector strengths between the model and the beam-based values has been observed*. This has motivated the reconstruction of the 3D finite element model for the LHC final focusing MQXA type magnet. The longitudinal higher orders magnetic field pseudo-harmonics are computed taking into account ovalization of the magnet, interconnections design, and beam screens. The effect of this 3D field on the computation of the nonlinear correctors is evaluated and compared with beam-based corrector values.
*E. H. Maclean et al., "New approach to LHC optics commissioning for the nonlinear era", Phys. Rev. Acc. B, vol. 22, pp. 061004, June 2019.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB225  
About • paper received ※ 18 May 2021       paper accepted ※ 08 July 2021       issue date ※ 12 August 2021  
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TUPAB238 Algorithm to Analyze Complex Magnetic Structures Using a Tube Approach quadrupole, multipole, octupole, sextupole 1995
 
  • B. Riemann, M. Aiba
    PSI, Villigen PSI, Switzerland
 
  Modern synchrotron light sources often require sophisticated multipole field distributions that need to be realized by complex magnet structures. To pre-validate these magnet structures via simulations, the extraction procedure needs to output standard multipoles as well as fringe effects. The approach presented in this manuscript uses a volumetric grid map of the magnetic flux density as input. After computation of the reference trajectory (leapfrog integration), a large linear system is solved to compute transverse polynomial coefficients of the magnetic scalar potential in a series of interconnected thin cylinders (linear basis functions) along with that reference. The import of these coefficients into a lattice simulation is discussed using a modification of the tracking code Tracy. The shown approach is routinely used to check models of SLS 2.0 magnets for their properties.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB238  
About • paper received ※ 18 May 2021       paper accepted ※ 17 June 2021       issue date ※ 31 August 2021  
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TUPAB272 Observation of Long-Range Wakefield Effects Generated in an Off-Resonance Tesla-Type Cavity cavity, electron, resonance, wakefield 2101
 
  • A.H. Lumpkin, D.R. Edstrom, A. Lunin, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • J.A. Diaz Cruz
    UNM-ECE, Albuquerque, USA
  • J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported 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 interest in controlling emittance dilution effects due to off-axis beam transport in accelerator cavities and the resulting dipolar modes is especially important for the facilities with lower emittance beams. The Fermilab Accelerator Science and Technology (FAST) facility has a unique configuration of two single cavities after the photocathode rf gun followed by a cryomodule. The second capture cavity (CC2) was run 15 kHz off resonance and without rf power while a 25-MeV beam was injected into it. The beam centroid effects were tracked by 10 rf button BPMs with bunch-by-bunch position readout capability downstream in a 12-m drift. Possible LRW effects seemed to dominate our previously observed near-resonant HOM effects at mode 14 in this cavity. This mode also shifted in frequency compared to that of the tuned case based on direct measurements. Submacropulse vertical position slewing of 1400 microns at 11 m downstream was observed with a 125 pC/bunch, 50 bunches per macropulse, and 25-MeV beam. The y-position slew amplitudes as a function of z were also measured. Horizontal positions also showed a slew effect. Both are emittance-dilution effects which one wants to mitigate.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB272  
About • paper received ※ 18 May 2021       paper accepted ※ 09 June 2021       issue date ※ 20 August 2021  
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TUPAB273 Observations on Submicropulse Electron-Beam Effects From Short-Range Wakefields in Tesla-Type Superconducting Rf Cavities cavity, electron, wakefield, laser 2105
 
  • A.H. Lumpkin, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • J.A. Diaz Cruz
    UNM-ECE, Albuquerque, USA
  • J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, F. Zhou
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported 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.
In previous experiments at the Fermilab Accelerator Science and Technology (FAST) facility, the effects of higher-order modes (HOMs) in TESLA-type cavities on submacropulse centroid motion were elucidated*. We now have extended our investigations to short-range wakefields (SRWs) in these cavities. The latter result in submicropulse effects where the transverse wakefields cause head-tail centroid shifts. We used a Hamamatsu C5680 UV-visible synchroscan streak camera to synchronously sum the OTR from each of the 50 micropulses in the macropulse. We generated the y-t effect in the 41-MeV beam by purposely steering the beam off axis in y at the entrance of the first capture cavity. The head-tail transverse kicks within the 11-ps-long micropulses of 500 pC each were observed at the 100-micron level for steering off-axis in one cavity and several 100 microns for two cavities. These SRW results will be compared to simulations from the ASTRA model of a single micropulse in FAST. Since the SRW kicks go inversely with energy, these emittance-dilution effects are particularly relevant to the LCLS-II injector commissioning plans where <1 MeV beam will be injected into a TESLA-type cryomodule.
* A.H. Lumpkin et al, Phys. Rev. Accel. and Beams 23, 054401 (2020).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB273  
About • paper received ※ 18 May 2021       paper accepted ※ 09 June 2021       issue date ※ 28 August 2021  
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TUPAB274 Investigations of Long-Range Wakefield Effects in a TESLA-type Cryomodule at FAST cavity, electron, cryomodule, wakefield 2109
 
  • A.H. Lumpkin, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • J.A. Diaz Cruz
    UNM-ECE, Albuquerque, USA
  • J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou
    SLAC, Menlo Park, California, USA
 
  Funding: *Work supported 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 preservation of low emittance of electron beams during transport in the accelerating structures of large facilities is an ongoing challenge. In the cases of the TESLA-type superconducting rf cavities currently used in the European X-ray Free-electron Laser (XFEL) and the under-construction Linac Coherent Light Source upgrade (LCLS-II), off-axis beam transport may result in emittance dilution due to transverse long-range wakefields (LRWs) and short-range wakefields (SRW)***. To investigate such effects, experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility with its unique configuration of two TESLA-type cavities after the photocathode rf gun followed by an 8-cavity cryomodule CM). We generated beam trajectory changes with the H/V125 corrector set located 4 m upstream of the cryomodule. At 125 pC/bunch, 50 bunches, 25-MeV input, and 100-MeV exit energy, we observed for the first time submacropulse position slews of up to 500 microns at locations ~3 m after the CM and a centroid oscillation at a difference frequency of 240 kHz further downstream. Both are emittance-dilution effects which we mitigated with selective upstream beam steering.
***W.K.H. Panofsky and M. Bander, Rev. Sci. Instr. 39, 206 (1968).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB274  
About • paper received ※ 18 May 2021       paper accepted ※ 09 June 2021       issue date ※ 31 August 2021  
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TUPAB338 Surface Roughness Reduction of Nb3Sn Thin Films via Laser Annealing for Superconducting Radio-Frequency Cavities laser, SRF, cavity, superconductivity 2283
 
  • Z. Sun, M. Ge, M. Liepe, T.E. Oseroff, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • A.B. Connolly, M.O. Thompson
    Cornell University, Ithaca, USA
 
  Superconducting radio frequency (SRF) cavities, a key component of particle accelerators, await new SRF materials beyond the state-of-the-art niobium. Nb3Sn is one of the most competitive candidates, since it increases the superheating field, allows the operation temperature up to 4K, and improves cavity efficiency. Surface roughness and grain boundaries, however, significantly affect the RF performance of current Nb3Sn cavities. Here, we explore a post laser annealing technique to reduce the surface roughness. In doing so, we deposited a TiN laser-absorber on Nb3Sn and Nb surfaces, and then annealed the samples by laser scanning via different laser systems. The Nb3Sn surface roughness was minimized to 101 nm (Ra) by laser annealing via 308 nm, 35 ns pulses. Surface imaging and Fourier analysis revealed laser annealing is able to remove sharp edges and <1 um wavelength features.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB338  
About • paper received ※ 20 May 2021       paper accepted ※ 09 June 2021       issue date ※ 19 August 2021  
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TUPAB341 Optimization of Two-Cell Cavities for the W and H Working Points of the FCC-ee Considering Higher-Order Mode Effects cavity, impedance, damping, ECR 2292
 
  • S. Udongwo, S.G. Zadeh, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • R. Calaga
    CERN, Meyrin, Switzerland
 
  Funding: The European Organization for Nuclear Research (CERN)
The lepton collider of the future circular collider (FCC-ee) aims at conducting precision measurements on the Z, W, and H bosons and the top quark. The present RF baseline considers single-cell cavities at 400 MHz for the high current Z-pole working point, four-cell 400 MHz cavities for the W and H working points, and a hybrid RF system composed of four-cell 400 MHz and five-cell 800 MHz cavities for the high energy tt working point. The W working point has shown limitations in the achievable HOM damping for beam stability requirements using four-cell cavities. A two-cell cavity is studied as an alternative scenario for the current W- and H-RF setups with a special focus on HOM damping during the optimization of the RF geometry.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB341  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 22 August 2021  
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TUPAB351 The Progress of 300 kW Home-Made Fully Solid-State Transmitter for TPS controls, power-supply, ISOL, operation 2328
 
  • T.-C. Yu, F.Y. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.D. Li, M.-C. Lin, Z.K. Liu, C.H. Lo, Ch. Wang, M.-S. Yeh
    NSRRC, Hsinchu, Taiwan
 
  To support the stable operation of Taiwan Photon Source (TPS) with 500mA beam current and the in-creasing beam line construction, a 3rd RF plant is thus constructed for such demand. The RF power source of the other 2 RF plants adopts klystron type transmitter and the 3rd RF plants is transferred to new technology of solid-state for better redundancy and easier mainte-nance. Base on the success of solid-state power ampli-fier development in 2020, a 3rd RF power source is thus decided to be made in house by solid-state tech-nology. The 500MHz 300kW solid-state transmitter is constructed by 4 80 kW solid-state power amplifier (SSPA) towers and power combined by 3 WR1800 3-dB hybrid couplers. Each tower is consisted of 110 850W final stage SSPA modules with 4 100W pre-amplifiers and 6 600W drive amplifiers. The pre and drive amplifiers are power combined for higher redun-dancy. The DC power are economical industrial 48V AC-DC rack mount power supplies which are parallel connected for higher total DC power and best redun-dancy. The architecture and present progress are pre-sented in this article.  
poster icon Poster TUPAB351 [2.348 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB351  
About • paper received ※ 20 May 2021       paper accepted ※ 11 June 2021       issue date ※ 20 August 2021  
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TUPAB363 Feasibility Study for the Novel CERN PS Fast Extraction Septum septum, extraction, simulation, emittance 2363
 
  • T. Helseth, M.G. Atanasov, B. Balhan, J.C.C.M. Borburgh, L. Ducimetière, M.A. Fraser, T. Kramer
    CERN, Geneva, Switzerland
 
  In the framework of accelerator consolidation, a feasibility study for a novel CERN PS extraction septum has been conducted. Functional requirements have been established and, accordingly, a system of two septa magnets and their associated pulse generator is proposed. The magnetic septum design is based on eddy current topology. Magnetic simulations in Flux 2D and Opera 3D of a conceptual design have been carried out. The short length and high amplitude of the current pulse required to drive the eddy current septa imply that none of the power converters currently used for septa magnets at CERN will be suitable. Pulse generator topologies derived from kicker generators have therefore been explored and simulated in Spice. The conceptual magnet and generator design along with simulation results are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB363  
About • paper received ※ 18 May 2021       paper accepted ※ 17 June 2021       issue date ※ 10 August 2021  
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TUPAB364 Dipole CR FAIR dipole, simulation, storage-ring, experiment 2367
 
  • K.K. Riabchenko, A.Yu. Pakhomov, T.V. Rybitskaya, A.A. Starostenko, A.S. Tsyganov, K.V. Zhiliaev
    BINP SB RAS, Novosibirsk, Russia
 
  The design of CR dipole magnets (24+2 pieces) for the FAIR project in Germany began in 2014 at BINP. CR is a special storage ring where the main emphasis is placed on efficient stochastic pre-cooling of intense beams of stable ions, rare isotopes, or antiprotons. This type of magnet is an iron-based electromagnet with a straight pole, sector form is realized by cutting ends. The maximum field value is 1.6 T. The integrated over the length of the magnet field quality as a function of radius is dBl/Bl = ± 10-4 with 190 mm good field region as required from the beam dynamics simulations. This challenging field quality is necessary mainly for precise experiments with ion beam in the ISO regime. Below 1.6 T the value dBl/Bl can be higher with a linear approximation up to ± 2.5× 10-4 at the field level of 0.8 T. The first prototype has been manufactured at the end of 2020. Here we describe features of the dipole, 3D calculations, and measurements of the magnetic field.  
poster icon Poster TUPAB364 [1.587 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB364  
About • paper received ※ 09 May 2021       paper accepted ※ 31 May 2021       issue date ※ 28 August 2021  
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TUPAB400 Manufacturing of Ceramic Vacuum Chambers for Sirius On-Axis Kicker vacuum, kicker, niobium, target 2457
 
  • R. Defavari, O.R. Bagnato, M.W.A. Feitosa, F.R. Francisco, D.Y. Kakizaki, R.L. Parise, R.D. Ribeiro
    LNLS, Campinas, Brazil
 
  Ceramic vacuum chambers were produced by LNLS for the Sirius kickers. Alumina tubes with an elliptical inner shape of 9.5 mm (V) x 29 mm (H) and 500 mm long were successfully manufactured by a Brazilian company. Metallic F136 titanium flanges were brazed to Nb inserts using Ag-58.5Cu-31.5Pd wt% alloy, these inserts were brazed to the ceramic using Ag-26.7Cu-4.5Ti wt% active filler metal. A titanium film was coated inside the chamber using argon plasma by RF Magnetron Sputtering technique. Samples have been investigated by Scanning Electron Microscopy (SEM) to measure film thickness along the inner section of the tube, coating morphology, chemical composition and homogeneity. The total electrical resistance of the tube was also monitored during the sputtering process to achieve the desired value (0.2 ohms/square). In this contribution, we present the results of an On-Axis kicker manufacturing process developed by LNLS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB400  
About • paper received ※ 18 May 2021       paper accepted ※ 31 May 2021       issue date ※ 29 August 2021  
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TUPAB416 Depth-Dose Distribution Dependence on the Energy Profile of Linear and Laser Wakefield Accelerator Electron Beams electron, radiation, linac, simulation 2502
 
  • T.A. Nguyen
    VNUHCM, Ho Chi Minh, Viet Nam
  • C. Rangacharyulu
    University of Saskatchewan, Saskatoon, Canada
  • C.V. Tao
    HCMUS, Ho Chi Minh City, Viet Nam
 
  The depth-dose distributions of 10 MeV electron beams used for food irradiation and sterilization purposes at Research and Development Center for Radiation Technology, HCMC, Vietnam are measured and the results are well reproduced by the MCNP simulations. We extend the simulations to predict the dose depth distribution for 10 MeV electron beams with the energy profiles of a model Laser Wake Field accelerator (LWFA). The dosimetry and simulation results show that the maximum dose of the depth-dose curve inside the product is 1.4 times surface dose with an area density limit of 8.6 g/cm2 for two-sided irradiation with nearly mono-energetic beams from the linear accelerator and the corresponding parameters for LWFA are 1.2 times surface dose and 13.0 g/cm2, respectively.  
poster icon Poster TUPAB416 [1.506 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB416  
About • paper received ※ 17 May 2021       paper accepted ※ 11 June 2021       issue date ※ 31 August 2021  
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WEPAB054 Electromagnetic and Beam Dynamics Studies of the ThomX LINAC linac, gun, electron, solenoid 2721
 
  • M. Alkadi, C. Bruni, M. El Khaldi, M. Jacquet
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • H. Monard
    IJCLab, ORSAY, France
 
  ThomX is a new generation compact Compton source. The machine is composed of a 50/70 MeV injector linac and a storage ring where an electron bunch collides with a laser pulse accumulated in a Fabry-Perot resonator. The compact source, built at Irene Joliot-Curie Laboratory (IJCLAB) in the Orsay campus of Paris-Saclay University, is designed to produce a total flux of 1013 ph/s and a brightness of 1011 ph / (s.mm2.mrad2) in 0.1% of bandwidth with a tunable energy ranging from 45 keV to 90 keV on the X-ray beam axis. The photo-injector is composed of a homemade 2.5 cell photocathode RF-gun, placed between two solenoids. An energy of 5 MeV is reached with a 80 MV/m electric field gradient. During the commissioning phase, a 4.8 m S-band LIL section will be used to achieve a 50 MeV corresponding to a 45 keV X-ray energy. The LIL accelerating section is a quasi-constant gradient traveling wave structure. The energy gain in the section is 45 MeV, corresponding to an average effective accelerating gradient of 10 MV/m for an input RF power of 9 MW. Here we present the electromagnetic and beam dynamics studies of the ThomX LINAC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB054  
About • paper received ※ 19 May 2021       paper accepted ※ 01 July 2021       issue date ※ 29 August 2021  
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WEPAB062 Investigation of the Thomson Scattering Influence on Electron Beam Parameters in an Energy-Recovering Linear Accelerator on the Example of MESA electron, photon, scattering, laser 2732
 
  • C.L. Lorey, K. Aulenbacher, A. Meseck
    KPH, Mainz, Germany
 
  Funding: funded by DFG through GRK2128 ACCELENCE
At the Johannes Gutenberg University (JGU) in Mainz, the Mainz Energy-recovering Superconducting Accelerator (MESA) is currently under construction. It is designed to deliver electron beams of up to 155 MeV. As it can be operated in an energy-recovery (ER) mode thus allowing for high repetition rate, it is a promising candidate for a high flux Thomson scattering based gamma source. This paper will provide a status update on the study of the impact of Thomson scattering on electron beam parameters and the underlying mechanics. Further, the implementation into a simulation code will be discussed.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB062  
About • paper received ※ 19 May 2021       paper accepted ※ 12 July 2021       issue date ※ 02 September 2021  
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WEPAB065 Studies of the Energy Recovery Performance of the PERLE Project linac, cavity, electron, radiation 2744
 
  • K.D.J. André, B.J. Holzer
    CERN, Geneva, Switzerland
  • S.A. Bogacz
    JLab, Newport News, Virginia, USA
 
  The Powerful Energy Recovery Linac for Experiments (PERLE) is an accelerator facility for the development and application of the energy recovery technique for an intense 500 MeV electron beam. The paper presents the studies that have been performed to assess the quality of the ERL lattice design and beam optics. The studies include the Coherent Synchrotron Radiation (CSR) emission and wakefields in the superconducting radio-frequency structures of the linacs. The lattice design and optics principles of the ERL structure are discussed, involving the vertical deflection system and the 180° arcs. Finally, the results of the front-to-end tracking simulations that consider the complete multi-turn energy recovery process are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB065  
About • paper received ※ 18 May 2021       paper accepted ※ 24 June 2021       issue date ※ 30 August 2021  
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WEPAB090 Higher Order Mode Damping for 166 MHz and 500 MHz Superconducting RF Cavities at High Energy Photon Source cavity, impedance, damping, storage-ring 2798
 
  • H.J. Zheng, Z.Q. Li, F. Meng, N. Wang, H.S. Xu, P. Zhang, X.Y. Zhang
    IHEP, Beijing, People’s Republic of China
 
  Funding: This work was supported in part by High Energy Photon Source, in part by the National Natural Science Foundation of China under Grant No. 11905232.
Superconducting rf cavities have been chosen for High Energy Photon Source, a 6 GeV diffraction-limited synchrotron light source under construction in Beijing. The main accelerating cavity adopted a quarter-wave β=1 structure operating at 166 MHz while the third harmonic cavity utilized the single-cell elliptical geometry at 500 MHz for the storage ring. The high beam current (200 mA) requires a strong damping of higher order modes (HOMs) excited in the superconducting cavities. To meet the beam stability requirements, enlarged beam pipes with a diameter of 505 mm for the 166 MHz cavity and 300 mm for the 500 MHz cavity were chosen to allow all HOMs to propagate along the beam tubes and to be damped by beam-line absorbers. This paper presents the HOM damping scheme and the cavity impedance analysis results. In addition, power losses due to HOMs were also evaluated for various operation modes (high charge and high luminosity) of the HEPS.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB090  
About • paper received ※ 17 May 2021       paper accepted ※ 22 June 2021       issue date ※ 20 August 2021  
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WEPAB117 Injection Feedback for a Storage Ring injection, feedback, kicker, simulation 2870
 
  • A. Moutardier, C. Bruni, I. Chaikovska, S. Chancé, N. Delerue, E.E. Ergenlik, V. Kubytskyi, H. Monard
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
 
  Funding: Research Agency under the Equipex convention ANR-10-EQPX-0051.
We report on an injection feedback scheme for the ThomX storage ring project. ThomX is a 50-MeV-electron accelerator prototype which will use Compton backscattering in a storage ring to generate a high flux of hard X-rays. Given the slow beam damping (in the ring), the injection must be performed with high accuracy to avoid large betatron oscillations. A homemade analytic code is used to compute the corrections that need to be applied before the beam injection to achieve a beam position accuracy of a few hundred micrometers in the first beam position monitors (BPMs). In order to do so the code needs the information provided by the ring’s diagnostic devices. The iterative feedback system has been tested using MadX simulations. Our simulations show that a performance that matches the BPMs’ accuracy can be achieved in less than 50 iterations in all cases. Details of this feedback algorithm, its efficiency and the simulations are discussed.
 
poster icon Poster WEPAB117 [2.422 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB117  
About • paper received ※ 28 May 2021       paper accepted ※ 01 July 2021       issue date ※ 25 August 2021  
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WEPAB118 Loss Maps Along the ThomX Transfer Line and the Ring First Turn electron, beam-losses, injection, diagnostics 2874
 
  • A. Moutardier, C. Bruni, I. Chaikovska, S. Chancé, N. Delerue, E.E. Ergenlik, V. Kubytskyi, H. Monard
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
 
  Funding: Research Agency under the Equipex convention ANR-10-EQPX-0051.
We report on studies of the loss maps for particles travelling from the end of the ThomX’s linac along the transfer line to the end of the ring first turn in preparation of the machine commissioning. ThomX is a 50-MeV-electron accelerator prototype which will use Compton backscattering to generate a high flux of hard X-rays. The accelerator tracking code MadX is used to simulate electrons’ propagation and compute losses. These maps may be projected at any localisation along the bunch path or plotted along the bunch path. This information is particularly relevant at the locations of the monitoring devices (screens, position monitors,…) where loss predictions will be compared with measurements.
 
poster icon Poster WEPAB118 [3.173 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB118  
About • paper received ※ 28 May 2021       paper accepted ※ 28 July 2021       issue date ※ 12 August 2021  
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WEPAB150 Monotron Beam Break Up Instability Analysis cavity, klystron, dipole, resonance 2968
 
  • V. Volkov, V.M. Petrov
    BINP SB RAS, Novosibirsk, Russia
 
  New features of monotron beam break up (BBU) instability such as the typing of high order monopole modes (HOMs)in each cavity by two classes one of them are stable and other ones are unstable, HOM effective quality factor depending on average beam current, and normalized invariable threshold current individually characterizes each HOM are investigated in this article in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB150  
About • paper received ※ 19 May 2021       paper accepted ※ 09 June 2021       issue date ※ 31 August 2021  
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WEPAB151 Regenerative Beam Break Up Instability Analysis cavity, dipole, linac, experiment 2971
 
  • V. Volkov, V.M. Petrov
    BINP SB RAS, Novosibirsk, Russia
 
  New features of regenerative beam break up (BBU) instability such as the typing of high order dipole modes (HOMs)in each cavity by two classes, one of them are stable and other ones are unstable, HOM effective quality factor depending on average beam current, and normalized invariable threshold current individually characterizes each HOM are investigated in this article in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB151  
About • paper received ※ 19 May 2021       paper accepted ※ 22 June 2021       issue date ※ 01 September 2021  
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WEPAB165 Metamaterial Waveguide HOM Loads for SRF Accelerating Cavities GUI, vacuum, cavity, SRF 2994
 
  • S.V. Kuzikov
    Euclid TechLabs, Solon, Ohio, USA
 
  Suppression of beam induced HOMs is necessary for most SRF accelerating cavities driven with high currents. One of the problems in design of a HOM load is that vacuum compatible materials with high enough imaginary part of the dielectric permittivity, which provides absorption, have also a high real part of the permittivity. This does not allow absorbing RF radiation at short distance and in broad frequency band. We propose considering artificial metamaterials where besides lossy dielectric pieces, an absorber with high magnetic permeability is included. In our proposal, we suggest composing a waveguide HOM load of a metamaterial consisted of well-known ceramic and ferrite plates placed periodically in a stack. Such a design provides low return losses, compactness and broad frequency range of the operation.  
poster icon Poster WEPAB165 [1.844 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB165  
About • paper received ※ 19 May 2021       paper accepted ※ 02 June 2021       issue date ※ 24 August 2021  
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WEPAB315 360 Degree Panoramic Photographs During the Long Shutdown 2 of the CERN Machines and Facilities database, site, interface, experiment 3410
 
  • T.W. Birtwistle, A. Ansel, S. Bartolomé Jiménez, B. Feral, G. Lacerda, A.-L. Perrot, J.F. Piñera Ovejero
    CERN, Geneva, Switzerland
 
  Studies and preparation of activities are key to the success of short technical stops and longer shutdowns in CERN’s accelerator complex. The ’Panorama’ tool offers a virtual tour of our facilities, and thanks to integration with other CERN tools, further complementary information can be easily retrieved, including layout information, equipment detail, and a history of changes. The tool was used to support the preparation and the execution of works during the Long Shutdown 2. It helped to optimize machine (accelerator/decelerator) interventions and hence reduce potential radiation exposure, as well as to ease integration studies. Thanks to its user-friendliness, the tool is now also used for educational and outreach activities. The current instantiation of the ’Panorama’ tool and related processes is presented, alongside the benefits that the tool can bring to the accelerator complex community. A particular focus is on the Long Shutdown 2. Future planned developments and improvements are also described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB315  
About • paper received ※ 11 May 2021       paper accepted ※ 14 June 2021       issue date ※ 21 August 2021  
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WEPAB342 Beam Induced Power Deposition in CERN SPS Injection Kickers impedance, simulation, kicker, coupling 3490
 
  • M.J. Barnes, O. Bjorkqvist
    CERN, Geneva 23, Switzerland
  • K. Kodama
    KEK, Ibaraki, Japan
 
  The SPS injection kicker magnets (MKP) were developed in the 1970’s, before beam power deposition was considered an issue and before any advanced tools for analysing beam coupling impedance were available in their current form. These magnets are very lossy from a beam impedance perspective, and the beam induced power deposition is highly non-uniform. This is expected to be an issue during SPS operation with the higher intensity beams needed in the future for HL-LHC. There is an existing design, with serigraphy, that will mitigate the heating issues, which is presently being implemented on a prototype for test and measurement. Models have been developed to aid in predicting the safe operating regions until the upgraded MKPs are installed in the SPS: these are reported herein. A novel measurement technique is also presented to confirm the non-uniform power deposition in the ferrite yoke. Beam coupling impedance, power deposition, field rise time and field uniformity data are also presented for an upgraded, prototype, MKP.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB342  
About • paper received ※ 16 May 2021       paper accepted ※ 02 July 2021       issue date ※ 25 August 2021  
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THPAB014 Matlab Simulations of the Helium Liquefier in the FREIA Laboratory simulation, cavity, interface, coupling 3781
 
  • E. Waagaard, R.J.M.Y. Ruber, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
 
  We describe simulations that track a state vector with pressure, temperature, and gas flow through the helium liquefier in the FREIA laboratory. Most components, including three-way heat exchangers, are represented by matrices that allow us to track the state through the system. The only non-linear element is the Joule-Thomson valve, which is represented by a non-linear map for the state variables. Realistic properties for the enthalpy and other thermodynamic quantities are taken into account with the help of the Coolprop library. The resulting system of equations is rapidly solved by iteration and shows good agreement with the observed LHe yield with and without nitrogen pre-cooling.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB014  
About • paper received ※ 13 May 2021       paper accepted ※ 14 July 2021       issue date ※ 26 August 2021  
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THPAB147 Preliminary Study of 500 MHz HOM-Free RF Cavity cavity, coupling, GUI, damping 4050
 
  • Zh.X. Tang
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  Funding: Work supported by National Natural Science Foundation of China(Grant No. U1832135 and 11805199)}
In this paper, we study the microwave characteristics of 500 MHz RF cavity, including the optimization of cavity structure, the simulation design of high-order mode (HOM) absorption structure and the design of coupler. The cavity structure is simulated by CST. The absorption waveguide is designed and optimized. The coupler is designed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB147  
About • paper received ※ 09 May 2021       paper accepted ※ 16 July 2021       issue date ※ 02 September 2021  
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THPAB174 T-BMT Spin Resonance Tracker Code for He3 with Six Snakes resonance, polarization, emittance, betatron 4101
 
  • V.H. Ranjbar, H. Huang, Y. Luo, F. Méot, V. Ptitsyn
    BNL, Upton, New York, USA
  • G.H. Hoffstaetter, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • F. Lin, V.S. Morozov
    JLab, Newport News, Virginia, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy .
Polarization lifetime for He3 using two and six snakes are studied using the T-BMT Spin Resonance Tracker code. This code integrates a reduced spinor form of the T-BMT equation including only several spin resonances and the kinematics of synchrotron motion. It was previously benchmarked against RHIC polarization lifetime under the two snake system *.
* Phys. Rev.Accel. Beams 22 (2019) 9, 091001
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB174  
About • paper received ※ 20 May 2021       paper accepted ※ 02 July 2021       issue date ※ 28 August 2021  
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THPAB178 The SIS100 Extraction and Emergency Kicker Magnet System vacuum, kicker, extraction, high-voltage 4115
 
  • J.H. Hottenbacher, K. Dunkel, M. Eisengruber, M. Osemann, A. Padvi, C. Piel
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • S. Heberer, I.J. Petzenhauser
    GSI, Darmstadt, Germany
 
  The extraction and emergency kicker system for SIS100 is a bipolar kicker system that allows for an in-situ choice between two directions: extraction to the experiments or to the beam dump. For that, both magnet ends are connected to a PFN each which are being charged simultaneously up to 80kV continuously. Due to the static HV operation, different to usually in other pulsed kicker systems, not only displacement current is flowing in the ferrite material. After less than 1s, the ferrite material is nearly field-free and the E-field is concentrated in the surrounding ceramic magnet clamp mechanism. As the field is further concentrated in gaps between ceramic and metallic parts, the HV layout of the magnet is a critical design task. As a magnetic field homogeneity of ±1% is required, special shaping of the coil is required as found during iterative 3D field simulations. The kicker chamber is designed to operate at a pressure level of 3·10-11 mBar. As one 3 meter-chamber contains 3.5 m² ferrite surface, careful vacuum heat treatment of the ferrite is required to reach this pressure level. The paper will describe design principles for HV and UHV and effects found by 3D modeling.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB178  
About • paper received ※ 18 May 2021       paper accepted ※ 28 July 2021       issue date ※ 26 August 2021  
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THPAB220 Multibunch Studies for LCLS-II High Energy Upgrade cavity, dipole, linac, emittance 4219
 
  • R.J. England, K.L.F. Bane, Z. Li, T.O. Raubenheimer, M.D. Woodley
    SLAC, Menlo Park, California, USA
  • M. Borland
    ANL, Lemont, Illinois, USA
  • A. Lunin
    Fermilab, Batavia, Illinois, USA
 
  Funding: The work is supported in part by DOE Contract No. DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) X-ray free-electron laser at SLAC is being upgraded to LCLS-II with a superconducting linac and 1 MHz bunch repetition rate. The proposed high-energy upgrade (LCLS-II-HE) will increase the beam energy from 4 to 8 GeV, extending the reach of accessible X-ray photon energies. With the increased repetition rate and longer linac of LCLS-II-HE, multi-bunch effects are of greater concern. We use recently introduced capabilities in the beam transport code ELEGANT to study dipole and monopole beam breakup effects for LCLS-II HE beam parameters. The results indicate that resonant dipole kicks have steady-state settle times on the order of 500 bunches or less and appear manageable. We also consider a statistical variation of the cavity frequencies and transverse offsets of cavities and quadrupoles. Resonant emittance growth driven by monopole kicks is found to be disrupted by frequency variation between cavities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB220  
About • paper received ※ 19 May 2021       paper accepted ※ 15 July 2021       issue date ※ 21 August 2021  
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THPAB222 Transverse Impedance Coaxial Wire Measurement in an Extended Frequency Range impedance, simulation, storage-ring, collective-effects 4227
 
  • E.E. Ergenlik, C. Bruni, D. Le Guidec, P. Lepercq
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • A. Gamelin
    SOLEIL, Gif-sur-Yvette, France
 
  The low energy accelerators are tend to have some instabilities especially the beam coupling impedances which comes from the interaction between the beam and accelerator components. As long as the longitudinal impedance are important, transverse impedance determination is crucial for determine the instabilities which will affect the working efficiency of the accelerators. However due to their small amplitudes and measurement setup configuration they are hardly measurable especially in wide frequency ranges. We developed a specific setup for small diameter pieces (28-40mm) for moving and two wire transverse impedance measurements. The dipolar and quadrupolar impedance measurement even with a few Ω level up to 6 GHz for the bellows of ThomX will be presented. Also the comparison with electromagnetic simulations have been performed and can be seen for dipolar impedance measurements.  
poster icon Poster THPAB222 [1.578 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB222  
About • paper received ※ 19 May 2021       paper accepted ※ 27 July 2021       issue date ※ 23 August 2021  
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THPAB318 Uniformization of the Transverse Beam Profile with Nonlinear Magnet target, synchrotron, radiation, extraction 4413
 
  • Y. Li, X. Guan, X.Y. Liu, X.W. Wang, Q.Z. Xing, Y. Yang, H.J. Yao, W.B. Ye, S.X. Zheng
    TUB, Beijing, People’s Republic of China
  • Y. Yang
    NINT, Shannxi, People’s Republic of China
 
  The beam generated after slow extraction of the synchrotron is always not uniform and asymmetrical in transverse distribution. In practice, radiation therapy or radiation irradiation requires a high degree of uniformity of beam spot. Therefore, it is necessary to adjust the beam distribution with a nonlinear magnet and other elements on the transport line from synchrotron ring to beam target station. Nonlinear magnet has high requirements on beam quality. Before passing through the nonlinear magnet field, the beam center can be adjusted by taking advantage of the gradient change distribution of the nonlinear magnet’s transverse field map to achieve uniform distribution at the target station. As an example, we use the parameters of heavy ions of XiPAF (Xi’an 200MeV Proton Application Facility) to simulate the beam transport from synchrotron ring to beam target station.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB318  
About • paper received ※ 20 May 2021       paper accepted ※ 08 July 2021       issue date ※ 21 August 2021  
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THPAB356 Progress and Status on Civil Construction of the SIS100 Accelerator Building site, controls, status, radiation 4493
 
  • M. Draisbach, N. Pyka, P.J. Spiller
    GSI, Darmstadt, Germany
  • J. Blaurock, M. Ossendorf
    FAIR, Darmstadt, Germany
 
  Besides the accelerator machine itself, civil construction of the accelerator ring tunnel building in the northern area of the FAIR campus is a core activity of the rapidly progressing FAIR project. It will facilitate and supply the future SIS100 accelerator at 17m underground level and has been growing continuously and according to schedule since groundbreaking in 2017. This contribution presents the current status of the civil construction progress and gives an optimistic forecast for the preparation of machine installation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB356  
About • paper received ※ 20 May 2021       paper accepted ※ 06 July 2021       issue date ※ 15 August 2021  
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FRXB02 Development of 36 GHz RF Systems for RF Linearisers cavity, klystron, linac, impedance 4518
 
  • A. Castilla, G. Burt
    Lancaster University, Lancaster, United Kingdom
  • M. Behtouei, B. Spataro
    INFN/LNF, Frascati, Italy
  • G. Burt
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J.C. Cai, A. Castilla, A. Latina, X. Liu, I. Syratchev, X.W. Wu, W. Wuensch
    CERN, Geneva, Switzerland
  • J.C. Cai, A. Castilla
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A.W. Cross, L. Zhang
    USTRAT/SUPA, Glasgow, United Kingdom
  • L.J.R. Nix
    University of Strathclyde, Glasgow, United Kingdom
 
  Funding: This project has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 777431.
As part of the deign studies, the CompactLight project plans to use an injector in the C-band. Which constitutes a particular complication for the harmonic system in charge of linearising the beam’s phase space, since it means its operation frequency could be higher than the standard X-band RF technologies. In the present work, we investigated a 36 GHz (Ka-band) as the ideal frequency for the harmonic system. A set of structure designs are presented as candidates for the lineariser, based on different powering schemes and pulse compressor technologies. The comparison is made both in terms of beam dynamics and RF performance. Given the phase stability requirements for the MW class RF sources needed for this system, we performed careful studies of a Gyro-Klystron and a multi-beam klystron as potential RF sources, with both showing up to 3 MW available power using moderate modulator voltages. Alternatives for pulse compression at Ka-band are also discussed in this work.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXB02  
About • paper received ※ 17 May 2021       paper accepted ※ 19 July 2021       issue date ※ 25 August 2021  
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