Keyword: impedance
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MOXC01 Combined Effect of Beam-Beam Interaction and Beam Coupling Impedance in Future Circular Colliders collider, synchrotron, luminosity, simulation 25
 
  • Y. Zhang, N. Wang
    IHEP, Beijing, People’s Republic of China
  • E. Carideo
    CERN, Geneva, Switzerland
  • M. Migliorati
    SBAI, Roma, Italy
  • M. Zobov
    INFN/LNF, Frascati, Italy
  
  Funding: This work is supported by National Key Programme for S&T Research and Development, China (Grant No. 2016YFA0400400), National Natural Science Foundation of China (No. 11775238, No. 11775239).
The future large scale electron-positron colliders, such as FCC-ee in Europe and CEPC in China, will rely on the crab waist collision scheme with a large Piwinski angle. Differently from the past generation colliders both luminosity and beam-beam tune shifts depend on the bunch length in such a collision scheme. In addition, for the future circular colliders with extreme beam parameters in collision several new effects become important such as beamstrahlung, coherent X-Z instability and 3D flip-flop. For all these effects the longitudinal beam dynamics plays an essential role and should be taken into account for the collider luminosity optimization. In this paper we discuss an impact of the longitudinal beam coupling impedance on the collider performance. 		 
slides icon Slides MOXC01 [2.269 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXC01  
About • paper received ※ 17 May 2021       paper accepted ※ 27 July 2021       issue date ※ 17 August 2021  
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MOPAB006 Optics Configurations for Improved Machine Impedance and Cleaning Performance of a Multi-Stage Collimation Insertion optics, collimation, collider, scattering 57
 
  • R. Bruce, R. De Maria, M. Giovannozzi, N. Mounet, S. Redaelli
    CERN, Geneva, Switzerland
  
  For a two-stage collimation system, the betatron phase advance between the primary and secondary stages is usually set to maximise the absorption of secondary particles outscattered from the primary. Another constraint is the contribution to the ring impedance of the collimation system, which can be decreased through an optimized insertion optics, featuring large values of the beta functions. In this article we report on first studies of such an optics for the CERN LHC. In addition to a gain in impedance, we show that the cleaning efficiency can be improved thanks to the large beta functions, even though the phase advance is not set at the theoretical optimum.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB006  
About • paper received ※ 17 May 2021       paper accepted ※ 28 May 2021       issue date ※ 11 August 2021  
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MOPAB030 Research and Development Progress of CEPC RF Shield Bellows vacuum, positron, electron, controls 142
 
  • J.M. Liu, Y.H. Guan, S.M. Liu, B. Tan, P.C. Wang
    DNSC, Dongguan, People’s Republic of China
  • H. Dong, Y. Ma
    IHEP, Beijing, People’s Republic of China
  • H.Y. He, T. Huang
    IHEP CSNS, Guangdong Province, People’s Republic of China
  
  The circular electron positron collider (CEPC) is a candidate for the next-generation electron positron collider, which can be used to accurately measure the Higgs and electroweak bosons. The RF shield bellow is a vacuum component necessary for the construction of CEPC. Therefore, a RF shield bellow model machine with an elliptical cross-section was designed and processed for technical verification. Based on the traditional interdigital structure, a special contact force testing device was also designed to reduce measurement errors. The on-off status of the circuit was used by the device to determine whether the spring finger was pulled up, thus reducing the influences of human factors in the measurement process. It can be known from the measurement results of the model machine that the contact force of the spring finger is between 120g and 130g, which can satisfy the technical requirements.  
poster icon Poster MOPAB030 [1.467 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB030  
About • paper received ※ 19 May 2021       paper accepted ※ 20 May 2021       issue date ※ 13 August 2021  
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MOPAB032 Estimates of Collective Effects for the FCC-e+e− Pre-Booster Ring electron, injection, emittance, collective-effects 148
 
  • O. Etisken, F. Antoniou, K. Oide, Y. Papaphilippou, F. Zimmermann
    CERN, Geneva, Switzerland
  • A.K. Çiftçi
    Izmir University of Economics, Balçova/Izmir, Turkey
  
  The FCC-e+e− injector complex needs to produce and to transport high-intensity e+ and e- beams at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: either using the existing SPS machine or designing a completely new ring. The purpose of this paper is to present the studies of collective effects with analytical estimates for both the pre-booster ring design options including space charge (SC), longitudinal micro-wave instability (LMI), transverse mode coupling instability (TMCI), ion effects, electron cloud (e-cloud), coherent synchrotron radiation (CSR), and intra-beam scattering (IBS).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB032  
About • paper received ※ 17 May 2021       paper accepted ※ 27 May 2021       issue date ※ 15 August 2021  
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MOPAB043 Validation of APS-U Beam Dynamics Using 6-GeV APS Beam HOM, simulation, cavity, lattice 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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MOPAB053 Progress of Lattice Design and Physics Studies on the High Energy Photon Source lattice, storage-ring, injection, booster 229
 
  • Y. Jiao, Y. Bai, X. Cui, C.C. Du, Z. Duan, Y.Y. Guo, P. He, X.Y. Huang, D. Ji, H.F. Ji, S.C. Jiang, B. Li, C. Li, J.Y. Li, N. Li, X.Y. Li, P.F. Liang, C. Meng, W.M. Pan, Y.M. Peng, Q. Qin, H. Qu, S.K. Tian, J. Wan, B. Wang, J.Q. Wang, N. Wang, Y. Wei, G. Xu, H.S. Xu, F. Yan, C.H. Yu, Y.L. Zhao
    IHEP, Beijing, People’s Republic of China
  • X.H. Lu
    IHEP CSNS, Guangdong Province, People’s Republic of China
  
  Funding: Work supported by High Energy Photon Source (HEPS), a major national science and technology infrastructure and NSFC (11922512)
The High Energy Photon Source (HEPS) is a 34-pm, 1360-m storage ring light source being built in the suburb of Beijing, China. The HEPS construction started in mid-2019. While the physics design has been basically determined, modifications on the HEPS accelerator physics design have been made since 2019, in order to deal with challenges emerging from the technical and engineering designs. In this paper, we will introduce the new storage ring lattice and injector design, and also present updated results of related physics issues, including impedance and collective effects, lattice calibration, insertion device effects, injection design studies, etc. 		 
poster icon Poster MOPAB053 [0.699 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB053  
About • paper received ※ 10 May 2021       paper accepted ※ 24 May 2021       issue date ※ 17 August 2021  
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MOPAB068 Collective Effects Studies for the SOLEIL Upgrade synchrotron, storage-ring, cavity, feedback 274
 
  • A. Gamelin, D. Amorim, P. Brunelle, W. Foosang, A. Loulergue, L.S. Nadolski, R. Nagaoka, R. Ollier, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette, France
  
  The SOLEIL upgrade project aims to replace the actual SOLEIL storage ring by a 4th generation light source. The project has just finished its conceptual design report (CDR) phase*. Compared to the SOLEIL storage ring, the upgraded storage ring design includes many new features of 4th generation light sources that will impact collective effects, such as reduced beam pipe apertures, a smaller momentum compaction factor and the presence of harmonic cavities (HC). To mitigate them, we rely on several damping mechanisms provided by the synchrotron radiation, the transverse feedback system, and the HC (Landau damping and bunch lengthening). This article presents a first estimate of the collective effects impact of the upgraded design.
* Conceptual Design Report: Synchrotron SOLEIL Upgrade, 2021, in press. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB068  
About • paper received ※ 17 May 2021       paper accepted ※ 02 June 2021       issue date ※ 12 August 2021  
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MOPAB069 Equilibrium Bunch Density Distribution with Multiple Active and Passive RF Cavities cavity, beam-loading, synchrotron, storage-ring 278
 
  • A. Gamelin
    SOLEIL, Gif-sur-Yvette, France
  • N. Yamamoto
    KEK, Ibaraki, Japan
  
  This paper describes a method to get the equilibrium bunch density distribution with an arbitrary number of active or passive RF cavities in uniform filling. This method is an extension of the one presented by M. Venturini which assumes a passive harmonic cavity and no beam loading in the main RF cavity*.
*M. Venturini, "Passive higher-harmonic rf cavities with general settings and multibunch instabilities in electron storage rings," Physical Review Accelerators and Beams, 2018. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB069  
About • paper received ※ 17 May 2021       paper accepted ※ 23 June 2021       issue date ※ 23 August 2021  
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MOPAB070 mbtrack2, a Collective Effect Library in Python cavity, collective-effects, simulation, synchrotron 282
 
  • A. Gamelin, W. Foosang, R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
  
  This article introduces mbtrack2, a collective effect library written in python3. The idea behind mbtrack2 is to build a coherent object-oriented framework to work on collective effects in synchrotrons. mbtrack2 is composed of different modules allowing to easily write scripts for single bunch or multi-bunch tracking using MPI parallelization in a transparent way. The base of the tracking model of mbtrack2 is inspired by mbtrack, a C multi-bunch tracking code initially developed at SOLEIL*. In addition, many tools to prepare or analyse tracking simulations are included.
* R. Nagaoka, R. Bartolini, and J. Rowland, Studies of Collective Effects in SOLEIL and Diamond Using the Multiparticle Tracking Codes SBTRACK and MBTRACK, in Proc. PAC’09, 2009. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB070  
About • paper received ※ 17 May 2021       paper accepted ※ 06 July 2021       issue date ※ 16 August 2021  
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MOPAB072 Single-Bunch Thresholds for the Diamond-II Storage Ring cavity, simulation, storage-ring, beam-loading 290
 
  • T. Olsson, R.T. Fielder
    DLS, Oxfordshire, United Kingdom
  
  The proposed Diamond Light Source upgrade will see the storage ring replaced with a multibend achromat lattice, increasing the capacity of the facility whilst reducing the emittance and providing higher brightness for the users. As part of the design work, tracking studies have been performed to determine the single-bunch thresholds including both the resistive-wall and geometric contributions to the impedance. As the machine design also foresees a third order harmonic cavity, the paper also provides an initial assessment of the effects of bunch lengthening on the single-bunch thresholds.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB072  
About • paper received ※ 18 May 2021       paper accepted ※ 01 June 2021       issue date ※ 23 August 2021  
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MOPAB087 Design of a Multi-Bunch Feedback Kicker in SPEAR3 kicker, simulation, coupling, feedback 327
 
  • K. Tian, J.B. Langton, NL. Parry, J.A. Safranek, J.J. Sebek
    SLAC, Menlo Park, California, USA
  
  The new Multi-bunch feedback kickers have been designed to replace the current device loaned from ALS. In this paper, we first present the specification of the kickers based on the beam physics requirements. Then the mechanical design of the kicker is elaborated. Numerical simulations, both in time domain and in frequency domain, are conducted for evaluating the shunt impedance and beam coupling impedance of the kicker. Surface heating induced from the beam or the external source is estimated from the numerical results as well.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB087  
About • paper received ※ 19 May 2021       paper accepted ※ 11 June 2021       issue date ※ 01 September 2021  
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MOPAB102 CSR Impedance in HEPS Storage Ring storage-ring, lattice, synchrotron, vacuum 379
 
  • H.S. Xu, X.Y. Li, N. Wang
    IHEP, Beijing, People’s Republic of China
  
  High Energy Photon Source (HEPS) is under construction in Beijing, China. The relatively complete impedance model has been built up based on the element-by-element impedance calculation. However, Coherent Synchrotron Radiation (CSR) impedance, which might affect the longitudinal performance of the beam, was not included in the impedance model of the HEPS storage ring in the preliminary design stage. For completeness, we would like to take the CSR impedance into consideration. The most important contributions to the total CSR impedance come from the bending magnets and insertion devices. We therefore calculate the CSR impedance from both above mentioned elements in HEPS storage ring. The influence of the CSR impedance on the microwave instability threshold is studied and presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB102  
About • paper received ※ 17 May 2021       paper accepted ※ 18 June 2021       issue date ※ 27 August 2021  
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MOPAB117 Single Bunch Collective Effects in the EBS Storage Ring simulation, SRF, synchrotron, vacuum 425
 
  • L.R. Carver, E. Buratin, N. Carmignani, F. Ewald, L. Hoummi, S.M. Liuzzo, T.P. Perron, B. Roche, S.M. White
    ESRF, Grenoble, France
  
  The ESRF storage ring (SR) has been dismantled and replaced by the Extremely Brilliant Source (EBS) which has now been commissioned. Beam based measurements have been performed to characterise the impedance of the new machine and to make a first comparison with predictions. The results from instability threshold scans and tune shift measurements will be presented, as well as bunch length and position variation with current and microwave threshold measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB117  
About • paper received ※ 11 May 2021       paper accepted ※ 31 May 2021       issue date ※ 25 August 2021  
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MOPAB127 Construction of an Impedance Model for Diamond-II simulation, lattice, dipole, cavity 455
 
  • R.T. Fielder, T. Olsson
    DLS, Oxfordshire, United Kingdom
  
  Impedance models for accelerators have traditionally been presented in a static form, usually as tables or spreadsheets which must be read manually. As part of the Diamond-II upgrade work, we have developed an impedance model using a lattice structure. This allows more direct integration with simulation codes while keeping important information easily human readable. We present here a description of this implementation method, along with an overview of the Diamond-II impedance model derived from the latest engineering design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB127  
About • paper received ※ 18 May 2021       paper accepted ※ 20 May 2021       issue date ※ 11 August 2021  
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MOPAB144 Investigation of Optimization of Dielectric Terahertz Acceleration Structures simulation, laser, acceleration, radiation 502
 
  • A.E. Gabriel, E.A. Nanni
    SLAC, Menlo Park, California, USA
  
  Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515 (SLAC) and by NSF Grant No. PHY-1734015.
THz-frequency accelerating structures could provide the accelerating gradients needed for next generation particle accelerators with compact, GV/m-scale devices. Current THz accelerators are limited by significant losses during transport of THz radiation from the generating nonlinear crystal to the electron acceleration structure. In addition, the spectral properties of high-field THz sources make it difficult to couple THz radiation into accelerating structures. Dielectric accelerator structures reduce these losses because THz radiation can be coupled laterally into the structure, as opposed to metallic structures where THz radiation must be coupled along the beam path. In order to utilize these advantages, we are investigating the optimization of THz accelerating structures for comparison between metallic and dielectric devices. These results will help to inform future designs of improved dielectric THz acceleration structures. 		 
poster icon Poster MOPAB144 [6.524 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB144  
About • paper received ※ 20 May 2021       paper accepted ※ 27 May 2021       issue date ※ 22 August 2021  
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MOPAB155 Magnetic Breakdowns in Side-Coupled X-Band Accelerating Structures coupling, simulation, cavity, accelerating-gradient 540
 
  • S.P. Antipov, P.V. Avrakhov, S.V. Kuzikov
    Euclid TechLabs, Solon, Ohio, USA
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • C. Jing
    Euclid Beamlabs, Bolingbrook, USA
  
  Funding: DOE SBIR
Side coupled accelerating structures are popular in the industrial realizations of linacs due to their high shunt impedance and ease of tuning. We designed and fabricated a side-coupled X-band accelerating structure that achieved 133 MOhm/m shut impedance. This structure was fabricated out of two halves using a novel brazeless approach. The two copper halves are joined together using a stainless steel joining piece with knife edges that bite into copper. This structure had been tested at high power at SLAC National Accelerator Laboratory. The performance of the structure had been limited by magnetic breakdowns on the side-coupling cells. In this paper we will present results of the high gradient tests and after-test analysis. Scanning electron microscopy images show a typical magnetic-field induced breakdown. 		 
poster icon Poster MOPAB155 [1.069 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB155  
About • paper received ※ 20 May 2021       paper accepted ※ 23 June 2021       issue date ※ 01 September 2021  
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MOPAB211 Beam Coupling Impedances of Ferrite-Loaded Cavities: Calculations and Measurements cavity, dipole, resonance, coupling 696
 
  • S.S. Kurennoy, R.C. McCrady
    LANL, Los Alamos, New Mexico, USA
  
  We have developed an efficient method of calculating impedances in cavities with dispersive ferrite dampers. The ferrite dispersive properties in the frequency range of interest are fitted in CST, which allows using both wakefield and lossy eigenmode solvers. A simple test cavity with or without ferrite inserts is explored both numerically and experimentally. The resonance frequencies and beam coupling impedances at cavity resonances are calculated with CST to understand the mode structure. The cavity transverse coupling impedances are also measured on a test stand using a two-wire method. We compare results of impedance calculations and measurements for a few different configurations, with and without ferrites, to ensure a complete understanding of the cavity resonances and their damping with ferrite. These results are important to provide adequate damping of undesired transverse modes in induction-linac cells.  
poster icon Poster MOPAB211 [1.105 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB211  
About • paper received ※ 10 May 2021       paper accepted ※ 21 May 2021       issue date ※ 19 August 2021  
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MOPAB330 Production and Performance Evaluation of a Compact Deflecting Cavity to Measure the Bunch Length in the cERL cavity, resonance, vacuum, coupling 1023
 
  • D. Naito, Y. Honda, T. Miyajima, N. Yamamoto
    KEK, Ibaraki, Japan
  
  At the KEK compact energy recovery linac, we try to generate an infrared free-electron laser (FEL). To generate the FEL, an electron bunch should be compressed along the longitudinal direction. The measurement of the bunch length is key to optimize the bunch compression. We plan to measure the bunch length by deflecting cavities in the burst mode. The deflecting cavities are required to be a time resolution of 33 fs in order to not only measure the bunch length but also resolve the structure inside the electron bunch. To achieve the requirement, we developed a c-band cavity whose RF input port is compact. The deflecting cavity is a single cell and normal conducting cavity. The deflection mode of the cavity is TM110. The 12 cavities will be located at the exit of undulators. In this presentation, we explain the design of our cavity and report the production of the first cavity. We also report the evaluation of the resonance frequency, the unloaded Q and the external Q of the cavity. From the measurements and simulations, the R/Q is estimated to be 1 mega orms. The time resolution of the cavity is expected to be 400 fs when the input RF power is 1 kW and the beam energy is 20 MeV.  
poster icon Poster MOPAB330 [12.920 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB330  
About • paper received ※ 12 May 2021       paper accepted ※ 08 June 2021       issue date ※ 28 August 2021  
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MOPAB331 Design Consideration of a Longitudinal Kicker Cavity for Compensating Transient Beam Loading Effect in Synchrotron Light Sources cavity, kicker, resonance, coupling 1027
 
  • D. Naito, S. Sakanaka, T. Takahashi, N. Yamamoto
    KEK, Ibaraki, Japan
  • T. Yamaguchi
    Sokendai, Ibaraki, Japan
  
  In ultra-low-emittance synchrotron light sources, bunch-lengthening using the combination of main and harmonic cavities is limited by the transient beam-loading (TBL) effect which is caused by gaps in the fill pattern. To manage this effect, we proposed a TBL compensation technique using a wide-band longitudinal kicker cavity*. In the future KEK-LS storage ring, for example, the kicker cavity should provide a compensation voltage of 50 kV with a -3dB bandwidth (BW) of about 5 MHz, as well as its higher-order modes (HOM) should be damped sufficiently. In this presentation, we report our conceptual design of the kicker cavity. We employed the single-mode (SM) cavity concept so that harmful HOMs are dumped by rf absorbers on the beam pipes. The distinctive feature of the SM cavity is its simple structure since it has no HOM damper on the cavity. Another feature is its low R/Q by which the TBL effect in the kicker cavity itself can be reduced significantly. We employed a frequency of 1.5 GHz (third-harmonic) and R/Q of 60 orms through optimizations. Using this kicker cavity with a double rf system, a bunch lengthening by a factor of 4.3 (i.e., 40.9 ps) is expected for the KEK-LS case.
* N.Yamamoto et al., Phys. Rrev. Acc. Beams 21, 012001 (2018) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB331  
About • paper received ※ 19 May 2021       paper accepted ※ 11 June 2021       issue date ※ 01 September 2021  
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MOPAB332 Design of 4th Harmonic RF Cavities for ESRF-EBS HOM, cavity, SRF, 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, HOM, 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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MOPAB337 Design Study of the Spiral Buncher Cavities for the High Current Injector at IUAC cavity, linac, bunching, rfq 1048
 
  • S. Kedia, R. Ahuja, R. Mehta, C.P. Safvan
    IUAC, New Delhi, India
  
  Two high energy beam transport (HEBT) cavities have been designed to provide the longitudinal beam bunching between drift tube linac and superconducting super-buncher of the superconducting linear (SC-LINAC) accelerator. The spiral type cavities were chosen over standard quarter wave-type geometry due to its higher shunt impedance. The TRACE-3D ion-optical codes have been used to determine the bunching voltage and physical location of the cavities. The two-gap RF cavity requires 80 kV/gap to provide the longitudinal beam bunching at the entrance of the superconducting buncher. The CST-MWS simulations were performed to design the spiral type bunching cavities. The various parameters including shunt impedance, quality factor, average accelerating field, and total power loss were determined using CST-MWS simulations. The ratio of drift tube radius to the gap was optimized to achieve the maximum effective electric field with minimum field penetration within the gap. The SolidWorks software has been used to prepare a mechanical model for the fabrication.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB337  
About • paper received ※ 15 May 2021       paper accepted ※ 26 May 2021       issue date ※ 26 August 2021  
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MOPAB339 Design Of An X-band 3MeV Standing-wave Accelerating Structure with Nose-cone Structure Made From Two Halves coupling, cavity, electron, bunching 1051
 
  • F. Liu, H.B. Chen, J. Shi, C.-X. Tang, H. Zha
    TUB, Beijing, People’s Republic of China
  
  This work presents an X-band 3MeV standing-wave accelerating structure with nose cones made from two halves. Milling two longitudinally split halves is one economic method to manufacture accelerating structure for decrease of welding, with increasing the difficulty in machining. This linear accelerator includes 4 buncher cavities and 4 accelerating cavities, and nose cone is applied to achieve high shunt impedance. A technical prototype is under fabrication to bring two milled halves manufacture way into practical application.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB339  
About • paper received ※ 19 May 2021       paper accepted ※ 26 May 2021       issue date ※ 15 August 2021  
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MOPAB343 Optimization of the Parasitic-Mode Damping on the 1.5 GHz TM020-type Harmonic Cavity cavity, damping, coupling, simulation 1064
 
  • T. Yamaguchi
    Sokendai, Ibaraki, Japan
  • D. Naito, S. Sakanaka, T. Takahashi, N. Yamamoto
    KEK, Ibaraki, Japan
  
  Bunch-lengthening harmonic cavity is one of the essential tools to mitigate the intrabeam scattering in the 4th-generation synchrotron light sources. For this purpose, we proposed a normal-conducting 1.5 GHz harmonic cavity* of TM020-type**. Thanks to its low R/Q (68 ohms) and high unloaded Q (34, 000), bunch gap transient in the harmonic cavity can be reduced to ~20% as compared to that in a typical TM010 cavity. Furthermore, harmful parasitic modes in this cavity can be heavily damped by installing ferrites where no magnetic fields of TM020-mode exist. However, some of the parasitic modes, e.g. TM021 and TM120 modes, are difficult to damp because their field patterns are similar to that of the TM020 mode. To damp such modes effectively, we optimized the cavity inner shape by tailoring the curvature at the cavity equator, the shape of the nose cones, and introducing "bumps" on the inner wall. Our goals of the coupling impedances are fxR < 2.4[kohm GHz] and RT < 23 kohm/m in the longitudinal and the transverse planes, respectively. As a result of optimization, we almost achieved these goals. To confirm our simulation results, fabrication of a low-power test cavity is in progress.
* N . Yamamoto et al., Phys. Rev. Acc. Beams 21, 012001 (2018).
** H. Ego et al., Proc. of the 11th Annual Meeting of Particle Accelerator Society of Japan (PASJ2014), MOOL14 (2014).
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB343  
About • paper received ※ 19 May 2021       paper accepted ※ 26 May 2021       issue date ※ 01 September 2021  
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MOPAB352 High Power Test of a Dielectric Disk Loaded Accelerator for a Two Beam Wakefield Accelerator wakefield, acceleration, linear-collider, multipactoring 1096
 
  • B.T. Freemire, C.-J. Jing, S. Poddar
    Euclid Beamlabs, Bolingbrook, USA
  • M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
    ANL, Lemont, Illinois, USA
  • M.M. Peng
    TUB, Beijing, People’s Republic of China
  • E.E. Wisniewski
    Illinois Institute of Technology, Chicago, Illinois, USA
  • Y. Zhao
    Euclid TechLabs, Solon, Ohio, USA
  
  Funding: Small Business Innovation Research Contract No. DE-SC0019864 U.S. DOE Office of Science Contract No. DE-AC02-06CH11357
As part of the Argonne 500 MeV short pulse Two Beam Wakefield Acceleration Demonstrator, a single cell X-band dielectric disk loaded accelerator (DDA) has been designed, fabricated, and tested at high power at the Argonne Wakefield Accelerator. The DDA should provide a short pulse (~20 ns) high gradient (>300 MV/m) accelerator while maintaining a reasonable r/Q and high group velocity. This will allow a significantly larger RF-to-beam efficiency than is currently possible for conventional accelerating structures. A low loss barium titantate ceramic, µr = 50, was selected, and a low temperature brazing alloy chosen to preserve the dielectric properties of the ceramic during brazing. High power testing produced breakdown at the triple junction, resulting from the braze joint design. No evidence of breakdown was observed on the iris of the disk, indicating that the maximum surface electric field on the dielectric was not reached. An improved braze joint has been designed and is in production, with high power testing to follow. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB352  
About • paper received ※ 19 May 2021       paper accepted ※ 08 June 2021       issue date ※ 21 August 2021  
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MOPAB355 Multi-Objective Optimization of RF Structures cavity, controls, RF-structure, ECR 1103
 
  • S.J. Smith, R. Apsimon, G. Burt, M.J.W. Southerby
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • S. Setiniyaz
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • S. Setiniyaz
    Lancaster University, Lancaster, United Kingdom
  
  In this work, we apply multi-objective optimization methods to single-cell cavity models generated using non-uniform rational basis splines (NURBS). This modeling method uses control points and a NURBS to generate the cavity geometry, which allows for greater flexibility in the shape, leading to improved performance. Using this approach and multi-objective genetic algorithms (MOGAs) we find the Pareto frontiers for the typical key quantities of interest (QoI) including peak fields, shunt impedance and the modified Poynting vector. Visualizing these results becomes increasingly more difficult as the number of objectives increases, therefore, in order to understand these frontiers, we provide several techniques for analyzing, visualizing and using multi-dimensional Pareto fronts specifically for RF cavity design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB355  
About • paper received ※ 19 May 2021       paper accepted ※ 15 July 2021       issue date ※ 30 August 2021  
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MOPAB357 The New Design of the RF System for the SPS-II Light Source cavity, storage-ring, booster, linac 1110
 
  • N. Juntong, T. Chanwattana, S. Chunjarean, S. Krainara, T. Phimsen, T. Pulampong
    SLRI, Nakhon Ratchasima, Thailand
  • K. Manasatitpong
    Synchrotron Light Research Institute (SLRI), Muang District, Thailand
  
  The new light source facility in Thailand, SPS-II, is a ring-based 3 GeV light source with a circumference of approximately 330 m. The target stored beam current is 300 mA with an emittance of below 1.0 nm rad. The injector has been changed from a full energy linac to a booster injector with 150 MeV linac. The main RF frequency has been reconsidered to a low-frequency range at 119 MHz. Low frequency is chosen with the benefit of low RF voltage for a high RF acceptance together with experience with the present ring RF system of 118 MHz. Details of RF frequency consideration will be discussed. The requirements and details of the RF systems in the booster ring and the storage ring will be presented.  
poster icon Poster MOPAB357 [1.696 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB357  
About • paper received ※ 17 May 2021       paper accepted ※ 08 June 2021       issue date ※ 14 August 2021  
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MOPAB360 Anomalous Skin Effect Study of Normal Conducting Film plasma, ECR, interface, vacuum 1119
 
  • B.P. Xiao, M. Blaskiewicz, T. Xin
    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.
For the radiofrequency (RF) applications of normal conducting film with large mean free path at high frequency and low temperature, the anomalous skin effect differs considerably from the normal skin effect with field decaying exponentially in the film. Starting from the relationship between the current and the electric field (E field) in the film, the amplitude of E field along the film depth is calculated, and is found to be non-monotonic. The surface impedance is found to have a minimum value at certain film thickness. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB360  
About • paper received ※ 17 May 2021       paper accepted ※ 25 June 2021       issue date ※ 17 August 2021  
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MOPAB393 Design of an RF-Dipole Crabbing Cavity System for the Electron-Ion Collider cavity, HOM, cryomodule, 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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MOPAB410 Preliminary Studies of a Compact VHEE Linear Accelerator System for FLASH Radiotherapy linac, radiation, electron, operation 1229
 
  • L. Giuliano, F. Bosco, M. Carillo, D. De Arcangelis, L. Faillace, L. Ficcadenti, M. Migliorati, A. Mostacci, L. Palumbo
    Sapienza University of Rome, Rome, Italy
  • D. Alesini, M. Behtouei, B. Spataro
    INFN/LNF, Frascati, Italy
  • G. Cuttone, G. Torrisi
    INFN/LNS, Catania, Italy
  • V. Favaudon, S. Heinrich, A. Patriarca
    Institut Curie - Centre de Protonthérapie d’Orsay, Orsay, France
  
  Funding: The work is supported by La Sapienza University, research grant "grandi progetti di ricerca 2020".
The Flash Radio Therapy is a revolutionary new technique in the cancer cure: it spares healthy tissue from the damage of the ionizing radiation maintaining the tumor control as efficient as in conventional radiotherapy. To allow the implementation of the FLASH Therapy concept into actual clinical use, it is necessary to have a linear accelerator able to deliver the very high dose and very high dose rate (>106 Gy/s) in a very short irradiation time (beam on time < 100ms). Low energy S-band Linacs (up to 7 MeV) are being used in Radiobiology and pre-clinic applications but in order to treat deep tumors, the energy of the electrons should achieve the range of 60-100 MeV. In this paper, we address the main issues in the design of a compact C band (5.712 GHz) electron linac-VHEE for FLASH Radio Therapy. We present preliminary studies on C-band structures at La Sapienza and at INFN-LNS, aiming to reach a high accelerating gradient and high current necessary to deliver a dose >1 Gy/pulse, with very short electron pulse. 		 
poster icon Poster MOPAB410 [0.650 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB410  
About • paper received ※ 19 May 2021       paper accepted ※ 09 June 2021       issue date ※ 21 August 2021  
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TUPAB010 Impact of Bunch Current on Optics Measurements in SuperKEKB optics, damping, quadrupole, radiation 1356
 
  • J. Keintzel, R. Tomás García, F. Zimmermann
    CERN, Geneva, Switzerland
  • T. Ishibashi, H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, S. Terui, M. Tobiyama, R.J. Yang, D. Zhou
    KEK, Ibaraki, Japan
  
  SuperKEKB has recently achieved the world record instantaneous luminosity of 2.8 × 1034 \si{cm-2s-1} and aims at reaching a target luminosity of about 6 × 1035 \si{cm-2s-1}. To accomplish this goal it is planned to increase beam currents up to §I{3.6}{A} and §I{2.6}{A} for the positron and the electron ring, respectively. Increasing the beam currents and, in particular, the number of leptons per bunch, can impact the optics parameters obtained by turn-by-turn measurements, such as the betatron tune or phase advance. Optics measurements performed at various bunch currents can give first indications of possible intensity dependent effects. In this paper, the effect of varying bunch current on optics measurements at SuperKEKB is explored.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB010  
About • paper received ※ 18 May 2021       paper accepted ※ 10 June 2021       issue date ※ 30 August 2021  
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TUPAB053 Design Progress of ALS-U 3rd-Harmonic Cavity cavity, HOM, damping, 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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TUPAB074 S-Band Transverse Deflecting Structure Design for CompactLight klystron, FEL, cavity, operation 1540
 
  • X.W. Wu, W. Wuensch
    CERN, Meyrin, Switzerland
  • S. Di Mitri
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  The CompactLight project is currently developing the design of a next generation hard X-ray FEL facility, which is based on high-gradient X-band (12 GHz) structures. However, to carry out pump-and-probe experiments in the project, two-bunch operation with a spacing of 10 X-band rf cycles is proposed. A sub-harmonic transverse deflecting structure working at S-band is proposed to direct the two bunches into two separate FEL lines. The two FEL pulses will have independently tunable wavelengths and can be combined in a single experiment with a temporal delay between pulses of ± 100 fs. The rf design of the transverse deflector is presented in this paper.  
poster icon Poster TUPAB074 [1.557 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB074  
About • paper received ※ 19 May 2021       paper accepted ※ 10 June 2021       issue date ※ 21 August 2021  
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TUPAB174 Basic Design Study for Disk-Loaded Structure in Muon LINAC accelerating-gradient, acceleration, linac, experiment 1801
 
  • K. Sumi, T. Iijima, K. Inami, Y. Sue, M. Yotsuzuka
    Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
  • H. Ego, T. Mibe, M. Yoshida
    KEK, Ibaraki, Japan
  • T. Iijima
    KMI, Nagoya, AIchi Prefecture, Japan
  • Y. Kondo
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • Y. Nakazawa
    Ibaraki University, Hitachi, Ibaraki, Japan
  • M. Otani, N. Saito
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • Y. Takeuchi
    Kyushu University, Fukuoka, Japan
  • H.Y. Yasuda
    University of Tokyo, Tokyo, Japan
  
  The world’s first disk-loaded structure (DLS) at the high-velocity part of a muon LINAC is under development for the J-PARC muon g-2/EDM experiment. We have simulated the first designed constant impedance DLS to accelerate muons from ß = 0.7 to 0.94 at an operating frequency of 1296 MHz and a phase of -10 degrees to ensure longitudinal acceptance and have shown the quality of the beam meets our requirements. Because the structure needs a high RF power of 80 MW to generate a gradient of 20 MV/m, a constant gradient DLS with the higher acceleration efficiency is being studied for lower operating RF power. In this poster, we will show the cell structure design yielding a gradient of 20 MV/m with lower RF power.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB174  
About • paper received ※ 19 May 2021       paper accepted ※ 31 August 2021       issue date ※ 18 August 2021  
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TUPAB239 Radiation of a Charged Particle Bunch Moving Along a Deep Corrugated Surface with a Small Period radiation, ECR, electromagnetic-fields, GUI 1999
 
  • E.S. Simakov, A.V. Tyukhtin
    Saint Petersburg State University, Saint Petersburg, Russia
  
  Funding: This work was supported by the Russian Science Foundation (Grant No. 18-72-10137).
We investigate the electromagnetic radiation of a bunch moving along a corrugated conductive surface. It is assumed that wavelengths under consideration are much more than the period of the corrugation. In this case, the corrugated structure can be replaced with a smooth surface on which so-called equivalent boundary conditions (EBC) are fulfilled*. In fact, we deal with anisotropic surface characterized by certain matrix impedance. Here, we consider the case of deep corrugation, i.e. we assume that the depth of the structure is much more than its period (the case of shallow corrugation was studied earlier**). Using the EBC we obtain electromagnetic field components which are presented in form of spectral integrals. It is shown that the bunch generates surface waves propagating in the plane of the structure, whereas volume radiation is absent at the frequencies under consideration. We also consider the energy losses of the bunch. Typical dependences of a spectral density of the energy losses on corrugation parameters are obtained and analyzed. It is demonstrated that the features of the surface waves can be used for the bunch diagnostics.
* E.I. Nefedov, A.N. Sivov. Electrodynamics of periodic structures. Moscow, Nauka, 1977, 208 p. (in Russian).
** E.S. Simakov, A.V. Tyukhtin, S.N. Galyamin, Phys. Rev. AB, 22, 061301 (2019). 		 
poster icon Poster TUPAB239 [0.637 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB239  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 23 August 2021  
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TUPAB241 Characterization of the RF-Cavities geometry in Order to Optimize the Beam Parameters in S-Band On-Axis LINACs cavity, electron, target, emittance 2005
 
  • A. Khosravi, B. Shokri
    LAPRI, Tehran, Iran
  • N. Khosravi
    ILSF, Tehran, Iran
  
  The RF characteristics of an accelerating tube are primarily assigned to geometrical features of a cavity. As a consequence of this geometry, the final electric field will make the shape of our Gaussian bunch and the final dose. The accelerating field can be studied considering the nose cone, gap, and bore radius. In dual electron linacs, the role of input power and bunch current is inevitable. Therefore, the geometrical issues of RF-cavities are studied in a 6MeV electron on-axis SW tube. To make an accurate comparison, each RF-cavity is designed and optimized by POISSON SU-PERFISH. The optimized cavities are imported to the PIC solver of CST. Then the beam characteristics are studied on a predefined target.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB241  
About • paper received ※ 18 May 2021       paper accepted ※ 14 June 2021       issue date ※ 30 August 2021  
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TUPAB242 The Beam-Study of the Side and On-Axis RF Cavities in S-Band 6 MeV LINACs cavity, target, emittance, coupling 2008
 
  • A. Khosravi, B. Shokri
    LAPRI, Tehran, Iran
  • N. Khosravi
    ILSF, Tehran, Iran
  
  The geometry of side and on-axis RF cavities are two magnetic-coupled designs for the different LINAC applications. The electromagnetic fields, RF power, beam parameters, thermal stability, and manufacturing costs are the most critical factors in cavity type selection in each application. In this article, both RF-cavities are optimized in POISSON SUPERFISH code to compare the beam parameters accurately. Then the optimized cavities are making a tube and compare in ASTRA 1D code and CST 3D software. At last, the thermal sensitivity of both models is studied in MPHYSICS module of the CST. As a result, the final decision can be achieved on the side or on-axis cavities considering the input power, costs, beam properties, and thermal stability for the different applications of the LINACs  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB242  
About • paper received ※ 18 May 2021       paper accepted ※ 21 June 2021       issue date ※ 30 August 2021  
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TUPAB243 Investigation of the Buncher Effect on Beam Properties in SW 3-6 MeV LINACs cavity, electron, emittance, target 2012
 
  • A. Khosravi, B. Shokri
    LAPRI, Tehran, Iran
  • N. Khosravi
    ILSF, Tehran, Iran
  
  The best quality of an electron beam is the primary goal of a linear accelerator design. Beam-study on a buncher section can lead us to a better perspective of the modulation and acceleration of a beam to optimize the final Gaussian beam. Five setups of different bunchers are designed, optimized, and presented in this article. A more brilliant and converged beam with a higher current, transverse emittance and smaller beam size is the study’s goal.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB243  
About • paper received ※ 18 May 2021       paper accepted ※ 14 June 2021       issue date ※ 26 August 2021  
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TUPAB244 THE WAKEFIELD STUDY OF THE RF-SHIELDED BELLOWS AT THE ILSF STORAGE RING wakefield, factory, vacuum, simulation 2015
 
  • N. Khosravi, E. Ahmadi, M. Akhyani
    ILSF, Tehran, Iran
  • M. Akhyani
    EPFL, Lausanne, Switzerland
  • A. Khosravi
    LAPRI, Tehran, Iran
  
  The corrugated geometry of the bellows made it critical to be shielded with an RF-Shield. Different types of RF shields can be applied to the ILSF vacuum chamber to cover this component’s destructive impedance peaks. Then, the Impedance study and optimization of the RF shields can improve the impedance budget. In this article, two common types of RF shields are simulated in CST software.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB244  
About • paper received ※ 16 May 2021       paper accepted ※ 02 June 2021       issue date ※ 14 August 2021  
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TUPAB245 WAKEFIELD AND HEAT LOAD STUDY OF THE GATE VALVES AT ILSF STORAGE RING storage-ring, wakefield, resonance, simulation 2018
 
  • N. Khosravi, E. Ahmadi, M. Akhyani
    ILSF, Tehran, Iran
  • M. Akhyani
    EPFL, Lausanne, Switzerland
  • S. Dastan
    IPM, Tehran, Iran
  • A. Khosravi
    LAPRI, Tehran, Iran
  
  As one part of the ILSF storage ring, the rf-shield of the gate valves generates considerable interest in terms of wake impedance and heat-load. Inside the gate valves, there is a vacuity, which causes low frequencies resonances, and it can lead to beam instabilities. Therefore, controlling and eliminating these frequencies will be substantial. A radio frequency rf-shield structure, which conceals this transverse gap of the gate valves, is indispensable for low emittance chambers. This paper analyzes the wake impedance and thermal behavior of a finger-band RF shield in the gate valve.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB245  
About • paper received ※ 16 May 2021       paper accepted ※ 14 June 2021       issue date ※ 13 August 2021  
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TUPAB251 Impedance Studies of a Corrugated Pipe for KARA resonance, simulation, radiation, electron 2039
 
  • S. Maier, M. Brosi, A. Mochihashi, A.-S. Müller, M.J. Nasse, M. Schwarz
    KIT, Karlsruhe, Germany
  
  Funding: DFG project 431704792 in the ANR-DFG collaboration project ULTRASYNC and the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology".
At the KIT storage ring KARA (KArlsruhe Research Accelerator) it is planned to install an impedance manipulation structure in a versatile chamber to study and eventually control the influence of an additional impedance on the beam dynamics and the emitted coherent synchrotron radiation. For this purpose the impedance of a corrugated pipe is under investigation. In this contribution, we present first results of simulations showing the impact of different structure parameters on its impedance and wake potential. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB251  
About • paper received ※ 19 May 2021       paper accepted ※ 17 June 2021       issue date ※ 26 August 2021  
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TUPAB252 Minimization of NICA Collider Impedance collider, simulation, space-charge, resonance 2043
 
  • S.A. Melnikov, I.N. Meshkov
    JINR, Dubna, Moscow Region, Russia
  • K.G. Osipov
    JINR/VBLHEP, Dubna, Moscow region, Russia
  
  The paper presents the results of the longitudinal impedance minimization for the beam tube section in the arches of the NICA collider ring, consisting of a pumping pipe, a BPM station, and a bellows assembly, and considers the contribution of the impedance of this section to the ion beam stability in the NICA collider ring. To confirm the efficiency of the optimized design, a BPM prototype was fabricated, and a test bench was built for further laboratory measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB252  
About • paper received ※ 13 May 2021       paper accepted ※ 14 June 2021       issue date ※ 10 August 2021  
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TUPAB256 Investigation of Damping Effects of the Crab Cavity Noise Induced Emittance Growth emittance, simulation, cavity, experiment 2054
 
  • N. Triantafyllou, L.R. Carver, A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
  • F. Antoniou, H. Bartosik, P. Baudrenghien, X. Buffat, R. Calaga, Y. Papaphilippou, N. Triantafyllou
    CERN, Meyrin, Switzerland
  • L.R. Carver
    ESRF, Grenoble, France
  • T. Mastoridis
    CalPoly, San Luis Obispo, California, USA
  
  Crab cavities will be installed at the two main interaction points (IP1 and IP5) of the High Luminosity LHC (HL-LHC) in order to minimize the geometric reduction of the luminosity due to the crossing angle. Two prototype crab cavities have been installed into the SPS machine and were tested with a proton beam in 2018, to study the expected emittance growth induced by RF noise. The measured emittance growth was found to be a factor 2-3 lower than predicted from the available analytical and computational models. Damping mechanisms from the transverse impedance, which is not included in the available theories, are studied as a possible explanation for the observed discrepancy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB256  
About • paper received ※ 18 May 2021       paper accepted ※ 18 June 2021       issue date ※ 23 August 2021  
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TUPAB257 Analysis of Multibunch Spectrum for an Uneven Bunch Distribution in a Storage Ring electron, collider, storage-ring, distributed 2058
 
  • R. Li, F. Marhauser
    JLab, Newport News, Virginia, USA
  
  Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Modern storage-ring designs often require an uneven bunch distribution pattern. An uneven bunch fill pattern can result in complex structures for the beam current spectra. Particularly at high average beam currents, these complex current spectra need to be taken into account in concern of beam-dynamical effects. In this study, we analyze a beam current spectrum for various filling patterns with bunch trains and gaps. The characteristics of the resulting beam current spectra are illustrated and discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB257  
About • paper received ※ 21 June 2021       paper accepted ※ 28 June 2021       issue date ※ 12 August 2021  
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TUPAB261 The Ferrite Loaded Cavity Impedance Simulation cavity, simulation, MMI, synchrotron 2070
 
  • L. Huang, X. Li, S. Wang, S.Y. Xu
    IHEP, Beijing, People’s Republic of China
  • B. Wu
    IHEP CSNS, Guangdong Province, People’s Republic of China
  
  Funding: Work supported by NNSF of China: N0. U1832210
The Rapid Cycling Synchrotron of the China Spallation Neutron Source is a high-intensity proton accelerator, it accumulates the 80 MeV proton beam and accelerates it to 1.6 GeV in 20 ms. The transverse coupling bunch instability is observed in beam commissioning. The source has been investigating from the commissioning. The RF acceleration system consists of eight ferrite-loaded cavities. The impedance is simulated and there is a narrow-band impedance of the ferrite cavity at about 17 MHz 		 
poster icon Poster TUPAB261 [1.145 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB261  
About • paper received ※ 13 May 2021       paper accepted ※ 31 May 2021       issue date ※ 21 August 2021  
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TUPAB262 The Characteristic of the Beam Position Growth in CSNS/RCS proton, neutron, MMI, synchrotron 2073
 
  • L. Huang, S. Wang
    IHEP, Beijing, People’s Republic of China
  • S.Y. Xu
    DNSC, Dongguan, People’s Republic of China
  
  Funding: Work supported by NNSF of China: N0. U1832210
An instability of the beam position growth is observed in the beam commissioning of the Rapid Cycling Synchrotron of the China Spallation Neutron Source. To simplify the study, a series of measurements have been performed to characterize the instability in the DC mode with consistent energy of 80 MeV. The measurement campaign is introduced in the paper and it conforms to the characteristics of the coupled bunch instability. 		 
poster icon Poster TUPAB262 [3.748 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB262  
About • paper received ※ 13 May 2021       paper accepted ※ 02 June 2021       issue date ※ 22 August 2021  
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TUPAB264 Shielding of CSR Wake in a Drift shielding, radiation, wakefield, synchrotron-radiation 2079
 
  • G. Stupakov
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by the Department of Energy, contract DE-AC03-76SF00515.
A one-dimensional model of coherent synchrotron radiation (CSR) wakefield developed in Refs. [*,**] is used in computer codes for the simulation of relativistic electron beams. It includes transient effects at the entrance and exit from a bending magnet of finite length. In the ultra-relativistic limit, v=c, the exit CSR wake decays inversely proportional to the distance from the magnet end. To calculate the total energy loss of the beam one needs to integrate this wake to infinity, but the integral diverges. This means that one has to either drop the assumption of the infinite value of the Lorentz factor or take into account the shielding effect of the metal walls in the vacuum chamber. In practice, the latter effect is often dominant. In this work, we derive formulas for the CSR wake in the drift after an exit from the magnet that incorporates the shielding by two parallel metal plates. They allow computing the energy loss of different particles in the beam.
* E. L. Saldin, E. A. Schneidmiller, and M. V. Yurkov. NIMA v. 398, p. 373 (1997).
** G. Stupakov and P. Emma. In: Proceedings of 8th EPAC. Paris, France, 2002, p. 1479. 		 
poster icon Poster TUPAB264 [0.661 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB264  
About • paper received ※ 10 May 2021       paper accepted ※ 25 June 2021       issue date ※ 22 August 2021  
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TUPAB267 Investigation of Beam Impedance and Heat Load in a High Temperature Superconducting Undulator undulator, laser, simulation, site 2089
 
  • D. Astapovych, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  • T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui, A. Will
    KIT, Eggenstein-Leopoldshafen, Germany
  
  The use of high temperature superconducting (HTS) materials can enhance the performance of superconducting undulators (SCU), which can later be implemented in free electron laser facilities, synchrotron storage rings and light sources. In particular, the short period < 10 mm undulators with narrow magnetic gap < 4 mm are relevant. One of the promising approaches considers a 10 cm meander-structured HTS tapes stacked one above the other. Then, the HTS tape is wound on the SCU. The idea of this jointless undulator has been proposed by, and is being further developed at KIT. Since minimizing the different sources of heat load is a critical issue for all SCUs, a detailed analysis of the impedance and heat load is required to meet the cryogenic system design. The dominant heat source is anticipated to be the resistive surface loss, which is one of the subjects of this study. Considering the complexity of the HTS tape, the impedance model includes the geometrical structure of the HTS tapes as well as the anomalous skin effect. The results of the numerical investigation performed by the help of the CST PS solver will be presented and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB267  
About • paper received ※ 18 May 2021       paper accepted ※ 26 July 2021       issue date ※ 12 August 2021  
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TUPAB269 Transverse Impedance of Lossy Circular Metal-Dielectric Waveguides GUI, radiation, resonance, wakefield 2093
 
  • M. Ivanyan, L.V. Aslyan
    CANDLE SRI, Yerevan, Armenia
  • K. Flöttmann, F. Lemery
    DESY, Hamburg, Germany
  
  The properties of the transverse impedance of a dielectric-loaded metallic circular waveguide are investigated taking into account losses in the outer metallic pipe and in the inner dielectric layer. The dispersion relations, impedances, and wake functions for dipole modes are analyzed and compared for thin and thick dielectric layer cases. The correspondence of the resonant frequencies of the longitudinal monopole and transverse dipole impedances is established.  
poster icon Poster TUPAB269 [0.906 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB269  
About • paper received ※ 16 May 2021       paper accepted ※ 28 May 2021       issue date ※ 10 August 2021  
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TUPAB278 The HL-LHC Beam Gas Vertex Monitor - Simulations for Design Optimisation and Performance Study detector, target, hadron, simulation 2120
 
  • H. Guerin, O.R. Jones, R. Kieffer, B. Kolbinger, T. Lefèvre, B. Salvant, J.W. Storey, R. Veness, C. Zamantzas
    CERN, Meyrin, Switzerland
  • S.M. Gibson, H. Guerin
    Royal Holloway, University of London, Surrey, United Kingdom
  
  The Beam Gas Vertex (BGV) instrument is a non-invasive transverse beam profile monitor being designed as part of the High Luminosity Upgrade of the LHC (HL-LHC) at CERN. Its aim is to continuously measure bunch-by-bunch beam profiles, independent of beam intensity, throughout the LHC cycle. The primary components of the BGV monitor are a gas target and a forward tracking detector. Secondary particles emerging from inelastic beam-gas interactions are detected by the tracker. The beam profile is then inferred from the spatial distribution of reconstructed vertices of said interactions. Based on insights and conclusions acquired by a demonstrator device that was operated in the LHC during Run 2, a new design is being developed to fulfill the HL-LHC specifications. This contribution describes the status of the simulation studies being performed to evaluate the impact of design parameters on the instrument’s performance and identify gas target and tracker requirements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB278  
About • paper received ※ 18 May 2021       paper accepted ※ 21 June 2021       issue date ※ 30 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, HOM, 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. 		 
poster icon Poster TUPAB341 [1.580 MB]  
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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TUPAB350 Design of 71 MHz Power Amplifier in a Single-ended Architecture for IRANCYC-10 Cyclotron cyclotron, simulation, factory, SRF 2325
 
  • F. Babagoli Moziraji, H. Afarideh
    AUT, Tehran, Iran
  • M. Dehghan
    Shahid Beheshti University, Tehran, Iran
  • F. Ghasemi
    NSTRI, Tehran, Iran
  
  In this paper, the design and simulation of a high power amplifier to provide the required power of a cyclotron accelerator (IRANCYC-10) is presented step-by-step. By combining four modules of this amplifier, a power of 2.5 kW can be achieved to start the main power amplifier. The single ended designs amplifier can generate 1 kW the operating frequency of 71MHz continuous wave (CW). The purpose of choosing this type of design is simplicity to build without the need for a balun, low weight to build high power, as well as cost-effectiveness. The gain and PAE of the SSPA are 21.21 and 71%, respectively. There are also ways to reduce the size of the amplifier.  
poster icon Poster TUPAB350 [1.008 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB350  
About • paper received ※ 19 May 2021       paper accepted ※ 25 August 2021       issue date ※ 11 August 2021  
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TUPAB358 Novel 500 MHz Solid State Power Amplifier Module Development at Sirius cavity, operation, synchrotron, storage-ring 2349
 
  • M.H. Wallner, R.H. Farias, A.P.B. Lima, F. Santiago de Oliveira
    LNLS, Campinas, Brazil
  
  A new solid state power amplifier (SSPA) module is being developed at the Brazilian Center for Research in Energy and Materials (CNPEM) to drive one of the superconducting RF cavities to be installed at Sirius, its new 3 GeV fourth generation synchrotron light source. Several prototypes have been built and tested in-house, and a planar balun was designed to achieve a push-pull configuration at deep class AB operation. Efforts to optimize heat exchange in various ways have been made. Results obtained thus far are presented and the next steps concerning development are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB358  
About • paper received ※ 19 May 2021       paper accepted ※ 18 June 2021       issue date ※ 19 August 2021  
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TUPAB399 RF Characterisation of New Coatings for Future Circular Collider Beam Screens laser, collider, electron, cavity 2453
 
  • P. Krkotić, F. Pérez, M. Pont, N.D. Tagdulang
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • S. Calatroni
    CERN, Meyrin, Switzerland
  • X. Granados, J. Gutierrez, T. Puig, A. Romanov, G.T. Telles
    ICMAB, Bellatera, Spain
  • A.N. Hannah, O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.M. O’Callaghan Castella
    Universitat Politécnica de Catalunya, Barcelona, Spain
  • D. Whitehead
    The University of Manchester, Laser Processing Research Center, Manchester, United Kingdom
  
  For the future high energy colliders being under the design at this moment, the choice of a low surface impedance beam screen coating material has become of fundamental importance to ensure sufficiently low beam impedance and consequently guaranteed stable operation at high currents. We have studied the use of high-temperature superconducting coated conductors as possible coating materials for the beam screen of the FCC-hh. In addition, amorphous carbon coating and laser-based surface treatment techniques are effective surface treatments to lower the secondary electron yield and minimise the electron cloud build-up. We have developed and adapted different experimental setups based on resonating structures at frequencies below 10 GHz to study the response of these coatings and their modified surfaces under the influence of RF fields and DC magnetic fields up to 9 T. Taking the FCC-hh as a reference, we will show that the surface resistance for REBCO-CCs is much lower than that of Cu. Further we show that the additional surface modifications can be optimised to minimise their impact on the surface impedance. Results from selected coatings will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB399  
About • paper received ※ 19 May 2021       paper accepted ※ 25 June 2021       issue date ※ 02 September 2021  
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TUPAB401 Mechanical Design, Fabrication and Characterization of Electron Beam Position Monitors for Sirius pick-up, operation, vacuum, storage-ring 2461
 
  • R. Defavari, O.R. Bagnato, M.W.A. Feitosa, F.R. Francisco, G.R. Gomes, D.Y. Kakizaki, R.L. Parise, R.D. Ribeiro
    LNLS, Campinas, Brazil
  
  Beam Position Monitors were designed and manufactured to meet Sirius operation requirements. Final dimensional accuracy and stability of the BPM were achieved by careful specification of its components’ manufacturing tolerances and materials. AISI-305 Stainless Steel was used for the BPM support fabrication due to magnetic and thermal expansion constraints. High purity molybdenum for the electrode pin and Ti6Al4V F136 G23 alloy for housing was used to manufacture the sensor components for their thermal characteristics. The electrical insulator was made of high alumina. The materials were joined by an active metal brazing process using 0,01mm accurate fixtures. The brazed sensors were subjected to dimensional, mechanical, and metallurgical testing, as well as leak detection and optical microscopy inspection at each stage. The sensors were joined in Ti6Al4V F136 BPM bodies using TIG welding. Dimensional sorting was used to choose groups of sensors-to-body, and body-to-support pairs during the final assembly. 160 BPMs are currently in operation on Sirius storage ring. In this contribution, we present the results of BPM manufacturing and testing processes developed for Sirius.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB401  
About • paper received ※ 18 May 2021       paper accepted ※ 31 May 2021       issue date ※ 29 August 2021  
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WEXA01 Successful Crabbing of Proton Beams cavity, luminosity, collider, emittance 2510
 
  • R. Calaga
    CERN, Meyrin, Switzerland
  
  Funding: Research supported by the HL-LHC project and by the DOE and UK-STFC.
Many future particle colliders require beam crabbing to recover the geometric luminosity loss from the non-zero crossing angle at the interaction point. A first demonstration experiment of crabbing with hadron beams was successfully carried out with high energy protons. This breakthrough result is fundamental to achieve the physics goals of the high luminosity LHC upgrade project (HL-LHC) and the future circular collider (FCC). The expected peak luminosity gain (related to collision rate) is 65% for HL-LHC, and even greater for the FCC. Novel beam physics experiments with proton beams in CERN’s Super Proton Synchrotron (SPS) were performed to demonstrate several critical aspects for the operation of crab cavities in the future HL-LHC including transparency with a pair of cavities, a full characterization of the cavity impedance with high beam currents and controlled emittance growth from crab cavity induced RF noise. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA01  
About • paper received ※ 14 May 2021       paper accepted ※ 28 July 2021       issue date ※ 24 August 2021  
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WEPAB081 The Broad-Band Impedance Budget in the Storage Ring of the ALS-U Project vacuum, cavity, wakefield, storage-ring 2779
 
  • D. Wang, K.L.F. Bane, R. Bereguer, T. Cui, S. De Santis, P. Gach, D. Li, T.H. Luo, T. Miller, T. Oliver, O. Omolayo, C. Steier, T.L. Swain, M. Venturini, G. Wang
    LBNL, Berkeley, 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. Like other 4th-generation light source machines, the ALS-U multiple-bend achromat storage-ring (SR) is potentially sensitive to beam-coupling impedance effects. This paper presents the SR broad-band impedance budget in both the longitudinal and transverse planes. In our modeling we follow the commonly accepted approach of separating the resistive-wall and the geometric parts of the impedance, the former being described by analytical formulas and the latter obtained by numerical electromagnetic codes (primarily CST Studio software) assuming perfectly conducting materials. We discuss the main sources of impedance. Results of our analysis are the basis for the single bunch instability study and would feedback on the design of critical vacuum components.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB081  
About • paper received ※ 20 May 2021       paper accepted ※ 01 July 2021       issue date ※ 20 August 2021  
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WEPAB082 Single Bunch Instability Simulations in the Storage Ring of the ALS-U Project simulation, cavity, storage-ring, operation 2783
 
  • D. Wang, K.L.F. Bane, S. De Santis, M.P. Ehrlichman, D. Li, T.H. Luo, O. Omolayo, G. Penn, C. Steier, M. Venturini
    LBNL, Berkeley, California, USA
  
  As the broad-band impedance modeling and the vacuum chamber design of the new Advanced Light Source storage ring (ALS- U) reach maturity, we report on progress in single-bunch collective effects studies. A pseudo-Green function wake representing the entire ring was earlier obtained by numerical and analytical methods. Macroparticle simulations using the computer code "elegant" and this wake function are used to determine the instability thresholds for longitudinal and transverse motion. We consider various operating conditions, such as without/with higher-harmonic RF cavities, zero/finite linear chromaticity, and without/with a transverse bunch-by-bunch feedback system. Results show enough margin for the broadband impedance budget when the single-bunch instability thresholds are compared with the design bunch charge.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB082  
About • paper received ※ 20 May 2021       paper accepted ※ 01 July 2021       issue date ※ 12 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, HOM, 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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WEPAB113 Stripline Kickers for Injection Into PETRA IV kicker, injection, electron, electronics 2863
 
  • G. Loisch, I.V. Agapov, S.A. Antipov, J. Keil, F. Obier
    DESY, Hamburg, Germany
  • M.A. Jebramcik
    CERN, Meyrin, Switzerland
  
  PETRA IV is the planned ultralow-emittance upgrade of the PETRA III synchrotron light source at DESY, Hamburg. The current design includes an on-axis beam injection scheme using fast stripline kickers. These kickers have to fulfill the requirements on kick-strength, field quality, pulse rise-rate and a matched beam impedance. 3D finite element simulations in conjunction with Bayesian optimisation are used to meet these requirements simultaneously. Here, we will discuss the requirements on the PETRA IV injection kickers and the current design status.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB113  
About • paper received ※ 19 May 2021       paper accepted ※ 24 June 2021       issue date ※ 15 August 2021  
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WEPAB122 Development of Fast and Super-Fast Kicker System for SLS 2.0 Injection kicker, injection, electron, damping 2889
 
  • M. Paraliev, M. Aiba, S. Dordevic, C.H. Gough, A. Streun
    PSI, Villigen PSI, Switzerland
  
  Swiss Light Source plans a major upgrade to turn the existing Storage Ring (SR) into a modern diffraction-limited light source called SLS 2.0. As part of this project, the injection system has to be upgraded as well in order to ensure reliable and efficient injection in the reduced beam aperture. A 4 kicker bump and a new thin septum will ensure the conventional injection in the SR. To further minimize the perturbation of the stored beam during injection two new schemes are in development: "Fast" and "Super-fast" one. The "Fast" injection scheme should be able to ensure single-bunch off-axis top-up injection affecting only 10 to 20 SR bunches that are 2 ns apart. The "Super-fast" one should bring the perturbed bunches down to only one. In on-axis mode it should be able to inject a top-up bunch between two SR bunches with minimum disturbance of the adjacent ones. To do this a combination of special beam injection schemes and an extremely fast (ns) kicker system is required. We will discuss the status of the development, the problems, and the solutions for reaching such a challenging goal.  
poster icon Poster WEPAB122 [1.371 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB122  
About • paper received ※ 18 May 2021       paper accepted ※ 09 June 2021       issue date ※ 28 August 2021  
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WEPAB133 First Numerical Wakefield Studies of New In-Vacuum Cryogenic and APPLE II Undulators for BESSY II simulation, vacuum, undulator, factory 2925
 
  • M. Huck, J. Bahrdt, A. Meseck
    HZB, Berlin, Germany
  • A. Meseck
    KPH, Mainz, Germany
  
  While the new in-vacuum cryogenic undulator is in its last commissioning stages, a worldwide new in-vacuum APPLE II undulator is being designed and constructed for BESSY II storage ring. Besides the challenging mechanical design of these small-gap and short-period undulators, challenges arise due to interaction with the electron beam. Therefore, detailed studies of this interaction is required to minimize the adverse effects on beam dynamics and the device itself. For this purpose, the wakefield effects have been computed numerically for critical parts of these devices i.e. the RF-shields, flexible tapers and taper sections. A brief overview of simulation results and discussions are presented in this paper.  
poster icon Poster WEPAB133 [0.795 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB133  
About • paper received ※ 19 May 2021       paper accepted ※ 23 July 2021       issue date ※ 23 August 2021  
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WEPAB134 Experimental Studies of the In-Vacuum-Cryogenic Undulator Effect on Beam Instabilities at BESSY II undulator, vacuum, feedback, damping 2929
 
  • M. Huck, J. Bahrdt, A. Meseck, G. Rehm, M. Ries, A. Schälicke
    HZB, Berlin, Germany
  
  A new in-vacuum cryogenic permanent magnet undulator (CPMU17) has been installed in summer 2018 in the BESSY II storage ring at HZB. Such a small gap in-vacuum undulator device increases the impedance of the storage ring and can contribute to the instabilities that adversely affect the beam quality and the device itself. To identify and explore the effects of CPMU17 on the instabilities at BESSY II, grow-damp and drive-damp experiments have been conducted using the installed bunch-by-bunch feedback system. In this paper, the first results of the mode and gap analysis of these studies with a brief overview of other impedance studies will be presented.  
poster icon Poster WEPAB134 [1.079 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB134  
About • paper received ※ 17 May 2021       paper accepted ※ 02 July 2021       issue date ※ 23 August 2021  
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WEPAB193 Optimization of the Hadron Ring Stripline Injection Kicker for the EIC kicker, simulation, injection, wakefield 3073
 
  • M.P. Sangroula, C.J. Liaw, C. Liu, N. Tsoupas, B.P. Xiao, W. Zhang
    BNL, Upton, New York, USA
  • X. Sun
    ANL, Lemont, Illinois, USA
  • S. Verdú-Andrés
    Brookhaven National Laboratory (BNL), Electron-Ion Collider, 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 Electron-Ion Collider (EIC) at Brookhaven National Laboratory is a high luminosity, (  ∼  1034  \textrm{cm}-2 \textrm{s}-1 ) accelerator facility colliding polarized electron beam with different ion species ranging from lighter nuclei (proton, deuterium) to heavier nuclei (gold, uranium). Design of a stripline injection kicker for the Hadron Storage Ring (HSR) of EIC for beams with the rigidity of  ∼  81 T-m poses some technical challenges due to expected shorter bunch spacing and higher peak current of EIC. This paper focuses on the optimization of the EIC hadron ring injection kicker. Starting from the 2D cross-section design which includes the selection of electrodes shape, we describe the optimization of the kicker’s cross-section. Then we discuss converting this 2D geometry to 3D by adding essential components for the stripline kicker and the 3D optimization techniques that we employed. Finally, we show simulation results for the optimized geometry including wakefields and Time Domain Reflection (TDR) from one feedthrough to another. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB193  
About • paper received ※ 21 May 2021       paper accepted ※ 28 June 2021       issue date ※ 14 August 2021  
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WEPAB194 Feasibility of Using the Existing RHIC Stripline BPMs for the EIC shielding, simulation, hadron, site 3077
 
  • M.P. Sangroula, C. Liu, M.G. Minty, P. Thieberger
    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.
The design of the Electron-Ion Collider (EIC) at Brookhaven National Laboratory (BNL) will utilize portions of the existing Relativistic Heavy Ion Collider (RHIC) for the EIC hadron ring. The EIC design calls for up to 10-times shorter ion bunches compared to the present RHIC operation. Higher single bunch peak currents will result in higher voltages to the output ports of the BPMs consequently producing more heating of the cryogenic signal cables connected to these output ports. Therefore, the existing stripline BPMs should be either upgraded or replaced with new ones. In this paper, we explore the potentially cost-effective approach by incorporating an RF-shielding piece into the existing BPMs as opposed to replacing them completely. Starting with the power delivered to the output ports, we present the proposed BPM modification with the RF-shielding piece. Then we discuss in detail the RF-shielding piece geometry including the dimension of RF slot and RF-fingers configuration. Finally, we present the optimization of the shielding piece and the mechanical tolerances required for its fabrication. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB194  
About • paper received ※ 21 May 2021       paper accepted ※ 28 June 2021       issue date ※ 15 August 2021  
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WEPAB222 Impedance Evaluation of Masks in the HEPS Storage Ring resonance, wakefield, radiation, synchrotron 3145
 
  • N. Wang, S.K. Tian, J.Q. Wang
    IHEP, Beijing, People’s Republic of China
  • J.Q. Wang
    University of Chinese Academy of Sciences, Beijing, People’s Republic of China
  
  Masks are commonly used in photon light sources to protect sensitive elements from synchrotron radiations. In the ultra-low emittance rings, small aperture vacuum chambers are adopted in order to reach the very high gradient in the quadrupoles, while many masks are required due to the high radiation power density. Therefore, the impedance of the masks becomes one of the dominant contributors to the impedance budget. In this paper, the impedance is evaluated among different mask designs. Meanwhile, the impedance cross-talk between adjacent masks is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB222  
About • paper received ※ 18 May 2021       paper accepted ※ 06 July 2021       issue date ※ 15 August 2021  
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WEPAB224 Update of the Transverse Proton Synchrotron Impedance Model factory, vacuum, injection, space-charge 3149
 
  • S. Joly, N. Mounet, B. Salvant
    CERN, Geneva, Switzerland
  • S. Joly
    La Sapienza University of Rome, Rome, Italy
  • M. Migliorati
    INFN-Roma1, Rome, Italy
  • M. Migliorati
    Sapienza University of Rome, Rome, Italy
  
  The CERN Proton Synchrotron (PS) was recently upgraded to allow reaching the ambitious performance goal of the High-Luminosity LHC Project. This upgrade is part of the LHC Injectors Upgrade project. The final part of the upgrade was performed during Long Shutdown 2 (LS2) to allow injection at higher energy from the PS Booster and a twofold increase in beam intensity and brightness. These changes must be considered in the PS impedance model. The effect on the impedance of the removal of obsolete injection equipment, changes of several accelerator components and new injection energy will be reviewed, as well as the wall impedance of the elliptic beam pipe, thanks to a newly developed code that allows taking into account both the ellipticity and the non-ultra-relativistic nature of the beam.  
poster icon Poster WEPAB224 [0.654 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB224  
About • paper received ※ 17 May 2021       paper accepted ※ 27 July 2021       issue date ※ 17 August 2021  
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WEPAB225 Transverse and Longitudinal Single Bunch Instabilities in FCC-ee wakefield, simulation, collider, coupling 3153
 
  • E. Carideo, D. Quartullo, F. Zimmermann
    CERN, Geneva, Switzerland
  • D. De Arcangelis
    Sapienza University of Rome, Rome, Italy
  • M. Migliorati, M. Zobov
    INFN/LNF, Frascati, Italy
  
  Improving the accuracy of the impedance model of an accelerator is important for keeping beam instabilities and power loss under control. Here, by means of the PyHEAD- TAIL tracking code, we first review the longitudinal mi- crowave instability threshold for FCC-ee by taking into ac- count the longitudinal impedance model evaluated so far. Moreover, we present the results of beam dynamics simula- tions, including both the longitudinal and transverse wake- fields due to the resistive wall, in order to evaluate the influ- ence of the bunch length on the transverse mode coupling instability. The results of the transverse beam dynamics are also compared with the Vlasov solver DELPHI.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB225  
About • paper received ※ 10 May 2021       paper accepted ※ 01 July 2021       issue date ※ 18 August 2021  
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WEPAB227 Mechanism of Longitudinal Single-Bunch Instability in the CERN SPS simulation, synchrotron, coupling, emittance 3161
 
  • I. Karpov
    CERN, Meyrin, Switzerland
  • M. Gadioux
    UCD, Dublin, Ireland
  
  Understanding the origin of beam instabilities is essential for reaching the highest performance of proton synchrotrons. In the present work, the Oide-Yokoya eigenvalue method of solving the linearised Vlasov equation was used to shed light on the mechanism of longitudinal single-bunch instability in the CERN SPS. In particular, semi-analytical calculations were done for the full longitudinal impedance model, taking into account the RF nonlinearity. The obtained results agree well with macro-particle simulations and are consistent with available beam measurements. For the first time, the instability has been interpreted as a coupling of radial modes within a single azimuthal mode, due to a strong potential-well distortion of the synchrotron-frequency distribution. To avoid this instability, a higher RF voltage is required at a given emittance. Thus, the instability mechanism is very different from the loss of Landau damping, which, in contrast, is mitigated by a lower RF voltage. This understanding also allowed us to optimise the RF voltage programmes during the acceleration cycle for high-intensity bunches used in the AWAKE experiment at CERN.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB227  
About • paper received ※ 12 May 2021       paper accepted ※ 01 July 2021       issue date ※ 15 August 2021  
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WEPAB235 TMCI Theory of Flat Chambers Revisited coupling, storage-ring, vacuum, simulation 3181
 
  • T.F. Günzel
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  
  By accounting for the transverse impedance’ quadrupolar component according to the work of R.Lindberg *, no TMCI-instability can be observed in case of a pure horizontal resistive wall impedance of flat vacuum chambers. In order to study this effect more closely, TMCI-theory is reviewed and Lindberg’s work is further developed by including the resonator model as impedance type. The theory is applied to the ALBA-impedance model for the calculation of horizontal TMCI-detuning and threshold. Moreover, a couple of example cases are presented including vertical TMCI-detuning and threshold. Results on both planes are compared to simpler descriptions which account for the quadrupolar impedance effect only by tune shift.
* Ryan Lindberg, Fokker-Planck analysis of transverse collective instabilities in electron storage rings, Phy. Rev. Acc. Beams 19, 124402 (2016) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB235  
About • paper received ※ 19 May 2021       paper accepted ※ 01 July 2021       issue date ※ 19 August 2021  
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WEPAB239 Effect of Chromaticity and Feedback on Transverse Head-Tail Instability feedback, coupling, damping, storage-ring 3189
 
  • V.V. Smaluk, G. Bassi, A. Blednykh, A. Khan
    BNL, Upton, New York, USA
  
  Funding: This work was supported by the US Department of Energy under contract DE-SC0012704.
The head-tail instability caused by the beam interaction with short-range wakefields is a major limitation for the single-bunch beam intensity in circular accelerators. The combined effect of the transverse feedback systems and chromaticity suppressing the instability is discussed. Theoretical and experimental studies of the head-tail instability and methods of its mitigation are reviewed. Results of experimental studies of the transverse mode coupling carried out at NSLS-II are compared with the theoretical model and numerical simulations. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB239  
About • paper received ※ 19 May 2021       paper accepted ※ 24 June 2021       issue date ※ 12 August 2021  
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WEPAB243 Longitudinal Microwave Instability Study at Transition Crossing with Ion Beams in the CERN PS emittance, simulation, controls, proton 3197
 
  • A. Lasheen, H. Damerau, A. Huschauer, B.K. Popovic
    CERN, Meyrin, Switzerland
  
  The luminosity of lead ion collisions in the Large Hadron Collider (LHC) was significantly increased during the 2018 ion run by reducing the bunch spacing from 100 ns to 75 ns, allowing to increase the total number of bunches. With the new 75 ns variant, three instead of four bunches are generated each cycle in the Low Energy Ion Ring (LEIR) and the Proton Synchrotron (PS) with up to 30% larger intensity per bunch. The beam was produced with satisfactory quality but at the limit of stability in the injectors. In particular, the minimum longitudinal emittance in the PS is limited by a strong longitudinal microwave instability occurring just after transition crossing. The uncontrolled blow-up generates tails, which translate into an unacceptably large satellite population following the RF manipulations prior to extraction from the PS. In this paper, instability measurements are compared to particle simulations using the latest PS impedance model to identify the driving impedance sources. Moreover, means to mitigate the instability are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB243  
About • paper received ※ 19 May 2021       paper accepted ※ 06 July 2021       issue date ※ 29 August 2021  
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WEPAB245 A Possible Modification of Ceramic Chambers in the Injection Area at the RCS in J-PARC simulation, injection, dipole, proton 3205
 
  • Y. Shobuda, K. Horino, J. Kamiya, K. Kotoku, T. Takayanagi, T. Ueno, T. Yanagibashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  
  The J-PARC RCS is composed of ceramic chambers covered over copper stripes to suppress the eddy current on the chamber. The inductance, comprising the copper stripes and flanges, in combination with the capacitors makes an LCR electric circuit with the chamber and can cause field modulation in the chamber. Though most chambers are not harmful at the RCS, the chambers at the injection area excite beam losses, because a trapezoid field pattern is excited to accumulate LINAC beam during the injection period. In this report, we consider several types of ceramic chambers to suppress the field modulation. One type is a ceramic chamber covered over copper stripes in parallel with damping resistors. Another is that covered over spiral copper stripes with only capacitors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB245  
About • paper received ※ 19 May 2021       paper accepted ※ 01 July 2021       issue date ※ 18 August 2021  
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WEPAB330 A Multirange Low Noise Transimpedance Amplifier for Sirius Beamlines feedback, operation, FEM, synchrotron 3447
 
  • L.Y. Tanio, F.H. Cardoso, M.M. Donatti
    LNLS, Campinas, Brazil
  
  In a typical synchrotron beamline, the interaction of photon beams with different materials generates free electric charges in devices such as ionization chambers, photodiodes, or even isolated metallic structures (e.g., blades, blocks, foils, wires). These free charges can be measured as electric current to diagnose the photon beam intensity, profile, position, or stability. Sirius, the new 3GeV fourth-generation Brazilian light source, may accommodate up to 38 beamlines, which combined will make use of hundreds of instruments to measure such low-intensity signals. This work reports on the design and test results of a transimpedance amplifier developed for low current measurements at Sirius’ beamlines. The device presents low noise, high accuracy, and good temperature stability providing 5 selectable ranges (from 500pA to 7.3mA) to measure bipolar currents achieving femtoampere resolution under certain conditions. Considering low bandwidth applications, the results suggest noise performance comparable to commercial bench instruments. Additionally, the project definitions and plans for the development of a family of low current ammeters will be discussed.  
poster icon Poster WEPAB330 [2.642 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB330  
About • paper received ※ 19 May 2021       paper accepted ※ 16 June 2021       issue date ※ 21 August 2021  
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WEPAB341 Injection and Extraction Kickers for the Advanced Light Source Upgrade Project (ALS-U) kicker, storage-ring, extraction, injection 3487
 
  • W.L. Waldron, D.A. Dawson, S. De Santis, T. Oliver, C. Steier
    LBNL, Berkeley, California, USA
  
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Advanced Light Source upgrade project (ALS-U) at Lawrence Berkeley National Laboratory includes the construction of a new accumulator ring and the replacement of the existing storage ring. Both ferrite-loaded kickers and stripline kickers are used in the ALS-U design for injection, extraction, and decohering the beam before storage ring extraction. In the accumulator ring, the rise and fall time requirements are based on the single bunch revolution time of 608 ns which allows the use of ferrite-loaded kickers. The 10 ns spacing between bunch trains in the storage ring requires stripline kickers to meet the rise and fall time requirements. Both types of kickers are driven by solid-state inductive voltage adders using MOSFETs. Modeling and prototyping efforts have characterized the kicker impedance and beam-induced heating, and explored the effects of beam strike on electrodes. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB341  
About • paper received ※ 20 May 2021       paper accepted ※ 27 July 2021       issue date ※ 24 August 2021  
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WEPAB342 Beam Induced Power Deposition in CERN SPS Injection Kickers simulation, HOM, 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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WEPAB345 Impedance and Thermal Studies of the LHC Injection Kicker Magnet Upgrade kicker, injection, simulation, coupling 3502
 
  • M.J. Barnes, O. Bjorkqvist, F. Motschmann
    CERN, Geneva 23, Switzerland
  
  The bunch intensities of High Luminosity (HL) LHC are predicted to lead to heating of the ferrite yokes of the LHC injection kicker magnets (MKI), in their current configuration, to their Curie temperature. Hence, the MKIs are being upgraded to meet the requirements of HL-LHC, which is planned to start in the mid-2020s. The upgraded design features an RF damping ferrite loaded structure at the upstream end of each magnet, which will absorb a large portion of the beam induced power deposition of the magnet. The ferrite damper is cooled via a copper sleeve, brazed to the ferrite, and a set of water pipes. The thermal contact conductance (TCC) between ferrite and copper is very important, as are the properties of the ferrite. In this paper, we present measurements of the TCC and ferrite properties. This data is used to predict temperatures during operation of the LHC. In addition, a measurement and prediction is shown for the longitudinal impedance of the magnet. The models developed in this study will be benchmarked during run III of the LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB345  
About • paper received ※ 19 May 2021       paper accepted ※ 06 July 2021       issue date ※ 13 August 2021  
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WEPAB346 Electromagnetic Modelling of Kicker Magnets to Derive Equivalent Circuits kicker, coupling, simulation, extraction 3506
 
  • M.J. Barnes, O. Bjorkqvist
    CERN, Geneva 23, Switzerland
  • L. Jensen, O.A. Nielsen
    Aarhus University, Aarhus, Denmark
  
  An equivalent circuit model of a kicker magnet system is an invaluable tool for predicting the performance, studying possible modifications and for helping to diagnose faults. The frequency content of pulses associated with a ferrite loaded transmission line kicker magnet generally extend up to a few tens of MHz: hence, it is feasible to accurately model such a kicker magnet using lumped elements. This modelling technique is powerful since it in general has a run time several orders of magnitude shorter than a full wave electromagnetic simulation. In this paper, we determine values, including those of parasitic components, using modern simulation tools, for use in the lumped equivalent circuit models. In addition, the paper describes a method to simulate coupling between beam and the electrical circuit of a kicker magnet at relatively low frequencies: this allows one to use circuit analysis tools to study means of mitigating beam induced resonances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB346  
About • paper received ※ 16 May 2021       paper accepted ※ 02 July 2021       issue date ※ 14 August 2021  
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WEPAB347 Design, Construction and Testing of a Magnetic Probe for Fast Kicker Magnets vacuum, kicker, injection, operation 3510
 
  • N. Ayala, A. Ferrero Colomo, T. Kramer
    CERN, Geneva, Switzerland
  
  The CERN PS injection kicker has been modified in the framework of the LHC Injector Upgrade (LIU) project to allow injecting proton beams with an energy of 2 GeV. One of the most important items of the system parameter validation is the measurement and analysis of the magnetic field in the magnet aperture. To meet the required measurement precision without compromising the magnet vacuum performance, a dedicated magnetic probe has been designed, constructed and tested. The results are presented in this paper highlighting the mitigations of electrical, mechanical and vacuum complications. The paper concludes with an analysis of the probe performance during the first magnetic field measurements in the laboratory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB347  
About • paper received ※ 19 May 2021       paper accepted ※ 07 July 2021       issue date ※ 02 September 2021  
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WEPAB351 Requirements for an Inductive Voltage Adder as Driver for a Kicker Magnet with Short Circuit Termination kicker, simulation, timing, flattop 3521
 
  • J. Ruf, M.J. Barnes, T. Kramer
    CERN, Geneva 23, Switzerland
  • M. Sack
    KIT, Karlsruhe, Germany
  
  At CERN pulse generators based on Thyratron switches and SF6 gas filled pulse forming lines, used for driving kicker magnets, are to be replaced with semiconductor technology. Preliminary investigations show the inductive voltage adder is suitable as a pulse generator for this application. To increase the magnetic field without raising the system voltage, a short-circuit termination is often applied to a kicker magnet. Because of the electrical length of a transmission line magnet, wave propagation needs to be considered. To allow for the wavefront reflected from the short-circuit termination back to the generator, a novel approach for an inductive adder architecture has been investigated. It is based on a modified generator interface, circulating the current back into the load, until the stored energy is absorbed at the end of the pulse. This approach allows for a smaller magnetic core size compared to a conventional design with a matched load. Moreover, it enables more energy-efficient operation involving smaller storage capacitors. This paper summarizes the conceptual design features and furthermore gives an overview of the parameter space for possible applications at CERN.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB351  
About • paper received ※ 18 May 2021       paper accepted ※ 11 June 2021       issue date ※ 17 August 2021  
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WEPAB358 Development of Low-Z Collimator for SuperKEKB cavity, electron, positron, operation 3537
 
  • S. Terui, T. Abe, Y. Funakoshi, T. Ishibashi, H.N. Nakayama, K. Ohmi, D. Zhou
    KEK, Ibaraki, Japan
  • A. Natochii
    University of Hawaii, Honolulu,, USA
  
  Collimator jaws for SuperKEKB main ring, which is an electron-positron collider, installed to suppress background noise in a particle detector complex named Belle II. The collimators are successful to reduce backgrounds when the collimator was closed. But, in high current operations with 500 mA or more, jaws were occasionally damaged by hitting abnormal beams. This trouble is a low-frequency, which is once-a-commissioning period currently, but a high-consequence one because we are not able to apply high voltage on detectors in Belle II by high backgrounds. Low-Z collimator jaw, that is durable through hitting uncontrollable beam, have been designed due to protect important component as the solution of the trouble. The low-Z collimator jaws are installable in a present collimator chamber, have a pair of vertically opposed movable jaws. One pair of low-Z collimator jaws was installed. The paper is to describe what did we calculate and measure to make a low-Z collimator, how did we make a low-Z collimator, the impact of the installed low-Z collimator, mainly transverse mode coupling instability.  
poster icon Poster WEPAB358 [0.788 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB358  
About • paper received ※ 16 May 2021       paper accepted ※ 22 July 2021       issue date ※ 10 August 2021  
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WEPAB401 Study for Alternative Cavity Wall and Inductive Insert Material proton, storage-ring, simulation, experiment 3650
 
  • C.E. Taylor, C.-F. Chen, T.W. Hall, E. Henestroza, J.T.M. Lyles, J. Upadhyay
    LANL, Los Alamos, New Mexico, USA
  • S. Biedron, M.A. Fazio, S.I. Salvador, T.J. Schaub
    UNM-ECE, Albuquerque, USA
  
  Funding: Contract No. 89233218CNA000001, supported by the U.S. Department of Energy’s National Nuclear Security Administration (NNSA), for the management and operation of Los Alamos National Laboratory (LANL).
The goal of this work was to develop a solution to the problem of longitudinal beam instability. Beam instability has been a significant problem with storage rings’ performance for many decades. The proton storage ring (PSR) at the Los Alamos Neutron Science Center (LANCE) is no exception. To mitigate the instability, it was found that ferrite inductive inserts can be used to bunch the protons that are diverging due to the electron background. The PSR was the first storage ring to successfully use inductive inserts to mitigate the longitudinal instability with normal production beams. However, years later new machine upgrades facilitate shorter, more intense beams to meet the needs of researchers. The ferrite inserts used to reduce the transverse instabilities induce a microwave instability with the shorter more intense proton beam. This study investigates alternative magnetic materials for inductive inserts in particle beam storage rings, including the necessary engineering for maintaining the ideal temperature during operation.
’ tjschaub@unm.edu 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB401  
About • paper received ※ 29 May 2021       paper accepted ※ 02 July 2021       issue date ※ 15 August 2021  
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THPAB043 A Superconducting Undulator for CompactLight: Resistive Wall Wakefield Analysis undulator, wakefield, electron, FEL 3841
 
  • K.B. Marinov
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  The CompactLight project is an advanced X-ray FEL light source, with high-frequency, high-gradient linacs and compact undulators. Lower electron energies give higher energy efficiency and a smaller environmental footprint. The extremely short bunch lengths (few fs) and narrow undulator gaps (4 mm) drastically increase the impact of resistive wall wakefields on the lasing process. The longitudinal resistive wall wakefield impedance is calculated in the framework of the surface impedance approach, in accordance with anomalous skin effect (ASE) theory. The dependence of the electron energy loss factor and the correlated energy spread of the bunch on the residual resistivity ratio (RRR) for both copper and aluminum is much higher for long (100 fs) than for ultra-short (6 fs) bunches. This is due to a known property of the longitudinal wakefield impedance - the field acting on a single particle traversing a resistive vessel does not depend on the conductivity of the vessel. The wakefields generated by the ultra-short bunch are already close to that of a single-particle regime and this leads to interesting consequences which are discussed in the present work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB043  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 21 August 2021  
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THPAB048 Design and Fabrication Concepts of a Compact Undulator with Laser-Structured 2G-HTS Tapes undulator, laser, simulation, FEL 3851
 
  • A. Will, T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui
    KIT, Karlsruhe, Germany
  • D. Astapovych, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  To produce small-scale high-field undulators for table-top free electron lasers (FELs), compact designs have been proposed using high temperature superconducting (HTS) tapes, which show both large critical current densities and high critical magnetic fields with a total tape thickness of about 50 μm and a width of up to 12 mm. Instead of winding coils, a meander structure can be laser-scribed directly into the superconductor layer, guiding the current path on a quasi-sinusoidal trajectory. Stacking pairs of such scribed tapes allows the generation of the desired sinusoidal magnetic fields above the tape plane, along the tape axis. Two practically feasible designs are presented, which are currently under construction at KIT: A coil concept wound from a single structured tape with a length of 15 m, which is a progression of a design that has been presented already in the past, as well as a novel stacked and soldered design, made from 25 cm long structured tapes, soldered in a zig-zag-pattern. In this contribution the designs are briefly recapped and the experimental progress is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB048  
About • paper received ※ 19 May 2021       paper accepted ※ 12 July 2021       issue date ※ 15 August 2021  
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THPAB057 Goubau-Line Set Up for Bench Testing Impedance of In-Vacuum Undulator Components undulator, vacuum, wakefield, radiation 3883
 
  • P.I. Volz, S. Grimmer, M. Huck, A. Meseck
    HZB, Berlin, Germany
  • A. Meseck
    KPH, Mainz, Germany
  
  The worldwide first in-vacuum elliptical undulator, IVUE32, is being developed at Helmholtz Zentrum Berlin. The 2.5 m long device with a period length of 3.2 cm and a minimum gap of about 7 mm is to be installed in the BESSY II storage ring. It will deliver soft X-radiation to several beamlines. The proximity of the undulator structure to the electron beam makes the device susceptible to wakefield effects which can influence beam stability. A complete understanding of its impedance characteristics is required prior to installation and operation, as unforeseen heating of components could have catastrophic consequences. Since its complex structure makes numerical calculations, such as CST simulations, at high frequency very resource intensive, bench testing the device may proof invaluable. A Goubau-line is a single wire transmission line for high frequency surface waves with a transverse electric field resembling that of a charged particle beam out to a certain radial distance. This can be used to measure the impedance of vacuum chamber components. A concept optimized for bench testing IVUE32-components will be discussed and progress towards the test bench set up will be shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB057  
About • paper received ※ 19 May 2021       paper accepted ※ 23 July 2021       issue date ※ 21 August 2021  
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THPAB075 Collective (In)stability Near the Coupling Resonance wakefield, coupling, resonance, simulation 3933
 
  • R.R. Lindberg
    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.
We show how to treat transverse collective instabilities when operating in the vicinity of the coupling (or tune difference) resonance. We begin by defining the approximate independent degrees of freedom including both linear coupling and chromatic effects. We then show how the destabilizing force due to wakefields and the stabilizing chromatic effects can be described by a linear combination of the horizontal and vertical motion that depends upon how close one is to the resonance. The theory agrees well with tracking studies, and will be relevant for those next-generation storage rings that plan to operate near the coupling resonance to produce nearly round beams, including the multi-bend achromat upgrade for the Advanced Photon Source. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB075  
About • paper received ※ 20 May 2021       paper accepted ※ 27 July 2021       issue date ※ 01 September 2021  
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THPAB171 mm-Wave Linac Design for Next Generation VHEE Cancer Therapy Systems linac, electron, simulation, coupling 4090
 
  • E.J.C. Snively, K.C. Deering, E.A. Nanni
    SLAC, Menlo Park, California, USA
  
  Direct electron therapy offers an attractive method for providing the high dose rates necessary for FLASH radiation therapy, a new treatment modality with the potential for enhanced healthy tissue sparing. Direct electron therapy has been limited by the low beam energies, up to 20 MeV, provided by today’s medical linacs, restricting the achievable dose depth to superficial tumors. Very High Energy Electron (VHEE) therapy could reach deep-seated tumors throughout the body. A clinically viable VHEE system must provide electron energies of around 100 MeV in a compact footprint, roughly 1 to 2 meters, with modest power requirements. We investigate the development of mm-wave linacs to provide the necessary beam energies on the sub-meter scale, taking advantage of the favorable scaling of high-frequency operation to support gradients well above 100 MeV/m. We discuss the design parameters necessary for high-efficiency structures, with shunt impedance on the order of 1 GOhm/m, producing high gradients with only a few megawatts of power. We present simulations of cavity performance in the mm-wave operating regime, with an emphasis on compatibility with the requirements of VHEE therapy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB171  
About • paper received ※ 19 May 2021       paper accepted ※ 26 July 2021       issue date ※ 15 August 2021  
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THPAB199 Studies of Longitudinal Beam Losses at LHC Injection injection, simulation, beam-losses, extraction 4164
 
  • L.E. Medina Medrano, T. Argyropoulos, R. Calaga, H. Timko
    CERN, Geneva, Switzerland
  
  Funding: Research supported by the HL-LHC project.
Due to higher beam intensities, the required rf power in the High-Luminosity LHC (HL-LHC) era is expected to be at the limit of the available rf power. To mitigate potential limitations of the rf system, the injection voltage can be reduced at the expense of beam losses. In this paper, the average and bunch-by-bunch losses are estimated from Run 2 beam intensity measurements in the SPS before extraction and in the LHC after injection. Macro-particle simulations are performed with CERN’s Beam Longitudinal Dynamics code to reproduce the observed SPS-to-LHC capture and LHC flat-bottom losses. First estimates of injection losses for the HL-LHC at different injection voltages and injection energy errors are discussed. 		 
poster icon Poster THPAB199 [2.428 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB199  
About • paper received ※ 18 May 2021       paper accepted ※ 28 July 2021       issue date ※ 14 August 2021  
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THPAB222 Transverse Impedance Coaxial Wire Measurement in an Extended Frequency Range simulation, HOM, 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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THPAB223 Energy Compression System Radio Frequency Design at the Canadian Light Source linac, GUI, simulation, RF-structure 4231
 
  • E.J. Ericson, D. Bertwistle, M.J. Boland
    CLS, Saskatoon, Saskatchewan, Canada
  
  The Canadian Light Source (CLS), Canada’s only synchrotron light source, is considering a linear accelerator (LINAC) upgrade. As a result, the radio frequency (RF) structure in the downstream Energy Compression System (ECS) needs to be redesigned. In this paper, we describe the design process followed to determine the geometry of the RF structure cells and coupler.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB223  
About • paper received ※ 18 May 2021       paper accepted ※ 28 July 2021       issue date ※ 28 August 2021  
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THPAB235 Detailed Electromagnetic Characterisation of HL-LHC Low Impedance Collimators simulation, operation, collimation, factory 4258
 
  • A. Kurtulus, C. Accentura, N. Biancacci, F. Carra, F. Caspers, N. Chitnis, F. Giordano, R. Illan Fiastre, S. Joly, I. Lamas Garcia, L. Mourier, E. Métral, S. Redaelli, B. Salvant, W. Vollenberg, C. Vollinger, C. Zannini
    CERN, Geneva, Switzerland
  
  The High Luminosity Large Hadron Collider (HL-LHC) project will upgrade the LHC machine to allow operation with increased luminosity for the experiments. In order to achieve this goal, different operational parameters of the machine need to be pushed beyond the present design values, including the stored beam energy. One of the main challenges related to the achievement of the upgraded performance is the beam collimation system and its contribution to the overall machine impedance budget. In this perspective, new low impedance collimators have been designed, fabricated, and installed in the LHC. In this study, we will present their detailed electromagnetic (EM) characterization by means of radio frequency (RF) measurements and EM simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB235  
About • paper received ※ 19 May 2021       paper accepted ※ 19 July 2021       issue date ※ 10 August 2021  
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THPAB239 Impedance Optimization of the EIC Interaction Region Vacuum Chamber electron, vacuum, detector, wakefield 4270
 
  • A. Blednykh
    Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
  • E.C. Aschenauer, M. Blaskiewicz, C. Hetzel, M.P. Sangroula, G. Wang, H. Witte
    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 interaction region chamber has a complex geometry at the crossing location of electron and proton beam pipes. In the direction of the electron beam, the pipe is designed in a way to avoid joints with cavity characteristics. The horizontal slot on the upstream side and the tapered transition on the downstream side are applied to minimize the IR chamber contribution to the total impedance of the electron ring and to avoid generating Higher Order Modes and heating-related issues. The synchrotron radiation mask is included to protect the IR chamber from synchrotron radiation without significant aperture reduction. In the direction of the proton beam, the main area for optimization is the transition area right after the detector. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB239  
About • paper received ※ 15 May 2021       paper accepted ※ 24 June 2021       issue date ※ 24 August 2021  
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THPAB244 Design of Interdigital H-Mode Re-Buncher at KoBRA Beamline cavity, bunching, heavy-ion, simulation 4285
 
  • Y. Lee, E.-S. Kim
    KUS, Sejong, Republic of Korea
  
  KOrea Broad acceptance Recoil spectrometer & Apparatus (KOBRA) is an experimental facility for low energy nuclear physics in the heavy ion accelerator complex RAON. Two re-buncher systems at KOBRA beamline are required to longitudinally focus the 40Ar9+ with 27MeV/u. The normal conducting IH resonator with seven-gap as the re-buncher structure was chosen because of the reduction in the risk of particulate contamination and total power consumption. In this paper, the detailed design results of the 162.5 MHz IH re-buncher cavity will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB244  
About • paper received ※ 19 May 2021       paper accepted ※ 27 July 2021       issue date ※ 24 August 2021  
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FRXB02 Development of 36 GHz RF Systems for RF Linearisers cavity, klystron, HOM, linac 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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