IPAC2021 - List of Keywords (damping)

Paper	Title	Other Keywords	Page
MOPAB088	Beam-Based Measurement on the Performance of Ferrite Dampers in an In-Vacuum Undulator	HOM, feedback, radiation, vacuum	331
	K. Tian, A. Ringwall, J.J. Sebek SLAC, Menlo Park, California, USA
	In this paper, we first present the tracking studies for SPEAR3 with the new BL17 ID and estimate its impact on the dynamic aperture of the low emittance lattice. Then the ferrite dampers installations in the device is briefly reviewed. After that, we will show that, based on beam-based measurements, the performance of the dampers is as being expected from earlier numerical studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB088
About •	paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 24 August 2021
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MOPAB112	A Modified Hybrid 6BA Lattice for the HALF Storage Ring	lattice, emittance, storage-ring, SRF	407
	Z.H. Bai, G.Y. Feng, T.L. He, W. Li, W.W. Li, G. Liu, Z.L. Ren, L. Wang, P.H. Yang, S.C. Zhang, T. Zhang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	In this paper, we propose a modified hybrid 6BA lattice as the baseline lattice of the Hefei Advanced Light Facility (HALF) storage ring. Similar to the Diamond-II lattice, the proposed lattice cell has one long straight section and one mid-straight section; but the two bend units adjacent to the mid-straight are LGB/RB units (LGB: longitudinal gradient bend, RB: reverse bend), which can give both lower emittance and shorter damping times. The designed HALF storage ring, with an energy of 2.2 GeV and 20 lattice cells, has a natural emittance of about 85 pm·rad.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB112
About •	paper received ※ 15 May 2021 paper accepted ※ 20 May 2021 issue date ※ 01 September 2021
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MOPAB212	3-D Quantum Lifetime	simulation, electron, radiation, emittance	700
	H. Zhao, M. Blaskiewicz 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 quantum lifetime of electron beam in storage rings is defined by the particle loss that caused by the aperture limitation. Based on the equilibrium beam distribution produced by radiation damping and quantum excitation, the 1-d quantum lifetime has been well studied by A. Piwinski. In this paper, we give the derivation of the 3-d quantum lifetime, which can be applied to the machines with elliptical aperture and momentum acceptance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB212
About •	paper received ※ 04 June 2021 paper accepted ※ 21 June 2021 issue date ※ 16 August 2021
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MOPAB240	Estimates of Damped Equilibrium Energy Spread and Emittance in a Dual Energy Storage Ring	emittance, storage-ring, photon, radiation	774
	B. Dhital, G.A. Krafft ODU, Norfolk, Virginia, USA Y.S. Derbenev, D. Douglas, A. Hutton, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, and Office of Nuclear Physics under Contracts DE-AC05-06OR23177 and DE-AC02-06CH11357. / Jefferson Lab EIC Fellowship2020. A dual energy storage ring design consists of two loops at markedly different energies. As in a single-energy storage ring, the linear optics in the ring design may be used to determine the damped equilibrium emittance and energy spread. Because the individual radiation events in the two rings are different and independent, we can provide analytical estimates of the damping times in a dual energy storage ring. Using the damping times, the values of damped energy spread, and emittance can be determined for a range of parameters related to lattice design and rings energies. We present analytical calculations along with simulation results to estimate the values of damped energy spread and emittance in a dual energy storage ring. We note that the damping time tends to be dominated by the damping time of the high energy ring in cases where the energy of the high energy rings is significantly greater than that of the low energy ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB240
About •	paper received ※ 17 May 2021 paper accepted ※ 27 May 2021 issue date ※ 13 August 2021
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MOPAB343	Optimization of the Parasitic-Mode Damping on the 1.5 GHz TM020-type Harmonic Cavity	cavity, impedance, 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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TUXA06	Loss of Transverse Landau Damping by Diffusion in High-Energy Hadron Colliders	wakefield, hadron, collider, feedback	1286
	S.V. Furuseth, X. Buffat CERN, Geneva, Switzerland S.V. Furuseth EPFL, Lausanne, Switzerland
	Circular hadron colliders rely on Landau damping to stabilize the beams. Landau damping depends strongly on the bunch distribution, which is often assumed to be Gaussian in the transverse planes. In this paper, we introduce and explain an instability mechanism observed in the LHC, where Landau damping is eventually lost due to a diffusion that modifies the transverse bunch distribution. The mechanism is caused by a wide-spectrum noise that excites the transverse motion of the beam, which consequently produces wakefields that drive a narrow-spectrum diffusion. It is shown that this diffusion efficiently lowers the stability diagram at the frequency of the least stable coherent mode, leading to a loss of Landau damping after a latency. A semi-analytical model agrees with measurements in dedicated latency experiments performed in the LHC. This instability mechanism explains the need for a stability margin in octupole current in the LHC, relative to the amount needed to stabilize a Gaussian beam. We detail the impact of this mechanism and possible mitigations for the LHC and HL-LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA06
About •	paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 10 August 2021
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TUPAB009	SuperKEKB Optics Measurements Using Turn-by-Turn Beam Position Data	optics, closed-orbit, collider, positron	1352
	J. Keintzel, R. Tomás García CERN, Geneva, Switzerland H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, M. Tobiyama, R.J. Yang KEK, Ibaraki, Japan
	SuperKEKB, an asymmetric electron-positron collider, has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} using crab-waist collision scheme. In order to reach the design value of 6×10³⁵ \si{cm^-2s^-1} a vertical beta function at the interaction point of §I{0.3}{mm} is required, demanding unprecedented optics control. Turn-by-turn beam position data could enable fast optics measurements for rapid identification of unexpected error sources. Experiments exploring various data acquisition techniques at different squeezing steps during commissioning are presented and compared to results obtained from closed orbit distortion.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB009
About •	paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021
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TUPAB010	Impact of Bunch Current on Optics Measurements in SuperKEKB	optics, impedance, 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, impedance, simulation	1481
	T.H. Luo, K.M. Baptiste, S. De Santis, D. Li, J.W. Staples, M. Venturini LBNL, Berkeley, California, USA H.Q. Feng TUB, Beijing, People’s Republic of China
	Funding: Director, Office of Science, Office of Basic Energy Sciences, and LDRD Program of Lawrence Berkeley National Laboratory, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 A higher-harmonic rf cavity (HHC) system is required in the ALS-U storage ring to lengthen the bunches, reduce intrabeam-scattering effects, and improve Touschek beam lifetime. A 3rd harmonic, normal conducting, passive-cavity system has been chosen based on beam-dynamics requirements and cost considerations. We have explored two options for ALS-U 3HC system: a high-R/Q re-entrant cavity with waveguide HOM dampers, and a low-R/Q system with two elliptical cavities and HOM beam line absorbers. In this paper, we present the recent progress on the cavity design and related beam dynamics studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB053
About •	paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 14 August 2021
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TUPAB062	Expediting APS-U Long-Term Particle Tracking with Arbitrary Order Taylor Map	simulation, lattice, collective-effects, resonance	1505
	Y.P. Sun ANL, Lemont, Illinois, USA
	Funding: The work is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Truncated power series algebra was integrated within explicit symplectic integration to formulate an arbitrary order multivariate Taylor map for any given particle accelerator lattice. Tracking simulation performed with these Taylor maps shows good long term stability and physics accuracy. There is good agreement in long term particle tracking simulations between Taylor map and element by element tracking of APS-U lattice, when the particle is within 1 to 10 σ of stored beam. It is demonstrated that most of the lower order resonance driving terms, plus chromatic and geometric aberrations are reasonably preserved by the Taylor map approach. Last but maybe most important, the computation time is reduced by a factor of 20 to 50, when compared to symplectic integration based element by element tracking.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB062
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 29 August 2021
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TUPAB258	Impact of Coherent Beam-Beam Interaction on the Landau Damping of the Transverse Coupled-Bunch Instability	dipole, electron, coupling, proton	2062
	R. Li JLab, Newport News, Virginia, USA M. Blaskiewicz BNL, Upton, New York, 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. In the EIC design, at high average-current operation, the transverse coupled-bunch instability (TCBI) induced by the long-range transverse resistive-wall wakefield in the electron storage ring (eSR) has a fast growth rate and requires efficient mitigation. A natural mitigation mechanism is provided by the beam-beam interaction at the interaction point (IP), which gives a strong Landau damping for the TCBI in the eSR. In this study, using a simplified simulation model, we investigate how this Landau damping from the beam-beam interaction behaves when the coherent beam-beam interaction at IP is considered. Our method and results will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB258
About •	paper received ※ 21 June 2021 paper accepted ※ 01 July 2021 issue date ※ 25 August 2021
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TUPAB265	Bunch Lengthening of the HALF Storage Ring in the Presence of Passive Harmonic Cavities	cavity, storage-ring, simulation, emittance	2082
	T.L. He, Z.H. Bai, G.Y. Feng, W. Li, W.W. Li, G. Liu, L. Wang, H. Xu, S.C. Zhang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	A passive 3^rd harmonic RF system, being necessary for the Hefei Advanced Light Facility (HALF) storage ring under design, will be employed to lengthen the bunches for suppressing the intrabeam scattering and improving the beam lifetime. However, the transient beam loading due to the fundamental mode may significantly reduce the bunch lengthening. Since the scale of transient effects is proportional to R/Q, the effects of R/Q on bunch lengthening, in uniform fill pattern with the near-optimum condition fulfilled, are analyzed by multibunches multiparticles tracking simulation. It indicates that the passive superconducting harmonic cavity with a lower R/Q is preferred by HALF.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB265
About •	paper received ※ 16 May 2021 paper accepted ※ 18 June 2021 issue date ※ 20 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, impedance, 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 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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TUPAB389	High Precision Four Quadrant Converter with GaN Technology	controls, simulation, operation, power-supply	2431
	M. Incurvati, T. Margreiter, R. Stärz MCI, Innsbruck, Austria T. Riedler NTUT, Taipei City, Taiwan
	New proton therapy facilities for the cure of tumors as well as high-energy photon sources are currently being installed all around the world. In this field, the request for special power supplies for corrector, scanning, and quadrupole magnets are increasing. For these applications, mandatory requirements are high bandwidth and current stability as well as low output ripple which are conflicting constraints. A feasibility study, prototype development, measurements, and investigations on the control methodology of a wide-bandgap GaN semiconductor-based power module is presented in the paper. The developed power module features the following characteristics: Eurocard standard PCB, bipolar 4Q operation, minimum switching frequency 100 kHz, bandwidth 5 kHz, output voltage and current up to 200 V / 8 A, output current ripple <20 ppm. The enlisted characteristics make it suitable for high inductive loads requiring fast transients (scanning magnets). An RST controller will be developed and a system identification approach to the transfer function of two parallel-connected power modules will be presented along with simulations assessing the performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB389
About •	paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 21 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, impedance, 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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WEPAB122	Development of Fast and Super-Fast Kicker System for SLS 2.0 Injection	kicker, injection, impedance, electron	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 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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WEPAB123	Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring	injection, simulation, feedback, kicker	2893
	M.P. Ehrlichman, S. De Santis, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang LBNL, Berkeley, USA
	For the ALS-U project, particles will be injected from the booster to the accumulator ring utilizing an injection scheme that leaves the stored and injected particles with a non-trivial transient. This transient requires that multibunch feedback be masked for those buckets into which charge is injected. The masking significantly diminishes the damping capability of the multibunch feedback system. This problem is exacerbated by the large injection transient. The higher order resistive wall wake fields in the accumulator ring exceed the radiation damping time. To study whether the beam will remain multibunch stable during an injection cycle, a multibunch tracking simulation is used that simulates the multibunch feedback system and also pseudomode representation of resistive wall wake fields.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB123
About •	paper received ※ 20 May 2021 paper accepted ※ 01 September 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, impedance	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 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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WEPAB229	Transverse Density Pileup and Pattern Formation in Dense Ultracold Electron Beamlets under Coulomb Expansion	electron, simulation, ECR, FEL	3169
	A.J. Tencate, K. Bhuyan, B. Erdélyi Northern Illinois University, DeKalb, Illinois, USA
	Funding: This work was sponsored by the US Department of Energy Office of Science under Grant DE-SC0020241. Dynamic Coulomb expansion of dense particle bunches can lead to transverse density shock-like propagation for nonuniform bunch distributions. Furthermore, under favorable circumstances, multiple bunches in close proximity can collide without crossing to form wheel-and-spoke patterns. This process has been observed experimentally for Rubidium ions, but not yet for electrons, where the dynamics occur over far shorter length scales. We simulate the interaction of electron bunches while varying the initial transverse temperature and density profiles to determine the thresholds that characterize this pattern formation. Additionally, we consider the effects of asymmetries and the impact of a low-density halo on the overall process. The simulations are conducted using a novel high-fidelity algorithm for collisional particle dynamics.
	Poster WEPAB229 [7.411 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB229
About •	paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 13 August 2021
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WEPAB239	Effect of Chromaticity and Feedback on Transverse Head-Tail Instability	feedback, impedance, coupling, 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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WEPAB246	Influence of Different Beam Energies on the Micro-Bunching Instability	bunching, synchrotron, radiation, operation	3209
	M. Brosi, A.-S. Müller, P. Schreiber, M. Schuh KIT, Karlsruhe, Germany
	During the operation of an electron synchrotron with short electron bunches, the beam dynamics are influenced by the occurrence of the micro-bunching instability. This collective instability is caused by the self-interaction of a short electron bunch with its own emitted coherent synchrotron radiation (CSR). Above a certain threshold bunch current dynamic micro-structures start to occur on the longitudinal phase space density. The resulting dynamics depend on various parameters and were previously investigated in relation to, amongst others, the momentum compaction factor and the acceleration voltage. In this contribution, the influence of the energy of the electrons on the dynamics of the micro-bunching instability is studied based on measurements at the KIT storage ring KARA (Karlsruhe Research Accelerator).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB246
About •	paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 11 August 2021
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WEPAB250	Interplay Between Space Charge, Intra-Beam Scattering, and Synchrotron Radiation Effects	resonance, emittance, space-charge, synchrotron	3220
	M. Zampetakis, F. Antoniou, H. Bartosik, Y. Papaphilippou CERN, Geneva, Switzerland M. Zampetakis University of Crete, Heraklion, Crete, Greece
	The objective of this research is to study the interplay of synchrotron radiation, intra-beam scattering, and space charge in the vicinity of excited resonances. In this respect, two modules were developed to simulate intra-beam scattering and synchrotron radiation effects and plugged into pyORBIT to be used together with its space charge module. Different regimes of synchrotron motion were used to study the response of the beam to a lattice resonance when space charge, intra-beam scattering and synchrotron radiation are present.
	Poster WEPAB250 [0.536 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB250
About •	paper received ※ 17 May 2021 paper accepted ※ 21 July 2021 issue date ※ 25 August 2021
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WEPAB271	Numerical Modelling of the Optical Stochastic Cooling Experiment at IOTA	simulation, radiation, undulator, emittance	3273
	A.J. Dick, P. Piot Northern Illinois University, DeKalb, Illinois, USA J.D. Jarvis Fermilab, Batavia, Illinois, USA P. Piot ANL, Lemont, Illinois, USA
	Funding: CBB NSF-PHY-1549132 DOE DE-SC0018656 DOE DE-AC02-07CH11359 A proof-of-principle optical-stochastic cooling (OSC) experiment is currently in its commissioning phase at the Fermilab’s IOTA ring. In support of this experiment, we recently implemented an OSC element in the ELEGANT tracking program. The model, based on a semi-analytic description of OSC [], supports the simulation of a large number of macroparticles (10⁴-10⁶) over many turns (10⁶). This paper showcases the simulation capabilities to investigate the beam dynamics in the presence of cooling (or self-interacting radiation field in general) and quantify the impact of various sources of error (e.g. transverse and phase jitter), guide data analysis. B. Andorf, V. A. Lebedev, J. Jarvis, and P. Piot Rev. Accel. Beams 21, 100702 (2018)
	Poster WEPAB271 [1.649 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB271
About •	paper received ※ 16 May 2021 paper accepted ※ 06 July 2021 issue date ※ 13 August 2021
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THPAB021	Status of VEPP-5 Injection Complex	injection, positron, electron, linac	3796
	F.A. Emanov, A.V. Andrianov, K.V. Astrelina, V.V. Balakin, A.M. Barnyakov, A.M. Batrakov, O.V. Belikov, D.E. Berkaev, Y.M. Boimelshtain, D. Bolkhovityanov, A. Butakov, A.R. Frolov, G.V. Karpov, A.S. Kasaev, A.A. Kondakov, N.Kh. Kot, E.S. Kotov, G.Y. Kurkin, R.M. Lapik, N.N. Lebedev, A.E. Levichev, Yu.I. Maltseva, P.V. Martyshkin, S.V. Motygin, A.A. Murasev, V. Muslivets, D.A. Nikiforov, A.V. Pavlenko, A.M. Pilan, Yu.A. Rogovsky, S.L. Samoylov, A.G. Tribendis, S. Vasiliev, V.D. Yudin BINP SB RAS, Novosibirsk, Russia
	VEPP-5 injection complex is being put into operation as beam source of VEPP-2000 and VEPP-4 colliders at the end of 2016. Since then injection complex demonstrated maximum positron storage rate 1.7·10¹⁰ e+/s and stable operation at the energy of 430 MeV. Latest operation results and prospects are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB021
About •	paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 27 August 2021
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THPAB076	Effects of Chromaticity and Synchrotron Emission on Coupled-Bunch Transverse Stability	simulation, synchrotron, wakefield, coupling	3937
	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 present a theory that can compute the transverse coupled-bunch instability growth rates at any chromaticity and for any longitudinal potential provided only that the long-range wakefield varies slowly over the bunch. The theory is expressed in terms of the usual coupled-bunch eigenvalues at zero chromaticity, and when the longitudinal motion is simple harmonic our solution only requires numerical root-finding that is easy to implement and fast to solve; the more general case requires some additional calculations but is still relatively fast. The theory predicts that the coupled-bunch growth rates can be significantly reduced when the chromatic betatron tune spread is larger than the coupled-bunch growth rate at zero chromaticity. Our theoretical results are compared favorably with tracking simulations for the long-range resistive wall instability, and we also indicate how damping and diffusion from synchrotron emission can further reduce or even stabilize the dynamics.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB076
About •	paper received ※ 20 May 2021 paper accepted ※ 26 July 2021 issue date ※ 26 August 2021
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THPAB147	Preliminary Study of 500 MHz HOM-Free RF Cavity	cavity, HOM, coupling, GUI	4050
	Zh.X. Tang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	Funding: Work supported by National Natural Science Foundation of China(Grant No. U1832135 and 11805199)} In this paper, we study the microwave characteristics of 500 MHz RF cavity, including the optimization of cavity structure, the simulation design of high-order mode (HOM) absorption structure and the design of coupler. The cavity structure is simulated by CST. The absorption waveguide is designed and optimized. The coupler is designed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB147
About •	paper received ※ 09 May 2021 paper accepted ※ 16 July 2021 issue date ※ 02 September 2021
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THPAB189	New Techniques to Compute the Linear Tune	collider, simulation, betatron, experiment	4142
	G. Russo, M. Giovannozzi CERN, Geneva, Switzerland G. Franchetti GSI, Darmstadt, Germany
	Tune determination in numerical simulations is an essential aspect of nonlinear beam dynamics studies. In particular, because it allows probing whether an initial condition is close to resonance, and it enables assessment of the stability of the orbit, i.e. whether the motion is regular or chaotic. In this paper, results of recently developed techniques to obtain accurate tune computation from numerical simulation data are presented and discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB189
About •	paper received ※ 18 May 2021 paper accepted ※ 26 July 2021 issue date ※ 19 August 2021
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THPAB241	Examination of Semi-Analytic Model for Mode Coupling Instabilities	space-charge, simulation, coupling, transverse-dynamics	4278
	M.A. Balcewicz, Y. Hao FRIB, East Lansing, Michigan, USA M. Blaskiewicz BNL, Upton, New York, USA
	Funding: Work supported by by Brookhaven Science Associates, LLC under contract number 364776. A semianalytic model for studying beams at high SC tune shift is shown. It is a generalization of SWM /ABS for an arbitrary number of longitudinal phase space cycles, yielding more realistic longitudinal physics. The consequences of this generalization are explored; model is benchmarked against TRANFT *** and analytical methods. * Blaskiewicz, Michael. Phys. Rev. ST Accel. Beams, vol. 1, p. 044201, 1998. Burov, Alexey. Phys. Rev. Accel. Beams, vol. 22, p. 034202, 2019. * M. Blaskiewicz, in Proc. PAC07, Albuquerque,
	Poster THPAB241 [0.894 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB241
About •	paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 14 August 2021
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THPAB282	Optimization Design of Four-Point Vibration Isolation Support for Spallation Neutron Source Vibration Magnet	ISOL, dipole, experiment, extraction	4352
	J.S. Zhang, J.X. Chen, H.Y. He, L. Liu, R.H. Liu, C.J. Ning, G.Y. Wang, A.X. Wang, J.B. Yu, Y.J. Yu, D.H. Zhu IHEP CSNS, Guangdong Province, People’s Republic of China L. Kang IHEP, Beijing, People’s Republic of China
	Chinese spallation neutron source (CSNS) RCS of the dipole magnets by 25 Hz sinusoidal alternating current (AC) with dc bias field, because the magnet will produce eddy current effect caused by the vibration, this safe and reliable operation of the long-term impact of magnets, so need to CSNS/RCS dipole magnets, a support system for dynamic characteristic research and the performance of vibration isolation design. The mechanical model of ac dipole magnet and support system is first established, and ANSYS theoretical modal analysis and experimental modal verification are carried out. On this basis, vibration isolation parameters of the four-point support system are studied. The theoretical analysis and the experimental results of modal parameters are consistent, which shows that the ANSYS analysis model is correct and reliable. The dynamic system parameter design method established in this paper can be applied to various equipment of AC power accelerator. The final experimental verification shows that the total displacement amplitude of the isolator to the Y direction of the magnet on the magnetic support decreases by 62.3%.
	Poster THPAB282 [0.426 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB282
About •	paper received ※ 16 May 2021 paper accepted ※ 02 September 2021 issue date ※ 27 August 2021
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Paper

Title

Other Keywords

Page

MOPAB088

Beam-Based Measurement on the Performance of Ferrite Dampers in an In-Vacuum Undulator

HOM, feedback, radiation, vacuum

331

K. Tian, A. Ringwall, J.J. Sebek
SLAC, Menlo Park, California, USA

In this paper, we first present the tracking studies for SPEAR3 with the new BL17 ID and estimate its impact on the dynamic aperture of the low emittance lattice. Then the ferrite dampers installations in the device is briefly reviewed. After that, we will show that, based on beam-based measurements, the performance of the dampers is as being expected from earlier numerical studies.

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paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 24 August 2021

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MOPAB112

A Modified Hybrid 6BA Lattice for the HALF Storage Ring

lattice, emittance, storage-ring, SRF

407

Z.H. Bai, G.Y. Feng, T.L. He, W. Li, W.W. Li, G. Liu, Z.L. Ren, L. Wang, P.H. Yang, S.C. Zhang, T. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

In this paper, we propose a modified hybrid 6BA lattice as the baseline lattice of the Hefei Advanced Light Facility (HALF) storage ring. Similar to the Diamond-II lattice, the proposed lattice cell has one long straight section and one mid-straight section; but the two bend units adjacent to the mid-straight are LGB/RB units (LGB: longitudinal gradient bend, RB: reverse bend), which can give both lower emittance and shorter damping times. The designed HALF storage ring, with an energy of 2.2 GeV and 20 lattice cells, has a natural emittance of about 85 pm·rad.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB112

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paper received ※ 15 May 2021 paper accepted ※ 20 May 2021 issue date ※ 01 September 2021

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MOPAB212

3-D Quantum Lifetime

simulation, electron, radiation, emittance

700

H. Zhao, M. Blaskiewicz
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 quantum lifetime of electron beam in storage rings is defined by the particle loss that caused by the aperture limitation. Based on the equilibrium beam distribution produced by radiation damping and quantum excitation, the 1-d quantum lifetime has been well studied by A. Piwinski. In this paper, we give the derivation of the 3-d quantum lifetime, which can be applied to the machines with elliptical aperture and momentum acceptance.

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paper received ※ 04 June 2021 paper accepted ※ 21 June 2021 issue date ※ 16 August 2021

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MOPAB240

Estimates of Damped Equilibrium Energy Spread and Emittance in a Dual Energy Storage Ring

emittance, storage-ring, photon, radiation

774

B. Dhital, G.A. Krafft
ODU, Norfolk, Virginia, USA
Y.S. Derbenev, D. Douglas, A. Hutton, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, and Office of Nuclear Physics under Contracts DE-AC05-06OR23177 and DE-AC02-06CH11357. / Jefferson Lab EIC Fellowship2020.
A dual energy storage ring design consists of two loops at markedly different energies. As in a single-energy storage ring, the linear optics in the ring design may be used to determine the damped equilibrium emittance and energy spread. Because the individual radiation events in the two rings are different and independent, we can provide analytical estimates of the damping times in a dual energy storage ring. Using the damping times, the values of damped energy spread, and emittance can be determined for a range of parameters related to lattice design and rings energies. We present analytical calculations along with simulation results to estimate the values of damped energy spread and emittance in a dual energy storage ring. We note that the damping time tends to be dominated by the damping time of the high energy ring in cases where the energy of the high energy rings is significantly greater than that of the low energy ring.

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paper received ※ 17 May 2021 paper accepted ※ 27 May 2021 issue date ※ 13 August 2021

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MOPAB343

Optimization of the Parasitic-Mode Damping on the 1.5 GHz TM020-type Harmonic Cavity

cavity, impedance, 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).

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 01 September 2021

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TUXA06

Loss of Transverse Landau Damping by Diffusion in High-Energy Hadron Colliders

wakefield, hadron, collider, feedback

1286

S.V. Furuseth, X. Buffat
CERN, Geneva, Switzerland
S.V. Furuseth
EPFL, Lausanne, Switzerland

Circular hadron colliders rely on Landau damping to stabilize the beams. Landau damping depends strongly on the bunch distribution, which is often assumed to be Gaussian in the transverse planes. In this paper, we introduce and explain an instability mechanism observed in the LHC, where Landau damping is eventually lost due to a diffusion that modifies the transverse bunch distribution. The mechanism is caused by a wide-spectrum noise that excites the transverse motion of the beam, which consequently produces wakefields that drive a narrow-spectrum diffusion. It is shown that this diffusion efficiently lowers the stability diagram at the frequency of the least stable coherent mode, leading to a loss of Landau damping after a latency. A semi-analytical model agrees with measurements in dedicated latency experiments performed in the LHC. This instability mechanism explains the need for a stability margin in octupole current in the LHC, relative to the amount needed to stabilize a Gaussian beam. We detail the impact of this mechanism and possible mitigations for the LHC and HL-LHC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA06

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paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 10 August 2021

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TUPAB009

SuperKEKB Optics Measurements Using Turn-by-Turn Beam Position Data

optics, closed-orbit, collider, positron

1352

J. Keintzel, R. Tomás García
CERN, Geneva, Switzerland
H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, M. Tobiyama, R.J. Yang
KEK, Ibaraki, Japan

SuperKEKB, an asymmetric electron-positron collider, has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} using crab-waist collision scheme. In order to reach the design value of 6×10³⁵ \si{cm^-2s^-1} a vertical beta function at the interaction point of §I{0.3}{mm} is required, demanding unprecedented optics control. Turn-by-turn beam position data could enable fast optics measurements for rapid identification of unexpected error sources. Experiments exploring various data acquisition techniques at different squeezing steps during commissioning are presented and compared to results obtained from closed orbit distortion.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB009

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paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021

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TUPAB010

Impact of Bunch Current on Optics Measurements in SuperKEKB

optics, impedance, 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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB010

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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, impedance, simulation

1481

T.H. Luo, K.M. Baptiste, S. De Santis, D. Li, J.W. Staples, M. Venturini
LBNL, Berkeley, California, USA
H.Q. Feng
TUB, Beijing, People’s Republic of China

Funding: Director, Office of Science, Office of Basic Energy Sciences, and LDRD Program of Lawrence Berkeley National Laboratory, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A higher-harmonic rf cavity (HHC) system is required in the ALS-U storage ring to lengthen the bunches, reduce intrabeam-scattering effects, and improve Touschek beam lifetime. A 3rd harmonic, normal conducting, passive-cavity system has been chosen based on beam-dynamics requirements and cost considerations. We have explored two options for ALS-U 3HC system: a high-R/Q re-entrant cavity with waveguide HOM dampers, and a low-R/Q system with two elliptical cavities and HOM beam line absorbers. In this paper, we present the recent progress on the cavity design and related beam dynamics studies.

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paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 14 August 2021

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TUPAB062

Expediting APS-U Long-Term Particle Tracking with Arbitrary Order Taylor Map

simulation, lattice, collective-effects, resonance

1505

Y.P. Sun
ANL, Lemont, Illinois, USA

Funding: The work is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Truncated power series algebra was integrated within explicit symplectic integration to formulate an arbitrary order multivariate Taylor map for any given particle accelerator lattice. Tracking simulation performed with these Taylor maps shows good long term stability and physics accuracy. There is good agreement in long term particle tracking simulations between Taylor map and element by element tracking of APS-U lattice, when the particle is within 1 to 10 σ of stored beam. It is demonstrated that most of the lower order resonance driving terms, plus chromatic and geometric aberrations are reasonably preserved by the Taylor map approach. Last but maybe most important, the computation time is reduced by a factor of 20 to 50, when compared to symplectic integration based element by element tracking.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB062

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 29 August 2021

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TUPAB258

Impact of Coherent Beam-Beam Interaction on the Landau Damping of the Transverse Coupled-Bunch Instability

dipole, electron, coupling, proton

2062

R. Li
JLab, Newport News, Virginia, USA
M. Blaskiewicz
BNL, Upton, New York, 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.
In the EIC design, at high average-current operation, the transverse coupled-bunch instability (TCBI) induced by the long-range transverse resistive-wall wakefield in the electron storage ring (eSR) has a fast growth rate and requires efficient mitigation. A natural mitigation mechanism is provided by the beam-beam interaction at the interaction point (IP), which gives a strong Landau damping for the TCBI in the eSR. In this study, using a simplified simulation model, we investigate how this Landau damping from the beam-beam interaction behaves when the coherent beam-beam interaction at IP is considered. Our method and results will be presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB258

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paper received ※ 21 June 2021 paper accepted ※ 01 July 2021 issue date ※ 25 August 2021

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TUPAB265

Bunch Lengthening of the HALF Storage Ring in the Presence of Passive Harmonic Cavities

cavity, storage-ring, simulation, emittance

2082

T.L. He, Z.H. Bai, G.Y. Feng, W. Li, W.W. Li, G. Liu, L. Wang, H. Xu, S.C. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

A passive 3^rd harmonic RF system, being necessary for the Hefei Advanced Light Facility (HALF) storage ring under design, will be employed to lengthen the bunches for suppressing the intrabeam scattering and improving the beam lifetime. However, the transient beam loading due to the fundamental mode may significantly reduce the bunch lengthening. Since the scale of transient effects is proportional to R/Q, the effects of R/Q on bunch lengthening, in uniform fill pattern with the near-optimum condition fulfilled, are analyzed by multibunches multiparticles tracking simulation. It indicates that the passive superconducting harmonic cavity with a lower R/Q is preferred by HALF.

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paper received ※ 16 May 2021 paper accepted ※ 18 June 2021 issue date ※ 20 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, impedance, 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 TUPAB341 [1.580 MB]

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 22 August 2021

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TUPAB389

High Precision Four Quadrant Converter with GaN Technology

controls, simulation, operation, power-supply

2431

M. Incurvati, T. Margreiter, R. Stärz
MCI, Innsbruck, Austria
T. Riedler
NTUT, Taipei City, Taiwan

New proton therapy facilities for the cure of tumors as well as high-energy photon sources are currently being installed all around the world. In this field, the request for special power supplies for corrector, scanning, and quadrupole magnets are increasing. For these applications, mandatory requirements are high bandwidth and current stability as well as low output ripple which are conflicting constraints. A feasibility study, prototype development, measurements, and investigations on the control methodology of a wide-bandgap GaN semiconductor-based power module is presented in the paper. The developed power module features the following characteristics: Eurocard standard PCB, bipolar 4Q operation, minimum switching frequency 100 kHz, bandwidth 5 kHz, output voltage and current up to 200 V / 8 A, output current ripple <20 ppm. The enlisted characteristics make it suitable for high inductive loads requiring fast transients (scanning magnets). An RST controller will be developed and a system identification approach to the transfer function of two parallel-connected power modules will be presented along with simulations assessing the performance.

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paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 21 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, impedance, 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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB090

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paper received ※ 17 May 2021 paper accepted ※ 22 June 2021 issue date ※ 20 August 2021

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WEPAB122

Development of Fast and Super-Fast Kicker System for SLS 2.0 Injection

kicker, injection, impedance, electron

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 WEPAB122 [1.371 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB122

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 28 August 2021

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WEPAB123

Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring

injection, simulation, feedback, kicker

2893

M.P. Ehrlichman, S. De Santis, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang
LBNL, Berkeley, USA

For the ALS-U project, particles will be injected from the booster to the accumulator ring utilizing an injection scheme that leaves the stored and injected particles with a non-trivial transient. This transient requires that multibunch feedback be masked for those buckets into which charge is injected. The masking significantly diminishes the damping capability of the multibunch feedback system. This problem is exacerbated by the large injection transient. The higher order resistive wall wake fields in the accumulator ring exceed the radiation damping time. To study whether the beam will remain multibunch stable during an injection cycle, a multibunch tracking simulation is used that simulates the multibunch feedback system and also pseudomode representation of resistive wall wake fields.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB123

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paper received ※ 20 May 2021 paper accepted ※ 01 September 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, impedance

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 WEPAB134 [1.079 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB134

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paper received ※ 17 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 August 2021

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WEPAB229

Transverse Density Pileup and Pattern Formation in Dense Ultracold Electron Beamlets under Coulomb Expansion

electron, simulation, ECR, FEL

3169

A.J. Tencate, K. Bhuyan, B. Erdélyi
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work was sponsored by the US Department of Energy Office of Science under Grant DE-SC0020241.
Dynamic Coulomb expansion of dense particle bunches can lead to transverse density shock-like propagation for nonuniform bunch distributions. Furthermore, under favorable circumstances, multiple bunches in close proximity can collide without crossing to form wheel-and-spoke patterns. This process has been observed experimentally for Rubidium ions, but not yet for electrons, where the dynamics occur over far shorter length scales. We simulate the interaction of electron bunches while varying the initial transverse temperature and density profiles to determine the thresholds that characterize this pattern formation. Additionally, we consider the effects of asymmetries and the impact of a low-density halo on the overall process. The simulations are conducted using a novel high-fidelity algorithm for collisional particle dynamics.

Poster WEPAB229 [7.411 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB229

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 13 August 2021

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WEPAB239

Effect of Chromaticity and Feedback on Transverse Head-Tail Instability

feedback, impedance, coupling, 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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB239

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 12 August 2021

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WEPAB246

Influence of Different Beam Energies on the Micro-Bunching Instability

bunching, synchrotron, radiation, operation

3209

M. Brosi, A.-S. Müller, P. Schreiber, M. Schuh
KIT, Karlsruhe, Germany

During the operation of an electron synchrotron with short electron bunches, the beam dynamics are influenced by the occurrence of the micro-bunching instability. This collective instability is caused by the self-interaction of a short electron bunch with its own emitted coherent synchrotron radiation (CSR). Above a certain threshold bunch current dynamic micro-structures start to occur on the longitudinal phase space density. The resulting dynamics depend on various parameters and were previously investigated in relation to, amongst others, the momentum compaction factor and the acceleration voltage. In this contribution, the influence of the energy of the electrons on the dynamics of the micro-bunching instability is studied based on measurements at the KIT storage ring KARA (Karlsruhe Research Accelerator).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB246

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paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 11 August 2021

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WEPAB250

Interplay Between Space Charge, Intra-Beam Scattering, and Synchrotron Radiation Effects

resonance, emittance, space-charge, synchrotron

3220

M. Zampetakis, F. Antoniou, H. Bartosik, Y. Papaphilippou
CERN, Geneva, Switzerland
M. Zampetakis
University of Crete, Heraklion, Crete, Greece

The objective of this research is to study the interplay of synchrotron radiation, intra-beam scattering, and space charge in the vicinity of excited resonances. In this respect, two modules were developed to simulate intra-beam scattering and synchrotron radiation effects and plugged into pyORBIT to be used together with its space charge module. Different regimes of synchrotron motion were used to study the response of the beam to a lattice resonance when space charge, intra-beam scattering and synchrotron radiation are present.

Poster WEPAB250 [0.536 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB250

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paper received ※ 17 May 2021 paper accepted ※ 21 July 2021 issue date ※ 25 August 2021

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WEPAB271

Numerical Modelling of the Optical Stochastic Cooling Experiment at IOTA

simulation, radiation, undulator, emittance

3273

A.J. Dick, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
J.D. Jarvis
Fermilab, Batavia, Illinois, USA
P. Piot
ANL, Lemont, Illinois, USA

Funding: CBB NSF-PHY-1549132 DOE DE-SC0018656 DOE DE-AC02-07CH11359
A proof-of-principle optical-stochastic cooling (OSC) experiment is currently in its commissioning phase at the Fermilab’s IOTA ring. In support of this experiment, we recently implemented an OSC element in the ELEGANT tracking program. The model, based on a semi-analytic description of OSC [*], supports the simulation of a large number of macroparticles (10⁴-10⁶) over many turns (10⁶). This paper showcases the simulation capabilities to investigate the beam dynamics in the presence of cooling (or self-interacting radiation field in general) and quantify the impact of various sources of error (e.g. transverse and phase jitter), guide data analysis.
* B. Andorf, V. A. Lebedev, J. Jarvis, and P. Piot Rev. Accel. Beams 21, 100702 (2018)

Poster WEPAB271 [1.649 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB271

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paper received ※ 16 May 2021 paper accepted ※ 06 July 2021 issue date ※ 13 August 2021

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THPAB021

Status of VEPP-5 Injection Complex

injection, positron, electron, linac

3796

F.A. Emanov, A.V. Andrianov, K.V. Astrelina, V.V. Balakin, A.M. Barnyakov, A.M. Batrakov, O.V. Belikov, D.E. Berkaev, Y.M. Boimelshtain, D. Bolkhovityanov, A. Butakov, A.R. Frolov, G.V. Karpov, A.S. Kasaev, A.A. Kondakov, N.Kh. Kot, E.S. Kotov, G.Y. Kurkin, R.M. Lapik, N.N. Lebedev, A.E. Levichev, Yu.I. Maltseva, P.V. Martyshkin, S.V. Motygin, A.A. Murasev, V. Muslivets, D.A. Nikiforov, A.V. Pavlenko, A.M. Pilan, Yu.A. Rogovsky, S.L. Samoylov, A.G. Tribendis, S. Vasiliev, V.D. Yudin
BINP SB RAS, Novosibirsk, Russia

VEPP-5 injection complex is being put into operation as beam source of VEPP-2000 and VEPP-4 colliders at the end of 2016. Since then injection complex demonstrated maximum positron storage rate 1.7·10¹⁰ e+/s and stable operation at the energy of 430 MeV. Latest operation results and prospects are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB021

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paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 27 August 2021

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THPAB076

Effects of Chromaticity and Synchrotron Emission on Coupled-Bunch Transverse Stability

simulation, synchrotron, wakefield, coupling

3937

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 present a theory that can compute the transverse coupled-bunch instability growth rates at any chromaticity and for any longitudinal potential provided only that the long-range wakefield varies slowly over the bunch. The theory is expressed in terms of the usual coupled-bunch eigenvalues at zero chromaticity, and when the longitudinal motion is simple harmonic our solution only requires numerical root-finding that is easy to implement and fast to solve; the more general case requires some additional calculations but is still relatively fast. The theory predicts that the coupled-bunch growth rates can be significantly reduced when the chromatic betatron tune spread is larger than the coupled-bunch growth rate at zero chromaticity. Our theoretical results are compared favorably with tracking simulations for the long-range resistive wall instability, and we also indicate how damping and diffusion from synchrotron emission can further reduce or even stabilize the dynamics.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB076

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paper received ※ 20 May 2021 paper accepted ※ 26 July 2021 issue date ※ 26 August 2021

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THPAB147

Preliminary Study of 500 MHz HOM-Free RF Cavity

cavity, HOM, coupling, GUI

4050

Zh.X. Tang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China(Grant No. U1832135 and 11805199)}
In this paper, we study the microwave characteristics of 500 MHz RF cavity, including the optimization of cavity structure, the simulation design of high-order mode (HOM) absorption structure and the design of coupler. The cavity structure is simulated by CST. The absorption waveguide is designed and optimized. The coupler is designed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB147

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paper received ※ 09 May 2021 paper accepted ※ 16 July 2021 issue date ※ 02 September 2021

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THPAB189

New Techniques to Compute the Linear Tune

collider, simulation, betatron, experiment

4142

G. Russo, M. Giovannozzi
CERN, Geneva, Switzerland
G. Franchetti
GSI, Darmstadt, Germany

Tune determination in numerical simulations is an essential aspect of nonlinear beam dynamics studies. In particular, because it allows probing whether an initial condition is close to resonance, and it enables assessment of the stability of the orbit, i.e. whether the motion is regular or chaotic. In this paper, results of recently developed techniques to obtain accurate tune computation from numerical simulation data are presented and discussed in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB189

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paper received ※ 18 May 2021 paper accepted ※ 26 July 2021 issue date ※ 19 August 2021

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THPAB241

Examination of Semi-Analytic Model for Mode Coupling Instabilities

space-charge, simulation, coupling, transverse-dynamics

4278

M.A. Balcewicz, Y. Hao
FRIB, East Lansing, Michigan, USA
M. Blaskiewicz
BNL, Upton, New York, USA

Funding: Work supported by by Brookhaven Science Associates, LLC under contract number 364776.
A semianalytic model for studying beams at high SC tune shift is shown. It is a generalization of SWM ** /ABS ** for an arbitrary number of longitudinal phase space cycles, yielding more realistic longitudinal physics. The consequences of this generalization are explored; model is benchmarked against TRANFT *** and analytical methods.
* Blaskiewicz, Michael. Phys. Rev. ST Accel. Beams, vol. 1, p. 044201, 1998.
** Burov, Alexey. Phys. Rev. Accel. Beams, vol. 22, p. 034202, 2019.
*** M. Blaskiewicz, in Proc. PAC07, Albuquerque,

Poster THPAB241 [0.894 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB241

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 14 August 2021

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THPAB282

Optimization Design of Four-Point Vibration Isolation Support for Spallation Neutron Source Vibration Magnet

ISOL, dipole, experiment, extraction

4352

J.S. Zhang, J.X. Chen, H.Y. He, L. Liu, R.H. Liu, C.J. Ning, G.Y. Wang, A.X. Wang, J.B. Yu, Y.J. Yu, D.H. Zhu
IHEP CSNS, Guangdong Province, People’s Republic of China
L. Kang
IHEP, Beijing, People’s Republic of China

Chinese spallation neutron source (CSNS) RCS of the dipole magnets by 25 Hz sinusoidal alternating current (AC) with dc bias field, because the magnet will produce eddy current effect caused by the vibration, this safe and reliable operation of the long-term impact of magnets, so need to CSNS/RCS dipole magnets, a support system for dynamic characteristic research and the performance of vibration isolation design. The mechanical model of ac dipole magnet and support system is first established, and ANSYS theoretical modal analysis and experimental modal verification are carried out. On this basis, vibration isolation parameters of the four-point support system are studied. The theoretical analysis and the experimental results of modal parameters are consistent, which shows that the ANSYS analysis model is correct and reliable. The dynamic system parameter design method established in this paper can be applied to various equipment of AC power accelerator. The final experimental verification shows that the total displacement amplitude of the isolator to the Y direction of the magnet on the magnetic support decreases by 62.3%.

Poster THPAB282 [0.426 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB282

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paper received ※ 16 May 2021 paper accepted ※ 02 September 2021 issue date ※ 27 August 2021

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