| Paper | Title | Other Keywords | Page |
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| MOPGW039 | Investigation of Longitudinal Beam Dynamics With Harmonic Cavities by Using the Code Mbtrack | cavity, impedance, operation, synchrotron | 178 |
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In diffraction-limited light sources, the study of collective effects is essential. With harmonic cavities (HCs), the ’flat potential condition’ can be achieved, lengthening the bunch by a factor of ~5. However, the effective rf voltage seen by the beam becomes sensitive to both positions and distributions of all bunches, as the beam-induced voltage of both HCs and fundamental cavities (FCs) contribute. In addition, when there are empty buckets, the transient beam loading induces considerable variations of the rf voltage impacting the beam performance*. Here the use of analytical approaches is difficult. Then we introduced the new functions to treat the high-Q resonators driven by either or both of the beams and external generators to the code mbtrack**. Using these features, various operating conditions with arbitrary fill patterns can be studied; coupled bunch instability induced by HOMs of the cavity, Robinson instabilities and general beam dynamics with HCs. The growth rates of the instabilities described above are compared with analytical results. The ring performance with HCs in several fill patterns shall be also reported.
* N.Yamamoto, et al., PRAB, 21, 012001 (2018). **G. Skripka, et al., NIM A806, 221 (2016). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW039 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| MOPGW084 | Beam Loading Compensation for the Future Circular Hadron-Hadron Collider (FCC-hh) | cavity, hadron, collider, impedance | 301 |
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| The power consumption of the rf system can be minimised by optimising the cavity detuning and the loaded quality factor. In high-current accelerators, the presence of gaps in the filling results in a modulation of the cavity voltage along the ring (transient beam loading) and as a consequence a spread in the bunch parameters. In addition longitudinal coupled-bunch instabilities can appear, caused by the cavity impedance at the fundamental. Both issues can be mitigated by using an rf feedback around the amplifier and cavity, a technique used in many high intensity machines including the Large Hadron Collider (LHC). Compared to the LHC machine, the energy increase and the radiation loss for the Future Circular hadron-hadron Collider (FCC-hh) will be larger, resulting in a synchronous phase deviating significantly from 180 degrees. The solutions adopted for the LHC must therefore be revisited. This paper evaluates several beam loading compensation schemes for this machine. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW084 | ||
| About • | paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| MOPGW091 | Capture and Flat-Bottom Losses in the CERN SPS | injection, emittance, impedance, feedback | 327 |
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| Particle losses on the flat bottom of the SPS, the last accelerator in the injector chain of the LHC at CERN, are a strong limitation for reaching the high intensities required by the high luminosity upgrade of the LHC. Two contributions to these losses are investigated in this paper. The first losses occur during the PS-to-SPS bunch-to-bucket transfer, since the bunch rotation in the PS creates halo particles and the bunch does not completely fit into the SPS RF-bucket. The effect of longitudinal shaving in the PS on the beam transmission was recently tested. At high intensities, further capture losses are caused by beam loading in the traveling wave RF system of the SPS, which is partially compensated by the LLRF system, in particular by one-turn delay feedback. While the feedforward system reduces the capture losses, it also increases the losses along the flat bottom due to the RF noise. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW091 | ||
| About • | paper received ※ 09 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019 | ||
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| MOPMP008 | Electron Driven Positron Source for International Linear Collider | positron, linac, simulation, cavity | 439 |
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Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI) To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented. To linear colliders, huge amount of positron has to be provided comparing to ring colliders, because the beam is dumped after the collision. Electron Driven ILC Positron source has been designed as a technical backup of the undulator position source including the beam loading effect, etc. The design of the detail will be presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP008 | ||
| About • | paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| MOPRB057 | An Approach to Alleviating Heavy Beam Loading Effect on the Synchrotron Machine Through the Existed Low Level RF Feedback System | cavity, feedback, impedance, simulation | 697 |
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| To pursue the highest brightness and intensity of the synchrotron light, the synchrotron machines are pushed to operate with as high as possible of the beam current. To suppress the heavy beam loading effects, the direct RF feedback is currently widely used. This paper provides an another approach to alleviating the heavy beam loading effects on machine operation. Different from the direct RF feedback technique, this approach need not add additional feedback loop to the existed RF feedback system. Applying a proper angle rotation to the I-Q error signals of the cavity voltage, before entering the existed feedback loop, is the only action required in this approach. The paper will explain the working mechanism and investigate the behaviour of this approach, through an example case, with numerical simulation. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB057 | ||
| About • | paper received ※ 16 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| MOPRB080 | Transient Beam Loading and Mitigation in JLEIC Collider Rings | electron, cavity, klystron, luminosity | 758 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, with additional support from U.S. DOE Award Number DE-SC-0019287 The Jefferson Lab Electron-Ion Collider (JLEIC) is an asymmetric high luminosity ring-ring collider proposed as the next major R&D facility for the nuclear physics community. Both of JLEIC’s electron and ion collider rings have high beam current with gaps serving the pur-poses of beam abort, ion clearing, etc. Such a time-varying beam loading in the RF cavities would generate modulation in cavity RF phase/voltage, causing cyclic shift of collision point and potential luminosity loss. We studied a few approaches to mitigate the RF phase modu-lation and IP shift, such as correcting the RF phase/voltage modulation with traditional LLRF feed-back, one-turn feedback (OTFB), or RF feedforward (FF); optimizing the bunch fill pattern to limit the RF phase/voltage modulation to a small fraction of the bunch trains in the collider ring; or matching the RF phase modulation in the two rings. The preliminary re-sults are discussed in this paper. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB080 | ||
| About • | paper received ※ 23 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019 | ||
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| TUPGW078 | Harmonic Cavity Design Choice for Lifetime Increase in Diamond-II | cavity, simulation, lattice, storage-ring | 1585 |
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| The ongoing trend towards synchrotron light storage rings with ultralow emittance leads to a requirement for strong magnet gradients, which reduce the dynamic aperture and thus the Touschek lifetime of the machine. This is also the case for the planned upgrade of the Diamond Light Source. One option to increase the Touschek lifetime is to lengthen the electron bunches with a harmonic cavity operated close to a harmonic of the fundamental RF frequency. This paper presents studies of a harmonic cavity for Diamond-II with the focus on maximising the lifetime increase. It is foreseen that the ring will have to operate with a gap in the fill pattern to avoid instabilities and therefore multiparticle tracking was used to determine the effect on stability and lifetime for various cavity parameters taking into account transient beam loading. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW078 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS045 | Simulation Analysis of LLRF Feedforward Compensation to Beam Loading for CiADS LINAC | cavity, simulation, controls, feedback | 2027 |
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| A simulation is coded to calculate the beam loading in the cavity of CiADS and the response of the LLRF system. In the pulse operating mode, the fluctuation of amplitude and phase of the cavity field contributed by the transient beam loading is traced. During the simulation the effect of beam current fluctuation, and timing jitter were determined. The deviation margin of relational parameters is lined out to meet the requirement for cavity stability with amplitude 0.1% and phase 0.1°. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS045 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB044 | Microphonics Simulation and Parameters Design of the SRF Cavities for CiADS | cavity, simulation, linac, proton | 2903 |
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| The CiADS (China initiative Accelerator Driven System) proton Linac is designed to accelerate CW beams of up to 500 MeV and 5mA, which is delivered to the spallation target. Since the beam power will eventually reach 2.5 MW, the beam loss should be restricted, which is sensitive to the SC cavity stability. On CW operating mode, the main perturbation to the cavity is microphonics. This paper will describe a set of tools developed to simulate performance of the cavity and its LLRF control system in order to ensure proper cavity operation under microphonics. The simulation tools describe a relationship between microphonics and the RF parameters. The microphonics effect to the cavity is simulated. The tolerated intensity of microphonics is determined by simulation, in order to satisfy the stability of amplitude and phase with 0.1% and 0.1 degree respectively. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB044 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| WEPTS016 | Longitudinal Beam Manipulation by RF Phase Modulation at the Karlsruhe Research Accelerator | simulation, experiment, synchrotron, cavity | 3123 |
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| At the storage ring KARA (Karlsruhe Research Accelerator) of the Karlsruhe Institute of Technology (KIT) we have installed a function for the RF phase modulation to the low-level RF system. By choosing proper conditions of the modulation, the electron distribution on the longitudinal phase space can be changed in a large range. There are several applications of this longitudinal manipulation to the accelerator operation: an improvement of the beam lifetime and suppression of collective instabilities. We have performed tracking simulations for the longitudinal beam manipulation by the RF phase modulation. The results have implied that the longitudinal phase space distribution strongly depends on the modulation frequency. We have also performed experiments, which aimed at improving the beam lifetime in 2.5 GeV KARA multi-bunch operations. In this contribution, the low-level RF system at KARA, the simulation and experimental results under the RF phase modulation will be presented. As one of the options of the modulation, we consider manipulation of the internal fine structure in the longitudinal phase space by the modulation. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS016 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| THPRB011 | Norm-optimal Iterative Learning Control to Cancel Beam Loading Effect on the Accelerating Field | controls, cavity, simulation, feedback | 3824 |
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| Iterative learning control (ILC) is an open loop control strategy that improves the performance of a repetitive system through learning from previous iterations. ILC can be used to compensate for a repetitive disturbance like the beam loading effect in resonators. In this work, we aim to use norm-optimal ILC to cancel beam loading effect. Norm-optimal ILC updates the control signal with the goal of minimizing a performance index, which results in monotonic convergence. Simulation results show that this controller improves beam loading compensation compared to a PI controller. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB011 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019 | ||
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| THPRB049 | MODELING AND SIMULATION FOR MULTI-FEEDING CAVITY WITHOUT BEAM LOADING | cavity, electron, impedance, simulation | 3921 |
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| The Multi-feeding cavity usually be applied in super-conducting and normal-conducting RF cavity. The differences between multiple input couplers in coupler coefficient, incident power and phase will cause the cavity field stabilities can not meet the requirements. For explore the influences of these differences and develop equations for measurement, a multi-feeding LCR transient model was developed. As two-feeding cavity, the VHF photocathode electron gun was model and simulated in this paper. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB049 | ||
| About • | paper received ※ 06 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPTS075 | Performance Tests of a Digital Low-Level Rf-System at the TPS | LLRF, cavity, storage-ring, controls | 4292 |
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| A digital low-level RF (DLLRF) control system for the cavity gap voltage is now common throughout the world. At the Taiwan Photon Source (TPS) we installed and operated a DLLRF in the booster ring in 2018 successfully and plan to install it also in the storage ring in 2019. Operational and beam loading tests of the DLLRF at the storage ring are ongoing. The performance of the DLLRF in the presence of a large number of 60 Hz harmonics and its stability for gap voltage and phase will be discussed. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS075 | ||
| About • | paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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