Architectures and Algorithms for Control and Diagnostics of Coupled-Bunch Instabilities in Circular Accelerators

Teytelman, D.

doi:10.2172/815292

Cited by 9 publications

(4 citation statements)

References 47 publications

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“…The technique for measuring the growth/damping rates in PEP-II operations were first presented by S. Prabhakar [10] and then refined by D. Teytelman [4]. Using a related technique, naturally stable modes were studied by injecting a narrowband excitation to drive specific beam modes for a short period of time and observing the resulting natural decay transients.…”

Section: Growth Rate Measurement Techniquesmentioning

confidence: 99%

“…to observe the variance of the measured growth rates which necessitate the margins defined above. 4 In the same plot, simulated data describing the performance of the HER operating at 18.5 MV is presented (green). This is the highest gap voltage that was considered for run 7 and shows a significant reduction of the growth rates.…”

Section: Llrf System Imperfectionsmentioning

confidence: 99%

“…The installation of klystron driver amplifiers with a more linear response was one of the technical 4 A large component of the measurement scatter reflects actual variations of the effectiveness of the impedance control techniques over time. At any given operating point, the system is continuously perturbed and the instantaneous effective impedance fluctuates due to klystron power supply ripple, line transients, beam signals, etc.…”

Section: Llrf System Imperfectionsmentioning

confidence: 99%

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Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators

Mastoridis

2010

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The longitudinal beam dynamics in circular accelerators is mainly defined by the interaction of the beam current with the accelerating Radio Frequency (RF) stations.For stable operation, Low Level RF (LLRF) feedback systems are employed to reduce coherent instabilities and regulate the accelerating voltage. The LLRF system design has implications for the dynamics and stability of the closed-loop RF systems as well as for the particle beam, and is very sensitive to the operating range of accelerator currents and energies. Stability of the RF loop and the beam are necessary conditions for reliable machine operation.This dissertation describes theoretical formalisms and models that determine the longitudinal beam dynamics based on the LLRF implementation, time domain simulations that capture the dynamic behavior of the RF station-beam interaction, and measurements from the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC) that validate the models and simulations. These models and simulations are structured to capture the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They also provide the opportunity to study diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven instabilities and single bunch longitudinal emittance growth.Coupled-bunch instabilities and RF station power were the performance limiting effects for PEP-II. The sensitivity of the instabilities to individual LLRF parameters, the effectiveness of alternative operational algorithms, and the possible tradeoffs between RF loop and beam stability were studied. New algorithms were implemented, iv with significant performance improvement leading to a world record current during the last PEP-II run of 3212 mA for the Low Energy Ring.Longitudinal beam emittance growth due to RF noise is a major concern for LHC. Simulations studies and measurements were conducted that clearly show the correlation between RF noise and longitudinal bunch emittance, identify the major LLRF noise contributions, and determine the RF component dominating this effect.With these results, LHC upgrades and alternative algorithms are evaluated to reduce longitudinal emittance growth during operations.The applications of this work are described with regard to future machines and analysis of new technical implementations, as well as to possible future work which would continue the directions of this dissertation.v

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Section: Growth Rate Measurement Techniquesmentioning

confidence: 99%

Section: Llrf System Imperfectionsmentioning

confidence: 99%

Section: Llrf System Imperfectionsmentioning

confidence: 99%

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Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators

Mastoridis

2010

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“…Bunch signals are then transformed into the even-fill eigenmode (EFEM) basis. Using joint estimation of modal eigenvalues we extract modal growth rates and oscillation frequencies from the open and closed-loop sections of the transients [6].…”

Section: Growth and Damping Rate Measurementsmentioning

confidence: 99%

Measurements of Transverse Coupled-Bunch Instabilities in PEP-II

Teytelman¹

2005

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At the design currents the PEP-II High and Low Energy Rings operate above the coupled-bunch instability thresholds in horizontal and vertical planes. Both machines have used analog bunch-by-bunch feedback systems to stabilize the beams since commissioning. Here we present a measurement technique that uses the capabilities of the PEP-II programmable digital longitudinal feedback system to provide transient diagnostics in X or Y directions. This technique allows one to measure instability growth or damping rates as well as oscillation frequencies in both open-loop and closed-loop conditions. Based on these measurements the configuration of the relevant transverse feedback channel can be optimized. The technique will be illustrated with instability measurements and feedback optimization examples. Comparisons of the measured modal patterns and growth rates to the theoretical predictions will be presented.

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Coupled-Bunch Instabilities in Storage Rings and Feedback Systems

Teytelman¹

2020

Synchrotron Light Sources and Free-Electron Lasers

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Architectures and Algorithms for Control and Diagnostics of Coupled-Bunch Instabilities in Circular Accelerators

Cited by 9 publications

References 47 publications

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators

Measurements of Transverse Coupled-Bunch Instabilities in PEP-II

Coupled-Bunch Instabilities in Storage Rings and Feedback Systems

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