Analysis of DSP-based longitudinal feedback system: trials at SPEAR and ALS

Hindi, H.; Eisen, N.; Fox, J.; Linscott, I. R.; Oxoby, G.; Sapozhnikov, L.

doi:10.1109/pac.1993.309319

Cited by 7 publications

(2 citation statements)

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“…It can be represented in a simplified version as depicted in Figure A.10 [4], [88]. In absence of the LFB system damping the beam presents some unstable modes, defining an open loop unstable system.…”

Section: A3 Feedback Modelmentioning

confidence: 99%

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: A3 Feedback Modelmentioning

confidence: 99%

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators

Mastoridis

2010

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“…Third, broadband noise as well as power line harmonics present in the input signal have to be suppressed.Model developed in Chapter 4 describes beam dynamics as an unstable harmonic oscillator. A controller of such a plant can be implemented as a differentiator[24,67]. Advantages of such a controller include insensitivity to resonant frequency and DC rejection.…”

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confidence: 99%

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

Teytelman¹

2003

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Modern light sources and circular colliders employ large numbers of high-intensity particle bunches in order to achieve high luminosity. The electromagnetic coupling of bunches via resonant structures causes coherent instabilities at high beam currents. Achieving high luminosity requires the control of such unstable motion. Feedback control is challenging None of the experimental measurements presented in this work would be possible without the longitudinal feedback system designed by SLAC/LBL/LNF-INFN collaboration. And this system would not exist without engineering wizardry of Jack Hoeflich, Jeff Olsen, Gerard Oxoby, Bill Ross, Leonid Sapozhnikov, and Andrew Young. I have been lucky to help Ric Claus with system software development, learning a lot in the process. Success of our hardware projects was guaranteed by our technicians Dave Anderson and Boni F.

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Longitudinal bunch-by-bunch feedback systems in storage rings: Phase vs. energy sensing

Venturini

2024

Nuclear Instruments and Methods in Physics Research Section A:

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Analysis of DSP-based longitudinal feedback system: trials at SPEAR and ALS

Cited by 7 publications

References 1 publication

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators

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

Longitudinal bunch-by-bunch feedback systems in storage rings: Phase vs. energy sensing

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