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Extended State Observer for Localized Fault Awareness in RF Accelerating Structures

Luke S. Baker, Sungil Kwon, Kwame Jyamfi, Quinten Cole, Isaac Roybal, AJ Garcia, Phil Torrez, Lawrence Castellano

Abstract

An observer framework is presented for robust regulation of RF cavity fields and localized identification of disturbances in RF systems. A standard cavity field observer is augmented with additional states to estimate the evolution of cavity detuning and phase drifts induced by the drive and receiver chains. Monte Carlo simulations are performed to assess the performance of the proposed estimator under realistic conditions for the intended high-power linear accelerator operation. Results showcase precise cavity field regulation and the reliability with which the observer assigns deviations to the correct subsystem. The resulting diagnostic capability provides a foundation for improved fault detection, faster troubleshooting during accelerator operation, and more informed maintenance of RF systems in large accelerator facilities.

Extended State Observer for Localized Fault Awareness in RF Accelerating Structures

Abstract

An observer framework is presented for robust regulation of RF cavity fields and localized identification of disturbances in RF systems. A standard cavity field observer is augmented with additional states to estimate the evolution of cavity detuning and phase drifts induced by the drive and receiver chains. Monte Carlo simulations are performed to assess the performance of the proposed estimator under realistic conditions for the intended high-power linear accelerator operation. Results showcase precise cavity field regulation and the reliability with which the observer assigns deviations to the correct subsystem. The resulting diagnostic capability provides a foundation for improved fault detection, faster troubleshooting during accelerator operation, and more informed maintenance of RF systems in large accelerator facilities.

Paper Structure

This paper contains 19 sections, 23 equations, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Baseband Cavity Model
  3. Drive Synthesis and Forward Path
  4. Cavity Voltage and Detuning
  5. Pickup and Receiver Chain
  6. State-Space Formulation
  7. Informed Observation
  8. State and Disturbance Observer
  9. Forward Drift Observer
  10. Detuning Observer
  11. Receiver Drift Observer
  12. Control Architecture
  13. Feedforward
  14. Feedback
  15. Regulation and Fault Localization
  16. ...and 4 more sections

Figures (5)

  • Figure 3: Illustration of a macropulse repeated at 120 Hz. Beam is present only during the regulated flattop with a bunch repetition rate of 805 MHz for the side-coupled cavities at LANSCE.
  • Figure 4: Simplified block diagram of the LLRF control system at LANSCE. Orange input boxes represent sources of disturbance, uncertainty, and noise.
  • Figure 5: Representative MC realizations (showing 10/10k) of true and estimated forward-path phase drift, detuning, and receiver-path phase drift for the proposed and standard observers. Realizations are depicted over the fill and flattop portions of the macropulse.
  • Figure 6: Likelihood that average amplitude and phase regulation errors over time exceed specified thresholds.
  • Figure 7: Likelihood that average error over time between true and estimated disturbances exceeds specified thresholds.