Estimation of superconducting cavity bandwidth and detuning using a Luenberger observer

TL;DR

This paper introduces a Luenberger observer-based method for real-time estimation of superconducting cavity bandwidth and detuning, enhancing accuracy and responsiveness in RF control systems for linear accelerators.

Contribution

It presents a novel application of a Luenberger observer for estimating cavity parameters directly at the control system's sample rate, improving over previous filtering-based methods.

Findings

Estimator operates at native control sample rate

Error convergence can be tuned via gain parameters

Test results validate the observer's effectiveness

Abstract

Enabled by progress in superconducting technology, several continuous wave linear accelerators are foreseen in the next decade. For these machines, it is of crucial importance to track the main cavity parameters, such as the resonator bandwidth and detuning. The bandwidth yields information on the superconducting state of the cavity. The detuning should be minimized to limit the required power to operate the cavity. The estimation of these parameters is commonly implemented in the digital electronics of the Low-Level RF control system to minimize the computation delay. In this proceeding, we present a way to compute the bandwidth and detuning using a Luenberger observer. In contrast to previous methods, a state observer yields estimations at the native control system sample rate without explicitly filtering the input signals. Additionally, the error convergence properties of the estimations can be controlled intuitively by adjusting gain parameters. Implementation considerations and test results on the derived observer are presented in the manuscript.