Comparative Investigations on Detuning Estimator for Experimental RF Cavity
Rajesh T. Keshwani, Siddhartha Mukhopadhyay, Ravindra D. Gudi, Gopal Joshi · IEEE Transactions on Instrumentation and Measurement · 2023
In an operational accelerator, RF cavity may operate in either CW (continuous wave) or pulsed mode. Value of detuning Δω needs to be determined for tracking of cavity resonance frequencyfras well as its tuning. However, direct sensor for knowing value of Δω is not available. Model/s of RF cavity may be employed to estimate detuning value from measured quantities. One needs to carry out or make a system well suited for secondary/inferential measurement. In this paper, main focus is on estimation of cavity Δω from RF cavity model using various approaches. The advantages and limitations of each approach are outlined. Kalman filter under stochastic state space framework is considered for detuning estimation. This framework helps to address practical issues like uncertainties in model and measurement. Experimental set up is made using lab prototype RF cavity of 650 MHz, tested in pulsed mode and frequency sweep mode. Subsequently, KF algorithm is evaluated. However, the successful operation of KF needs tuning it, which is one of main concerns while using KF. Adaptive KF helps to assess values of tuning parameters to an extent. One of the adaptive KF is based on innovation based adaptive estimation. It is applied to detuning estimator in this paper and shown to minimizeRMSestimation error.