Obvious and non-obvious aspects of digital Self-Excited-Loops for SRF cavity control
Abstract
In 1978, Delayen showed how Self-Excited Loops (SEL) can be used to great advantage for controlling narrow-band SRF cavities. Its key capability is establishing closed-loop amplitude control early in the setup process, stabilizing Lorentz forces to allow cavity tuning and phase loop setup in a stable environment. As people around the world implement this basic idea with modern FPGA DSP technology, multiple variations and operational scenarios creep in that have both obvious and non-obvious ramifications for latency, feedback stability, and resiliency. This paper will review the key properties of a Delayen-style SEL when set up for open-loop, amplitude stabilized, and phase-stabilized modes. Then the original analog circuit will be compared and contrasted with the known variations of digital CORDIC-based implementations.
Keywords
Cite
@article{arxiv.2510.14835,
title = {Obvious and non-obvious aspects of digital Self-Excited-Loops for SRF cavity control},
author = {Larry Doolittle and Shreeharshini Murthy and Matei Guran and Lennon Reyes and Shrividhyaa Sankar Raman and Philip Varghese},
journal= {arXiv preprint arXiv:2510.14835},
year = {2025}
}
Comments
Poster presented at LLRF Workshop 2025 (LLRF2025, arXiv: 2510.07603)