Modeling a High-Power RF System Using a Circuit Optimizer

The increasing demand for higher beam intensities to reach higher luminosities puts significant stress on high-power amplifiers driving the RF cavities in particle accelerators. It is therefore essential to understand their large signal behavior in detail. The need to characterize the high-power nonlinear amplifiers of the 80 MHz RF systems of the CERN proton synchrotron (PS) at the circuit level, including their distributed and stray components, only accessible for a limited amount of time due to accelerator operation, led us to develop a novel modeling approach. It is based on low-power and high-power measurements, as well as a numerical circuit optimizer. This allowed us to build a model that replicates the beam-cavity interaction across the entire dynamic range of the system with good agreement between simulations and measurements. Furthermore, observations indicate that the three 80 MHz RF systems interact differently with the beam. The model was used to identify the specific components responsible for these distinct beam–cavity interactions, and provides valuable insights into the components responsible for the potential limitations of the amplifier chain.