Non-Invasive Beam Diagnostics with Schottky Signals and Cherenkov Diffraction Radiation

This dissertation reports on the developments made regarding two techniques used for non-invasive beam diagnostics: the analysis of Schottky signals and the observation of Cherenkov Diffraction Radiation (ChDR). The Schottky signal manifests itself in the beam intensity in the form of statistical noise, which is typically more conveniently analysed in frequency domain. The analysis of Schottky signals is a fundamental technique for estimating various physical parameters of unbunched hadron beams, but the task is far more challenging in the case of beams accelerated with RF systems, i.e. bunched beams. A new approach based on simulating Schottky signals and comparing them with the exper- imentally obtained ones is proposed and developed herein. The relevant beam characteristics serve as input parameters for the simulations, and with the help of optmisation routines one obtains the values which fit best to the measured Schottky signals. The proposed approach has been applied to the data acquired by the LHC Schottky Monitor and benchmarked against the results of alterna- tive measurement techniques. The theory of Schottky signals in the presence of bunched beams is revisited as well, and a formal derivation of the relation between the width of the synchro-betatron sidebands in the Schottky spectrum and the value of chromaticity is presented. The second part of this dissertation discusses the application of Cherenkov Diffraction Radiation in beam diagnostics. The concept is relatively new and still requires extensive studies from both theoretical and practical points of view. A brief presentation of the theoretical models used so far for describing ChDR emission in simple geometries is followed by a systematic study of how relevant beam parameters express themselves in the properties of the emitted radiation. This is supplemented with the development of a new semi-analytical framework, which allows for calculation of the expected radiation yield in the case of a more complex multilayered radiator, and fills the gap between simplified theoretical models and detailed numerical simulations, which often require large computing resources. The performance of the new framework is illustrated with studies on the impact of thin coatings deposited on the radiator surface, either for signal enhancement or to mitigate undesirable effects, such as the creation of electron clouds. In addition, the feasibility of using ChDR-based diagnostic devices in the Large Hadron Collider is preliminarily assessed. This part of the thesis is concluded with the results of a dedicated experiment carried out in 2021 on the CLEAR accelerator at CERN, whose aim was to understand the range of validity of the currently used theoretical models. The obtained results do not confirm the investigated theoretical models and may constitute a starting point for further research on the use of ChDR in beam diagnostics.