Stripper foil characterization from beam energy measurement in the Low Energy Ion Ring at CERN

The Linear Accelerator 3 (LINAC3) and the Low Energy Ion Ring (LEIR) at the European Organization for Nuclear Research (CERN) constitute the first stage of acceleration of Pb ion beams towards the Large Hadron Collider (LHC). In LINAC3, different stripper foils are strategically placed to maximize the beam transmission along the linac and the beam lifetime in the downstream machines. On one hand, the stripper foils play a crucial role in producing highly charged ions by stripping away electrons, thus preparing the ions for injection into other accelerators. On the other hand, as the ion beam passes through the foils over time, it significantly affects their stripping efficiency, potentially affecting the overall performance of the downstream machines. This thesis introduces an innovative method to study the performance evolution of the stripper foils. This is accomplished by means of longitudinal Schottky measurements performed in LEIR at injection, while tuning the phase properties of the Ramping cavity (RC) and the Debuncher cavity (DC) in LINAC3. By varying the phases of the RC and DC, it is possible to measure and control the energy spread of the beam in different operational conditions. Moreover, when systematically recording mean and standard deviation of the beam energy in LEIR over time, one can observe the evolution of the stripper foils performance and identify potential performance loss. Energy measurements are compared with simulations, allowing for a deeper understanding and providing means to correct possible energy deviations in advance. Furthermore, an online monitoring tool has been developed to continuously scan and record energy measurements automatically. This approach facilitates the timely foil replacement, thereby preventing beam intensity loss and performance loss in the ion injector chain.