Design and Manufacturing of an RF power amplifier for linear accelerators

Abstract

The European Spallation Source (ESS) is a multidisciplinary research facility that is being built in Lund, Sweden and is the most powerful linear proton accelerator ever built. Even though ESS will contribute greatly to the future research, the facility will be a large power consumer with significant environmental impact. Therefore, environmentally- sustain-able developments are undertaken towards the adoption of energy savings and improved energy-efficient approaches. One example of that approach will be the new system that will be implemented to power 26 spoke cavities. The Spoke cavities are the first stage of superconducting acceleration at the ESS linear accelerator (LINAC), consisted of 26 double spoke cavities, with 400kW power per cavity requirement to operate. The new system is a Solid-State Power Amplifier (SSPA) that will replace the tetrode amplifiers due to their high-power consumption. This thesis focuses on designing, simulating and manufacturing a Solid-State Power Amplifier (SSPA) tailored specifically to serve as the first stage of the driver within the 400kW SSPA system that will be installed to power the superconducting double spoke cavities at European Spallation Source. This study begins with an in-depth analysis of the system requirements and operational parameters of the entire system, identifying key performance metrics such as output power, linearity and efficiency. Through rigorous simulation and optimization using software tools (Advanced Design System (ADS) and Altium Designer), a robust SSPA architecture is developed, capable of meeting the stringent specifications demanded by the application while mitigating issues such as harmonic distortion and power dissipation. Special attention is given to the selection and integration of high-power transistors, impedance matching networks, and cooling systems to ensure optimal functionality and longevity under varying operating conditions. Furthermore, experimental validation of the de-signed SSPA prototype is conducted, involving comprehensive testing and characterization across the entire operational range. Performance metrics including output power, efficiency, frequency response, and linearity are thoroughly evaluated, demonstrating the efficacy and reliability of the proposed design.