Multi-MHz Multi-kV Power Amplifier for Compact Particle Accelerators

This paper presents the design and implementation of multi-MHz multi-kV switch-mode power amplifiers suitable for accelerating ion beams in compact particle accelerators. Ion beams are sped up to mega-electron-volt levels by sending them through a series of acceleration cells driven by large high-frequency ac voltages. High frequency operation of these cells allows the length of the accelerator to be reduced. The presented power amplifiers utilize full-bridge inverters and matching networks to achieve high voltages. A comprehensive design methodology that enables high voltage gain while achieving soft switching of the inverter transistors is presented. The inductors of the matching networks are designed to achieve high quality factors, enabling large voltage gain without excessive losses. Furthermore, the matching network capacitor is realized using the parasitics of the accelerator structure, reducing the size and enhancing the reliability of the system. Two prototype power amplifiers are designed using the proposed approach, and are built and tested. The first prototype operates at 13.56 MHz and generates up to 10 kV output voltage, while the second prototype operates at 27.12 MHz and generates up to 8.3 kV output voltage. The output voltage achieved by the 27.12-MHz prototype exceeds the state-of-the-art by a factor of four.