Low Level RF System of the LIGHT Proton Therapy Linac

TL;DR

This paper describes the design, features, and performance of the Low-Level RF system used in the LIGHT proton therapy linac, which is crucial for stable and precise beam acceleration.

Contribution

It introduces a customized, high-stability LLRF system for the LIGHT proton therapy accelerator, detailing its integration, control, and real-time RF management capabilities.

Findings

High amplitude and phase stability achieved

Real-time RF monitoring at 200 Hz implemented

Effective RF breakdown detection and thermal correction

Abstract

The LIGHT (Linac for Image-Guided Hadron Therapy) project was initiated to develop a modular proton accelerator delivering beam with energies up to 230 MeV for cancer therapy. The machine consists of three different kinds of accelerating structures: RFQ (Radio-Frequency Quadrupole), SCDTL (Side Coupled Drift Tube Linac) and CCL (Coupled Cavity Linac). These accelerating structures operate at 750 MHz (RFQ) and 3 GHz (SCDTL, CCL). The accelerator RF signals are generated, distributed, and controlled by a Low-Level RF (LLRF) system. The LIGHT LLRF system is based on a commercially available solution from Instrumentation Technologies with project specific customization. This LLRF system features high amplitude and phase stability, monitoring of the RF signals from the RF network and the accelerating structures at 200 Hz, RF pulse shaping over real-time interface integrated, RF breakdown detection, and thermal resonance frequency correction feedback. The LLRF system control is integrated in a Front-End Controller (FEC) which connects it to the LIGHT control system. In this contribution we present the main features of the AVO LLRF system, its operation and performance.