Development of a Beam Monitoring System for Ion Therapy Quality Assurance based on Pixelated Ionization Chambers

To address the quality assurance requirements for heavy-ion radiotherapy equipment, a functional prototype of a beam monitoring system based on a 1024-channel free-air pixelated parallel-plate ionization chamber was developed. The system comprises an ionization chamber module and a low-noise readout electronics module, with the overall channel noise controlled at a baseline RMS ≤ 1.0 fC (integration time 50.7 μs). Multi-parameter voltage calibration tests demonstrated a linear fitting coefficient (R²) ≥ 0.9994, meeting the signal precision requirements for clinical dose monitoring. Furthermore, the study innovatively introduced an alpha source (Am-241) for functional verification, successfully obtaining its two-dimensional beam distribution image, which confirmed the device's capability for spatial resolution of heavy-ion beams. The experimental results verify that the functional prototype can detect and collect ionizing radiation signals, consistent with the proposed beam monitoring system design. The constructed 1024-channel high-density ionization chamber system provides a critical foundation for the subsequent development of a full-scale beam monitoring system prototype. Its low-noise and high-linearity performance offers significant engineering support for improving dose accuracy in clinical heavy-ion radiotherapy applications.