IDPMS: A New Integrated Dose-Position Measuring System for Ion Therapy

For proton or carbon ion therapy, when using the point scanning method to control a pencil beam for treatment, rapid measurement of the position of each spot, the absorbed dose, and even the angle of incidence, as well as rapid feedback and interlocking signals, are necessary to ensure the accuracy of beam delivery. In this article, we present a new integrated dose-position measuring system (IDPMS) developed by the Institute of Modern Physics that is highly integrated and scalable, with fast measurement speed and no dead time. The system can rapidly measure the beam position and the relative absorbed dose. Optical ports can also synchronize the two systems to measure beam incidence angularity rapidly. A new Gaussian fitting algorithm has been developed on the field programmable gate array (FPGA) of this system, which has been tested by many beams and operated stably and reliably and can complete the Gaussian fitting within $4~\mu $ s. In point scanning mode, the detector system can achieve a spot position measurement with a maximum deviation of 0.15 mm and generate a beam spot position interlock signal within $55~\mu $ s. Using two ionization chambers (ICs) working in synchronization with a distance of more than 103 mm, the virtual source axis distance of ~7 m, the maximum deviation of the elevation angle is 0.03°, and the maximum deviation of the azimuth angle is 1.38°. The system’s scalability and multiple modes of operation make it capable of meeting the beam monitoring needs of most current ion therapy devices and achieving machine quality assurance (QA). In addition, the system can also monitor the beam state in real-time in particle physics experiments, providing powerful technical support for scientific research and medical applications.