High-Precision Annular Beam Spot Energy Distribution Model and Beam Spot Optimization

The stable supply of medical radioisotopes is crucial for national health and medical security. Accelerator-driven production represents a pivotal approach to addressing the current shortage in medical isotope supply. A key technical challenge in this process is the effective management of the extremely high power density generated when the beam bombards the target material. This challenge must be addressed to prevent local overheating and potential target melt-through. Circular scanning is a widely adopted beam homogenization technique. However, the traditional energy distribution model, which underpins its steady-state simulation, contains inherent inaccuracies. This conventional model is constructed by rotating a one-dimensional Gaussian distribution, neglecting the superposition effect in the central region. This simplification leads to a significant underestimation of the energy density at the rotation center, especially when the beam’s rotation radius is small, introducing considerable safety risks. To address this issue, this study reconstructs the physical process of circular scanning. We established a high-precision annular beam spot energy distribution model by employing a differential method to account for the beam superposition effect. The results demonstrate that the high-precision model agrees well with transient simulation outcomes and significantly improves the accuracy of energy density estimation in the central region. Furthermore, this work systematically analyzes the energy distribution characteristics and utilization efficiency under various combinations of beam spot standard deviation and rotation radius. The findings provide critical theoretical foundations and data support for the optimization of beam spot parameters and the safe design of medical isotope production facilities.