Fig. 1. Simulation model

Fig. 2. Dose distribution of the 10 cm bremsstrahlung radiation field after the target

Fig. 3. Dose peak and center uniformity at different inner diameters

Fig. 4. Relationship between the area of the maximum uniform radiation field and the inner diameter

Fig. 5. Radiation field parameters for different ring widths

Fig. 6. Double ring model

Fig. 7. Dose distribution of the 10 cm bremsstrahlung radiation field after the target

Fig. 8. Radiation field parameters under different inner diameters of outer rings

Fig. 9. Dose distribution of the 10 cm bremsstrahlung radiation field after the target (r₃=43.5cm)