Fig. 1. Diagram of cavities（a）the traditional ladder type cavity，（b）the novel cavity

Fig. 2. TM310 mode distribution in xOz plane of two different cavities，（a）the traditional ladder type cavity，（b）the novel cavity

Fig. 3. Axial field distribution at center gaps and side cavities of two different cavities，（a）the traditional ladder type cavity，（b）the novel cavity

Fig. 4. Comparison of transverse electric field distribution between the traditional ladder type cavity and the novel cavity

Fig. 5. The resonant frequencies of the three axial modes as a function of sh

Fig. 6. Effect of dimensional deviation on resonant frequency of two kinds of cavities that operate at TM310 mode，（a）the novel cavity，（b）the traditional cavity

Fig. 7. Effect of dimensional deviation on the characteristic impedance of the novel cavity that operates at TM310 mode

Fig. 8. Diagram of the interactive circuit

Fig. 9. Normalized beam conductance versus beam voltage of three cavities

Fig. 10. Output signal and its frequency spectrum

Fig. 11. Particles phase diagram and electric field distribution

Fig. 12. Output power vs. input power

Fig. 13. Frequency sweep curve