Fig. 1. Schematic of the disk amplifiers used in experiment. (a) Slab cavity; (b) distribution of gas cell and gas purging holes; (c) gas cell and gas purging holes; (d) photo of nitrogen gas pipes and connection

Fig. 2. Simulated flowing trail in slab cavity.(a) Simulated nitrogen gas flowing trail;(b) simulated motion trail of the particles within vortex area

Fig. 3. Particle quantity residual in slab cavity during continuous purging with different flowing rates

Fig. 4. Particle quantity residual in slab cavity during intermittent purging with different flowing rates

Fig. 5. Swirl in slab cavity and cleanliness comparison with different flow fields. (a) Smoking experiment for swirl in slab cavity; (b) cleanliness comparison with different outlet settings; (c) cleanliness comparison with different gas flowing rates

Fig. 6. Change of aerosol concentration with purging time under different nitrogen flowing rates

Fig. 7. Change of the cavity cleanliness during intermittent purging procedure. (a) Overview of the cavity cleanliness change; (b) details of cavity cleanliness change corresponding with purging procedure; (c) long-term monitoring results of cavity cleanliness after intermittent purging