Fig. 1. Testing apparatus

Fig. 2. Nitrogen supply system of air knife

Fig. 3. Influence of measurement period on the number of particles

Fig. 4. Removal efficiency of Al₂O₃ particles with different sizes. (a) 2550 μm; (b) >50100 μm; (c) >100 μm

Fig. 5. Influence of inlet pressure on removal efficiency of Al₂O₃ particles

Fig. 6. Removal efficiency of different types of particles

Fig. 7. Removal efficiency of particles under different purging times

Fig. 8. Removal efficiency of stainless steel particles under different inlet pressures

Fig. 9. Relationship between wind speed at the end of transmission mirror and inlet pressur under different outlet gaps of air knife

Fig. 10. Removal efficiency of stainless steel particles under different outlet gaps of air knife

Fig. 11. Purging process of Al₂O₃ particles. (a) Before purging; (b) during purging; (c) after purging