Fig. 1. Measurement of spatial distribution of particles. (a) Schematic of laser path and sampling; (b) CCD imaging result after binarization; (c) optical microscopic imaging result

Fig. 2. Arrangement of particle counters on neutral surface

Fig. 3. Relative proportion of contaminants

Fig. 4. Cloud charts of particles number in neutral surface. (a) Particles with diameter of 0.3 μm; (b) particles with diameter of 10.0 μm

Fig. 5. Relationship between number of pollutant particles with different diameters and longitudinal distances