Fig. 1. The prototype FOA is composed of fixed interfaces to the target chamber and five modules that house eight full-aperture optics. The clear aperture size is .

Fig. 2. Numerical model of the FOA generated by ICEMCFD.

Fig. 3. Schematic of the observed cross-section distributions in the prototype FOA.

Fig. 4. Density distribution of the contaminants in cross-section 2 as the flux ranges within after 30 s.

Fig. 5. Distribution of the gas inlets and outlets in the FOA.

Fig. 6. Two types of inlet and exhaust pipes.

Fig. 7. Graph showing the real-time contaminant quantity.

Fig. 8. Surface damage morphologies induced by contaminants: (a) film damage located on the clear aperture brim, (b) surface spot outside the clear aperture, (c) clear aperture brim and (d) surface ‘mooning’ damage outside the clear aperture.

Fig. 9. Results obtained by x-ray fluorescence spectrometry: (a) unused silica coated by sol-gel film (including Al, Si, Pd, Cr, Mn, Fe, Cu and Zn) and (b) used silica coated by sol-gel film (including Zn, Al, Si, P, S, K, Ca, Ti, Cr, Mn, Fe, Ni and Cu; because the Pb amount is negligible, it is not labeled).