Hi Miguel,

Thanks for posting on the community!

We do not have tools or methods that directly correspond to the simulation of particles. We will still give different advice according to different situations. According to your instructions. If it is this very small and random particles. Indeed using Mie scattering model is the way to go. When you adjust the size or density. You may see a combined effect of the increased particle size, the relatively large density (taking into account the increased particle size), and the small number of rays hitting the detector. If the number of rays hitting the detector is comparable to the number of pixels in the detector, then you will see large noise on the detector results. You can try to avoid this by increasing the number of analysis rays, or by decreasing the number of pixels on the detector.

You may read more details about the Mie scattering model in this knowledgebase article: https://support.zemax.com/hc/en-us/articles/1500005489241-How-to-simulate-atmospheric-scattering-using-a-Mie-model

Best Regards
Sean Lin