Abstract: A particle detection system includes a light source configured to generate a light beam, a first collimator lens configured to channel the light beam into the chamber through a first sidewall, the chamber including openings on a second sidewall opposite the first sidewall, and a second collimator lens configured to channel light received from the openings to a light detector. A method for detecting particles flowing through a chamber includes generating a light beam, channeling the light beam into the chamber via a first collimator lens, detecting light escaped from the chamber via a plurality of openings formed at a second sidewall of the chamber opposite the first sidewall, at a light detector via a second collimator lens located outside the second sidewall, and determining parameters of the one or more particles flowing through the chamber based on the received escaped light.