Beam dumper for particle counter

A beam dumper for a particle counter includes an installation plate 207; a detector 203 mounted on the plate, comprising a photodiode 290 which receives excitation light; a housing 210 assembled with the detector, arranged in the path of non-scattering light of the excitation light, with a chamber 211 that guides the nonscattering light; a control circuit that measures intensity of the non-scattering light on the photodiode, calculates beam loss generated due to the optical path to detect actual intensity of the excitation light, and controls the intensity of the excitation light; a beam guide 205 with a beam stopper 230 that prevents a portion of the non-scattering light from returning to a condensation-inducing path, a beam dumper lens 270; and a beam hole structure 201 into which non-scattering light reflected from the photodiode is guided.