Oscilloscope signals of light scattering from individual suspension droplets passing through a Gaussian light beam

The light scattering of droplets illuminated by a Gaussian laser beam was measured using the commercial ParticleTensorAI(R) system. The setup employs a single laser source with a wavelength of 405 nm and two photomultiplier detectors, referred to here as detector A and detector B. The laser and both detectors are aligned with a monodisperse droplet chain generated by a commercial droplet generator from FMP Technology GmbH.

The photomultiplier detectors record the light scattered by droplets passing through the Gaussian beam. The resulting optical signals are converted into voltage signals using a transimpedance amplifier. These measurement signals are digitized by a PicoScope 6404B digital oscilloscope. Each recording consists of 32 measurement frames with an individual duration of 20 ms, sampled at 312.5 MS/s. A single frame typically contains about 1000 individual light-scattering events. Because two independent detectors are used, two separate oscilloscope channels are recorded, referred to as Channel A and Channel B.

Measurements were performed over a concentration range from 0 % to 100 %. In the range from 0 % to 25 %, the concentration was increased in steps of 1 % (1 %, 2 %, …, 25 %), whereas in the range from 25 % to 100 % the concentration was increased in nominal steps of 2.5 %, corresponding to approximately 3 % steps in the dataset (25 %, 28 %, 30 %, …, 100 %).