Charge detector for airbone particles

Abstract

The detector developed consists of a collector made of a rod or wire stretched along the axis of a grounded metal cylinder which serves as a shield. Two narrow slots made along the cylinder side wall allow the aerosol to flow throughout the internal zone of the probe. A single charged airborne particle entering through one of these slots induces a measuring signal on the inner electrode. A fraction of the number of the particles entering the measuring zone impact on the collector and are discharged. Only for the impacting particle, the amplitude of the voltage signal induced depends uniquely on the particle charge. The method presented in the paper allows the charge on aerosol particles to be measured in real time. The advantage of the device developed is the reduced distortion error due to gas ions and electromagnetic fields. The coincidence error and the number of pulses induced by non-impacting particles are also reduced. Theoretical studies and laboratory tests show that the method enables measurements of the charge on a single particle down to 10 −14C. The conditions for correct measurement have been formulated in the paper.