A small mixing-type unipolar charger (SMUC) for nanoparticles

A small mixing-type unipolar charger for nanoparticles (SMUC) was developed to increase the charging efficiency and throughput by using a small charging chamber (0.5 cm 3 ) to reduce particle loss caused by electrostatic dispersion. The two main components of the SMUC are a high-pressure corona ionizer (HPC Ionizer) in which high concentration unipolar ions are generated, and a charging chamber in which the unipolar ions are mixed with nanoparticles without an external electric field. The charging performance of the SMUC was evaluated experimentally by measuring the charging ratio fc and the penetration ratio fp . For positive charging in the particle size range of 5–40 nm, fc + = 0.91–0.95 and fp + = 0.71–0.90, at an ion concentration of Ng + = 5.25 10 9 ions/cm 3 and a charging time t R = 0.025 s. For negative charging, f – c = 0.74–0.93 and fp – = 0.73–0.85, at Ng – = 6.24 × 10 9 ions/cm 3 and tR = 0.025 s. Based on these results, the extrinsic charging efficiency defined as fe = fc ×fp /fd (where fd i...