A system and method comprising an ion production chamber having a ultra-violet light source disposed towards said chamber, a harvest gas disposed to flow through the chamber from an inlet to an outlet, and a jet, said jet operable to introduce a sample into the harvest gas flow. In some embodiments the system includes using helium as the harvest gas. Certain embodiments include introducing a sample perpendicular to the harvest gas flow and using multiple sample introduction jets to increase mixing efficiency. The charge sample may be coupled to a MEMS-based electrometer.