Charge-carrier extraction from air and nitrogen gas streams that entrain charge from a radioactive ionizer

Charge decay upon a pre-charged target was studied in a gas flow channel that contained a 210Po ionizer. Unlike electrical corona, the radioactive ionizer produced positive and negative charge-carrier pairs in the absence of an external electric field. The initial charge extraction currents Ice for a negative target in nitrogen and positive/negative target in air were approximately the same. The Ice for the positive target in nitrogen was significantly higher due to the higher negative carrier mobility in nitrogen. Exponential dependences of Ice on temperature were very similar in both gases. The steady state residual potential on the target was zero in the temperature ranges tested.