Electrical mobility of radioactive small ions (218Po) in the atmosphere

The electrical mobility distributions of radioactive ions are obtained by using the mobility separation chamber and the position sensitive counter. The separation chamber is the condenser of parallel plate type in basically. The face of ion collecting plate is covered with a thin film and serve as the window of proportional counter. The both ends of resistive anode wire of the counter are used as signal output terminals, and the ratios of one side output pulses to the sum of both ends pulses are proportional to the position of generating alpha pulses. The mobility distributions of radioactive ions can be obtained from the position analysis of a detected events. The resolution of the instrument is about 3 percent in position of alpha decay events. As a results, Bimodal distributions, with peaks of 0.4 - 0.7 and 1.5 - 2.7 cm2/sec.volt., were found on the naturally occurring radioactive ions (218Po) in the room air. (author)