Behavior of 220Rn progeny in diffusion chamber

The distribution of 220Rn (thoron) within the cylindrical diffusion chamber decreases exponentially with the distance from the entry filter. The first 220Rn progeny 216Po follows its parent due to its very short half life. Other 220Rn progeny are almost completely deposited, but the deposition is not uniform. Deposition occurs on all internal surfaces of cylinder including vertical wall as well as its bases. Deposition on the upper and lower base is enhanced in the middle and drops toward to the end while the deposition on “vertical” wall is larger closer to the entry membrane.