[Alpha-recoiling behaviour of 222Rn on 226Ra-sources]

By using electroplated 226Ra-sources, the ejection and injection behaviour of alpha-recoil atoms, 222Rn, which generates on the source surface during alpha-decay process of its parent 226Ra, has been basically investigated. The thinly and uniformly distributed 226Ra-sources were prepared with high deposition yield by the molecular plating technique, in which radium was deposited on a stainless-steel cathode from an isopropanol media by adopting a rotating platinum anode, applied potential of 900 V, and deposition time of 40 min. The ejection efficiency of 222Rn was determined by using the relationship between the 226Ra strength on source and the 222Rn-one transferred on a stainless steel collector in vacuum. It was found that the ejection (or injection) efficiency was greatly influenced on the source preparation methods. The highest ejection efficiency (up to 30%) could be obtained from the electroplated source, whereas the same source could be resulted in the significant decrease of this value (till 2%) after simple ignition treatment. The retention efficiency of 222Rn injected on some collector materials was evaluated to be more than 70% over the tested collectors. From these results, it was concluded that the recoil effects should be most important to interpret the emanation phenomena even in nature.