THE ATTACHMENT OF INERT GASES TO POWDERS FOLLOWING (n,γ) EVENTS

It has been found that, when argon, krypton, and xenon are irradiated with neutrons in the presence of various powders, a portion of the inert-gas activity becomes "attached" to the powder. The attached activity was shown to be highly enriched, and to be distinguishable from adsorbed activity. Expressing the attachment in terms of the attachmentefficiency, A ≡ (inert-gas activity attached to target)/(total inert-gas activity), it was found that A was independent of irradiation time and neutron flux, and for fine powders was also independent of pressure between 0.7 and 700 mm. The use of a very coarse powder or no powder at all led to a decrease in A, on the basis of which it was estimated that the maximum distance from a surface that attached activity can originate is about 200 mean free paths. The following miscellaneous relations were observed to hold:[Formula: see text] (ii) AAr > AKr > AXe, (iii) Aoxide > Ametal (approximate). The results were in general consistent with a mechanism of attachment based on electrical attraction: inert-gas atoms first acquire a high charge due to vacancy cascades initiated by the conversion of capture gamma rays; they then wander about, and, upon approaching a solid surface, are accelerated electrically into it.