Our understanding of the evolution of extended defects during irradiation has progressed considerably since 1990 following the proposal of production bias by Bachu Singh and C. H. Woo. One of the important phenomena underlying this concept is that self-interstitials and interstitial clusters can migrate a long distance via one-dimensional motion. There have been a number of indirect experimental evidences supporting this mode of migration. However, the direct evidence has not necessarily been sufficient. In this paper, we revisit our former experimental results of in-situ observation of ion irradiation damage from the stand point of an internal probe for detecting point defect fluxes in an irradiation environment or those coming from nearby cascades. Surfaces, giving rise to specimen size effects, preexisting dislocations, intentionally preintroduced vacancy loops with stacking fault, irradiation induced vacancy clusters and loops, precipitates and precipitate-matrix interfaces, etc., are utilized to monitor the influx of point defects, particularly those of interstitials nature. Some of the reanalysls of the former results will be presented.