Specimens of 316L stainless steel are irradiated with 2.5 MeV He+ ions at temperatures of 400,500 and 550℃,respectively.For each implantation the dose and dose rate are separately 2.5×1021 ion/m2 and (3.2—3.8)×1016 ion/m2s-1.Bubble structures are investigated with cross sectional transmission electron microscopy(XTEM).The measured apparent activation energies provide evidence that the formation of bubbles is controlled by He diffusion via the self interstitial/He replacement mechanism.Good agreement is found between our results and other low dose experimental data,indicating that the underlying mechanism holds constant for different implantation conditions.The pre implantation cold working enhances significantly the nucleation of bubbles,and the dislocations are favorable sites for bubble nucleation in the investigated temperature range.