2017 | AFC ACCOMPLISHMENTS 174 manner and to a large extent. Our work found that in order to avoid this issue for high dose ion irradiations, the beam energy should be at least 1.8 MeV. Ion irradiation programs within AFC have always been using at least 1.8 MeV energy beams. The second issue that was found and assessed was a strong propensity for materials to become contaminated with carbon during ion irradiations.This is a very important issue in the AFC because all the core materials of interest are ferritic alloys whose mechanical properties and microstructure are strongly affected by small changes in carbon content.As with the sputtering issue, it was found that the structural materials ion irradiation community was largely unaware of this issue. One of the accelerators used by the AFC was found to not produce carbon contamination while another was found to have intermittent issues.Analysis of the accelerator revealed that for what is considered a clean beamline, there were still hydrocarbons in the vacuum chamber, and these were getting pulled down the beamline to the specimen where the ion beam would then break down the hydrocarbon and release carbon.This carbon is then either ballistically injected into the specimen or enters through radiation enhanced diffusion processes.The amount of carbon contamination can greatly exceed the amount of carbon that is meant to be in the material causing substantial changes in the material properties and radiation response.An example of the level of carbon contamination that occurred in tempered martensitic steel specimens irradiated to low or moderate dose levels is presented in Figure 1.The addition of these high amounts of carbon causes the formation of precipitates in the material (Figure 2) that wouldn't normally occur and will affect the properties of the material and how it responds to further irradiation. Several means to mitigate the possibility of carbon contamination have been devised. Some accelerator operators are fitting additional equipment that prevent the hydrocarbons from reaching the surface.Within the AFC, coatings are being developed that can be applied to specimens to prevent carbon ingress.