**Abstract**

One of the major problems not only in nuclear fusion but in all the fields that have to face irradiation damage is to predict the microstructural evolution of all the features that are involved in the good response of the material. In the case of nuclear fusion, it is well known that structural materials that will be a fundamental piece in the future reactor must withstand severe neutron irradiation damage, high temperatures, and cyclic stresses which will result in a reduction of the lifetime of the component. For that reason, a big effort is being done for the scientific community in order to understand the complex mechanisms that lie in the relationship between irradiation damage, microstructure, temperature, stresses, etc. However, neutron irradiation brings inherently transmutation and nuclear activation, which makes extremely hard to study those samples. Therefore, the scientific community is using since long time ago ion beam facilities to emulate the neutron damage, without the worst inconvenience. In this chapter, the authors described briefly the facility located at Centro de MicroAnálisis de Materiales (CMAM), Madrid, and presented afterward some examples of experiments that Spanish Nuclear Fusion Laboratory at CIEMAT has been carrying out related to this matter.

**Keywords:** structural materials, nuclear fusion, ion beam irradiation, irradiation damage, modeling
