Due to increased needs for electricity new energy sources are sought for. Nuclear fusion is one of them. Under the proper conditions the light element nuclei react and convert mass in to energy. To obtain suitable conditions for nuclear fusion light element plasma is heated to 107 K inside the magnetic confinement devices, mainly in tokamak or stelerator configurations.

One of the most critical issues in the construction of a thermonuclear reactor based on magnetic confinement in the tokamak configuration is the inner wall of the reactor. The inner wall is directly in contact with hot plasma. During the operation of a fusion device, the wall is subjected to a combination of neutron and charged particle bombardment, large and uneven thermal loads, photon irradiation and neutral hydrogen exposure. This leads to erosion, deposition, adsorption of hydrogen and material lattice damage. The processes at the surface of the material or in its bulk lead to accumulation of fusion fuel (mainly hydrogen isotopes) in the vessel walls.

Ion beam analytical (IBA) methods provide an non-destructive tool to perform post mortem analysis of sample materials exposed in experimental thermonuclear reactors. With focused ion beams, we are able to investigate process on micrometer level or in some special cases on sub-micrometer level [1]. Thickness of eroded or deposited layers are determinate with Rutherford back scattering spectroscopy (RBS). The concentration of impurities for elements with Z>10 is determinate with particle induced x-ray emission (PIXE). While for lighter we employ nucler reaction analysis (NRA). Mainly the D(3He,p) 4He for detection of trapped deuterium [2].