[en] Charged Particle Activation technique was generally used for elemental analysis in materials; its advantages, performance, limitations and critical aspects have been described in review works. Recently, we demonstrated that a new application of interest for industry and special technologies where high precision thickness of thin materials (≤ μm range) is necessary, might be developed. The method employs the linear dependence of the increasing part of the parameter Y_i-j (E_p) - Radionuclide Activation Yield of an activation reaction _Zi^A_iX(p)_Zj^A_j producing γ-ray emitting nuclides - on the particle energy E_p. There are many nuclear reactions induced by light ions (p, d, α, ³ H, ³ He) on various elements _Zi^A_iX with high productivity, that can be employed in the range (6 - 100) MeV. The method implies two experimental stages: - determination of a calibration curve Y_i-j (E_p) of a certain ion type in the accelerator energy range using as target a reference material - a natural element or of known composition, using γ-ray spectrometry; - irradiation of the sample to be investigated mounted in front an identical Reference target, followed by evaluation of the corresponding activation yield parameter. The thickness is determined from the energy loss in the analyzed sample.Experimental verifications of thin Ta foils (6 μm ± 10%) irradiated by (13-14) MeV protons supplied by the IFIN-HH Tandem Accelerator, by employing metallic targets (NiCr, Cu, Nb) as Reference materials, are presented.Use of several Reference materials increase accuracy; a high precision is obtained if the investigated sample composition is known and the yield curve slope is ≥ 60 deg. For thin metallic foils the precision could be 2% . The activation method is simple, allowing development of a routine technique; it is applicable to self-supporting materials but it may be also applied to thin layers deposited on thick materials. (authors)