Elaboration and characterization of hydrogen standard stable under heavy ion irradiation: application to nuclear astrophysics

It is from the need to use a hydrogen standard in very different domains that a reverse kinematics study of nuclear reactions within a proton capture arises. Such domains of application are for example material analysis or astrophysics. Reverse kinematics requires the interaction of relatively heavy ions with hydrogen-containing targets. Thus, the hydrogen standards must be stable under irradiation and exhibit a very high degree of isotopic purity. Two different implantation energies were applied to samples to obtain a flat hydrogen distribution from the surface to a depth of ~100 nm, the convolution of two Gaussians being a rectangle. This was achieved with a first implantation at 3 keV to a fluence of 1.1017 1H+/cm2 followed by a second at 1.5 keV to a fluence of 6.1016 1H+/cm2. Characterization of the different samples obtained was carried out by means of Elastic Recoil Detection Analysis (ERDA), using 1H(4He,1H)4He and 2D(4He,2D)4He reactions, and Resonant Nuclear Reaction Analysis (RNRA), using the 1H(15N,ag)12C reaction with a narrow resonance at 6385 keV. All important properties of the hydrogen standard have been controlled: isotopic purity, flat depth profile, stability under ion irradiation and reproducibility. The hydrogen standards were validated by measurement of the resonant cross-section of the 13C(p,g)14N reaction. The similarity of the resonance energy, resonance width and strength measurements with those reported in literature confirms the validity of the proposed procedure for hydrogen standards.