Investigation on helium bubbles in FeNiCr by small-angle neutron scattering: Guinier analysis using a size-dependent contrast factor

The helium bubbles produced by annealing a homogeneously implanted specimen of a model ternary alloy (FeNiCr) at a high temperature are characterized by a size‐dependent gas density. Hence, the contrast factor, which is given by the difference between the scattering‐length density of the matrix and of the inhomogeneities, is not constant. A quantitative analysis of the small‐angle neutron scattering data is performed taking into account a size‐dependent contrast factor. The Guinier radii found from the experimental data agree with those predicted by the theory under the assumption of a non‐constant factor.