On the Material Selection of Gauge for the Comparison of X-Ray and Neutron Tomography

In the quality control of manufacturing, dimensional metrology is crucial. The parts made through additive manufacturing are becoming more complex. Undercut and inner surfaces are inaccessible for measurement data collection by the most popular dimensional measurement methods, such as tactile coordinate measurement and 3D scanning. The use of X-ray tomography for quality control in additive manufacturing is expanding due to its advantages. Neutron tomography is another method for acquiring volumetric data. Instead of X-rays, neutron tomography uses neutrons to penetrate the examined parts. Both benefits and drawbacks of neutron tomography over X-ray tomography exist. It is not well known how neutron tomography can be used for dimensional metrology. The material of the gauge for a comparison measurement must be carefully selected regarding the fact that the two types of radiations behaving differently with materials. The attenuation of X-rays is dependent on the fourth power of the atomic number. The attenuation of the neutron radiation is dependent on the scattering cross-section of the nuclei. Low mass elements such as hydrogen has a high scattering cross-section and consequently materials which containing hydrogen cannot be chosen for the test. The irradiated materials are become activated by neutron radiation, which means they are emitting ionising radiation. The energy, activity, and half-life of the residual radiation of the produced isotopes are changing between wide limits. The article provides information on selecting a gauge that can evaluate and compare X-ray and neutron tomography.