New methods for alignment of instrumentation for residual-stress measurements by means of neutron diffraction

Adequate alignment of instrumentation and specimens is imperative for the successful performance of residual-stress measurements by means of neutron diffraction. This paper presents a number of alignment methods that enable the user to align reproducibly a stress-measurement setup and a specimen positioned therein. Most of these methods employ the position and the direction of the incident neutron beam as their primary source of geometric reference. A mathematical description for each of the proposed alignment steps is given, which makes the alignment quantitative and enables quantitative assessment of the alignment quality after each alignment step. Examples from actual practice show that the alignment quality that can be achieved using these methods is better than 0.05 mm for translations and better than 0.05° for rotations.