Abstract: A radioisotope based x-ray residual stress analysis apparatus having a shielded, monoenergetic radioisotopic source to emit x rays for measurement of the stress state of a polycrystalline material. The isotropic source is selected from spontaneously emissive radioisotopes emitting photons in the 5-100 keV energy range. The emissions of the source assembly are measured using either a conventional, solid-state, position sensitive detector or a gas filled position sensitive proportional counter (PSPC). In addition to normal residual stress analysis, the use of a PSPC allows the identification of characteristic photons emitted by particular isotopes to identify trace elements within a sample. As a result of the minimal shielding required for the source assembly and the small size of the isotropic source, the x-ray residual stress analysis apparatus of the present invention is uniquely suited to be configured with an area detector.