A focusing Laue diffractometer is used to analyze the strain field in silicon in situ during different thermal treatments up to 1000 degrees C. A high energy X-ray tube is the source for this so-called strain field diffraction (SFD) setup. The SFD setup is utilized to monitor in situ the strain generated by growing oxygen precipitates (bulk micro defects. BMD) in Czochralski grown silicon. Subsequently, the in situ investigated samples are characterized subsequently with ex situ techniques including FT-IR, infra red light scattering tomography (IR-LST) and TEM. By correlating enhancements of the integrated intensity (Ell) of an investigated 220 silicon Bragg peak with BMD diameters obtained with TEM measurements a strong dependency of the total BMD volume and Ell is found. The detection limit of the SFD setup is determined at a BMD diameter of 7 nm and a density of 10(13) cm(-3), and at 40 nm at a density of 10(8) cm(-3). Thus SFD reaches into a detection range only covered by TEM so far and having additional advantages in in situ capability and minimal sample preparation requirements. (C) 2010 Elsevier B.V. All rights reserved.