The powder diffractometer was the first instrument installed (in 1987) and is situated in the experimental hall of the G.A Siwabessy reactor of the Neutron Scattering Laboratory (NSL) – BATAN. It is a standard two-axis type diffractometer with a Si (311) monochromator system that is slightly bent horizontally and focused vertically to enhance the neutron flux at the sample position. The take-off angle of the monochromator can be varied from 0 to 90 degrees, allowing for various neutron wavelengths to be used. Collimators with angular divergences of 40′ before the monochromator system and 20′ or 40′ after the sample are used. In collaboration with the Japan Atomic Energy Research Institute (JAERI), the diffractometer was modified in 1995 for residual stress measurement.