Use of double Göbel mirrors with high-temperature stages for powder diffraction - a strategy to avoid severe intensity fade

This paper describes an approach for countering an issue that can occur when using a high-temperature stage with a diffractometer equipped with double Göbel mirrors. The optical characteristics of the dual-mirror configuration make it more susceptible to intensity loss with sample displacement than conventional parallel-beam secondary optics. This issue has been apparent in the use of a high-temperature stage on a diffractometer equipped with dual mirrors, where data could not be obtained from the full room temperature to 1273 K range without resetting the sample height manually part way through the experiment. A simple technique involving controlled contouring of the sample surface has been demonstrated to allow data to be collected uninterrupted over the full temperature range, while retaining satisfactory intensities. The extent to which this technique extends the tolerable sample displacement range has been quantified using a computer-controlled XYZ stage.