AN IMAGING PLATE SYSTEM FOR HIGH-PRESSURE POWDER DIFFRACTION - THE DATA-PROCESSING SIDE

The use of an imaging plate as a two-dimensional (2-D) detector removes many of the difficulties that arise in performing angle-dispersive powder diffraction at high pressures in a diamond-anvil cell. Due to the 2-D nature of the imaging plate, a substantial part of each Debye Scherrer ring is intercepted and recorded. The averaging of the intensities around a ring so as to create a conventional one-dimensional (1-D) powder pattern results in a significant improvement in counting statistics and powder averaging, both severe problems in high-pressure diffraction due to the very small sample volumes involved. For an accurately known plate geometry the 2-D to 1-D conversion is straightforward; however, considerable complications arise when inaccuracies in plate to sample distance, plate orientations, poor powder averaging/preferred orientation, and the presence of diamond Bragg spots are considered. The current status of the software used to analyze the imaging plate data is presented along with test data to illustrate its use.