| Summary: | A program is presented for the accurate characterization of any Bragg analyser, using both theoretical and experimental techniques. A series of computer programs are developed for calculating the single and two reflection parameters, for three crystal models. Results for the reflection integrals for the Darwin zero al sorption and zero extinction models are given, and the single and two reflection response functions based on the Prins model of a perfect lattice with absorption are generated, giving peak intensity, width, and integral values. All these parameters are calculated as functions of wavelength. For the experimental measurement of the reflection response, a number of methods are discussed, and a two reflection technique chosen for the measurement of the reflection integral. A new method is introduced for obtaining the single reflection profile, based on a simple two reflection measurement. This involves comparing the measured rocking curve with the calculated two reflection function based on the Prins model. If they differ, a perturbation is introduced into the Prins calculation (to model the effects which could be expected from lattice defects) until the generated function agrees with the experimental curve. To test the reliability of these methods, a thorough investigation is made of the x-ray reflection properties of three analysers: KAP(00l), RbAP(00l), and TlAP(00l). Excellent agreement with the Prins curves is found when measurements are made on new samples of the analyser, showing that the calculated functions give a reliable prediction of the x-ray response. A detailed study is also made of the reflectivity spike at the oxygen K absorption edge in KAP. Finally, theoretical data are presented for two other acid phthalate crystals, NH?AP and NaAP.
|
|---|
