Analytical Comparison of Parallel Beam and Bragg-Brentano Diffractometer Performances

摘要

The Bragg-Brentano diffractometer is an ingenious invention as it is a commonly used instrument where the sample performs a tricky function as it focuses the x-ray beam. And like other focusing devices, the Bragg-Brentano diffractometer combines a high efficiency with high resolution [1]. Simple optical components as slits and axial Soller collimators allow optimize trade-offs between efficiency and resolution. Bragg-Brentano diffractometers contributed enormously to a wide use of the x-ray diffractometers thanks to their combination of the efficiency, simplicity, and flexibility. Nevertheless, Bragg-Brentano diffractometers are not entirely free from some disadvantages [2-4], which will be a topic of the following discussions. Parallel beam diffractometers have became more common in the use in the recent years and have captured some applications from traditional Bragg-Brentano diffractometers. In addition to high resolution diffractometry parallel beam diffractometers became common in thin film measurements and reflectometry. Multilayer parabolic mirrors proved their efficiency as they collimate incident beams and are used in a variety of applications. Some experimental comparison of parallel beam diffractometers with traditional Bragg-Brentano diffractometers were performed [5-6], but their results do not give clear conclusions about preferable areas of applications. It is our attempt to compare efficiency of these diffractometers on the base of simple calculations in this paper.