To obtain high-quality data in X-ray CTR measurements, it is desirable that the detected intensity be on the order of at least 10 9 p h o t o n s m m 2 s . To achieve this level of output, the X-ray source must typically be a synchrotron source. More traditional, inexpensive sources such as rotating anode sources provide 2-3 orders of magnitude less X-ray flux and are only suitable for studying high-atomic number materials, which return a higher diffracted intensity. The maximum diffracted intensity is roughly proportional to the square of the atomic number, Z . Anode X-ray sources have been successfully used to study gold ( Z = 79 ) for example.