Principles of differential energy-dispersive X-ray spectroscopy (DEDXS)

Conventional methods and problems of differential X-ray spectroscopy using characteristic radiation are briefly described. The principles of energy-dispersive methods of differential spectroscopy are then described, covering both high- and low-resolution systems. By using digital electronics to control the modulation, errors associated with timing are reduced to well below those associated with the random nature of X-ray emission. By delaying demodulation until the final counting stage, thus using only one chain of electronic processors, errors associated with two chains of different characteristics are eliminated. Stability of the source is no longer an important criterion and the method is ideally suited for use with synchrotron radiation sources where beam intensity decays with a half-life of a few hours. It is also possible to derive the modulation cycles from the oscillator that controls the electron bunches in the storage ring, thereby making possible time-resolved and phase-sensitive studies.