Feedback system for improving the performance of extended x-ray absorption fine structure measurements.

A rapid fine energy tuning method for a double-crystal monochromator (DCM) is developed by combining a feedback control system with a phase sensitive detector. This method maintains both a parallel angle between the first and second crystals of the DCM and the peak of the rocking curve. The method is used to perform a continuous energy scan of the DCM without readjustment of the angle between the two crystals. The time taken by this method to measure the extended x-ray absorption fine structure is 60% of that taken by a conventional procedure.