The estimated standard deviation of a step-scan-measured Bragg reflexion intensity

Step-scan measurements of profiles supply ample information about the background, and it is suggested that as a first approximation a least-squares line fitted to the background is used for background subtraction rather than that the mean value of the background points is subtracted when the integrated intensity is calculated. In addition, an expression for the estimated standard deviation is derived, which takes into account setting errors in the scanning shaft. These errors can be quite appreciable - in the worst case of the order of one percent - and can well be the limiting factor for the precision, rather than errors coming from counting statistics.