A comment on the paper Coherent crystal radiation affects the measurements of the X-ray linewidths (Das Gupta & Welch, 1968)

Das Gupta & Welch have introduced the concept of `coherent crystal radiation' to explain their experiments. As a consequence of their interpretation the fundamental X-ray line widths taken with the double-crystal spectrometer are in error. As shown in the present paper, the results of Das Gupta & Welch can be explained by means of the existing theories of the double-crystal spectrometer and triple-crystal diffractometer.