Note: Narrow x-ray reflections are easier to locate with sandpaper.
Nino PereiraA T MacranderPublished in: The Review of scientific instruments (2018)
Synchrotrons can provide almost perfectly unidirectional and monochromatic x-rays. Such x-rays reflect from ideal crystals only over a minute part of the angular range that must be searched for the reflection. Spoiling the incoming x-rays' directionality with sandpaper makes it easier to find the reflection.