Complex sentence: Here the X-rays are focused to a point and the sample is mechanically moved in a raster fashion, with the transmitted X-rays at each point measured with a detector such as a proportional counter or an avalanche photodiode.
Split into simpler sentences: Here the X-rays are focused to a point and the sample is mechanically scanned through the produced focal spot. At each point the transmitted X-rays are recorded with a detector such as a proportional counter or an avalanche photodiode.