Direct measurements at the sub-pixel level of the X-ray detection efficiency of the CCD on board the ASCA satellite

We present here a measurement at sub-pixel resolution of the X-ray detection efficiency of the CCD detector on board the ASCA satellite. A mesh placed in front of the CCD restricted the interaction position of the X-ray inside the CCD pixel. We clearly show that all the primary charge is collected in one pixel when the X-ray interaction is sufficiently far from the pixel boundary. Conversely, some photo-ionized charge is collected in neighboring pixels when the X-ray interacts near the pixel boundary. We also obtained the thickness of various elements gate structure, and measure channel stop dimensions. From these data, we can obtain more accurate estimates of the X-ray responsivity of the CCD.