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