4.2.2. Precise evaluation of spatial resolution The reference pattern used in the above test does not have perfectly straight edges, probably because the gadolinium foil is too thick to form sharp edges. The variations from a straight slit edge are observed to be 1–2 µ m by optical microscopy. The spatial resolution evaluated using the reference pattern (Table 2) includes this effect [4]. To evaluate the intrinsic spatial resolution in our detector, we fabricated a more precise reference pattern at the Center for Integrated Nano Technology Support of Tohoku University. Fig. 7 shows the layout of the reference Gd pattern. The pattern consists of stripes that have different widths of 1–40 µ m. The pattern is fabricated by a damascene process, usually used for semiconductor devices [7]. The damascene process is shown in Fig. 8 This process produces an edge to the pattern that is sufficiently sharp. The thickness of the gadolinium is 2–5 µ m, which corresponds to an absorp- tion probability of 75–97% for CNs. Fig. 9 shows the 5 µ m-wide trench after 14 Figure 7: Reference pattern created by damascene process. The black areas are Gd-less areas.