Direct Measurement of the Resolving Power of X-ray CT System in SPring-8

Resolving power of high spatial resolution X‐ray computed tomography (CT) system was evaluated by taking CT images of artificial test patterns at BL47XU in SPring‐8 (SP‐μCT BL47XU). The system consists of an in‐vacuum type undulator, a double crystal monochromator cooled with liquid nitrogen, a high precision sample stages and a high spatial resolution X‐ray detector. For the precise measurement of the resolving power, the artificial test patterns of Cu/Al concentric multilayer were fabricated by DC sputtering deposition at AIST Kansai. 7 or 5 layers of Cu/Al are deposited by period of 2 μm and 1 μm. Therefore the resolving power could be measured at 4 μm and 2 μm with each test pattern. It was confirmed that the system had a resolving power of 2 μm at 15keV from the CT images of test patterns. The resolution is not independent on the used energy. At 30keV, the resolving power was slightly poorer than 2 μm. The result was consistent with the point spread functions of the high resolution detector measured by focused micro‐beam.