Abstract. We investigate the finite source size effect in the context of the wave optics in the gravitational lensing. The magnification of an extended source is presented in an analytic manner for the singular isothermal sphere lens model as well as the point mass lens model with the use of the thin lens approximation. The condition that the finite source size effect becomes substantial is demonstrated. As an application, we discuss possible observational consequences of the finite source size effect on astrophysical systems.

We investigate the electromagnetic fields in the vacuum exterior to a rotating relativistic star endowed with a magnetic dipole moment, and with the stellar surface behaving as a perfect conductor. While the stellar rotation is treated in the slow approximation of general relativity, we do not restrict our attention to slowly rotating electromagnetic fields, and take our analysis beyond the low‐frequency approximation considered so far. When the dipole moment is misaligned with the rotational axis, our approach does not yield analytic solutions, but determines the properties of the electromagnetic fields approximately and semi‐analytically by computing the coefficients of simple expressions for the fields through the numerical solution of two partial differential equations. Because our approach provides a solution that is in principle valid throughout space, we can evaluate the accuracy and/or invalidity of previously known analytic expressions at different distances from the stellar surface. Overall, the solutions found in this way represent an efficient way of bridging in a single semi‐analytic formalism the strongly relativistic and the asymptotic regimes for which analytic solutions have been found.

We report on a direct comparison in the detectability of individual sub-pixel-size features between the three complementary contrast channels provided by edge-illumination x-ray phase contrast imaging at constant exposure time and spatial sampling pitch. The dark-field (or ultra-small-angle x-ray scattering) image is known to provide information on sample micro-structure at length scales that are smaller than the system’s spatial resolution, averaged over its length. By using a custom-built groove sample, we show how this can also be exploited to detect individual, isolated features. While these are highlighted in the dark-field image, they remain invisible to the phase and attenuation contrast channels. Finally, we show images of a memory SD card as an indication towards potential applications.

A 950 kV X-ray source with small focal spot using a linear accelerator (LINAC) has been developed. By installing a focusing mechanism for electron beam in this system, a small focal spot (less than 0.3 mm in FWHM of Line Spread Function) is successfully achieved at 950 kV with the target electron beam current greater than 30 mA. Several comparison data of conventional focal spot are also acquired and clearer images are obtained with the small focal spot. We are convinced that this new X-ray source is useful for industrial non-destructive inspection of large structures because of high transmission ability and spatial resolution.

A projection X-ray microscope useful for industrial non-destructive inspections and various biological observations has been developed. By installing a Schottky type electron source, a nano focus X-ray source with 100 nm focal spot size that is easy to handle in various laboratories is successfully achieved at 20 to 80 kVp. An imaging system has been composed of a vertical type that can adjust a sample position on the optical axis, and high-resolution imaging can be achieved by using a high precision stage unit. A test chart with 200 nm line width can be clearly confirmed by a transmission image, and CT images with high spatial resolution were also obtained for a test sample of glass containing air micro-bubbles. Finally, we confirmed that the spatial resolution of the obtained CT images does not contradict the measurement conditions by using the evaluation formula of spatial resolution including the effect of X-rays diffraction.