[en] Effects of main magnetic field time-variation upon MR (Magnetic Resonance) images are presented. In permanent magnet MRI system, main magnetic field strength varies linearly with time according to the magnet's temperature variation. The effects of this field strength time-variation upon MR images are simply. (author)

[en] The inverse Smith-Purcell effect is theoretically investigated in the submillimeter wave region for planning experiments. The effect in which coherent light waves interact with charged particles resonantly through a diffraction grating is one of the candidates for laser-driven linacs. The optimum grating dimensions with a rectangular groove profile are designed by analyzing the fields just in front of the grating surface. The energy spreads of the electrons resulting from interactions with the laser field were evaluated by computer simulations. It can be seen from the simulations that a laser power of 1 W can produce ∼ 30 eV increase in the electron energy spectrum. (author)

[en] A millimeter-wave scanning near-field microscopy using a slit-type probe, which permits the observation of electrical anisotropy in the viewed object, is proposed. The slit probe is sensitive to any electrical anisotropy along the object surface direction that is inherent in the object to be imaged, because the electric field at its aperture is linearly polarized. An electrical anisotropy model is incorporated into the image reconstruction process that enables two-dimensional image reconstruction. The details of the model and the reconstruction method adopted in this work are described and experimental results to demonstrate the feasibility of this microscopy format are presented