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This paper reports on the reduction limit of switching loss in Si-IGBTs without increasing the on-state voltage. We focused on surge decrease and turn-off loss saturation with small gate resistance. It became clear that the surge decrease derives from a dynamic avalanche adjacent to the trench bottom and leads to the turn-off loss saturation. This avalanche phenomenon is suppressed by the reduction of the electric field and positive space charge near the trench bottom. A 20 % improvement in the trade-off relation with small gate resistance was realized by the suppression of the dynamic avalanche, which is close to the turn-off loss reduction limit.

Retinal prosthesis or artificial retina is a promising modality of treatment for outer retinal degeneration, caused by primary and secondary loss of photoreceptor cells, in hereditary retinal dystrophy and age‐related macular degeneration, respectively. Okayama University‐type retinal prosthesis (OUReP) is a photoelectric dye‐coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. The dye‐coupled films were implanted by vitreous surgery in the subretinal space of monkey eyes with macular degeneration which had been induced by cobalt chloride injection from the scleral side. A pilot 1‐month observation study involved 6 monkeys and a pivotal 6‐month observation study involved 8 monkeys. Of 8 monkeys in 6‐month group, 3 monkeys underwent dye‐coupled film removal at 5 months and were observed further for 1 month. The amplitude of visual evoked potential which had been reduced by macular degeneration did recover at 1 month after film implantation and maintained the level at 6 months. Optical coherence tomography showed no retinal detachment, and full‐field electroretinograms maintained a‐wave and b‐wave amplitudes, indicative of no retinal toxicity. Pathological examinations after 6‐month implantation showed structural integrity of the inner retinal layer in close apposition to dye‐coupled films. The implanted films which were removed by vitrectomy 5 months later showed light‐evoked surface electric potentials by scanning Kelvin probe measurement. The photoelectric dye‐coupled film (OUReP), which serves as a light‐receiver and a displacement current generator in the subretinal space of the eye, has a potential for recovering vision in diseases with photoreceptor cell loss, such as retinitis pigmentosa and age‐related macular degeneration.

This paper presents the first laboratory-based study to measure the azimuthal velocities of ions in the beam of a gridded ion thruster. Through the operation of gridded ion thrusters in space, it has been confirmed that these thrusters cause an unexpected roll torque about the ion beam axis. To reveal the physical mechanism that produces this torque, laser-induced fluorescence spectroscopy has been applied to a microwave ion thruster that was installed in Japanese asteroid probes. This technique can be used to measure the azimuthal velocity by estimating the Doppler shift of the Xe II 5p 4 ( P3/2 transition at 834.659 nm. The measurement was conducted without a neutralizer cathode to avoid the possibility of the cathode affecting the trajectory of the ion beam. The measured velocity functions are the sum of the spectra of the high velocity beam ions and those of charge exchange ions. By deconvolving these spectra, the azimuthal velocities were successfully measured and were found to range from −700 to 620 m s −1 with an accuracy of±25%. The measured azimuthal velocity profile was accurately reproduced by the simulated velocity profile obtained using a model, which includes the effects of the maximum possible misalignment of the accelerator grid with respect to the screen grid and the Lorentz force produced by the magnetic field leaked from the discharge chamber. A roll torque of 0.5±0.1 μN m about the thrust axis was calculated from the velocity profile, which is lower than that reported in flight data, but additional mechanisms are suggested to explain this discrepancy.

Thermocapillary deformations of an ultra-thin liquid film caused by temperature distribution were threedimensionally analyzed using the unsteady and linearized long wave equation considering the temperature and film thickness dependence of surface tension. The temperature and film thickness dependence equation for the surface tension of a liquid was firstly established. The temperature dependence of the surface tension was obtained experimentally using a surface tensiometer and the film thickness dependence was obtained theoretically from the corrected van der Waals pressure equation for a symmetric multilayer system. Time evolutions of depression and groove of the ultra-thin liquid film caused by local heating were obtained quantitatively.